When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I have a new TRW spring rated at 340# and a RideTech spring and installation kit rated at 200#. The RT spring is stamped Hyperco who I suppose is the manufacturer. I spoke to my buddy Darrell at RT who subscribe to the Herb Adams philosophy of a softer spring with a stiffer shock. I’m going to install the RT set up with adjustable QT1 shocks in the rear. I have adjustable QT1 coilovers in the front already. Darrell feels this will be the best set up for aggressive street/road course handling, but I will be the judge. The RT installation kit comes with 10” bolts w/castle nuts, new bushings and four spacers used to adjust ride height (no spacer for lowest setting with two for highest setting on each side). Currently, I have a new steel nine leaf spring where the rear sits way to high. I replaced the stock spring bolts with 8” bolts and it was still too high. It’s easy enough to replace the spring and shocks, so I’m all in on the RT and QA1 shocks and will let you know what I discover.
I’d appreciate any thoughts or recommendations before I crawl under the car this weekend.
The rear sits about 2” too high. When I replace the rear spring and shocks, I’ll also adjust the front coilovers to lower the front properly. The RT and installation kit are on the left. Again RT on the left. I replaced the rear spring bolts with 8” and it still sits high (this picture was taken before I tightened the locknut to achieve at least 1.5x the bolt diameter in threads showing.
How is each spring 'rated'? Are the load numbers intended for the entire spring or for each wheel (one side of the spring)? Do both springs use the same rating method?
The 8" bolts are what a Chevrolet dealer replaced my 10" bolts with and the end result was a "jacked up" rear end with half-shafts that started to bind. The 10" bolts on the 1968 work perfectly with the heavy duty spring back there.
The handling suffers greatly with the rear all jacked up like that, the extra wear on the half shaft U-Joints was bad. What really surprised me was how hard it was to get an answer. I spent a lot of $$ trying at two Corvette Shops and neither could help. It was the man from VBP who enlightened me and solved my problem by selling me a set new longer (10") bolts. After I installed them the car felt better driving and the Corvette's rear end was no longer in the mirror.
On a Mark IV Big Block Corvette wouldn't it help to still use the heavier steel spring out back for help balancing the Corvette's weight distribution? I rebuilt my rear spring and it is still in use after 53 years.
I have the F-41 suspension. The back was way to high. After I set the Z and D height, the car lowered and note the half shafts are parallel to the ground (no binding)
The bolts were a bit too long. So once set I cut off excess.
This makes me want to smash my head against the wall. So many install a super stiff, aftermarket, fancy rear spring, to improve the ride, in their C3 and wonder why the *** end is way up in the air. Then they go to crazy changes to fix it. The rear end of a C3 only has about 3 inches of travel. All the fancy gizmo stuff isn't going to change the ride all that much. If you are building a race car, of course, stiff as hell will make it a good track car, but not both.
This makes me want to smash my head against the wall. So many install a super stiff, aftermarket, fancy rear spring, to improve the ride, in their C3 and wonder why the *** end is way up in the air. Then they go to crazy changes to fix it. The rear end of a C3 only has about 3 inches of travel. All the fancy gizmo stuff isn't going to change the ride all that much. If you are building a race car, of course, stiff as hell will make it a good track car, but not both.
Here's my "super stiff, aftermarket, fancy rear spring", a VB&P 360 lb spring. Using only 7" of the 8" bolts, and leaving an inch spacer above the spring (I could move it below and get more lowering), my half-shafts are level, and the rear of my car is lower than the front.
And the catch? The rear end still isn't stiff enough.
The super stiff spring doesn't jack up the *** end of the car, the high-arch spring does that. I see way more photos of chrome bumper cars with steel rear springs that have the 4x4 look for some reason. After 5 hours in the mountains of Virginia over the weekend, the second-stiffest spring VB&P ever sold stock is still a bit of a marshmallow on the street.
And the catch? The rear end still isn't stiff enough.
