Corvette IFS questions

[orphancars]

Hello folks!

I'm creating a semi-custom chassis for my PT project -- a TVR
(British car w/tube frame and fiberglass body). Using late
model C4 suspension front and rear. Regarding the front suspension:


- Is there an easy way to remove the transverse spring with
ordinary tools? I have a factory Vette shop manual and see
that the recommended removal method uses "GM approved"
tools. Yuk.

- Suggestions on coilovers/shocks? I'd like to switch over to
coilovers since I'll be narrowing the front end, the factory
transverse spring won't work.

- What angle should the upper or lower "A" arms be at normal
ride height? I'm not sure how to figure out how high/low the
suspension crossmember needs to be.

- Any recommendations on vendors for custom steering racks?
I'll be narrowing the suspension approx. 4", so I'll be needing
a new rack. Also don't need a power rack :)

Many thanks in advance,

-jeff d
Fort Worth, TX
1986 Fiero GT/V8
1973 TVR 2500M

[astroracer]

Just keep in mind that narrowing the suspension, without addressing the changes this will make in the suspension geometry, will make for an ill-handling car. Upper and Lower control arm pivot points will need to be adjusted for Roll Center height and migration and the steering inner and outer pivot points will have to be optimized for Ackerman and bump steer. This is not an impossible task but it is necessary to make your "new" suspension work properly AND as you envision it... Sure it's a "Corvette" suspension but, as soon as you start moving things around, it may as well be out of a dump truck...
Mark

[ProdigyCustoms]

- Is there an easy way to remove the transverse spring with
ordinary tools? I have a factory Vette shop manual and see
that the recommended removal method uses "GM approved"
tools. Yuk.
See answer in your rear question post

- Suggestions on coilovers/shocks? I'd like to switch over to
coilovers since I'll be narrowing the front end, the factory
transverse spring won't work. See answer in your rear question post

- What angle should the upper or lower "A" arms be at normal
ride height? I'm not sure how to figure out how high/low the
suspension crossmember needs to be. The upper arm sould be close to level at ride height, try to avoid droop in the arms.

- Any recommendations on vendors for custom steering racks?
I'll be narrowing the suspension approx. 4", so I'll be needing
a new rack. Also don't need a power rack :) Street rods use real narrow racks sometimes, even some center gear. Look in Custom Rodder.

[orphancars]

Thanks for the responses!

Mark -- Any recommendations on a good book for suspension geometry? I think I know what I'm doing, but always try to read up on what I'm doing _right_now :)

Unless I'm missing something major, narrowing the suspension shouldn't be a huge deal, just have to make sure that the rack I select keeps the inner tie rod joint in line with the pivot points for the UCA and the LCA. Trickier thing is to make sure that I keep the mounting points for the arms the same if I decide not to use the factory crossmember.......

Thanks again all!!


-jeff d

[WS6]

have you ever removed the front suspension off a regular coil spring car? do it the same way for the vette. support the lower arm before you release the ball joints so that the arms wont launch downward from the spring tention. make sure the jack or whatever you use to support the lower arm will not slide off the arm. lower the arm so that tention is slowly released and the spring is not loaded. do the other side the same way. once the spring is unloaded you can push down on the arm to get the spring out of it. youll need to pull off the lower shock mount that covers the spring first. im not sure what year C4 your dealing with. some of the springs have a simple square pad under them while the earlier cars had a rubber end that usually gets snug in the lower aarm. so you may need to push downward hard to the get the spring to come free from the lower arm. the spring is not glued down to the arm in case its in there that tightly.

to get the center mounts out and this allows the whole spring to be free from the car there are two mounts on either end of the front frame crossbrace. the nuts i believe are 15mm and i know the bolt heads are 13mm. you may get lucky and be able to remove just the nuts and not have the bolts spin. if not youll have to hunt for the rear mount bolts. if the engine is out of the car you should be able to get to them easily. if not it could be a pain. take all the nuts down fairly evenly. if not then the spring may push to the side that is not loose and this will make it hard to get a socket in and onto it due to its angle change. once you get near the end of the bolt try lifting up on the spring end to check tention. again some springs carry more tention that others. so some may still be loaded at the mounts while others may not.

to get the spring out the car needs to be on a lift or way up in the air on jack stands. the front spring is very cresent shaped and has to come out and roll under the car to get all the way out of the frame.

[astroracer]

There are a few good books out there but most of them deal in the basics. There isn't anything available (that I have found) that really gets into the specific "numbers" involved in complete suspension design.
There are a number of good programs available though. I used this one to design the suspensions for my BAD AST project...
http://www.performancetrends.com
If I recall correctly there is a C4 style suspension that is canned in the program. You could use that as a jump point for your redesign. Get familiar with how the program works then start adjusting the numbers to get it where you need it to be. This program will also optimize for roll, bump and ackerman so this is what I will recommend to you.
Go to the site and download the demo. It's good for 9 days and I actually had the entire BAD AST design done on the demo... I finally bought the program so I could verify everything.
Mark