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I've been trying to design a set of custom control arms for my Trans am using solidworks/autocad, but I haven't gotten super far because I don't know a bunch about the factory geometry of the cars. I scoured the search option, but surprisingly, I came up with next to nothing.
Basically, I want to widen the arms by about 2-3 inches on either side(It's widebody, and wider typically=better suspension wise), but I also want to make them high clearance, sort of like a wisefab control arm. In doing this, I want to correct the geometry as much as possible.
So, what/where is the third gen lacking? scrub radius? camber gain? C.O.G? caster, toe, etc?
I got into this car because of my dad, and I really love it, but I want to try and improve it as much as possible
I've been trying to design a set of custom control arms for my Trans am using solidworks/autocad, but I haven't gotten super far because I don't know a bunch about the factory geometry of the cars. I scoured the search option, but surprisingly, I came up with next to nothing.
Basically, I want to widen the arms by about 2-3 inches on either side(It's widebody, and wider typically=better suspension wise), but I also want to make them high clearance, sort of like a wisefab control arm. In doing this, I want to correct the geometry as much as possible.
So, what/where is the third gen lacking? scrub radius? camber gain? C.O.G? caster, toe, etc?
Oh boy... can, worms, opened...
Scrub radius tends to be good if you keep stock offsets, camber and caster tend to be good compared to other cars, but when you go to the extreme ends you end up having to compromise, gain one and lose some of the other. Typically you run out of room in the strut tower before you can really fix that. Traditional tuning on these cars tends to go along the lines of lower it and then limit travel to keep things where you want them, and you get a pretty good gocart type handing. the less traditional approach which has sort of taken on the "if you want to do it right" place here is to change the roll center/instant center by using drop spindles or extended ball joints. That tends to limit backspacing on the front wheels and the people that run really large front wheels/tires end up doing the first (I labeled traditional) and the the less traditional "do it right" ones tend to end up limiting themselves to roughly 8-9" wide tires.
Originally Posted by morrow
welll hello
Originally Posted by SlickTrackGod
Gentleman?
Oh boy... you did it now...
These discussions tend to go to **** quickly here.
Scrub radius tends to be good if you keep stock offsets, camber and caster tend to be good compared to other cars, but when you go to the extreme ends you end up having to compromise, gain one and lose some of the other. Typically you run out of room in the strut tower before you can really fix that. Traditional tuning on these cars tends to go along the lines of lower it and then limit travel to keep things where you want them, and you get a pretty good gocart type handing. the less traditional approach which has sort of taken on the "if you want to do it right" place here is to change the roll center/instant center by using drop spindles or extended ball joints. That tends to limit backspacing on the front wheels and the people that run really large front wheels/tires end up doing the first (I labeled traditional) and the the less traditional "do it right" ones tend to end up limiting themselves to roughly 8-9" wide tires.
Oh boy... you did it now...
These discussions tend to go to **** quickly here.
Nick and I are very good friends on a personal level.
On the note of wheel and tire width, Nick is the first and only person in the world to tuck 315's under front fenders on a third gen properly. My advice is to leave any suggestions and experience on a subject to the person who's actually done it.
Last edited by SlickTrackGod; Jun 25, 2019 at 12:42 AM.
Nick and I are very good friends on a personal level.
On the note of wheel and tire width, Nick is the first and only person in the world to tuck 315's under front fenders on a third gen properly. My advice is to leave any suggestions and experience on a subject to the person who's actually done it.
I believe ackerman is measured on a percent of how the steering arms line up on the center section of the rear axle. While I don't know what mine is, I can tell you that for an example when the inside tire is turned 25 degrees the outer is only 22 degrees. As far as scrub, strut cars are going to suck with wide tires unless you have a lot of SAI, and I do not. My wheels are also 18x11 with 6.25 backspace. I'm not sure what 40mm offset is equal to, about 4.5?