If you have the Bilstein HD rear shocks then that's the problem. I had to switch mine out for the Bilstein Sport shocks and then the rear was perfect. I kept the HD shocks in the front.
If you have the Bilstein HD rear shocks then that's the problem. I had to switch mine out for the Bilstein Sport shocks and then the rear was perfect. I kept the HD shocks in the front.
Those are Bilstein Sports in the picture (though there's no way to tell unless you can read the tiny part number). I need to swap out for QA-1 double adjustables.
This makes me want to smash my head against the wall. So many install a super stiff, aftermarket, fancy rear spring,
Not all springs are of the very **** poor over arched design! In this picture my rear tires are off the ground. You can see how the trailing arm has pushed my 4 1/2 inch spring end bolts through the spring. Guess the weight of my rear custom made spring? I tried a 420# VB&P and found it to be way too wimpy
The idea of a 200 lbs spring is ?????? That idea unless you have no power and skinny hard tires would not work. I'd worry about bottoming out the shocks or whacking into the bump stops. Herb Adams was a race person in the 60's and 70's and his claim to fame was helping out on solid axle cars like firebirds.
Those are Bilstein Sports in the picture (though there's no way to tell unless you can read the tiny part number). I need to swap out for QA-1 double adjustables.
I'm surprised it's still too soft with the sports, I have not been able to bottom the car out after switching. Guess it goes to show that these cars are not all the same. Sounds like QA-1 will be a good fit you.
Bikespace,,,, You don't fall into the "so many" group. That's a good thing. Steel and composite springs both have this issue. Long spring bolts can fix a very stiff spring. I just wish the new springs were properly made for the C3.
Bikespace, I really got to looking at your spring end bolt length and angle compared to my setup. It's like the spring isn't long enough and I can't see if you have a spacer above the spring. With our older non batwing differential setup it's possible to lower the body down or raise the diff depending on how you want to look at it. My differential is raised @ 3/4 inches. I've seen cut and welded diff crossmembers on this forum that was even more. When I get back home I need to take a picture of my static on the ground half shaft angles. I used to break posi housing annually. The problem is excessive weight on the yokes pushing against the posi cross pin. I had people take videos of launching on the drag strip with big goodyear slicks. rear end squat was a big issue. So if you really went around a turn body roll and loading on the tire would put excessive pressure on the posi cross shaft pin and break the posi housing. I would take off on a freeway on ramp and hear a bad noise out of the rear end and limp it home. The fix was very high spring rates to limit vertical wheel travel.
The outside rear wheel in a turn causes the suspension to try and pull the stub out of the differential, not push it in harder against the differential cross shaft. The strut rod is the lower link and it gets put under compression while the stub shaft tis the upper link and it is put in tension.
Bikespace,,,, You don't fall into the "so many" group. That's a good thing. Steel and composite springs both have this issue. Long spring bolts can fix a very stiff a spring. I just wish the new springs were properly made for the C3.
The more threads like this, and the more times we can shout from the rooftops not to buy the high-arch TRW/Hyperco-style spring, the better. Who knows how many Corvette owners never have to post another "my C3's butt is too high up in the air" thread, asking for help.
AFAIK, the low-arch VanSteel spring is again in production, and should function the same as the old VB&P spring. Even at up to 400 lbs, it still may not be stiff enough for all applications. Hopefully the QA-1 shocks solve my problem.
And while the 4x4 look is unappealing (the reverse "Carolina Squat" for C3s), adding 10" bolts with 15" wheels can be dangerous. I'll keep posting the thread I linked.
