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My 73 has a composite leaf spring. Question is to level the car I have to run the driver side busing all the way tight and put the passenger at the lowest level. Frame measures correct from the ground at 4 points. Anyone know why?
One front spring pushing harder against the rear? Improperly made rear spring? Improperly centered rear spring?
my bet would be one front spring stronger than the other. Pushing the car on a angle
Mine's the same way. Left rear has to be raised relative to the right rear, about the same amount as yours. Been through 3 sets of front springs over the years and none made any difference. It hasn't affected anything driving wise at all so I don't worry about it.
I'm not sure what you mean by "composite leaf spring", what you have looks like a stock multi leaf steel spring. Composite rear springs are fiberglass or similar material single leaf springs. That said, from looking at your pictures it appears to me that you might need a new rear spring. It looks like the spring's main leaf has lost it's arch, especially on the right side, though it does look like the spring was previously replaced. While the cut of the ends of the main leaf and the up turned ends of the other leaves are typical of factory springs, stock springs did not use with spring clamps.
Besides the front springs, I would check the rear spring's center mount for a broken or or missing bolt holding the "dog bone" anchor plate.
First of all, you don't have a composite spring. That is a stock steel leaf spring.
Are the bolts the same length? If so, most likely the spring has lost its tension for some reason and will need to be replaced. To confirm I would support the front of the frame to take the front springs out of the equation. If the problem still exists, it has to be the spring. If you are going to replace it, I highly recommend going to the composite spring if there is a good one available these days.
After you sort out the rear spring and you still have the unevenness, check to make sure the front springs are installed or "indexed" correctly. The front spring must be indexed in the top of the frame pocket. The top edge of the spring must be within 3/8" of the inspection hole in the frame. If not, the stance, front and back, will be uneven. Jerry
My sbc 76 is the same way.
The front measures 27.5" side to side and 28" in the rear side to side. It drove me crazy at first (ok still does) but the car sits the way I like. I have a feeling my rear spring is in need replacing which my cure the difference in the rear bolts.
Well at least I know I am far from the only guy that has this issue. And you are right my friend, mine is not a composite, as I should have rephrased that, it is a replacement that was installed about 10 years ago. It was a less expensive one that has the rubber cushions between the layers.
Im going to first replace the front springs with the correct ones for the build as she is a small block no air car, then move to the back.
I do notice that when I “get on it”, during shifting manual trans, the car gets a bit squirrelly requiring a tad of movement on the wheel, as if she’s trying to “bend”, which may all tie into the rear spring.
350 rebuilt stock with exception of a mild cam for torque. She pulled about 318hp at the wheels on the dyno after rebuild. That was 12 years ago.
But so far guys, I couldn’t have asked for more great suggestions. Really glad I joined this thing. Keep up the fine work!
That looks like a 2" difference in spring height from left to right in the rear.
That is a big difference.
A car that does not sit level should always be checked out.
A stock spring has a 98# per inch rate, per wheel.
I doubt your 850# left corner suddenly gained 200#. Or that your frame is bent that much, or that a front spring mis-indexed by 1/2" would cause that.
I would suspect one cracked leaf in the rear spring, lowering it's stiffness rate. on one side only.
On the driver's side, left of center.
There are nine leaves in there, one cracked one would lower the spring rate a lot, and cause that.
A change from a 98# to 78# spring rate would need to be cranked up ~2 more inches to hold the weight and keep the car level.
And sooner or later another leaf will crack .....
Last edited by leigh1322; Jun 8, 2025 at 01:19 AM.
Body mounts and shims will also affect the ride height. If the rubber body mounts have deteriorated/collapsed then the ride height will be changed. Perhaps the body mount steel perch has rusted out. I purchased my 1980 Corvette in 1983 and noticed early on that the ride height in the rear was different from side to side in the rear. The factory workers installed a lot more body shims on the right rear body mounts compared to the left. Show us pictures of the #4 body mounts that are visible in the rear wheel wells.
Back in the day I worked in a body shop , I did all the alignments , most of the time the frame was bent on vettes when you had to adjust like that , they bent on light hits cause the glass really does nothing so the frame takes the punishment. This conclusion is only after all the basics were checked.
Back up and take some more pictures of the entire rear suspension.
There could be several items causing your issues.
One that I see is that the shipping straps were never removed from the spring.
You also answered a possible problem already when you stated the spring was a less expensive one.
What front springs are you running?
Have you recently made changes to the suspension and if so what?
It sounds like you’ve owned this car for a long time.
Has it always had this problem or is this something new?
I thought I read that you had measured the frame and thought it was straight.
But it is easy enough to check that at home, without dissasembling anything.
You just need a tape measure. And a concrete floor.
You are just looking for numbers that vary more than 1/4 inch.
X type measurements are the most accurate. Even 1/2" on those should be OK.
When measuring to the floor, you need to account for the floor, which will also likely droop by 1/2" somewhere. Like toward the door.
I use a 5 foot 1" Aluminum I-Beam, from Home Depot, and a few 1/8" linoleum floor tiles, to make level spots on the floor. For good measurements.
Don't forget, a 1/4" +/- is a close as these frames were when they were new.
There are a lot of numbers in that chart. I would probably just pick 4 vertical from front to back. each side, and then 2 x- measurements. And call it good. Also measure grease cap to axle center wheelbase on both sides and make sure they match. My wheelbase was off 1/2" and the left front 1" high, due to impact with a ditch. Sat real crooked like yours. And bent front lower a-arm brackets.
Last edited by leigh1322; Jun 9, 2025 at 09:52 AM.
Composit leaf spring question
