B4CYA

Ok guys. I have put my C6 Z06 up for sale and I am getting back on my first love. My 1987 IROC-Z. I've owned the car for 15 years, it was my 2nd car and I never plan on selling it. So I have no reservations about sinking money into my car. My goal is to build an over the top resto-mod, all purpose IROC with no expense spared. I already have a fully forged 750hp 440ci LS7, Faceplated RPM Transmissions T56, carbon fiber driveshaft, built SLP Dana 44 rear end and C6 Z06 brakes for this car. I want to build the best suspension package I can put under the car without cutting up the chassis. C5 front suspension and a C4 Dana44 would be awesome. But I just can't chop the car up that much.

I would like to see some ideas from the autocross/road racing seasoned veterans here on TGO. What would you personally do if you have no budget to build the best handling 3rd gen you could build.

Some of my questions are would you convert to rack and pinion steering? Would you run a Watts link or retain the panhard bar? Is there a coilover strut designed just for road racing and autocross?

Thank you very much in advance for all of your input.

Base91

iTrader: (1)

You can go to the suspension board and start reading the stickies. There are many links to discussion threads and components. etc. etc. etc. Start making a list.

Alice89

iTrader: (6)

I cant type for long because I'm at work... But light weight multi-piece wheels should be at the top of your list if you have no budget.

I'll come back later to throw out a few more suggestions.

High end custom valved shocks/struts would be next.

All adjustable light weight rod-end pan hard bar & rear lower control arms should be on your list.

Are you willing to stick with the MacPherson strut front suspension? There are some pitfalls; but I can tell you from experience that they can be built to handle well as long as you keep your A-arm geometry intact.

B4CYA

This is the suspension board I read the stickies and there was a lot of things that seemed like they were best "for the money" but I just wanted opinions from seasoned 3rd gen racers on what they would do with the stock "style" suspension if they had no budget.

I have been in contact with Forgeline about a set of 3 piece wheels.

The customer valves shocks and struts are an interesting idea. This is the kind of information I am looking for. I'd like to know where to go to get that done.

The rod-end LCAs are definitely on the list. The PHB is up in the air since a Watts link may be used.

I plan on keeping the MacPhearson strut style front suspension. An upper and lower A-arm style suspension would definitely be ideal. But I don't want to cut the car up to do something like that.

Base91

iTrader: (1)

If you're going ***** out you need to start with stiffening. Inner and outer sub frame connectors. 3-point strut tower brace and wonderbar. Quick ration steering box. Lower the car with drop spindles or the right springs. There are complete tubular k member and control arm set ups with coil overs for the front. Make sure all steering components are good. Get aluminum billet tie-rod adjusters. Bump steer kit. Trans cross member and all rear components replaced with tubular units with spherical bearing ends. Watts link or panhard bar lowering kit. All adjustable. Poly replacements for mounts sway bar end links etc. etc. Then you can pick which struts, shocks, wheels and tires work best with the set up. All will need to be aligned and tuned to get the best out of the complete set up. Spohn, UMI, Summit, JEGS, AJE, Fays (watts link), top-downsolutions, RaceCraft (drop spindles. Belltech if you can get them) and others should have everything you may want. You may get conflicting opinions about what is the 'best' set up and which things give the most bang for the buck and the best order to do the upgrades. At least that's what usually happens.

Jay_rich

iTrader: (4)

if you research Big Modz on here or just check Austins site out, i would say he is probably one of the most active 3rd gen auto X guys. he runs Weight Jacks all around. Nothing too fancy.

http://www.f-bodysport.com/

TEDSgrad

iTrader: (4)

Stiffen Chassis: SFC, WB, STB, Move TA off trans
Raise front RC, lower rear RC a little. Drop spindles if you can find strong ones (may limit you to 8" wide, OR ext ball joints with 9.5" 275's).
https://www.thirdgen.org/forums/susp...2307-grip.html
https://www.thirdgen.org/forums/susp...p-part-ii.html
Keep unsprung weight as low as possible: Alum hubs, 2 pc 13" rotors w/FSL 6 pots (ducting to keep cool); 12" rears w/4 pots, lightweight 17" wheels. Bigger is not better. Sell off the 'Vette brakes.

Spend more $$ at the track, with good instructors, rather than on parts in your garage.

B4CYA

Ive been looking at welding up all the seems in the engine bay and around the rear lower control arms and panhard bar mount, gusseting the front frame rails to the firewall, welding up and reinforcing the upper strut mounts, ect. I built a chromoly wonder bar for the car years ago because I sold the factory one for $75 lol. I have a BMR 3 point STB on the car currently. I've considered welding the mounts to the strut towers and fire wall for extra rigidity.