Originally Posted by gkull
Bikespace, I really got to looking at your spring end bolt length and angle compared to my setup. It's like the spring isn't long enough and I can't see if you have a spacer above the spring. With our older non batwing differential setup it's possible to lower the body down or raise the diff depending on how you want to look at it. My differential is raised @ 3/4 inches. I've seen cut and welded diff crossmembers on this forum that was even more. When I get back home I need to take a picture of my static on the ground half shaft angles. I used to break posi housing annually. The problem is excessive weight on the yokes pushing against the posi cross pin. I had people take videos of launching on the drag strip with big goodyear slicks. rear end squat was a big issue. So if you really went around a turn body roll and loading on the outside tire would put excessive pressure on the posi cross shaft pin and break the posi housing. I would take off on a freeway on ramp and hear a bad noise out of the rear end and limp it home. The fix was very high spring rates to limit vertical wheel travel.
It is a cut spring, and I do have the spacer. Even though I could probably use 6" bolts if I moved the spacer, it would make the angle even worse.
I didn't mean to hijack this thread, so I didn't elaborate, but that is a NOS VB&P spring that was cut down 1" at the factory. They marked it as 385 lb. I'll end up buying the stiffest VanSteel spring I can get, and move this setup to my 79, as it's just about perfect for my wife's car (with 475 lb front springs, instead of the 550s I have).
Here are some better composed photos, with terrible lighting.
Again, sorry for hijacking the thread, but friends don't let friends use high-arch springs.
with what everyone said. With one exception. The original Hyperco 200# high arch spring is made from the original GM molds as used on the 80+ cars. It is the only currently available spring, steel or composite, that gives the exactly correct ride height. BUT it is so soft you can easily bottom out the car on bump stops etc in performance driving. It is really only acceptable in a pure cruiser. The Van Steel high rate / low arch are second best correct for height, and have much better performance spring rates. They should be OK for height as long as you use longer bolts.
I absolutely would not use a soft spring rate with a strong motor, it will bottom out, and you can break parts. Even my stock 270HP 72 454 half-shafts showed signs of being bottomed out.
Stiff shocks would slow the rear droop under power, but it will ultimately sag as much as the rear spring allows. Your blue 69 is beautiful! And with that hood I bet you have some HP under there, and know how to use it!
Great info in this thread! I am experimenting and learning as I go. I have almost 500hp with EFI under the hood and a TKO600. The suspension, brakes, steering and drive train were all done by the PO who was too tall for the car and sold it after discovering how challenging it was for him to drive. His loss, my gain. The steel 9-leaf replacement spring he had installed has way too much arch. He had low profile 17s and I replaced them with 255/45-18s which I love. I replaced the rear spring bolts with 8” bolts and it made little difference. I read on the C2 forum that on these aftermarket high arch 9-leaf steel springs that removing the second leaf up will lower the rear perfectly (your mileage may vary). This is one of the options I may explore. I have QA1 coilovers in the front and they need to be dialed down an inch. My first attempt will be the ridetech (Hyperco) spring with the existing 8” bolts and the new QA1 adjustable shocks cranked to firm. I’ll report back.
Here are the ride heights in my other two Corvettes:
1964 coupe (still under construction). It has Ridetech coilover suspension all around. This picture has the suspension raised as I am getting ready to put it on a trailer. No transverse spring in the back, true coilovers and a Ford 9” to handle the power. This is my completely stock (other than the wheels/tires which are 235/55-17) 1966 L72 with F41 suspension. I think the ride height is perfect with the 427 and 7-leaf rear spring. The wheels just tuck in nicely.
I will get my ‘69 to the right height. I just need to test a few things.
Composite spring comparison
In this picture my rear tires are off the ground. You can see how the trailing arm has pushed my 4 1/2 inch spring end bolts through the spring. Guess the weight of my rear custom made spring? I tried a 420# VB&P and found it to be way too wimpy
with what everyone said. With one exception. The original Hyperco 200# high arch spring is made from the original GM molds as used on the 80+ cars. It is the only currently available spring, steel or composite, that gives the exactly correct ride height. BUT it is so soft you can easily bottom out the car on bump stops etc in performance driving. It is really only acceptable in a pure cruiser. The Van Steel high rate / low arch are second best correct for height, and have much better performance spring rates. They should be OK for height as long as you use longer bolts.
