Real world first Gen F-body front suspension evaluation

[Tinker]

Hi all,

I am finally posting this in hopes someone out there can give me factual feedback.

I, like some or many am at a standstill on my project. I got caught up in the scandal a number of years back. (yeah THAT one).
I DO NOT WANT THIS TO BE ABOUT THE PERSON. If this goes off on a tangent I will ask the admin to shut this post down.

What I am looking for feedback from those with experience of front end geometry.

I have all the parts that have been sitting for three or four years now.
I am not worried about the quality of parts. The control arms are from Ridetech, as well as the shocks. The hubs are speedway engineering large hubs with their 3 piece sway bar as well.
The spindles are the fabricated ones which I am almost sure are manufactured by Coleman. The brakes are 14/13 inch Wilwoods.

Before I start cutting as intended, I would like to have some assurance that all my work will not be in vain.

I have all my measurements where I they look good on paper, but has anyone run a similar setup?

Am I going to be alright with 9 deg static caster that will near 12 degrees dynamic in a turn? I would hate to end up with a car that shakes like your local grocery store shopping cart.

Have the fabricated spindles been holding up?

From previous posts it sounds like the shocks should be de-sauced.

I really can't afford to start over, $10,000 in parts is too much to scrap or sell for pennies on the dollar.

I understand these are now dated parts. I am not looking to compete in any large autocrosses or the like.

My goal is to have a car that is fun to drive, reliable and safe to bring out to the track. I would love to be able to do 275's on all corners so tires could be rotated.

I can furnish more parts/setup details if needed.

I thank anyone in advance for their constructive thoughts and advice.

[Musclerodz]

That sounds like alot of caster, but it depends on how low the car sits. I think the new vettes are around 8? but they are LOW. Typically I run around 6 static for street on a first gen with Ridetech kit or DSE sub.

[Tinker]

That sounds like alot of caster, but it depends on how low the car sits. I think the new vettes are around 8? but they are LOW. Typically I run around 6 static for street on a first gen with Ridetech kit or DSE sub.

Is this due to jacking effect? Do the new vettes only get away with high caster due to the deep offset and low scrub radius?

At 20 degrees steer, outside wheel has neg 7 degrees camber and inside around 4. Will this only wear the tire edges and overwork the power steering?

[SSLance]

Chris, as you know I have run a lot of the similar stuff you have for a long time,, and I have beat the wee out if it. I'm certain it will all work out just fine for you. In fact, I wouldn't even worry about revalving the shocks, they'll work great as is. Ridetech, Speedway and Coleman all make tough parts that are on a lot of cars on the road today.

Regarding the geometry, I run 9.75 degrees caster and I love it. The car tracks so well on the road and never once has it been a concern. Tire wear has not been an issue either. It does create a bit of a jacking effect at sharp turn angles but for street driving, you'll only see that pulling into parking spaces and it is not a big deal.

I'm sure once you get it all installed and dial in the alignment, you'll be pleased.

I have un-done some of the sauce we had in my car but that was strictly for on track performance. Those changes did not change the street characteristics much at all.

I say get just, get it all on the car and start enjoying the enhanced performance.

[SSLance]

I thought about this further and realized the first gen is a rear steer car which is different than mine. But that still doesn't change my opinion.

I think you should reach out to Rodney Prouty. He knows the first gen stuff as well as anyone and has studied (and tested on track) all types of suspension theory around them. He's also just a great guy willing to help out anyone who is willing to learn.

If you'd like, I can help steer you his direction as he doesn't spend a lot of time in the forums much anymore.

[Tinker]

Thanks much Lance. This is what I was looking for. I should have reached out to you knowing your car. I believe you run the corvette style spindles, but geometry is geometry.
What other parts of sauce did you undo?
I know I already ditched the locker.

[SSLance]

I still have the locker but I'm looking for an excuse to change it out. It actually worked very well for me until I put the massive front bar in, then I didn't need the pluss of the locker as much and the minuss started to bother me more.

I did have my shocks revalved after having Chris Smith watch my car on a Good Guys course. Chris also showed me a completely different way to adjust my shocks which had an immediate affect on my times.

I also went to a much softer rear spring setup. The big rear spring setup worked fantastic at SCCA style high speed corners but not so much with forward grip on GGs style courses. My tires last twice as long or even longer now and the car is faster.

