Spring Rate Suggestions for '68 Camaro

[Mkelcy]

You may recall that I've got my '68 Camaro "No Name," with a 21st Century Street Machine subframe, a Lateral Dynamics 3 link rear, LS3 engine and T56 transmission. Because of the intrusion of the upper link into the rear seat area, I've elected to eliminate the back seat, so it will never carry more than two people. The car is Dynamatted but doesn't otherwise have weight added. The battery in in the trunk.

I've just gotten the car on the road. Although I've got very little seat time, my impression is that it's over sprung for my use, which is spirited local driving and long distance trips with little to no auto-cross or track time.

For the front I'm using 450 lb./in. springs, a 1.15" hollow sway bar that has a rate of 300lbs./5 degrees of twist and QA1 single adjustable coilover shocks dialed down to the softest setting. For the rear I'm using 200 lb./in. springs on AFCO double adjustable M2 coilover gas charged shocks with a remote reservoir, both compression and rebound dialed down to the softest settings and, having just checked, the former gas charge on the shocks has leaked away over the years, so they are not charged; no rear sway bar. As I said, I'm just starting to get miles on the car, so the shock settings are simply to get a baseline from which to make adjustments (and I'll throw a 50 lb./sq. in. nitrogen charge on them when I get my fill kit).

I'm thinking of stepping down to 400 lb./in. springs for the front and 175 lb./in. springs for the rear.

Anyone have any thoughts on whether that's enough of a step down (especially after I get a charge on the rear shocks) or too much; am I looking at the wrong part of the suspension (say the front sway bar, and/or adding bar for the rear if I go with softer springs); or should I get the rear shocks charged and get more seat time before doing anything?

Thoughts?

I'm looking for a little smoother ride while still allowing for excellent street handling.

[David Pozzi]

I'd drop the front to 350, that would yield a wheel rate similar to a stock subframe with a 600 LB coil.

I wouldn't go lower on the rear unless you have a pretty high ride height. Shipka's car had bottoming in the rear with 220 rear coils, but it was pretty low.

With no rear bar, I'd raise the watts link to the 3rd or 4th hole up. Watch out for clearance issues at the upper hole settings.

Check for bottoming out. If the shocks have no o ring as a travel indicator, put a tie wrap around the shock shaft. Check that your bump stops are the proper height to prevent damage to the driveshaft in the rear. If you have an aluminum driveshaft, it will probably contact the upper link crossmember on the left side of the tunnel.

[Mkelcy]

I'd drop the front to 350, that would yield a wheel rate similar to a stock subframe with a 600 LB coil.

I wouldn't go lower on the rear unless you have a pretty high ride height. Shipka's car had bottoming in the rear with 220 rear coils, but it was pretty low.

With no rear bar, I'd raise the watts link to the 3rd or 4th hole up. Watch out for clearance issues at the upper hole settings.

Check for bottoming out. If the shocks have no o ring as a travel indicator, put a tie wrap around the shock shaft. Check that your bump stops are the proper height to prevent damage to the driveshaft in the rear. If you have an aluminum driveshaft, it will probably contact the upper link crossmember on the left side of the tunnel.

David: Thanks for the reply; you were my target audience because you've got so much experience with LD cars. The car sits pretty high. I'll post a picture.

Where do you install bump stops for the rear end? As I recall, the factory pieces won't work because they interfere with the tires.

[David Pozzi]

They can go on the shock shafts, but it requires removing the shock eye. Some have just a jam nut, some use loctite which has to be heated to be unscrewed, requires a special vise grip pliers to grab the shaft without marring it.

Best bet is to weld a bracket to the inside of the frame rail & bolt in a single stud mount urethane bump stop. I did that on Bad Penny because I suspected Steve Rupp would switch shocks in the future. He did.

OLC ran a 250 rate coil for quite a while but the Penske shocks were pretty stiff, even when turned down.

Shocks have more control of ride quality than spring rates do.
When we went to Ride a Tech shocks we went up in rate & still saw more suspension travel due to the difference in shock valving. The ride was way better even with the stiffer springs.

Most gas shocks add 45 lbs to the rate, they can raise the rear 1/2" on a leaf spring Camaro.