I believe ackerman is measured on a percent of how the steering arms line up on the center section of the rear axle. While I don't know what mine is, I can tell you that for an example when the inside tire is turned 25 degrees the outer is only 22 degrees. As far as scrub, strut cars are going to suck with wide tires unless you have a lot of SAI, and I do not. My wheels are also 18x11 with 6.25 backspace. I'm not sure what 40mm offset is equal to, about 4.5?
yes thats how its measured, i fixed mine with a custom set of tie rods and center link i made, as far as my scrub, its dead nuts centered, i am still on a strut and its a coilover but lots of time and energy went into the front suspention alone, even the coilovers were built front scratch. i also sit abourt 7 inches wider than a stock car to though
I believe ackerman is measured on a percent of how the steering arms line up on the center section of the rear axle. While I don't know what mine is, I can tell you that for an example when the inside tire is turned 25 degrees the outer is only 22 degrees. As far as scrub, strut cars are going to suck with wide tires unless you have a lot of SAI, and I do not. My wheels are also 18x11 with 6.25 backspace. I'm not sure what 40mm offset is equal to, about 4.5?
Nick has 7.6" backspacing. His scrub radius hits the ground within an inch of the tire centerlin- Which means his car does not yank all over the road back and forth under hard braking.
Also note this is with a coilover setup. He and I developed an idea to keep the SAI down. Whether he wants to share this idea or not I am guarding it but will leave it up to him since it is his car.
I honestly don’t remember lol I have it all written down though in my files, it’s a 18 x11 with 7.38 back space 40mm off set . Scrub hits with in .5 inches of the center line of the tire while on coilovers. The control arms are three inches wider on each side over stock and there tubular arms with heims, upper camber plates use a 7/8 uniball cartridge on top , currently at 1 Degeer of camber,7 degrees of caster and zero toe. The track width is 7 inches wider than stock. It’s a design that dean and my self have been working on for a while now and so far works very well, I’m going to modify my arms for more steering angle du to the wheels turn in to the arms at full lock. I think my sai is around 10 degrees but I’m not positive on that, I would need to check my notes. Center link is a modified forged peice and my tie rods are chromoly 1in od with heims on each end. If you look up equilibrium in the search bar some on the suspension is there
I honestly don’t remember lol I have it all written down though in my files, it’s a 18 x11 with 7.38 back space 40mm off set . Scrub hits with in .5 inches of the center line of the tire while on coilovers. The control arms are three inches wider on each side over stock and there tubular arms with heims, upper camber plates use a 7/8 uniball cartridge on top , currently at 1 Degeer of camber,7 degrees of caster and zero toe. The track width is 7 inches wider than stock. It’s a design that dean and my self have been working on for a while now and so far works very well, I’m going to modify my arms for more steering angle du to the wheels turn in to the arms at full lock. I think my sai is around 10 degrees but I’m not positive on that, I would need to check my notes. Center link is a modified forged peice and my tie rods are chromoly 1in od with heims on each end. If you look up equilibrium in the search bar some on the suspension is there
You guys are getting me excited about trying some ideas on the front of mine as well, to run 18X11's with correct scrub and better ackerman. I may buy a cheap donor to use as a mockup or maybe just use mine since it will be off the road anyway next year working on paint.
The only way to keep the SAI down is to change the mounting relationship between the spindle and strut, thus moving the strut to a more vertical position. The side effect being that while a strut suspension cannot have camber gain now it will have camber loss, that may or may not be of concern. I would still like to know the actual SAI though.
Dont forget.... my a arms at 3 inches longer that stock and the camber plates are custom made specifically for my front suspension 😉
Originally Posted by tvc 15
The only way to keep the SAI down is to change the mounting relationship between the spindle and strut, thus moving the strut to a more vertical position. The side effect being that while a strut suspension cannot have camber gain now it will have camber loss, that may or may not be of concern. I would still like to know the actual SAI though.
Like I stated before, Nicks car is the first and only 3rd gen to properly fit 315's up front. I guess I need an education on basic alignment lingo (that was sarcasm)....go figure. This is all you are going to get, stop fishing for any more. The car was completely custom fabricated and has proper geometry. If anyoine has a clue what they are looking at you will see something very different in this picture you've not ever seen on a 3rd gen. Bye
edit to add: I will note that all of you can not do this unless you custom build a wider track. Your strut will hit your frame. As Nick hinted and TVC didn't get it, the upper strut mounts were also custom positioned to coordinate with the wider lower track.
.
Last edited by SlickTrackGod; Jun 30, 2019 at 07:39 AM.
...almost 20 years ago I was the first person to fudge my SAI to over 14 and reduce my caster...SAI has direct correlation with Caster- you increase one, you reduce the other. I had no issues with camber because with my light weight V6 running an extremely low 24.75" fender lip height I had good angle with the shorter overall strut length. Everyone needs to understand that every car you see may be different than yours and not everything you see on here can be duplicated.