The geometry is all still pretty much still the same as it has been all along. The contact patch is awesome, I've just changed the speed with which the suspension gets to where it wants to be and how long it stays there. None of that at all affected its street manners, more of a fine tuning for different style tracks.

[rickpaw]

I think you'll be fine. I have the shocks/springs from him, and besides the front springs be a bit soft (maxed out on my coil over adjustment); and front sway bar interference, it's been fine for my Firebird. I have the shocks/springs/sway bar from him.

So far no issues

[Beechy]

Am I going to be alright with 9 deg static caster that will near 12 degrees dynamic in a turn? I would hate to end up with a car that shakes like your local grocery store shopping cart.

My goal is to have a car that is fun to drive, reliable and safe to bring out to the track. I would love to be able to do 275's on all corners so tires could be rotated.

I thank anyone in advance for their constructive thoughts and advice.


Chris,
Shopping carts have zero caster, that's why they shake. Having more caster gets you away from that shake but in my experience/opinion 9* is too much in the wet. With reduced grip the tire can't deform enough to stay in full contact so lifts the outside wall (because geometry), you will experience massive push. More so with a wide, low profile tire. I have just gone from 8 to 6 for this reason.
Previously, from a stationary start, I could NEVER flick turn my daily........it would push straight forever. Also giving it gas at low speed around residential blocks (sharp turns) it just pushed.
Factory first gen geometry with upper arm drop and Global West rigid bushing/half height body mounts.....but like u say "geometry is geometry "

[Tinker]

With reduced grip the tire can't deform enough to stay in full contact so lifts the outside wall (because geometry), you will experience massive push. More so with a wide, low profile tire. I have just gone from 8 to 6 for this reason. "

Good info.
I imagine this will be the same effect depending on a 300tw, 200tw, or slick. Once I assemble everything I will check how much adjustment I have. Both the frame is slotted and the upper arms are slotted/slugged. Wouldn't be too bad to adjust upper arms depending on conditions or current use. As long as the wheels stay relatively centered in the wheel well for proper clearance.
Checking Temps across the front tires should be a good indicator.
Good notes of tire Temps with conditions should eventually get me where I need to be.

[SSLance]

Autocross in the rain with 9.x positive caster...

qyizpS4eYIU

[Tinker]

Autocross in the rain with 9.x positive caster...

qyizpS4eYIU

Attaboy Lance.
None too pushy when you went arse backwards.

[SSLance]

Attaboy Lance.
None too pushy when you went arse backwards.

That day was so much fun! :D

8 runs in the morning totally soaked, then 8 more runs in afternoon session on same course totally dry. One of my all time favorite autocross events.

[Tinker]

Thanks for all your input everyone.
I hopefully will stay at this now.

A quick shout out to Speedtech.
Got my frame today. Very nice piece. This will save me some cutting and necessary tweaking on my original frame to align everything and install the coilovers.
It's like I just finished weeks of work in one day!
I bolted the arms spindles and rack on...everything is coming out right where my measurements should be spot on.
Added shims on uca's to get my distance side to side and bam! 1/2-1 degree camber. Checked caster right at 9.5 degrees.
I will have some obstacles ahead putting in the Pontiac motor and attaching the tie rods to the steering arms, but this is the most progress in many years.
Thanks again. I hope to continue updates in my build thread.

[rickpaw]

So, it looks like you were able to use the arms/spindles on the Speedtech frame?

[Tinker]

So, it looks like you were able to use the arms/spindles on the Speedtech frame?

Yes I was. The speedtech pro touring frame has the same mounting points as a stock frame(without the huge tolerances of a factory frame) and the upper arm mounts are slotted from factory points to guldstrand mod points and anywhere in between. With the narrow frame rails my goal of 275's should work out. I read in a post on PT.com Blake stated a few guys had installed a Pontiac engine successfully in this frame, so now its my turn to figure out how. The only difference is the upper shock mount is higher than the Ridetech setup and the ridetech spindles have a lower shock mounting point than speedtech arms. In each company, a 12.5 ride height shock is called for, but with this setup I will need 14.5 inch shocks. Not terrible, it might just be a sign to upgrade to triple adjustable front shocks. At least I can reuse my springs, as the triple adjustables use a shorter spring than the singles.