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Hello,
I plan to restore my rear suspension this winter. The strut rods bushings and spring hangers bushings are worn out.
I've on my car the standard suspension : 3/4'' front sway bar and no rear bar. The rear spring is 9-leaf.
I'm currently thing of an suspension upgrade because I find that my Corvette is too soft on little roads. However, she's comfortable for long runs.
My ideas are :
1-1/8'' front sway bar with poly bushings
No rear bar
550 lbs/in front springs
restoring my 9-leaf spring (or buyinng a new Eaton ?) with poly spring hangers.
I've already mounted QA1 shock one way adjustable. I think they are too soft, but I can still adjust them.
What do you thing about this combo ? Maybe 550 springs are a little bit too much ? I want to keep some comfort on car because of the long runs I sometimes do.
Best regards from Switzerland and keep safe !
Chris
Last edited by chris383; Oct 25, 2020 at 05:36 AM.
I've always been a "Soft spring -big sway bar" guy. If you run that big front sway bar go with 450 coils up front. However, I like a 360 composite spring in the rear with no sway bar. Don't waste your time with steel leaf springs.
Thank you.
Bilstein are certainly good, but I think QA1 are also good as wel...l and adjustable ;-)
Monoleaf is a good option for sure. But I've always wanted to keep the look of my Corvette as close as original....
Of course, I can keep the steel spring and change it for composite. It'll be always possible to change it if necessary.
Mate, I can't ever remember anyone looking that close up underneath the back of my car. In fact if I did I would probably give em a kick up the ***.
worried about stock look? How many onlookers would even know the difference?
bottom line. Most everyone on this forum will recommend the composite mono spring.
I replaced my steel spring with a Mono about 25 years ago, give or take. HUGE improvement.
My original Bilstien's gave up about 2007. They were about 30 years old. And again. For ride quality. Most will agree, these are excellent bang for the buck. The shocks you have that you can adjust. Well, I have no experience with them at all.
you did ask for opinions.
and as the forums is meant to work. You've gotten a couple.
Now you get to decide what makes the most sense to you.
In my 80, I did both ends of the car. All poly, plus heim jointed strut rods. 550 lb front springs with Bilstein HDs. VB&P composite 385 lb rear spring with Bilstein Sports. 1 1/8" front bar (stock in 80), 9/16 rear bar (OEM bar, added). The closest available equivalent to that spring is likely the Van Steel low-arch spring.
For long drives on the street, the front end is too stiff, and I should have used 450 lbs springs. I'll have to see how it handles the track (with different tires) before I tweak the rear spring and/or swaybar, but I'll never run a steel spring again. You'll understand if you swap it out yourself.
After reflexion, the composite rear spring seems to be fine for me : it's weight is only 8 lbs, which is great for shipping costs until here ;-)
I think springs about 450-480 lbs front and maybe the 340 lbs from Zip rear composite spring are a good compromise between good handling and quiet long trips.
Always with 1-1/8 front bar and no rear bar.
I'll use poly only for bar bushings and rear spring hangers.
I think you have a great combo going.
And the shocks are responsible for about 75% of the ride quality vs the spring stiffness.
So with the adjustable QA1s you should be able to find the "sweet spot" that the Bilsteins already have, plus you can adjust it up or down a notch or two.
Honestly it is almost exactly the same suspension setup I am building into mine, and I have 27 years of suspension tuning for auto-cross and Pro-Solo under my belt.
I will however run the factory 9/16 sway bar. You may want to try that. It will depend on how much push/understeer you like or how neutral you want it when you are sliding it around! LOL
Long trips in Switzerland in the Alps in an LT-1. What a life!
Last edited by leigh1322; Oct 26, 2020 at 09:50 PM.
I have 550 front springs a 360 VBP rear spring and QA-1 non adjustable shocks that they custom tuned for the car. It rides great. More modern wheels and tires would improve it more. QA-1 Shocks are every bit as good as any other.
I have 550 front springs a 360 VBP rear spring and QA-1 non adjustable shocks that they custom tuned for the car. It rides great. More modern wheels and tires would improve it more. QA-1 Shocks are every bit as good as any other.
What size front bar? I'm not complaining that the front end is too stiff. The rear is too soft, and my solution will be to stiffen the rear end at some point, probably when I move to 18" tires. But with a very similar setup to yours, with a 1 1/8" bar, poly bushings, and 550 springs, my car doesn't seem balanced.
I did the math on wheel rates and ride frequency etc.
It's all about making the front and rear "feel" the same.
The math says a 474 front spring matches really well with a 360 rear.
The 330 rear would really like something like a 420 front and I have not found a front coil that size.
The 550 lb fronts match really well with a 420 lb rear.