The spindle/strut relationship is what dictates the SAI
Sorry, I must have touched a nerve.
No, you are over your head and talking remedial topics. You are trying but you really do not know what you are doing.
You came into here showing a picture of your car with a 315 stuffed under it trying to insinuate you also did it correctly...you did not. Now you are prying into some top secret stuff and I gave you a few hints to show how your picture of "you also did it" is not proper and how proper "kind of looks" because I am not showing you top secret stuff...just enough to show you that yours is not proper
Last edited by SlickTrackGod; Jun 30, 2019 at 09:30 AM.
Well that seemed to have escalate pretty quickly.
Did the OP ever get his question answered about where the weak link is in the suspension geometry of a 3rdgen? He wants to "improve" it but doesn't mention tracking the car. I've always though the stock suspension was pretty good for most uses.
Well that seemed to have escalate pretty quickly.
Did the OP ever get his question answered about where the weak link is in the suspension geometry of a 3rdgen? He wants to "improve" it but doesn't mention tracking the car. I've always though the stock suspension was pretty good for most uses.
When someone comes on saying they are trying to design something ...but ask for everyones help since they are not capable of doing all the hard effort and advance knowledge it takes to build a part to make profit? They will not get an answer.
Well that seemed to have escalate pretty quickly.
Did the OP ever get his question answered about where the weak link is in the suspension geometry of a 3rdgen? He wants to "improve" it but doesn't mention tracking the car. I've always though the stock suspension was pretty good for most uses.
Thanks for bringing that back up. the car in question has sadly since been sold, and the project temporarily abandoned. I found a ton of rust I was not aware of, and bailed, for fear the chassis was too far gone... damn northeastern cars lol. I have since gotten a 4th gen that is much cleaner. I'm still on the hunt for a clean 3rd gen shell however, and would love to get back to said project when funds allow. the good thing about the situation is that I had wanted to do a rack and pinion swap on the old car, but the 4th gen comes factory with one, making my job that much easier.
to answer your question about my orignal post, the original plan for the car was to make it a dedicated drift car. I know many people on here dislike drifting, but I enjoy it, and I want to prove that the F-body platform is better than everyone thinks it is for said sport. the only real downfall was the lack of angle, which also brought into question the geometry. I had been attempting to design a custom set of lower control arms on solidworks, and also modify the steering pickup on the spindle to both widen the track(similar to Morrow's) and correct the geometry, all the while netting me somewhere in the realm of 60-70 degrees of steering angle. unlike morrows however, I didn't want to run a massively wide tire. I wanted to run around a 265, but widen the track a ton to help prevent rubbing on the frame at full lock.
at the moment, my 4th gen firebird is the new drift project, and thanks to duncan motors, there is already an angle kit produced for it that does exactly what I wanted to do with a third gen. when I finally find a good base shell to start the build again, I will definitely be revisiting this thread, as there is a bunch of good information here that should help me out, so I don't mind at all that it went off on a bit of a thread-jack.
When someone comes on saying they are trying to design something ...but ask for everyones help since they are not capable of doing all the hard effort and advance knowledge it takes to build a part to make profit? They will not get an answer.
I find that rather rude..... I'm currently studying mechanical engineering at college, and simply wanted some pointers and helpful information from those who better understood the cars. I know a bit about suspension on my own, but I didnt know enough about the specific chassis that is the third gen to warrant creating an entirely new setup that may or may not improve where the cars were lacking. by having someone with experience like morrow help out, I would have been able to know what needed improvements, which would have saved me from messing up what is already fine. why fix what isnt broken?
I didn't want to make profit... I simply wanted to create a part that would have helped me do what I wanted with the car easier, rather than fighting the stock stuff. I wasn't planning on selling or marketing anything.
with all respect, don't assume you know who you're talking to. it makes you sound like a dick.
It sounds like he built a 'hiper strut'. Pretty much the only way to make wide tires work with a strut type suspension and keep the scrub under control. Just look up that term and you can read all about it.
What Morrow did is not my cup of tea, but I like to learn from everyone. From what I can see from my monitor, he did a good job.
Until the 2017 rule changes, F1 fronts were using 245/660/R13 (now using 305/670). Of course, not an apples to apples comparison. Tire width ain't the be-all-end-all. I like some sidewall at high speeds, but not quite 660!, and certainly more than what Morrow is running - application dictates a lot of decisions, so does build philosophy. Tire weight, heat, rolling resistance, longevity (track & street), and cost all have to fit the application and build philosophy. If Morrow stayed true to his and is happy with the results - Kudos to you!
