Suspension / ChassisQuestions about your suspension? Need chassis advice?
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I have been wanting to do this since someone asked me to list what I would buy and setup if I ever do a 3rd gen again.
Its not just what you buy, but also mainly how you set those parts. Every car is different in chassis weight, brake efficiency and bias, shock valving sway bar choices, and spring rates. THERE IS NO "PERFECT" ONE SPRING RATE FOR ALL APPLICATIONS so a starting guideline is just that, a starting guideline based off of many that have raced these in autoX, as well as road racing- YET those cars mostly are stripped down lighted roll weight with bare interiors and such. SO where is a good decent starting point on spring rates? Well that lies with basic trial and error or even just educated guessing. There are many factors in ultimate time trail tesdting such as tire pressure , weather, ground temp, and tire brand choice and age of rubber combined with the overall condition of that tire's cycling and care of. So in light of all that, we will just have to get you close for starters and arm you with the info to taylor it yourself for that days racing conditions and the tire's integrity.
With that siad, always note this basic fact- A car's suspension optimum is ALWAYS CHANGING. What is good now, may have to be tweaked with adjutments next month, or even later that day. WHat may be loose during the day may be tight at night. The last 5% of ultimate handling is a constant hunt! Look at NASCAR or any other form of racing and see even the professionals struggle to keep on top.
There are many combinations that will work. For example, lets take my race truck. I have run 19.9sec times at Irwindale (Toyota Speedway) on two different suspension setups with two different spring rate packages on the same 2700lb weight car and driver. One being a 325LF/350RF 175LR/275RR package, and the other being a 350/350 and 160/175 package- but NOT WITH THE SAME SHOCK VALVING not X-weights. Both with the same tire brands but different pressures. Shows that a car can have multtiple GOOD spring packages- it really boils down to driver feel. My driver though fast on both setups, favored the second to feel and consistant lap times throughout the race. Another driver might feel differently in the same car- I have first hand knowledge of this fact being true and visa versa. Only YOU experimenting with different feels will know YOUR personal choice- that means you have to learn what you are feeling and learn to adjust things accordingly.
With that said- there are some things that just are not argueable when it comes to baseline setups- thats where we will start next post......
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1st topic-Non changable built in factory suspesion points and engineered geometry as a result of that.
What does that mean? Just as its stated, we are limited to factory suspension points for the most part unless we do extensive cutting and welding and alterations- we are not going to go very deep into changing factory mounts, just slightly in the rear with the panhard (track bar) as needed.
There are two purchases that are undeniably NEEDED for optimum baseline chassis geometry setups.
1) Racecraft 2" drop spindles
2) Jegs panhard relocator kit (axle side only needed-for the most part The ride height dictates this)
OK, So what dictates the ride height then?
Factory suspension mount points and suspension articulation. We ultimately want the center of gravity of the vehicle to be as low as possible WHILE maintaining the best possible suspension articulation geometry through travel. How much travel do we anticipate?(Here's the $1,000,000 question) it will vary on tire grip, road quality, chassis weight, roll angle, ride ratio (ie unsprung weight- lighter cost BIG $$$$. Things like Aluminum shocks, lightweight CCW racing wheels, custom lightweight machined parts, lightweight large brakes, etc speed is lightness, lightness is money) I will try and use things readily availiable for purchase from vendors. Best bang for the buck. Some are even home made things you can peice together from race car vendor supply shops for cheaper, lighter and stronger than some of the vendors most of you come to know associated with 3rd gens.
To move on with what ride height? I will pick what I want based on 17" x 9" wheels and tires all 245-45-17. My wheel choice would be 3 pc BBS race wheels (Light, strong, and look great on a TTA- oh yeah, that would be my car of choice to build, but we will do this build for an iron SBC TPI 3rd gen since that by far is most common) http://www.hrpworld.com/index.cfm?fo...roduct_picture
That is a standard 25.7" tire height- designed for third gen geometry. RIDE HEIGHT will be based on 3" of travel MAXIMUM. So with Racecraft spindles installed, we want the stagnant chassis height to be "non argueably" set by the front A-arm ear height off the ground to be 1 1/2" higher than the centerline of the balljoint swiivel. This will allow for articlulation 1 1/2" up and down from centerline A-arm length- Spring rate used will ultimately be adjusted so roll in a corner yeilds about 3* and the outside compression travel at that max lateral grip be about 2" without bumpsteer (in other words- on a smooth asphalt surface)
Once you get the tire on the ground and the chassis weight loaded with this A-arm height measurements, the rest of the chassis will followw suit proportionately. This A-arm height dictates ultimate ride height & ultimate articulation when measured against cg leverage laterally. This is so hard to put into words- I hope you all are understanding this. Its not My way- it is a factual BEST way based on the factory pickup points.
I am really interested in this so I am going to follow along and drop questions if you do not mind.
What do 2" drop spindles actually do and how do they differ from the factory spindles? I am gone to complete aftermarket suspension parts - Spohn and UMI. I have been looking into the drop spindles but do you know if they will work with my Spohn tubular A-arms and coil-overs for a 1992 z28?
__________________ 1992 z28 - soon to have 383 LT1 w/ fully ported aluminum heads and intake w/ T-56
I will be reading this when I don't have a headache from these newly discovered allergies lol. Subscribing.
__________________ KONIs I Eibach Pro-Kit I 36mm/24mm sway bars I Spohn: Adjustable PHB I Wonder Bar I SFCs Custom LCAs I LCARBs I J&M Products Camber/Caster plates I Hawk's Ceramic Pads I 4th Gen 3.23 Posi I LS1/LT1 Brakes
I am really interested in this so I am going to follow along and drop questions if you do not mind.
What do 2" drop spindles actually do and how do they differ from the factory spindles? I am gone to complete aftermarket suspension parts - Spohn and UMI. I have been looking into the drop spindles but do you know if they will work with my Spohn tubular A-arms and coil-overs for a 1992 z28?