For the steering, I assume the quick ratio box is the way to go vs. over complicating things with a rack and pinion setup?

Do many people use the Racecraft spindles on a road race application? They are designed for drag racing so I wasn't sure if they are strong enough for extreme side loads.

Ive seen his car. Its freakin amazing! It is a little more hard core than I want to go but has fantastic information.

Thanks again guys.

Base91

iTrader: (1)

You don't really need all that seam welding but sub frame connectors for sure. There are threads on the best way to weld them. Do not weld the strut mounts. Forgot them in the list. Get solid spherical mounts. They have a proper bearing and are way more adjustable. Keeping the stock style steering box is easier unless you get a tubular k member that is set up to take the Pinto (or other) rack and pinion. Just get at least the two turn lock to lock which you may already have. Racecraft used to do a beefed up version of their drop spindle but they don't do them any more and their web site now shows they are not for racing. Belltech spindles are the way to go if you can find them but as stated you run into wheel clearance issues if you want to go wide. Also as stated, instruction and seat time return the biggest improvements all round. Certainly to start with. You haven't said what your experience/skill level is. May help. Also, you'll find may threads covering just about every single one of the components that gets listed. There is not always agreement on which is the best.

TEDSgrad

iTrader: (4)

I do, but they no longer offer the road race version. The regulars are not strong enough. With no budget limit, you could purchase the regulars and send them out to be rebuilt (taken apart, re-welded, re-gusseted).
Read through the two 'Grip' links above and make your own decision. To remain street-able it's: drop spindles w/245's, or ext bj w/275's.

Often overlooked, is a quality seat:

Orr89RocZ

iTrader: (20)

Www.frrax.com

Base91

iTrader: (1)

I was going to mention seats but the original question was just about the underside stuff. As well as good seats there are restraints, fiberglass hoods and doors etc. plastic instead of glass, no interior. It's a long, daunting and expensive list! Even more daunting if you have a budget. And not a very big one.

plum92_camaro

Great info there. No street only or drag cars to confuse you. Sometimes its hard to determine if they are discussing 3rd or 4th gens though.

SlickTrackGod

Hi B4Cya, First off are you located anywhere near So Calif (My backyard)? Much easier to help someone if they are local.

When it comes to great handling, one thing and one thing only comes into play. Low unsprung weight. The car itself needs to go on a diet, which alone causes problems with the sprung to unsprung weight ratio which decreases ride ratio and handling quality. This in itself is why exotic cars cost so much---in order to ge the unsprung weight low on an already lightweight car it takes exotic lightweight/expensive materials to decrease unsprung weight.

The reason why I am first listing this is because I see in your opening post you are debating a Dana44 which is HEAVY. For an ultimate build when budget is (I think you mean "unlimited", not "no budget" meaning broke). I would first look at a Currie track9+ aluminum diff and aluminum axle housing. They can retrofit you with 3rd gen bracketry for the Tqarm.
Moser drilled flange axles, Wilwood 4th gen rear brake package with 12.2 SRP rotors and 4pot calipers bolt right to a 3rd gen. Definately keep the panhard rod setup over a watts. The panhard has a lateral migration of the RC which is much more beneficial in weighting the inside rear wheel on the chassis setup- more on this way down the road.. but ditch the watts idea.

CF driveshaft from ACPT is a very nice addition- I owned a few of them in a few different vehicles...well worth the critical speed benefits, lightweight rotation, and overall lowered unsprung weight. Would recommend the Global West TQarm setup- A little shorter than stock with good chassis balance and lift benefiting bite off corners. I've driven on these and really like them when setup properly with adequate spring rates and roll centers...also very light unsprung weight compared to others on market.

Wheels? keep them fairly small for unsprung weight with 17x9.5's in rear and 17x8 fronts is perfectly fine on a lightweight sorted 3rd gen. I have proved this with 16x8's on a street tire 3rd gen pulling 1.07g's. Chromemoly rear links (panhard and LCA's) are lighter and stronger than aluminum- go that route with the biggest HD rodends made to man (check on QA1 specs for those. afterm,arket vendors will not sell best ones OTC, call and ask for Better from someone like Spohn, Umi, etc.

