C3/C4 Spring Rate Question

[Rawkkrawler]

Corvette suspension users,

I posted a question in the past about this and have learned quite a bit since. I can't be sure I added it correctly but the link is below.

Anyway, I'm using a narrowed C4 suspension and had some issues with stiffness and wear. I found that Vette Brakes was not only local but Gary and his team are as professional as I've seen. They custom make everything in house.

I recently installed their entire tubular system to include trailing arms, camber smart struts and toe bars as well as a new narrowed leaf. This leads me to my question. What rate spring do you have in your car?

My TRW spring was measured at 681 lbs. Factory Corvette is closer to 300-400 lbs. They shortened a softer rate one for me and it's still 517 lbs. I also understand that Everett Morrison ordered 500 lb springs for their cars.

Anyone have any ideas as to what a good rate would be for a Cobra?

Mike


http://clubcobra.com/forums/showthread.php?t=107568

[john chesnut]

I've built alot of cars wth the C4 suspension. My cars are at 2000lbs and without driver have a 52% rear weight. I run 300lb springs. I run this in my cars with the C5 parts as well. Mine are coilovers.
One of the problems with narrowing the C4 axles is that it accentuates the camber change as the wheels travels. I don't know how EM mounted the diff.I have never had the pleasure to inspect or drive their car. They probably have it right but the first kit that I bought had it wrong. It's very important that the rearend is mounted at the correct height(4 bars too). If the height is wrong the camber control is adversely affected. With the C4 parts, when power is applied the rear of the car will squat. Since the C4 uses a modified swing arm design(axles are a fixed length) the rear tires tend to have excessive camber change. When power is applied the car squats which tilts the tires in at the top and limits traction. As more power is applied this make the situation worse. When traction is broken the stored energy in the springs will be released violently and the car will experience instant rear lift and wheel hop. The severe change in axle angle can cause the axle or ujoints to snap. If this happens the axle will most likely swing and break the Corvette "Bat Wing" which mounts the diff. I have experienced this in a Beck Lister. I discovered the diff was mounted almost 2 inches to high. The incorrect mounting also adversely affects handling. It can cause a severe snap oversteer condition. The C4 can be made to work well when mounted properly. The parts that you have purchased will help temendously. You probably got new lower control arm brackets which lower the pivot point for the camber control rod. The lower pivot point results in better camber control.

Have fun, John