2" drop spindles do the drop at the spindle, which means the angle of the front control arms is kept as parallel to the ground in a stock resting position. Simply dropping the car via springs will cause the control arm chassis mounting point to be lower than the ball joint.
Imagine holding your arms out level, this is the neutral position from which suspension movement should start. Drop springs cause your hands to be higher than your shoulders, where as 2" drop spindles will maintain your arms parallel to the ground while making YOU 2" shorter.
In radio controlled world the neutral position is usually called "Bones level" because when the dog bones are parallel to the ground the power is transmitted to the wheels with optimum efficiency.
Why? Delrin bushings, factory type spring perches (I do not like coilovers on a 3rd gen because the strut and spring has to turn with the steering) the Delrin mounts are also adjustable in length to allow for just a slight better length angle on Camber and Caster to the factory upper strut mount adjustment. How much length added? Will be determined by how much you can get away witwithout misaligning the factory spring pocket and still negate any rubbing of the spring. Its the ONLY A-arm made I know of allowing for all these factors.
Then we go to front weight jackers so we can set our spring rates to what we want while maintaining that stagnat ride height mentioned above. Without weight jackers, YOU CAN NOT HAVE OPTIMUM SPRING RATE AND OPTIMUM RIDE HEIGHT GEOMETRY COMBINED!!!
NEXT- Allstar spring cup swivelers installed above conventional 5" springs into upper spring pockets
A V8 car Iron SBC car I would install 850 front coils/ progressive 175-225 rear coils
Swaybars 34 and 36 mm fronts 19-21-and 23mm rears to play with in fine tuning.
{IMPORTANT NOTE: I wold not actually be buying a V8 car, nor would I be using some of these parts such as over the counter sway bars- however, for this hypothetical build I am once again stating that I am trying to use over the counter equivilant parts to what I would actually truy and somewhat do. In reality, I would use custom in-cocpit adjustable swaybars from HRPworld. These are VERY costly, AND would still have to be custom fitted to a third gen.}
I am really interested in this so I am going to follow along and drop questions if you do not mind.
What do 2" drop spindles actually do and how do they differ from the factory spindles? I am gone to complete aftermarket suspension parts - Spohn and UMI. I have been looking into the drop spindles but do you know if they will work with my Spohn tubular A-arms and coil-overs for a 1992 z28?
2" drop spindles allow you to get the cg of the car 2" lower than you could without them while retaining the same A-arm geometry. 2" lower cg leverage on the roll center is major! We can use lower spring rates to control roll rate and thus not loose mechanical grip with softer rates to follow road contours.
Edit with picture also-
The attached picture will show lowering a strut front suspension car with only spring drop. You can see how dramatically the roll center drops. The roll center is the point that the body rolls around that circle. With the 2" drop spindles, the car drops 2" the roll center drops 2" proportionately and the geometry stays factory.
IMPORTANT NOTE: You can see by studying the example that more negative camber on a strut front suspension RAISES the roll center......Things that make you go hmmm.
There is alot of factors in a strut suspension. Next chapter I get into SAI (strut Angle Inclination)
I'm curious about some of your ideas along the same lines for the v6! I was looking back at some of your old posts the other day. I've done some stock car racing now and understand a lot more about suspension than I used to but still have to go back and reread a lot of stuff you say to try to understand it!! (simply put, I know I can still learn a lot, knowing how much you know.)
Would you mind posting some baseline spring rates for the v6? I've got bigger plans for my car now (for suspension) than I ever used to but unfortunately it'll be a slow process getting it there.
__________________ highly modded 3.1.....
best 1/8 mile time...9.51@74 mph
2.04 60' on street tires
I'm curious about some of your ideas along the same lines for the v6! I was looking back at some of your old posts the other day. I've done some stock car racing now and understand a lot more about suspension than I used to but still have to go back and reread a lot of stuff you say to try to understand it!! (simply put, I know I can still learn a lot, knowing how much you know.)
Would you mind posting some baseline spring rates for the v6? I've got bigger plans for my car now (for suspension) than I ever used to but unfortunately it'll be a slow process getting it there.
Hi (Alan? I think it is, veen a few years since we've conversed)
My V6 I ran aprox 825lb front springs and a front roll center that was in the dirt trying to get the cg down without drop spindles AND minimizing suspension travel and camber loss in body roll due to limited poor geometry- they now once again have drop spindles for our cars. I tried years back to get the old Beltech drop spindles but were discontinued by the time I built my Camaro.Rears were progressive 130-210 and cut softer progressive rate to a 'guestimate" 160-225rate. I later futher rasied the rear VIA shaft style progressive bump stups on my Koni's set to actiate in 1 1/4" travel and progress into about 260 by 1bout 1 3/4 travel. I am typing this off of memory, I had the actual specs I set it at somewhere in this forum I believe it could be search under "Koni bumpstops". Anyways, I added extended ball joints up front and altered the front roll center raising the axis more level, plus lowered the rear roll center leveraging the rear more, lowering the CG for and aft, and increasing the rear bar back to the massive 25mm one I had originally bought. I had stepped down to the 23 until I made the changes. After the changes, rear was perfect, front was just a td too high in compression valving with the fixed-valved Koni Yellow's (only rebound adjustable.) I would run the front on full rebound adj and the rears on '2' on range 0-3 clicks. panhard was lowered on the axle side 1 1/4". The nose of this car would take bumps great, AND would not dive more than 1" under extreme hard braking in suspension travel. (personal note- I miss that car.........ok, I'm back from daydreaming) Oh yeah, front bar was a 34mm solid/and as stated, rear bar was a 25MM solid with the axle mounts adjusted 2" narrower than the 23mm bar.