A stock 260 front likes a 198lb stock rear.
I don't think one step up or down from the "math ideal" is going to make all that much of a difference.
But those values would give you a "flat ride" at 75 mph over concrete seams, tar strips, etc without any "head pitching"
But if you get too far off.....I am sure a lot of you have ridden in a heavy duty truck that just "wore you out" after a short ride..... some of them ride just horrible when un-loaded.
I have 7/8" front sway bar with poly bushings, (no rear bar), 550 front springs, 7 leaf rear spring, 17" with Michelin Pilot tires. Works well for me...
After reflexion, the composite rear spring seems to be fine for me : it's weight is only 8 lbs, which is great for shipping costs until here ;-)
I think springs about 450-480 lbs front and maybe the 340 lbs from Zip rear composite spring are a good compromise between good handling and quiet long trips.
Always with 1-1/8 front bar and no rear bar.
I'll use poly only for bar bushings and rear spring hangers.
Chris
Do not the TRW style spring! There are known ride height issues. I would contact Van Steel for their recommendations.
It seems there are several solutions for several people ! I think one important thing is to have a balanced package between front and rear.
I've understand that the Van Steel springs are better than TRW srpings (although they are more expensive...).
I would keep my original 15'' x 8'' Corvette Rallye Wheels, although I know that larger wheels (17-18'') allow much better tires to be fitted !
Tonight, I've checked the front sway bar replacement.
What my surprise to see that's, for me,impossible without modification to mount a bigger than 15/16'' front bar on a LT-1 Corvette :
My caliper is, of course, on mm scale (I'm in Switzerland!), but the dimension 23.8 mm match the 15/16'' bar diameter.
We can see quite clearly that the radiator hose will hit a bigger sway bar !
I think this is due to the special copper radiator for the LT-1 model.
I have a 78 L-82 4 speed car with the gymkhana sport suspension (67,000 miles) that I have owned for 34 years and I have tinkered with the suspension one part at a time over all those years to achieve the perfect balance of superb handling, steering response and a firm but not harsh ride. Not knowing if you have a base suspension (most likely since most did not have the sport suspension from the factory) or the sport suspension, below is what you need for truly sportscar handling with a great ride for your 78:
Front:
550 lbs front coil springs/1 inch lower than stock-$100 1 1/8 inch solid front sway bar (OEM Bar size)-$200 poly upper and lower control arm bushings-$50 Bilstein HD shocks-$150 Front Spreader Bar-$100 Custom blueprinted/rebuilt OEM steering box- GTR 1999-Gary Ramadei-$300 This modification will make your OEM box about as good as it gets with the OEM steering and very close to a borgeson.....not quite but close Rear:
360 monospring-$300 Bilstein Sport shocks-$150 OEM Style Rear Sway bar (not the aftermarket type bars. I highly discourage NON OEM/GM style rear sway bars)-7/16 or 9/16 or 3/4 inch (I have this one replacing the stock 7/16 inch bar)-$200 Competition adjustable strut rods with heim joint ends-$200
Total Cost $1750
This suspension will get you a FAR SUPERIOR suspension than what came on the car when it was new, X3 if the car had a base suspension from the factory. You will need to add 17/18 inch rims and tires (ZR rated only W/Y sub rating) later to maximize the superior suspension setup. I have ultra high performance summer only tires Front-255/45/17 ZR and rears 255/50/17 ZR's.
In my Opinion, you need a rear bar of some size, especially if you want balanced handling with a C3.
My 78 above is far superior to any stock handling C3 BY FAR. Does it handle like my 10C6Z06? NO! It will smoke just about any stock lightly modified C3 in the curves..no contest.....and no Stock SBC C3 of any year or engine designation can even come close to the rebuilt/upgraded 355 L-82.
Last edited by jb78L-82; Nov 11, 2020 at 12:54 PM.
I'm quite sure your car has a far better performance than original base car with all these modifications.
For my LT-1, which is pretty stock for now, I think the situation is a bit different because I want to keep it as original as possible, but with some modifications in order to improve its handling.
I've checked all the possibilities and a lot of comments and posts. I've also read some issues with composite springs, apart the fact it's clearly not an original part on a quite original LT-1.
It seems that the F41 option was not mounted on 1972 cars (appart some ZR-1, perhaps...).
BUT it look like an original option for this time and it is the most important thing to me.
I would make a compromise and use a 474 lbs/in coil spring instead of 550.
I would also use a 15/16'' reproduction front sway bar and a 7-leaf rear spring from Eaton.
I wont add a rear bar for the moment and try the combo on our little roads without it.
Last edited by chris383; Nov 11, 2020 at 12:17 PM.
72' LT-1 Suspension options
