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This winter I will finally start the restoration of the rear suspention. My C3 is a 1977 with:
- L48
- AC system (still in place and will keep it)
- Th350
- All emission components removed.
- Standard original factory suspention package.
I already have the following mayor parts:
- SU-661 Front coil springs(ZIP Corvette)
Spring Rate = 474 lbs/inch
Load = 1500lbs
I know this is meant for the front but I think it's important to add...
- Koni adjustable shocks (Classic Red) at 'softest' setting
- Energy Suspention poly bushings
- Global West adjustable strut rods TBC-7
I want to replace the original steel leaf spring with a Van Steel composite leaf spring.
I’m a street driver so I find both comfort and handling equally important. What would be the best spring rate considering the parts listed above?
Van Steel has them in 300, 330, 360. Also why do they sell some springs 0.5” shorter & 1” shorter? Is this important?
The shorter rear leaf spring provides more wheel clearance. Look under your car and you will notice how close the spring ends are to your wheels. Now imagine wider wheels and if you use a longer spring bolt to lower the rear, how the end of the spring then moves towards the tires.
As far as I know, the Van Steel composite springs are still on back order like they have been for many months so I hope you find one within your desired time frame. Ridetech still has some in stock, but they are more pricey and I don’t know who makes them.
Are you running a rear sway bar? I would probably go with the 330# given your set up.
Place your order now and maybe you'll get your spring this winter.
It's not just Van Steel, its a problem industry wide.
It took me 6 months to get my new steering wheel and I've been waiting on a set of new door pulls for months.
ell in the meantime you can order all the parts. Even install everything else and wait for the composite.
Konis are good choice, and you are right about begin at full soft with those.
If you really want to up the handling, I would add a 78-81 1-1/8" front sway bar, and a stock GM rear one. The stock BB ones were 9/16" and IIRC the 78-81 ones were just slightly smaller.
I have a VB&P 385 lb spring (the recalculated number, since it has been cut an inch at the factory). Plenty of clearance for bigger tires.
It seems too soft for my 550 lb front springs, but might be just right for your car (or 360). I'd call VanSteel and ask them what they think, and get a delivery estimate.
I also wanted a composite spring.. I gave up since they have been backorder all year. Bought a 7 leaf steel spring. I have been waiting since may myself for a backordered l88 freshair box.
I gave up too and ordered a 9 leaf spring for my black 80 when we rebuilt the suspension, it sat too high with no exhaust or spare tire so I put the original spring back on, my white 80 had a weak spring so I installed my 9 leaf on it , with stock exhaust and spare tire it sits perfect
edit to add … I spoke with Van Steel a month ago and he said they can’t purchase the materials yet to make the spring due to Covid . My bet is it’ll be a while before we see anything
I had a #330 VBP and it was a little to soft for me. Went back to a 7 leaf steel
Greg I am very interested in your feedback on the 330 since I have one myself to put in.
The 330 composite is actually a little stiffer than the 7 leaf 304#.
Although the steel one has more friction and hits impact strips harder.
What shocks do you have?
Why / where did you feel it is too soft?
Greg I am very interested in your feedback on the 330 since I have one myself to put in.
The 330 composite is actually a little stiffer than the 7 leaf 304#.
Although the steel one has more friction and hits impact strips harder.
What shocks do you have?
Why / where did you feel it is too soft?
The composite spring is progressive where the steel is not. Progressive means it starts off soft and progressively gets stiffer and the steel starts off stiff. Trust me there is a big difference. The composite had a bounce I didnt like also. Prob. my KYB shocks had something to do w/ it.Prob a stock C3 w/a #330 is fine. It just didnt work for me.
The composite springs will definitely feel bouncy if not mated to shocks that are valved to control this. The 330 has been the spring of choice by many for the 15 years I have been on this forum. But, You do need to run the correct shock.
I do, and I find it a HUGE improvement over the gymkhana spring my car came with.
