A composite spring rated at 360 lbs will have very different ride and handling characteristics from a steel version of the same rated springs. This difference is the reason that my 78 with the 360 lb rated spring rides so much better than the much less rated OEM steel gymkhana spring and the reason that i mentioned in a prior post of potentially going to the 420 composite in the future. As long as the front and rear spring rates are compatible, you can go much higher in spring rate with a composite versus a steel rated spring. Last word on shocks with composites, don't waste your money on mass market shocks like KYB, Monroe, Delco-go Bilstein-they cost more because they are worth it!

Sorry to disagree with others here, but respectfully...

Despite notions to the contrary, IMOE it's quite easy to create a BB C3 that oversteers at the limits (where balance matters most). Thing is, BB C3's usually require more front spring relative to the rear than SB's - which translates to less (not more) rear spring requirement relative to the front - to achieve a good balance.

When I first swapped a BB into my '78 back in the day, due to my own SB based preconceptions I had missed that point, and was fortunate not to have crashed out while chasing my tail (pun intended) before Dick Guldstrand set me on the path to getting it fairly well sorted. FWIW, "only" an F41 rear spring here, and I'm on 860# fronts! Before you think that's whacked, Mr G ran a an even softer rear than that with 860's on his A Prod BB C3.

But, I digress. I'd really rather not completely derail the OP's central topic with all this. Suffice it to say, I'm not particularly speculating when I urge conservative steps rather than giant leaps here. You don't have to understand roll couple distribution theory to know that expensive noises often result from getting it wrong, even if pressing the limits on purpose isn't on one's menu.

OK, that's $.04. PayPal accepted. :D

Hi, new to the Corvette world, so dumb question time. When a guy goes to that spring, is there any kind of spacer for the differential cover that has to be ordered to make up the difference in thickness, or is it built in/included with the spring?

Everything comes with VBP spring kit.

You have to add the heat shields. Instructions make this very clear.

http://img.photobucket.com/albums/v1...nsion005-1.jpg

Like to thank all that replied on the post. Opinions are great and I tried to listen and make an educated choice. Went ahead and ordered the 360 rear and to help the balance upgrading the front to the 550 SS from VBP. I hope this was the right way to go, guess we'll see.

That is the combo I run-you should be very happy with the balance-ride is persona preference. What kind of shocks are you using? I also use the OEM 1 1/8 inch bar with poly bushings and use a 3/4 rear OEM type bar with poly mounting bushings. Let us know.

Right now I have the basic KYBs. From what I gather I might need to go to an upgraded shock. Doesn't hurt to try what I have before upgrading. Great to know the solution before you experience the problem. I'll post back when I get it all installed.

Years ago I had KYB Gas A Just's, not the GR2's, and the ride was very bouncy on the highway. The Gas A Just did not properly damp the spring on my car. I run the Bilstein Sports in the rear with the 360 spring and Bilstein HD's in the front with the 550 coil springs.

Would you say the 360 is enough, or would you go a step up if you had the chance?

The short answer is I would go 420 on my car!

Here is my setup:

Front:

Blue Printed/rebuilt Gary Ramadei OEM steering box
Speed Direct spreader bar
Poly upper and Lower Control arm bushings
550 springs, 1 inch lower than stock
OEM 1 1/8 inch sway bar with Poly endlink and mounting bushings
255/45/17 ZR ultra High Performance Summer only tires
Bilstein HD shocks

Rear:

360 monospring with poly cushings
Competition adjustable strut rods with heim joints
3/4 OEM type sway bar with poly bushings
Bilstein Sport shocks
255/50/17 ZR tires like in the front

The car rides, steers, and handles better than 99% of the C3's I have been in. I still would stiffen the rear just a tade with a 420 spring.

Fellow forum member, Karol, recently rode in my 78 and he could not believe how much better my car rode than his 78 L-82 4 speed with the base suspension (including the base steel spring) and 255/60/15 tires! You would never think that reading and hearing some folks comments about poly control arm bushings, low profile Z rated tires, high composite spring rates etc. My car simply rides MUCH better than the OEM suspended cars, Gymkhana as well as base!

Just picked up my new rear 360 spring from VBP today. They were out of the standard size 360 for the next few weeks (a supply issue with the materials) but they had a shorter spring that was available. It is 1 inch shorter on each end than the standard 360 spring. The VBP tech (by the way nice people over there) said the shorter spring wouldn't make any difference in performance or the way it rides vs. the standard length spring. He said if I wasn't happy they'd exchange it no problem. Well I don't have experience with this spring so I wouldn't know the difference one way or another if the shorter was not performing like a regular length. Not my favorite past time swapping springs, so I rather not do it more than once. So, is there a draw back to the shorter spring even if it rates out at 360?

The shortened main leafs are SOP for gaining additional tire/wheel clearance, and don't adversely affect operation. Many of us have had them for years.

So what spring would you suggest with stock front springs on a 1980?

The right question is, what is it doing wrong (according to your own backside, and assuming it's sufficiently calibrated) when you press hard now? Unless your car is actually suffering from what you know to be moderate to severe understeer (mild understeer is actually preferrable on the street anyway), and you aren't planning to do anything else, I'd stick pretty close to the stock rear sping rate.

My stock spring is sagging. My vette mechanic says it needs to be replaced.

I just did the swap as you can read in this post and I think the 360 is just about right. My Vette is a BB but as far as weight in the rear not sure there is too much of a difference from a SB. It's Definately not stiff by any measure. Not sure if this helps you or not but calling the folks at VBP helped me make my choice.

Vehicle Dynamics 101...
 

FACT: If you stiffen the rear spring without stiffening the front (assuming no other significant issues are working against you), your balance WILL shift towards or into oversteer; how much so a matter of degree relative to how far you move the roll couple percentage towards the rear. It doesn't matter what are your purposes or how comfortable may be the ride (or not), that's just the way it is.


Seems I'm constantly trying to pound this point home, but an oversteering car will often feel spectacular right up to the point it bites you in the backside. ...and there's also a little surprise called TTO (trailing throttle oversteer) which can even occur in an otherwise mildly understeering car. So, with the potential costs of overstepping here being pretty high, on which side do you wish to err? Sorry, there's no perfect setup however many may claim to have found it.


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