Ride heights were 24.75" front fender lip, and 25 7/8 rear fender lip. Front tires NEVER rubbed the upper fender plastic liners which were only about 2" from the tire stagnant. This car was so light nosed it never traveled more than 1 1/2" on the front under the most extreme hit. It steered like a frikin jet fighter. Only one member on here ever rode in it- George Laura (Forget Georges call name, something like 12secSS) I offered to let him drive it after I gave him a run of what it could do in the passenger seat and he graciosly admitted it would make him nervous driving it like he just passengered. Had it not had the bolstered Momo seats, it would be impossible to keep your *** in the factory seat- no BS. Before I added them, I unfortunately bounced the ex-wifes head against the passenger window a few times- opps Once I remember well getting off by LAX on El Segundo Blvd and kissing it inches form a bigrig as we mergered laterally pulling hard g's off the ramp onto the blvd- she landed on top of my right arm steering and I dam near put it into the inside retainer wall- long ride home after that one.
True story
Dean
your Spohn link isn't working BTW could be just me. thats true what you were saying about suspension qualities. same goes for the rear. when a 3rd gen is lowered, many extensive suspension mods need to occur, not just the simple coil fix. After a coil drop, the rear, in my opinion, needs to modify to keep up with some positive tractions and positive results. For example, new adjustable Rear lower control arms need to be adjustable, and also include drop brackets for both sides, the pan-hard bar would need the drop bracket and the adjustable threads. the torque would need to be adjustable with the right angle. the front struts would need the special offset camber kit to correct some minor difference and reduce tire tread wear on one side of the tire. . again with your analogy about neutral, thats great example. little confusing but understandable. i can see that idea about the coil-overs and second the spring figures. With cars, Ive seen some that are so light, practically all sheet metal. and nobody wants a bouncing Cadillac type touring suspension and others don't like the railroad track feel. Lower profile tire help some sway. Its great you have posted some good info. I think think there should be just a forum about third gens and ones experience.
Rear springs I would set on coilovers utilizing an SSS progressive 150/350 rate spring 10" length and cut off one lighter tight wind and one heavier wind making it to an aprox 175/250 and about 8" height (That an off the top of my head guess, I would have to better calculate the actual cuts)
I like progressive rear springs because they reduce rear jacking of the chassis under hard braking. However, They need to build rate quickly to eliminate wheel hop under extreme braking while promoting rear chassis set into a corner earlier than a higher linear rate spring. I would combine this onto a Penske 4-way coilover so I could independently control both lower piston speed compression and rebound as well as higher piston speed compression and rebound to get control of wheel hop at low speeds but keep rates from building too quickly and allow rebound drop at higher levels and eliminate wheel skipping. These rates and shock dampers would be adequate for massive power with the shorter GW trac link setup used to lay down power and get acceleration bit off the corner with its shorter length, YET not being too soft to cause the dreaded short TQarm braking wheelhop experienced with lower rates. i would also (and here is the major key to it working also with progressive rates) is to outfit the front TQarm mount with a Tq Absorber designed for 3rd link rearends that would act as my slider and in essence a decoupler to take away hard brake pedal wheel hop "initial shock" (this is a secret design- sorry, no more to be said on this topic= it is theory I would have to experiment and work the bugs out. A trial and error process to get the outcome I would be searching for). Otherwise, just use a Xmember mounted TQarm and use the shock and spring rates I have already somewhat perfected on my prior setup and adjust from there to get front to rear balance of the chassis. The progressive rate building as the chassis sets wil keep the car;s rear low and tight on initial turning yet allowing rotation as it sets and the rate builds, it then reverses this principle reducing off corner rear rate again tightening the tailend under hard throttle exits. shock valving aids this process to a pefected dynamic balance of entrance and exit states.
If at first it no worky? spring rate changes are cheap at about $65 a coil. Its trail and error till I get the feel I want.
Front struts would be Aluminum double adjustable custom valve Varistruts.
Adjustable Caster bolt kits would be used to mount the struts to the spindles to change SAI angles for a reduction of the positive SAI gain through brake hat mount offset of larger brake package and combined wider wheel centerline. Keeping the SAI closer to the contact patch centerline helps traction and makes an easier handling steering wheel under hard braking (it reduces sawing of the wheel)
Relocation brakets are of course a must on a lowered 3rd gen to correct the paralell LCA angles. Once set to reduce slight roll understeer in chassis corner squat to attain a better front to rear tire contact slip angl simply cut off excess LCARB material not used (that is excess unsprung weight) LCA's And Panhard would be made out of Coleman Racing Aluminim trailing arms material and the ends would be Spohns Delrin bushings at chassis ends and high end Aurora PRM series massive roadends on the articulation ends of the arms (rod ends are lighter weight than the delrin joints, yet the delrin will help reduce chassis vibration on one end.
I am not getting into chassis bracing (this is all about suspension and handling movement parts)
I like the Hotparts Strut mounts, I also like racecrafts desgin. I think I would go to Racecraft just becuase I have a great idea for a chassis brace I am not going to get into any more info about either. Basically, any solid bearing mounts to eliminate the crappy rubber bushing factory strut mounts. (Besides good shocks and tires- This is I feel the 3rd most inportant improvement to any 3rd gen to get more percise steering control and strut effectiveness in dampering slop due to the factory rubber mount. It makes ANY strut work better!)
Driveshaft? It is both unsprung AND rotation weight. So consider it as part 'effecting' suspension movement. Nothing better tan the two ACPT carbon fiber driveshafts I have owned on two different vehicles, ACPT all the way.
