jgcable

Put one in my 77. Its too stiff. Car sits perfect but it's so stiff it almost feels like I have no rear suspension. I am going to need to replace this with a softer spring. I would think this would be a great spring for a hardcore track car. My car handles great with it... its just too darn stiff.

jb78L-82

TRW 315 Composite? I have never heard anyone say that a 315 composite is too stiff. My VBP 360 composite (since 1986 replacing the 7 leaf steel gymkhana spring) with Bilstein HD shocks was very comfortable and too bouncy in the rear so I switched to Bilstein Sports in the rear only...firm but not harsh. What shocks are you using and do you have any other suspension changes that may contribute to the stiff ride? My neighbor who is not a car guy with a Lexus LS430 who rode in my car could not believe at how well my car rode since he had always heard that C3's rode like trucks. C3 corvettes are not cadillacs and should ride somewhat stiff but certainly not harsh with a composite spring. Are you sure that your TRW spring is a 315 and not something much higher?

jgcable

My spring is definitely a TRW 315lb spring. I am using 8" bolts. They are adjusted all the way down to the cotter pins. For shocks.. I have a new set of KYB GR2 Gas-Matic Shocks. Front coil springs are new Moog OEM replacements. Everything regarding the suspension and steering on my car is new or rebuilt.
Car is very stiff with what I would consider.. a harsh ride. It handles like its on rails around turns but I notice its a little "skippy" in the rear end if I am taking a turn hard that has some bumps in it. 4 wheel alignment was done. Tires are not new but they have plenty of life to them. The car isn't bouncy at all. Its firmly planted. If the road is smooth and flat the car rides great. If there are any bumps in the road its a pretty rough ride. It may be normal.... I have never driven a Corvette except for mine.

jb78L-82

Thanks...from what you said, I would strongly suggest Bilstein HD's as shocks as they are far superior to the KYB Gas A Justs which I had for years on my 78 before the Bilsteins but was not happy with them and the ride with the 360 composite. 4 Bilstein Heavy Duty's (not the Sports) will run about $300 but are worth it. Also, just curious, I am assuming you do not have a rear sway bar since you are using a base suspension type replacement rear composite spring rate?

jim-81

Yeah I have TRW 330# spring and Bilstein HD's and not stiff at all.

gkull

You can't compare a 40 year old vette to a modern smooth riding car!

You have a lot more going on than just a spring weight. Are your trailing arms rusted and binding? Are your strut rods binding or bent? sway bar? Shock type?

Really anything under 360 is wimpy and will cause large amounts of vertical wheel movement. Large amounts of wheel travel are hard on the Yoke ends and Posi unit. Instead of the spring and struts maintaining the trailing arm, you get the yokes puting weight on the posi cross pin. I used to have yoke ends ware away and the cross pin eventually cracking the posi housing


The best shocks I have used on the rear. I took off Koni adjustables

https://www.summitracing.com/parts/q...model/corvette

wendellp601

I have the QA-1 shocks installed with my 360lb. spring and actually find it rides softer than the old stock 9-leaf spring with KYB gas shocks.

bluedawg

I haven't either, it's a sports car and composite along with good shocks made it feel as such.

Metalhead140

What tyres and tyre pressure? You mention the tyres are not new - have you checked the date code to see how old they are? Tyres and tyre pressure can make a big difference to ride quality.

mrvette

I have a VBP 360 spring and 460 coils up front, used to have KYB shocks on it, but noticed that over the local 3.5 mile bridge, the undulating ride due to the construction was irritating, so I swapped over to Billy stein shocks, the model I forget.....at any rate, the car smoothed out, the bounce at 60-80 is gone....I have a stock size sway bar front and rear....Wheels are '89 vette, 275/50/17 in back 255/50 in front......with proper mods I feel these cars can ride/handle as well as 99% of what is out there now, with stock multi leaf spring in back, the ride feels like that of a buckboard wagon no matter WHAT shocks are on the car.....

muskegonbrake

I don't usually hear much of our composites being too stiff... You're running a good combination with regards to spring and shock. Bilstein HD's might help a little, but I would be more questioning the rest of your rear bushings/components. A picture of the rear suspension may help identify potential issues, otherwise give me a call and I would be more than happy to help troubleshoot and get your ride a bit more to your liking.

Thank You,
Jeff Cady
Manager
jcady@muskegonbrake.com
231-733-0874

MelWff

how old are the tires? over 10 years they have probably hardened. The 315 is about the softest you will find.

Priya

No its not.


Try this:

Hyperco 200 lb Easy ride spring

http://www.vansteel.com/index.cfm?fu...p=1955&ID=2897

I bought one because my factory Gymkhana suspension rides as bad as my husbands 84 Dodge 3/4 ton 4X4 with 80 psi in the tires. Also bought some 300 lb front springs for a C2 as no one sells the base equipment springs for a C3, only the much stiffer 460 and 550 lb versions. Years later I have yet to install them though, lol.

jgcable

They are probably old. I need to check the date

Jason Staley

Do you have a large rear aftermarket sway bar? If so, this can cause the car to ride harsh. Years ago I had a 1 1/4" front & 7/8" rear sway bar on my car and it rode horrible. Didn't matter what spring rate I tried or which shock I used. The 7/8" bar tied the rear together so much, that the car rode really flat, but had terrible over steer and the ride quality suffered. I'm currently running a factory 9/16" rear sway bar.

Just something to look at and consider. The spring rate and the GR2 shocks (which are the best riding shock I've ever had) you are using shouldn't be your issue.

Countryside Cafe

Interesting - I just put a 315# TRW spring and holes would not .line up - jacking the spring up would lift car off stands and be nowhere near being able to put bolts through spring hole. Extremely stiff spring. Waiting on Corvette Central to see if they shipped the wrong spring. No numbers on that match invoice or part numbers.

muskegonbrake

The holes lining up is an act of finding the sweet spot between jacking the spring on one end and raising/lowering the box end of the trailing arm where the bolt holes can be aligned.

Countryside Cafe

I would like to get your thoughts based on the following: The car is on a lift. When I put a jack under the spring and raise it - the car comes up off the lift long before the hole in the spring lines up with the hole in the arm. I loosened all strut rod bolts and removed shocks so the arm moves freely up/down just to make sure no resistance was added. I tried a ratchet strap but the spring tension way too much to move spring up high enough to get the bolt through. The closest I can get the bolt is at a 20 degree angle with car off the lift pads. I am waiting for Corvette Central to verify the stick numbers on the spring. Any thoughts appreciated.Thx!!

Mooser

Are you using 8" bolts instead of the stock 6" ones ?
M

Countryside Cafe

8" Bolts.