I went with Van Steel rear coil over setup. Single adjustable. My Trailing arms needed work, shocks were wore out, along with wheel bearings, bushings, strut bushings, rear steel spring bushings, spring and struts as I am freshening up my 1975 4-spd car . I found venders who offered rear springs were backordered so I spent a bit more to go coil over. Waited 3 weeks for Vansteel to fill the order and just got the new stuff 3 days ago. Looks like they did a great job building the trailing arms as it all looks super. New trailing arms with new wheel bearings, spindles, brake rotors, SS parking brake stuff, heim joint struts, new coil overs and bushings, along with all mounting hardware. I turned my old trailing arms in as cores but when they checked them out, nothing was reuseable. Working the install now and anxious to feel the difference in ride quality. Eliminated leaf spring.
The composite spring is progressive where the steel is not. Progressive means it starts off soft and progressively gets stiffer and the steel starts off stiff. Trust me there is a big difference. The composite had a bounce I didnt like also. Prob. my KYB shocks had something to do w/ it.Prob a stock C3 w/a #330 is fine. It just didnt work for me.
Probably the KYBs contributed to the bounce. A stronger shock like a Bilstein or an adjustable shock would have cured that. he composite probably has 30% or so less friction due to not having leaves sliding against each other. So it moves faster/more easily initially and needs stronger compression dampening.
If you kept the spring you may want to try it again with a different shock. Or if you still have it and want to sell it I am sure you will find a ready outlet for it here, since they are on indefinate National Backorder right now.
I have a vbp 360 spring and qa 1 shocks. Very happy. Check the parts for sale section or eBay you may get lucky
I am curious which QA1s you have? Single, double or no adjustment?
Were you able to adjust it to get a good ride and good handling at the same time?
Do you remember the settings?
A composite spring will be very different from the steel counterpart of the same rating, since as stated above, the composite starts out when compressed softer and stiffens through the cycle with more compression.
The later C3's 7 leaf steel Sport gymkhana steel spring was rated at 292 lbs (not 305) and the base 9 leaf steel spring in the late 70's was 192 lbs or lower, VERY soft. I have had the VBP 360 composite on my OEM Gymkhana suspension 78 since 1986 with Bilstein Sport shocks and my ride is firm but not harsh. It is most definitely NOT soft! To approach the stiffness of the OEM steel 292lbs steel spring (which was VERY harsh riding), I would probably need to go to a 420 lbs composite.
As noted, you CANNOT use mass market shocks like Monroe, Delcos, KYB's with a composite since the compression and rebound control will not be adequate. You must use a top quality shock like Bilstein, QA1, Koni, etc.
A composite spring will be very different from the steel counterpart of the same rating, since as stated above, the composite starts out when compressed softer and stiffens through the cycle with more compression.
The later C3's 7 leaf steel Sport gymkhana steel spring was rated at 292 lbs (not 305) and the base 9 leaf steel spring in the late 70's was 192 lbs or lower, VERY soft. I have had the VBP 360 composite on my OEM Gymkhana suspension 78 since 1986 with Bilstein Sport shocks and my ride is firm but not harsh. It is most definitely NOT soft! To approach the stiffness of the OEM steel 292lbs steel spring (which was VERY harsh riding), I would probably need to go to a 420 lbs composite.
As noted, you CANNOT use mass market shocks like Monroe, Delcos, KYB's with a composite since the compression and rebound control will not be adequate. You must use a top quality shock like Bilstein, QA1, Koni, etc.
Hope this helps!
i have basically built my car from you and others advice..
i will be shortly putting in an original 6.. yes 6 leaf spring. i learned the 7 leaf was a replacement? at least for 79.. i have the HD bilsteins all around.. and they are shorter than OEM shocks..and cost more for some reason?? even though the other shock says for lowered..
should be interesting.. not going plastic at this time..
Just FYI. One of my car buddies is an engineer at local plastic molding company and the plastic shortage is no joke. Serious rationing depending on the plastic type.
Composite leaf springs