Rearend-Currie trac9 lightweight CM housing fitted with the TQarm package. Moser drilled flange axles. aluminum 3rd member, yokeplate etc. Gold trac diff.Richmond lightweight ring& pinion
Brakes? If you are not familiar with my custom builtssetup I made on my prior 3rd gen, then take a look at my profile page. Brakes would be custom Wilwood setups. Huge and lightweight. http://www.thirdgen.org/techboard/album.php?albumid=991
setting the rear- Now that the front is assembled, I check fender height and set the rear 1" higher than the front fender height for stance- I know this to be my liking based on my prior Camaro rake and figures. (If I had a 3rd gen still I could give all the measurements of heights from ground on a machined flat surface- in other words, a very good concrete floor. Unfortunately, I no longer have my 3rd gen to measure and give you all accurate figures and resulting calculated fender heights) I will guess the front to be in the 25-26" range and the rear to be in the 26-27" range
lets say the front is at 25" with the Aarm bolt at a hypothetical 8" and the balljoint pivot (center ball) is at 6 1/2" (1 1/2" lower than the pivot bolt for great camber gain lateral deflection angle in cornering roll), then dial the rear coilover to where the rear fender lip is one inch higher at 26"
roll centers- {front and rear somewhat imaginary points that the chassis pivot on when you roll into corners} with the above fender heights, you have a low cg (center of gravity) without an extremely low front roll center. Usually otherwse, it would be in the dirt low if not added drop spindles. So, the rear may only need to drop about one inch on the panhard Jeg's adjuster. Test driving will help confirm this once car is assembled through spring choice feel. If the panhard needs to stay up for steady state balance (I work on steady state balance FIRST, then work on coner entry and exit through other adjustments.) but is too loose still on entrance of corner, then I put the panhard down and slightly increase the spring rate, and visa versa.
1) I check Oring movement on shock shafts for travel and roll in corners. I calculate roll angle and contact patch change making sure I have my footprint flat with my camber gain vs roll. I increase or decrease as needed and keep tayloring steady state roll until I get the lateral grip, roll and footprint with combined front and rear balance and a good feel of corner entrance range with roll axis choice. I fine tune with swaybars and shocks. and then I play with shock valving further to get the baby to respond best on both entry first independantly using front compression adn rear rebound, then corner exit using front rebound and rear compression. Yes this makes most peoples head hurt. You either get it or you don't, unfortunately- most don't and need someone that does.
I had mentioned also a little about setting the Rear LCA's somewhat parallel to the ground using LCARB's (relocation brackets) Now when you are playing with spring rates and roll measurements, you can calculate where the inside (meaning left LCA on a left corner) LCA is fully extended laterally in distance from the front chassis mount and the outer LCA is arched upward slgihty shortening its distance from the front chassis mount in full lateral roll of the chassis. This brings the outside of the rear axle forward inducing rear steer of the axle towards the corner..Or what is call "roll induced understeer" This is optimum setting for tire slip angle.
This was a run down of setup strictly based off the top of my head but I think I pretty much covered most settings and how they affect the chassis for ultimate "baseline" settings when dealing with chasiss fixed mounting points and ususpension angles. Some things sould be set to the best values and not touched. I feel by touching these to correct bad handling problems would be a "bandaid fix" becasue they are reduce from optimum only for trying to acheive balance- this often is a wrong move when balance could have been accomplished by changing other setting than moving these things like SAI, slip anlges, scrub radius, camber gain values, cg level pertaining to body movement and suspension leverage.
Other settings like rear roll center, swaybars, tire pressure, tire diameter, alignment specs, and brake bias will constantly need little tweaking to maintain optimum handling. Thesed are the setting that should be touched, not the others mentioned in the paragraph above this. These adjustments are not what I call chassis baseline setting. This post was mainly about the baseline setup ONLY for ultimate handling. It takes alot of work and time in trial and error, but pays off if done.
I'll bet there is alot of things I have mentioned here that alot of you never knew you could do to a 3rd gen like for example resetting the SAI to correct srub radius. You now are seeing why I was able to reach an amazing 1.07g's on street tires.There was alot I did to my car that has never been talked about until now.{A little major tip- Increase SAI makes for a better front inside tire footprint= that equal better lateral grip. I could do a whole novel on this alone}
Note: Do not expect 1.07 g's with a iron block V8 car. It is too nose heavy. I am sorry to say it is a fact based on laws of physics that you are just not going to acheive a near 50/50 weight bias to accomplish this on street tires. racing tires? yes, a Yugo could acheive 1.07 g's on racing tires, but not anywhere close to that on harder street rubber.
Anything I missed or any question then feel free to ask and I can try to explain things more detailed if I come accross confusing anywhere- I know my own head hurts when I try to re-read what I write.
Dean
You can tell how hard I am stuggling to stay in the seat by how much my head is leaning towards the passenger seat- This Autox run was on worn street tire before I installed the Momo race seats. Also, look at he inside tire footprint- beautiful contact patch.
Stephen, the thread is called "ultimate" 3rd gen suspension, not "how to build a fun daily driver". I do think a majority of the information can also be applied to a street car. But, I'm no expert.
Edit: I think it is obvious that this is "real world, real budget, street car advice". There are a lot of people that have more money invested in their street cars than what it would cost to do what is described in this thread, most likely including you.
This would be a street car, as was my original Camaro was.
Thats the whole point. I don't know why you are missing that. It is optimum setting wheather it goes on a track or not. If it goes on a track with race tires, then lateral grip goes up, roll goes up, and ire distortion goes up. Concequently I would have to increase spring rates, and alignment for track used and readjust balance to the new grippier tires.
All hat I listed above would be for a full time street tire car.
No one ever asks me why I do not race anymore. Its really a simple answer. I get bored racing under rules when I know a car can go faster. driving under rules is all about everyone can go the same speed for the most part, but it boilds down to the guy that screws up his driving lines the LEAST. I do not like driving a car I now I can get more of a rush or thrill out of. I like building and testing my own car against the clock...Lap times. No one else crashing into you, just you and engineering/setup skills helping you make your own car as fast as a thrill you can get.
To a relistic point like Stephen asks- can I do something the average person can afford? whos the average person. We are not talking Lamborghini's here, nor are we talking Vettes, and we certainly not so low budget we are trying to modify a Yugo or a motorcycle.
A 3rd gen is a very inexpensive car to build. If you can not afford to build it correctly then just simply put Tires and Shocks on it and drive it til it wears out. Then sell it and move on.
HOWEVER, If you are looking to build a car to keep for long term- then throw money at it you will never reclaim.
It is a luxury. Unfortunately, not all people can afford luxuries. A Luxury for me would be this, I drive it sometimes and get enough to frustrated that I can't have one, even though I can drive it far better than its owner. yes life sucks because it revolves around money. But do it right or don't wate a penny on that car you may soon have to sell. You will be better off in the long run not putting money into a moneypit you may have t sell someday and break you.