Shocks? need I say Penske 4ways. I would do coilovers in the rear, but long after you have the rearend brackets all sorted and braced with strong but focus on lightweight bracketry in the proper geometry for a lowered car. This is where you will have to do your homework long before you just buy and then have to have things added to the aluminum housing setup. ie- lowered panhard adjustment provisions as well as lowered LCA provisions. After the car is fully sorted you will cut off all but one hole lower than sorted setup- this gets rid of unneeded weight.

The front is well documented on here. extended ball joints is the way to go, stock Kmember is fine. Go to some lightweight aftermarket arms with GOOD rodends again(not OTC stuff-over the counter). Spohn bilet strutmounts is a must...PERIOD..go to SPohn here and no other. Front struts? I would custom make some Koni lowered front struts out of Koni bare racestruts and try to make the overall tp mount as low as possible not to add height to geometry.(if you do thisthen have Spohn make shorter version strut mounts because you will not need the clearance.

Front brakes? Hubs? there is no lighter and more proprtioned kit ever made then my 12.90 6pot radial mount Wilwood custom setup with aluminum hubs- search it and copy that. Lighter by 4pounds each side then the OEM 10.5" setup

All that will get you started. Good luck.

Dean

TEDSgrad

iTrader: (4)

Lightweight 9", yes.
Then you can sell me the Dana-44

SlickTrackGod

Smartallec..LOL

Actually Currie makes very lightewweight CM axlehousings which are probably lighter and stronger than the aluminum one they sell. That would be a better option plus will not be as bulky in material off the back side so the panhard rod has adquete room.

I checked their site and the standard 9" housing is over 30lbs while the Track9 Competition-lite housing is 18.8 pounds.

For every 5 pounds you shed of sprung weight, you need to shed 1 pound of unsprung weight. THis alone allows for about 50lbs of top of the car. (IE lexan rear windshield)

TEDSgrad

iTrader: (4)

I was just about to suggest the lexan back hatch & fiberglass hood. These are easy to unbolt for the track and keep the regulars for street. Don't need a perfect glass hood. The lexan you can mount to entire hatch assembly and fab a more aggressive wing on it.

Homer23

For the best suspension for a 3rd gen for autocross and road racing, an independent rear suspension is the best set-up for that and daily driving. Since you would need to cut the car some to do it, you probably wouldn't go that route. What are you going to use the car for? If you're not racing, you probably won't need or want to go crazy with some stuff like Penske 4 way adjustable shocks when you won't ever use that level of damping. Your car's usage will also determine the spring rates, which rear suspension setup you use, sway bar size, wheel width, wheel diameter, tire compound, and many other parameters that we have just touched on. I would suggest that you get subframe connectors, a limited slip differential, and good shocks like Koni yellows or Bilstein sports to help with structural rigidity and handling. Also remember that depending on certain race organizations and classes, some modifications will bump you up into a seriously fast class or make you ineligible for any class.

Alice89

iTrader: (6)

He said its for autocross in the title. He is definitely going to need some nice shocks to keep him planted.

Alice89

iTrader: (6)

Good on the wheels then. Definitely get the lightest wheels you can get. I'm planning on getting a set of BBS LM's in the near future my self.

As far as struts go, I agree with STG on going through Koni. I have used their struts for years and can highly recommend them.

Good to know. You can get a very good alignment with the 3rdgens factory modified set up.

Do you plan on having the car corner weighted once you install your desired parts?

Like STG touched apon in post #14; your going to want to get your weight distribution as close to 50/50 & your polar weight will need to come down. You would be surprised how big of a difference in steering feel you can achieve by just taking 40lbs of the front of your car (I say this from experience).

TEDSgrad

iTrader: (4)

Since I'm researching 12 bolt assemblies w/Truetrac, I'll share my personal opinions (they're just that):
Currie had growth problems that caused QA to go in the toilet years ago. They have regrouped. Today, they are a very strong option.
Moser had growth problems that sank QA, and they just have never learned.
Strange is the one now having growth, and it remains to be seen how they will handle/manage growth and QA.
Today, if you hear of customer complaints concerning rears/axles, it's probably coming from a Moser/Strange customer.
Mark Williams - they are the Quality standard everyone compares to.


Aftermarket rears allow for Big Bearing Ford ends: set-20 on the rear!

You need better bearings up front!
Smart chassis builders & racers pay attention to the thrust load rating on the outer bearing of the front hubs. This smaller bearing is the weak link. When you drive a heavy full size car deep into the corner, brake hard & corner at high g loads … the weakest link is the small outside front hub bearing … and you know what happens to the weakest link.

Bearings used in the hubs on 3500# cars won’t have failure problems unless run too long, but will have wear issues & need to be checked on a regular basis. They may need to be replaced more often than expected.