Off the top of my head, I seem to recall that stock SAI was 14.5 considering variations in factory assembly.
I chose the RC improvements with Drop Spindles & .5" ext. BJ's. It does limit me to about an 8.5" front wheel. In the last year or so, I did lengthen the rear ear of the a-arm a little, and changed springs from #850 9.5" Eibach to Hyercoil #900 11". The Hypercoils (#100 increments only) were #7.4 compared to Eibach's #8.4 even though they were smaller!
It sounds like he built a 'hiper strut'. Pretty much the only way to make wide tires work with a strut type suspension and keep the scrub under control. Just look up that term and you can read all about it.
What Morrow did is not my cup of tea, but I like to learn from everyone. From what I can see from my monitor, he did a good job.
Until the 2017 rule changes, F1 fronts were using 245/660/R13 (now using 305/670). Of course, not an apples to apples comparison. Tire width ain't the be-all-end-all. I like some sidewall at high speeds, but not quite 660!, and certainly more than what Morrow is running - application dictates a lot of decisions, so does build philosophy. Tire weight, heat, rolling resistance, longevity (track & street), and cost all have to fit the application and build philosophy. If Morrow stayed true to his and is happy with the results - Kudos to you!
As you stated, it is not at all apples to apples for much greater reasons then apparent.
as for tire sidewall in F1, you do not have your specs written and interpreted correctly. You have in written as an aspect ratio when it is not. The tire went from a 55AR to a 56AR- Reletively no change at all. The 660 is overall diameter- wheel is 13" or 330- thus 340 for sidewall divided by 2
Hi Dean,
OK, but the main premise still is valid - a bit of sidewall is a good thing! If the wheels are too close to the asphalt, sparks will fly!
You are a smart guy. You know vehicle dynamics in theory, and you put them into practice in multiple car platforms. You can make a suspension absorb shocks, maintain tire traction, and keep the chassis under control.
Emotionally, you seem to have no sidewall and shock curving so that all road surface imperfections (real and/or perceived insults) are completely transferred into your chassis causing a loss of control. Absorption is needed in order to maintain control. Prozac Dean would be dull - so passion is a good thing. I would like to see you put into practice emotionally what you are so good at with car control. Road surface imperfections are part of a lap, so you have to prepare for them. You can't dwell on what just happened, as many more are just up ahead. Put them in the rear view mirror and keep on the gas.
Bean gone for a bit lol . No my strut/coilover is not technically a hyper strut, just a heavily modified idea on the factory on ... kinda lol. It works very well.. I have only driven it once since I did my new front end set up on the 315s . It’s now stored at my uncles waiting for me to find time to tear it apart again to modify the control arms , and do the brembos. Entered a clover leaf on ramp at 70 mph exited onto the freeway @85 not one chirp/slide or hiccup... just grip ( laugh like a little girl the whole time up to my uncles lol I’ll post pics when it’s done
Bean gone for a bit lol . No my strut/coilover is not technically a hyper strut, just a heavily modified idea on the factory on ... kinda lol. It works very well.. I have only driven it once since I did my new front end set up on the 315s . It’s now stored at my uncles waiting for me to find time to tear it apart again to modify the control arms , and do the brembos. Entered a clover leaf on ramp at 70 mph exited onto the freeway @85 not one chirp/slide or hiccup... just grip ( laugh like a little girl the whole time up to my uncles lol I’ll post pics when it’s done
I know you only drove it once but how was the steering feel with the scrub and ackerman fixed? Was it heavier? more stable? are you running Neg or Positive scrub radius?
I know mine with the large positive scrub doesn't love uneven surfaces, hoping to remedy that soon with some similar mods.
Its awesome to see someone really working hard to fix this stuff Good Job!!! I hope to join you soon, in a couple months I will begin the process. I purchased turn plates, bump steer gauge and a wheel rite tool to help measure stuff out.
Steering feel is amazing. I have a zero scrub radius with 315 up front. Rolls down the freeway at 85 with two fingers on the wheel.. rolls like a dream.
), but I also want to make them high clearance, sort of like a wisefab control arm. In doing this, I want to correct the geometry as much as possible.