I could buy this Ferrari right now http://www.thirdgen.org/techboard/al...pictureid=5450 , but I could not afford the maintinace it woiuld take to keep it running- so I do not buy it I could own it but not afford to drive it! The auto clutch assembly for the paddle shifter alone runs $10,600 to replace and is done as often as every 30K miles. We all have to pick what we can afford. I can not tell you to do something that is wrong, it just will not work. You start altering things without an overall budget and plan then you are going to have a mess and alot of wated money abondoning a half finished project.
Stephen, you seem like a decent guy. I read alot of your postings here and have the opinion that you will sometimes speak your thoughts before you think about things (thats called youth, We all experience that, some of us grow out of it, some don't- I am 42 and I am still guilty of that sometimes) I think the answer you are looking for is how can I make YOUR car as fast as any 3rd gen on your budget. If you want to try and do this here. I am pretty much finished with what I had to say on my opinion of the ultimate baseline setup... so we can have some useful time and see if I can help you get your car to its optimum with your budget. I already showed everyone what I suggest you need to buy and listed why- with that you get a prety good idea what it would cost. So lets do it in reverse fashion with you and see what I can suggest you do with what you have already and what budget you are on. I need a budget, a time frame, and a parts list of what you have already done.
that list needs to even intel tire band size and curerent condition as well as its expected lifespan with your driving need and habit.
this is a really great thread.
i will be making sure that i follow this more or less in my planned mods.
one question though:
are weight jacks necessary?
seems like they add a lot of excess weight when you could simply use urethane spacers or make your own spacers (i cant but some people have the ability)
any input?
another thing that you alluded to but did not actually say outright is that proper racing bucket seats and a harness (worn correctly) will improve anybody's driving even in a Cadillac Deville.
recently i had a chance to drive a friends 2004 Z06. the suspension was amazing and i found myself much more in control of what i was doing. later i realized that my knees and elbows were not all tired out from bracing myself while i was cornering. good seats can make a huge difference.
__________________
Last edited by RED_DRAGON_85; 09-14-2009 at 04:37 PM.
Install ones like this. They only add a few pounds, and they don't add any unsprung weight. There is a nut welded to the bottom side of the subframe, and usually the rod you see sticking up through the center of the hole there would be threaded, and the weight jacks would be adjustable from above. What you see now is unadjustable, since the threaded ones were often removed to comply with rules at a certain track.
Can't get pic to upload...
this is a really great thread.
i will be making sure that i follow this more or less in my planned mods.
one question though:
are weight jacks necessary?
seems like they add a lot of excess weight when you could simply use urethane spacers or make your own spacers (i cant but some people have the ability)
any input?
another thing that you alluded to but did not actually say outright is that proper racing bucket seats and a harness (worn correctly) will improve anybody's driving even in a Cadillac Deville.
recently i had a chance to drive a friends 2004 Z06. the suspension was amazing and i found myself much more in control of what i was doing. later i realized that my knees and elbows were not all tired out from bracing myself while i was cornering. good seats can make a huge difference.
WWeight jackers are not necessary but can save alot of headaches in buying, cutting and screwing up then buying another set of coils etc etc until you do enough lavor and trial and error on spring choice til you get it right. I did this with 3 different sets of coils on the front of my Camaro when I first lowered it. The bad part is once you cut a coil you can not return it. Uncut coils can be removed and most places will swap them out till you get the right rate you desire (as long as you didn't scratch them to death or beat on them for whatever reason getting them in and out. jackers make life so much easier.
Seats- I only mentioned in a quick funny (to me) story I listed above but still am not concerned with listing them here ... I stated this thread is SOLELY for ultimate suspesion geometry baseline, its not even about chassis bracing.
One thing I shoudl say in doing an aproch like I just listed in this thread with spring choices I use and short Tqarm is the critical marraige of ALL componants to make this setup work. You can't just keep buying and adding as you get money. Its got to progress fairly quickly in evolution or its just not going to be safe. A short TQ arm can be damgerous if not setup with the correct pelated componants as well as progressive rear coil springs combined with them can actually make things worse, not better. The heights and roll travels need to be balanced to come into play percisely or you will have car doing weird things. It takes alot of adjustments like the 4way rear shocks or dual shocks on each rear corner (4 separate rears- 2 linear valved, and 2 digressive valved) to get away with no low end wheelhop or high end skipping or glancing over the road imperfections loosing mechnical grip. High piston speed rebound can ANNOY THE HECk out of you driving at speed, yet too low starting point with a single 2way shock rebound will lack the needed slow piston speed chassis control.
I have played with this on my 'Vetruck' I run 8 shocks on it. One digressive valved AND one linear valved on each wheel. Its one heck of a work truck. I blow out the rears quite often due to the heavy loads I carry in it weekly. When the rear rebound goes on the linear shocks (which always seems to wear quickest) the truck is annoying to drive low speeds, and better but still lacking just not as much at higher speeds. The weight I carry kills my componants fast- I am rebulding rear shocks twice a year on it. But it carries 3000lbs in the bed on average once a week.- the amazing part is this truck will do 150MPH and corner great for a truck(heck, great compared to most cars) yet still carry a load in the longbed of 3000lbs while lowered down empty- and nothing rubs or sags. I have never seen anyone build a truck like it. It is just that...STILL A TRUCK that is USEFULL and a sports car. Try that with your Ford lightnig trucks, or your Eddie Bauer Trucks, or your Viper motor truck, etc. It ain't gonna happen. I have had YEARS of experience driving this vehicle (21 years now) with everyday changing loads in the bed and full in cockpit controls to taylor the ride via 2 rear cockpit controlled shocks and cockpit controlled rear axle mounted airbags assiting the normal suspension. My weight bias, changes, my brake bias changes- I still haul *** everywhere and blip the controls to dial it in on-the-fly. This truck is where I really learned about constant changing suspension situations- and then learned how to deal with them.
Vetruck,
Nice to see you back posting on here... Haven't spoke with you in a while.