Just for reference, here are the thrust load ratings for other outer hub bearings:
• Pinto/Mustang II/Granada/Willwood Pro Spindle use LM12749 Bearing rated at 921#
• Most GM mid-size cars (A, F & X Body) from 60’s & 70’s use LM11949 Bearing rated at 917#
• GM ‘79-‘81 G & F-Bodies use M12649 Bearing rated at 1130#
• GM ‘82-‘88 G-Bodies use LM12749 Bearing rated at 921#
• GM 70’s Impala & C10 Pickup use M12649 Bearing rated at 1130#
• Oval Track 5x5 hubs (many brands) use 368A Bearing rated at 2540#
• Oval Track Wide 5 Hubs (many brands) use 18690 Bearing rated at 1800#

A good reason to use the Kore3 7075 aluminum hubs as they are designed for the larger SET3 outer wheel bearing. PM John (87350IROC), he can set you up.

Homer23

Actually, a few organizations have tested cars with lightweight wheels vs. factory alloy wheels and have found negligible performance from them. Going with Forgeline custom wheels is good to get the perfect offset for this platform with a good design wheel and the perfect size wheel for your needs. I would go with a rack and pinion steering if you have a good steering box and you hate the feedback that it gives you. I don't have a good box so I couldn't say for sure which one is best. I do know that an average steering rack won't give you good steering feel either. I would also get a fiberglass hood to lighten the front end of the car for better handling.

SlickTrackGod

trhe typical "Hearsay" tgo answer. Why do people post when they have no expertise and only repeat hearsay?

Light weight wheels Do make a huge difference when it comes to any unsprung weight loss as well as rotation weight loss. I also speak my words from tons of experience.

TEDSgrad

iTrader: (4)

I think Homer has listened to too many sirens, and has become shipwrecked - Classic. The temptations and baubles just get more shinier - resist and live!

Maybe a little real world experience in a centrifuge will teach the lost soul.

"A man convinced against his will, is of the same opinion still."

InfernalVortex

iTrader: (4)

Has anyone solved the dustboot issue for extended ball joints? They're on my list but until I have a good solution for that it's hard to justify it.


Also werent the guys on Frrax having a lot of trouble with the Kore3 hubs wearing out bearings lately?

Homer23

Can you show me hard data that you have measured from using factory wheels and lightweight wheels? I don't desire to spend a large amount of money gathering data when several magazines, racing organizations, and some individuals have gathered the same data. I'm talking about real-world race data, like improved dragstrip times, road race times or autocross times. Even improved mpg would convince me some to look towards that, but right now, I'm mentioning what reputable sources have found.

Base91

iTrader: (1)

It's unarguable that lighter wheels reduce unsprung weight and have less angular momentum. Both good things. You can argue about how much difference it makes relative to other changes and if the cost is worth it. But once all the big gains have been made you look at the smaller ones.

InfernalVortex

iTrader: (4)

Making these cars handle well isnt about shiny, expensive suspension parts. I dont think coilovers are a good way to do anything except spend a bunch of money. Cut weight, allow the suspension to articulate, and get nice shocks. Subframe connectors and a good spring(weight jacks)/sway bar combo and you're pretty much there aside from some optimization of factory geometry with LCARBs and PHBRB and extended ball joints.

Orr89RocZ

iTrader: (20)

I have no data on how light wheels effect turning and handling grip but its very well known that light wheels and "skinnies" up front can cut 50-80 lbs depending on what street tires and normal factory or aftermarket wheels you run. That is always good for .1-.2 seconds off et in most cars. My bolton l98 gained .2 with slicks skinnies race wheel setup over stock iroc wheels and was key compontent to my 12.95 et on just a bolt on tpi L98. Not an easy feat with 254 whp

Fact is less weight moved by same hp always results in faster acceleration. F=m*a.

InfernalVortex

iTrader: (4)

If wheel weight didnt matter why do you think the leading edge companies are experimenting with things like carbon fiber wheels?

It may true in a steady state turning situation that maybe heavy wheels and light wheels will turn the same G's on perfectly flat ground within a certain range of weight differences... but look into the effects of unsprung mass. This isnt a scam, this is a serious, serious area for massive performance gains.

http://en.wikipedia.org/wiki/Unsprung_mass
This is why you had F1 teams mounting their brakes inside the monococque in the 70's despite the safety concerns. They wanted to get mass off the suspension and back into the car.



