C-3 1970 Rear Height Adjustment/Alignment

[Clark E.]

Guys...During the frame-off restoration I took apart the replacement 9 leaf spring, refinished the leafs and installed the required liners that were not part of the spring. I discovered a broken long center bolt holding the leafs together and replaced it. Prior to the restoration the ride height visually appeared OK but I did not take the measurements before removing it. Since the restoration, the ride height is over 1 1/2 inches higher than specifications. The car has been driven over 100 miles (without a full gas tank) and the height hasn't changed. The car has not had a wheel alignment since the restoration and I'm certain is out of spec.

Will a wheel alignment affect the ride height and should the alignment be completed before attempting to adjust the spring?

I've read several posted threads regarding adjusting the ride height via rear spring modifications but to this point not sure of what the next step(s) should be. In a 2000 thread, Terry alluded to Winter and Summer 2000 Restorer articles that addressed the subject in detail but my archives don't contain the issues. I'd appreciate a member faxing me copies of the articles.

If replacing the spring is the best solution, a supplier(s) recommendation will be appreciated. Thanks...Clark

[Michael W.]

Re: C-3 1970 Rear Height Adjustment/Alignment

It's very unusual for an original GM spring to cause a car to ride high. An alignment won't change the ride height by more than a fraction of an inch (if at all) but I'd get the ride set first as ride height can affect alignment.

[Clark E.]

Re: C-3 1970 Rear Height Adjustment/Alignment

Thanks Michael...Didn't mean to mislead. This is the 3rd spring for the car. The original broke decades ago as did its replacement. From your comments my takeaway is the spring has considerably more impact on the ride height than does the alignment...Clark

[Leif A.]

Re: C-3 1970 Rear Height Adjustment/Alignment

Clark,
During the installation of the spring, were all the attaching bolts tightened with the car in the air or with the full weight of the car on the ground?

[Clark E.]

Re: C-3 1970 Rear Height Adjustment/Alignment

Leif...The car was on a lift with all 4 wheels suspended...Clark

[Michael W.]

Re: C-3 1970 Rear Height Adjustment/Alignment

Ah- the car must be sitting with the full weight on the wheels when tightening the fasteners.

[Richard M.]

Re: C-3 1970 Rear Height Adjustment/Alignment

Leif asked the right question. Bingo! Lucky one of the differential rear bolt flanges didn't break off.

Also be sure the spring center bolt head isn't bottoming out on the diff underside locating hole causing a space between the top spring and the diff. The heads of the center bolt are too high on the repros AND GM replacements.

Many recent threads regarding rear leaf spring issues and choices. Here is the most recent including other links to details.....

https://www.forums.ncrs.org/showthre...-Am-I-too-High