Your insight was very helpful in the past & hopefully this will spark some research by anyone wanting to maximize their suspension.
As for your mods listed, everything here can be useful in a street car. One thing you mentioned was roll center, which is very important. Most get lost in lowering the car without respect to the roll center effect.
The key here is to make changes & test your car out. The setup has to match your driving style, & what works for one person may not work for another. If you are trying to achieve the perfect handling car, some trial & error is required & you may have to swap springs or swaybars to get it where you want it. Remember it has to work or you, not what someone else says is the "setup" to have.
Some conessions will have to be made to ride quality, but you cannot expect to outhandle a Vette & ride like a Cadillac at the same time. The interesting part is you will start to notice flaws in other cars when you drive/ride in them as you make your car better. Today I drove a 17,000 mile original 88 Formula WS6 to work. It is original in every respect & literally like a new car. It was a good benchmark comparison to my 91 Formula (that I normally drive) which I have done a lot of work to. The difference is night & day, & now I fully realize how much I improved the handling.
It's good to see a large in depth tech post from you. I know I learned some stuff.
I know what you mean when you say people shouldn't buy parts solely on what others say is best. I bought my Eibach Pro-kit springs this way and I regret it. It feels like the front spring rate is too soft but the back is alright. I plan on going with weight-jacks when I build up the motor and tranny.
Since you keep referring to chassis bracing, would you mind making another thread about that? I think I have a pretty good idea of what kind of bracing you would recommend, but it would be good for everyone to see.
Also, you mention you were generating 1.07 lateral g-forces on street tires in your camaro... What kind of "street tires" are you talking about? There are a lot of DOT approved tires that are pretty much just a step below real race rubber. Another thing I was wondering is if your camaro was gutted or if it still had a full interior and what not.
Thanks again for the great thread.
Mike
__________________ I started racing when I was 7 years old and here I am now... KONI Yellows | Pro-Kit | J&M Strut Mounts | Edelbrock STB | Spohn SFC | 9-bolt disk 3.27
36mm/24mm | UMI Adj LCA/PHB/LCARB | Corbeau seats | plus more ...and I'm only 18
Since you keep referring to chassis bracing, would you mind making another thread about that?
Also, you mention you were generating 1.07 lateral g-forces on street tires in your camaro... What kind of "street tires" are you talking about? There are a lot of DOT approved tires that are pretty much just a step below real race rubber. Another thing I was wondering is if your camaro was gutted or if it still had a full interior and what not.
Thanks again for the great thread.
Mike
Thank you Mike,
I guess I need to continue a new post and put it "part 2" chassis bracing. I can get into the weakness'es I have discovered on them, pretty much all of which I have already discussed in scattered posts. I guess I can try and consolidate the info.
The tires I was on were Goodyear GS-D3's 245/50-16 on factory IROC wheels. 220 hardness, not a 50 tw DOT racing tire.
The car has full interior creature comforts including A/C and back seats, but it was a lightweight V6 with polar weight decrease on the rear, and an already light nose weight with the 60*V6. Weight load was more in between the wheelbase....and smooth driving. I pulled 1.03 to the right, and 1.07 to the left.
Chassis flex in relation to crippling tire footprint is the key focus, as it also obviously is for suspension geometry flaws crippling footprint. Its not just about outside tire grip, its inside radius tire grip that aids in lateral g's. its keeping the inside rear tire weighted without using a high rate spring- this is done through leverage....etc. Its a whole package of stuff. Weight is major (cg, bias, polar,roll), unsprung weight is major, chassis stiffness pertaining to suspension pickup points is major, suspension geometry in relation to contact patch is major, chassis control through dampering is major. You have to have all of them.
I will start part two in a few days when I have more time.
Another very knowledgable person on here is NormPeterson. We have some good discusion on STB's alone (Strut Tower Braces)on a good post in the fabrication forum unde something like "homemade STB" where we get into triangulation bracing in relation to the towers so as not to have both towers flex in unison even though tied together, they need firewall trangulation bracing (aka 3pt). I will try and find all that and reference archive postings in a chassis bracing post. TGO should make these a "sticky" since most questions on here are about what to buy performnce wise- people need to know how to set what they by and how what affects whatelse.
Thanks for the great info. I have some questions pertaining to my 1986 Camaro. This was my first car back in the day of highschool. Back then I did Bilstein shocks and struts with Hotchkis springs. Well, the shocks (blue and yellow ones) are worn out, so I am shopping around for replacements. I want to redo the shocks and struts and prob the springs all over and do it the right way. Do you know what you would consider to be the best ones out for my '86 Camaro? I want to have a perfect stance and harder corner features, I HATE BODY ROLL! Interested what you think, thanks!
PS: Do they make a strut tower brace that works with our cars that are carb'ed? Would the TBI strut tower brace work with a carb'ed car?
Last edited by ChrisCamaro86; 09-22-2009 at 08:32 AM.
Thanks for the great info. I have some questions pertaining to my 1986 Camaro. This was my first car back in the day of highschool. Back then I did Bilstein shocks and struts with Hotchkis springs. Well, the shocks (blue and yellow ones) are worn out, so I am shopping around for replacements. I want to redo the shocks and struts and prob the springs all over and do it the right way. Do you know what you would consider to be the best ones out for my '86 Camaro? I want to have a perfect stance and harder corner features, I HATE BODY ROLL! Interested what you think, thanks!
PS: Do they make a strut tower brace that works with our cars that are carb'ed? Would the TBI strut tower brace work with a carb'ed car?
so.. quick question... an upper panhard bar, panhard bar relocator and adjustable panhard bar (with what kind of bushings) would be a great imporvement for a street car that is driven hard..... when compared to stock rusting stamped steel... would it not? kinda dumb question, but im wondering if i need the adjustable panhard bar .. and if i need the upper panhard bar part too? my car is lowered 2" up front with 2" drop spindles, and i cut 3/4 of a coil out of some brand new moog 5665 spings for a 1 1/4" drop in the rear.. so yes the rear is lowered.. is it worth doing the upper ph bar, ph bar relocator, and adj ph bar?
yest you should change ph bar to adjustable as now your drivetrain is not centered (after lowering). as for upper ph bar part there is no need to replace it if it is not damged, as for ph relocator you use it only if you have problem with fitting exhaust
A V8 car Iron SBC car I would install 850 front coils/ progressive 175-225 rear coils
Just tripped over this thread.