Formula 1 teams wouldnt be trying to cut unsprung mass if it didnt make a difference. Whether or not hte cost is worth it depends on what wheels you're changing to and from and what your money is worth you, but the benefits are real.

Homer23

Actually, Koenigsegg makes carbon fiber wheels in house. I haven't found out yet if Ferrari and Lamborghini are going to use carbon fiber wheels for their flagship car.

SlickTrackGod

There is a very simple test you can do to mock this type of unsprung -to sprung movement....by using your body.

COnsider your body the chassis, and your arm the suspension and wheel assembly- your shoulder socket is the control arm pivot point. and the size of your muscle determines the spring rate. Here's what you do-

1)Stand straight up with both hands to your sides and feet at shoulders width.
2) With a straight arm at all times. Lift your right arm directly 90* extended out to your side parallel to the ground...and then back down to your hip in about 3 seconds.
3) now do it in one second...Result? the faster you move the more it unsettles your body.
4) now pick up an aprox 2lb pbject and repeat steps 2 & 3, then a 5 lb object.

Conclusion-You will see the heavier the object will 1) move slower, 2) take longer to stop and reverse direction, and 3) will have more inertia that will casue further travel movement upward once speed of movement is increased....this is what unsettles the chassis of a car and causes the body attitude in relation to the ground to change...THUS, the suspension mount points of all four corners change more in relation to the ground...THUS tire footprints change with more articulation and thus a greater potential for loss of mechanical grip (or tire traction as most address it).

Lighter wheels move up and down more rapidly and follow the conture of bumpy track surfaces- all while creating less of an unsettling effect on the chassis in upward thrust inertia from those bumps and dips.

Dean

SlickTrackGod

Now to take this a little further in discussion-

I proved this simple basic widly know in the racing and chassis dynamics engineering world priciple to the 3rd gen community many years ago when I took a lightweight V6 car (yes lighter motor, lighter nose weight, lighter roll weight, and better fore & aft weight bias) and built some very light weight componants into it like my massive brakes that wiere 4 lbs lighter each side then the 10.5" fatory base model brakes, carbon fiber driveshaft, drilled flange axles, alum hubs, etc etc etc. I had a light car to begin with, and then focused on making my suspension componants lighter than most here have.

I then did another thing???? I used factory 16x8 "rear" IROC wheels on all four corners becasue they only weigh 19lbs each (not bad at all for a factory alloy) I also proved you did not need the extra width of wide tires becasue the cars lack ackerman. The added front width will work, but at a cost of wearing out very fast. My tires yeild me 25,000 HARDstreet miles with several occational track uses in that term. When they were about all washed up, I presented a local challange to 10 other 3rd gens that all had modifications. The car closest to me had 11"x17" rear wheels and was 4 seconds slower on an aprox 80 sec SCCA santioned autox course...and the slowest was over 11 seconds off. I was a whopping 135 rwhp with a slightly built 2.8L 60* V6, some of them had 400hp.

Focusing on sprung AND unsprung weight is key and mainly keeping a high sprung to unsprung ratio. My car could carry its speed through corners where I did not have to slow down as much..THUS!!!...that meant I also did not have to speed back up as much either.

If you are not familiar with my self or my old Camaro, you can see pictures in my profile gallery.

Zach/90\irocZ

iTrader: (6)

some member still amazes me and make me laugh
slicktrack thats a really basic basic explanationi like it
like beaten to death and the post above
me personally driving same car and other ones with heavier then stock wheels , stock wheels and lighter wheels are like driving 3 diffrenent cars and can be felt either braking accelerating turning etc

but here is some hard data if you still dont believe what some people are saying

http://www.carcraft.com/projectbuild...ls_comparison/

https://www.thirdgen.org/forums/whee...eels-good.html

B4CHawk

Which organization do you plan on autocrossing with? While a lot of these suggestions are good, some, or a combination of all of those mods will put you in C-prepared, at least at SCCA events. I don't think they care about mods at Good Guys events.

plum92_camaro

What about the new CAM class?

B4CHawk

It seems that that class is offered on a region by region basis.

InfernalVortex

iTrader: (4)

Yeah it's more or less a tentative rollout. I assume if it's popular enough it will be a national class soon enough. Or maybe they're waiting to see how the rules shake out on it.

87 Camaro Dude

This is probably the best explanation of the effect unsprung mass has, nicely done.

B4CHawk

Light wheels are nice, but if you are on a budget it's not a requirement. One of the fastest STU prepared 350z in National level autocross runs heavy XXR CCW knockoffs. It's still fast as all get out.