Questions: are these true progressive springs or "bilinear" springs that have two different coil spacings (and suddenly jump up to the high rate once the close coils all close up at about the same time)? What happens when the inside rear gets back into the "soft" rate?
Norm
Last edited by Norm Peterson; 09-25-2009 at 09:14 AM.
Seats- I only mentioned in a quick funny (to me) story I listed above but still am not concerned with listing them here ... I stated this thread is SOLELY for ultimate suspesion geometry baseline, its not even about chassis bracing.
But it's amazing how much having only a cheapie chest strap helps you actually use the potential that you're building into the car. Tires are Falken Azenis RT615, although they do have quite a lot of runs on them. I'm guessing I'm at worst only a little shy of 1.0 lateral g.
This car is 100% street legal and is fully daily driveable with full interior (and everything remains functional, even the A/C). Some of Dean's tips I am not easily able to add to this car, but there isn't anything in his list that I wouldn't consider 100% streetable.
Norm
Last edited by Norm Peterson; 09-25-2009 at 10:17 AM.
yest you should change ph bar to adjustable as now your drivetrain is not centered (after lowering). as for upper ph bar part there is no need to replace it if it is not damged, as for ph relocator you use it only if you have problem with fitting exhaust
best regards
At stock height, with the stock PHB & with good bushings, my rear end was already off by a good 3/4"!
I HATE BODY ROLL! Interested what you think, thanks!
Just my opinion, but once you've got your tire treads as flat against the pavement as you can, body roll becomes rather meaningless. And if you've got enough shock/strut damping, it happens a little slower. I know my 85EP car rolls a lot more than Dean's 3rd Gen does. But quite honestly I hardly notice it during a run, and if anybody told me to forget all about what I know about that car's amount of roll per lateral g and then forced me to estimate how much it was rolling, I'd likely guess it to be about half of what it really was. With only a few of the tweaks, once you stop looking at the hood line and focus down-course, you really don't pay much attention to the roll.
I notice the pitch under braking (nose dive/tail rise) in my '08 Mustang GT to a much greater extent.
I know I'm introducing a bit of "driver" into a suspension discussion, but the whole picture is "car" + "driver" + "road" and I don't think you can fully separate them.
Norm
Last edited by Norm Peterson; 09-25-2009 at 10:22 AM.
There isn't much need to replace the PHB brace, with a couple of exceptions.
If it's been damaged. (duh)
If you've lowered the chassis-side PHB attachment. Then you'd perhaps want the brace to attach a little closer to the relocated PHB attachment point for structural reasons, and the OE brace might not fit right (needs to be a tiny bit longer).
Questions: are these true progressive springs or "bilinear" springs that have two different coil spacings (and suddenly jump up to the high rate once the close coils all close up at about the same time)? What happens when the inside rear gets back into the "soft" rate?
Norm
A progressive spring design will not shot up from one rate to the next, It progressively goes into coil bind on each tight wind coil. As each coil is deadened, the rate increases "linearly progressive" is the best way I can describe because the coils make a constant increase change as the coils circularly wind the contact in deadening as the spring progresses. the trick is to have the coil hit full coil bind of the tighter winds in normal roll set into the hardest corner. That is the rate we are after for lateral balance.
This gets complex, so I will get into it. The front "linear springs" resting in the A-arm helix slot actually acts alot like a progressive rate spring in articulation. The rate climbs quickly with that open coil resting intothe helix as it makes more deadening contact in the arm pocket under compression. So, in other words, its rate climbs quickly also in 1 1/2" travel....
...I like the rear to match doing the same. It is an inherent defect in design of conventional spring pockets up front that I ACTUALLY LIKE and retaylor the rear to follow suit.
I have spoke before in other posts about roll center "yaw" (as in roll, pitch, and yaw) and how it migrates.
On a solid rear axle car where the roll center is centered under equal load at static height, upon differing spring rates, the roll center will migrate dynamically to the stiffer spring rate under roll. I use this effect by the use of progressive springs that will lighten the inside wheel rate upon roll and will greater leverage the wheel via roll center yaw with chassis weight-HOWEVER- the tire dynamically being lightened with chassis weight unloading off it, also unloads in spring rate maintaining mechanical grip and not causing the car to roll over onto the diagonally opposite tire (outside front). that migration of the rear roll center to the outside yields a greater chassis weight leverage back onto the reduced inside rear keeping the corner from jacking while maintaining grip planted on the pavement.
In other words, lighter progressive inside rear chassis weight? Lighter progreesive inside wheel rate
I hope that made sense, there is alot of dynamics going on back there. It is ALOT harder to get right with spring rates and heights in setting the rear. My old Camaro I was shy on the rear rates but good on the hitting heights, so I simply added Koni Shaft style bump stops onto the rear Koni Yellows and they too progessively come into comtact at the right height raising my set corner rate at travel indication of shock shaft and lossened the rear to balnce the front at corner set. I went bavk doen on swaybar from 25mm to 23mm when I did this and keep the axle bar mounts closer mounted to further keep the bar stiffness reduced.
A progressive spring design will not shot up from one rate to the next, . . .
Thanks. Exactly what I was looking for, as sometimes the term 'progressive' is used inappropriately. I suspect that many of the mass-market "lowering springs" that are advertised as being "progressive" are really "bilinear" with a "knee" in the load vs compression plot.
Quote:
I have spoke before in other posts about roll center "yaw" (as in roll, pitch, and yaw) and how it migrates.
On a solid rear axle car where the roll center is centered under equal load at static height, upon differing spring rates, the roll center will migrate dynamically to the stiffer spring rate under roll. I use this effect by the use of progressive springs that will lighten the inside wheel rate upon roll and will greater leverage the wheel via roll center yaw with chassis weight-HOWEVER- the tire dynamically being lightened with chassis weight unloading off it, also unloads in spring rate maintaining mechanical grip and not causing the car to roll over onto the diagonally opposite tire (outside front). that migration of the rear roll center to the outside yields a greater chassis weight leverage back onto the reduced inside rear keeping the corner from jacking while maintaining grip planted on the pavement.
In other words, lighter progressive inside rear chassis weight? Lighter progreesive inside wheel rate
OK, I see what's going on here. We're actually looking at the point that the sprung mass actually rotates about (or at least an indication of its lateral position), which certainly would affect spring compression on one side and extension on the other. Not necessarily the same "roll center" that is used to determine lateral load transfer in a corner with no banking, though.
Yes, as I am sure you know Norm that when the individual wheel instantaneous centers change based on individual suspension geometry charateristics (ie- for simple explination, one side compressed and one side extended in body roll) the static roll center will then migrate dynamically and yaw the roll axis (being the imaginary line conecting the fornt roll center and the rear roll center- for those that do not know this term.)
Also note- I edited my post #8 above with test and a picture of front roll center info
if the stagnant roll center of lets say (we will use any front or rear for this example) the rear is centered on the chassis left to right. Then in motion of a left corner the cg moves right under roll-----the roll center is also migrating right under roll fighting staying under the cg vertically helping trying to maintain left side leverage of the roll circle to the cg. If the cg falls to the right of the rc the cg drops easier and thus the car rolls easier at that end of the vehicle. (this is only attained on a solid rear axle suspension ONLY if the outer spring rate is higher.)
Iknow when are causing people to run for aspirin. I know....
It illustrates quite nicely what I keep telling people who want to lower a strut suspension with springs - that the roll center will drop about double the amount of ride height lowering. I cringe at the word 'Sportline'.
So anyway, a 2" body drop via springs ==> 4" loss of front RC height, which probably buries it an inch or two in the dirt. As bad as it sounds, if not worse (been there, done that on the 85EP, could hardly fix it fast enough).
Norm
Last edited by Norm Peterson; 09-25-2009 at 03:41 PM.
The next great side effect of lower a strut front suspension isbased on the antidive characteristics of a double wishbone suspension. On a strut suspension, we do NOT have adjustments of upper control arm mounting pitch to control braking motion through the upper ball joint in order to reduce nose brake dive- obviously becasue we do not have upper control arms.
What we do have is leverage of the strut shaft acting upon the strut tower/mount to jack the rear of the car under hard braking.
The lower the car, the shorter the strut, the less jacking leverage of the rear under hard braking.
But wait, lets say we only have drop spindles so the strut is actually not lower since only the spindle is raised 2"? Well, its still 2" higher in rotation closer to the strut via spindle center rotation, so it still does reduce leverage. What is gained on the bottom side is still alot closer to center leverage wise than the reduction of two inches from spindle center to strut mount. Hope that made sense.
I will do a picture of the braking rotation leverage. Think of this again as a breaker bar. The shorter it is, the harder you have to exert pressure to get the same force- so shorter distance means less leverage, thus less rear jacking effect.
This is not really an adjustment, just a byproduct of lowering the car. You get many benefits of vehicle lowering when it comes to handling. Some settings fall into place, others fall out of place and need to be corrected for better ultimate handling. This one happens to gain benefit. Lucky us... Lower cg movement into the front spindle rotation.
Purple line is the distance from spindle (center wheel rotation) to the strut mount bolted to the chassis. This distance shortens the lower the car is unless you keep raising the strut mount height. A shorter strut like the Varistrut version becomes beneficial not to have to run an extended hieght strut mount for strut body clearance in travel.
back to a double wishbone suspension, the taller the spindle, the greater the effect to control dive and antidive- but here its rear jacking effect and shorter is better. Just giving a comparison of suspension types and what we face. yes, now I am just having fun thinking about most of you pulling your hair out.
2" drop spindles do the drop at the spindle, which means the angle of the front control arms is kept as parallel to the ground in a stock resting position. Simply dropping the car via springs will cause the control arm chassis mounting point to be lower than the ball joint.
Imagine holding your arms out level, this is the neutral position from which suspension movement should start. Drop springs cause your hands to be higher than your shoulders, where as 2" drop spindles will maintain your arms parallel to the ground while making YOU 2" shorter.
In radio controlled world the neutral position is usually called "Bones level" because when the dog bones are parallel to the ground the power is transmitted to the wheels with optimum efficiency.
so is it bad for the ball joints if I only put lowering springs in my 90 IROC for now?
Where do you suggest purchasing the custom springs?
If you were anywhere close understanding this info I have posted then you would already know how to answer your own post.
You would also realise that no one can answer this question except you. you will have to read and learn. Then simply type in "coil springs" in the google bar.
Nothing custom about it. Coils springs are ready made in all rates- nothing custom made needed.
People might think I am an *** for responding like this, but really folks, I spent hours typing this info for free and then I get a silly question like this from a guy with a masive heavy stereo system in his car...go figure. Do kids even think nowdays? (Kids in general, but not always the case. I used to think there was no such thing as a dumb question, but after reading a thread like this and then asking that?....Just lazy stupidity.)
Anyways....sorry about the last post......I came into here to add some more info on basic geometry.
This is a baseline 101 in suspension geometry. It pertains to artuclation swing and the length of the span (ie- span meaning contol arm, a-arm, etc..) in relation to the ground both parallel AND perpindicular fashions.
Why the ground? it is the surface you are traveling on and the direction of the chassis weight. Ulimately, It is you main focus of attention= tire contact patch to the ground.
This graph shows basic changes in arc of an LCA in parallel motion to the ground. It can ALSO show basic changes in arc in perpendicular motion to the ground as pertinaing to a front A-arm.
Note:actual graph figures are estimated only for quick example. Figures are not exact calculations
Makes comprehension a lil' difficult sometimes. 
