Rear Spring Arch

[Scott M.]

Just wondering...
Several years ago I purchased a new 9 leaf standard rear spring for my 72 instead of refurbishing my original. When I installed it, it made the rear of the car way too high compared to the original. So I took it back out and decided to redo my old spring. Is it common for new springs to have such a difference compared to the old one? Is it common for new springs to need to be de-arched? For the last couple years I have had that new spring sitting on my shelf. I would get rid of it but I don't want to sell it to someone thinking it will be too high.

Thanks
Scott

[Dick W.]

Re: Rear Spring Arch

Just wondering...
Several years ago I purchased a new 9 leaf standard rear spring for my 72 instead of refurbishing my original. When I installed it, it made the rear of the car way too high compared to the original. So I took it back out and decided to redo my old spring. Is it common for new springs to have such a difference compared to the old one? Is it common for new springs to need to be de-arched? For the last couple years I have had that new spring sitting on my shelf. I would get rid of it but I don't want to sell it to someone thinking it will be too high.

Thanks
Scott

If you had removed your original spring several years ago, left it stored, and reinstalled today, it would be too high. It takes time for the spring to settle.

[Scott M.]

Re: Rear Spring Arch

If you had removed your original spring several years ago, left it stored, and reinstalled today, it would be too high. It takes time for the spring to settle.

Really? I wouldn't think it would be that much difference. It's just that after I put the new spring on it seemed to give the car what I call a "chicken rod" stance. I had it mounted on the car for about a month or so. Well, at least I know that there is nothing wrong with the spring now and I can feel better about selling it.
Thanks

[Edward J.]

Re: Rear Spring Arch

Scott, sometimes the height problem is not the leaf spring, Its the rubber cushions get old and depress over the years and you'll loose you original ride height. I always prefer to try and refurbish the originals with new liners, cushions and repaint. And I am not a big believer of sand blasting the old spring just sand it and clean as you can and use a light gray etching primer( Eastwoods sells this). If the old spring has serious rust then don't bother as it will likely not sit correctly.

[Steven B.]

Re: Rear Spring Arch

If you had removed your original spring several years ago, left it stored, and reinstalled today, it would be too high. It takes time for the spring to settle.

Correct. I have 3 sets of springs on the shelf that have been there since mid 60's and late 70's. They would be high as Dick says. The springs I put on the cars did settle over time. You aren't using the long bolts, are you?

[James B.]

Re: Rear Spring Arch

Scott:

Many years ago, I too had purchased and installed a replacement 9 leaf spring on my 1972 and as a result, the car sits very high in the rear to this very day. I was hoping the ride hight would normalize with time, but no such luck. A little investigation revealed that this was a common problem with replacement springs. I then purchased an appropriate used original 9 leaf spring in good condition and will install it one of these days. Hopefully, this will resolve the problem.

Jim

[Scott M.]

Re: Rear Spring Arch

Correct. I have 3 sets of springs on the shelf that have been there since mid 60's and late 70's. They would be high as Dick says. The springs I put on the cars did settle over time. You aren't using the long bolts, are you?

I think I have the correct bolts. They are 6.5 inches and the distance between the bottom of the trailing arm to the top of the bottom spring is about 3.25 inches. Seems like longer bolts would make the car sit lower. I refubished my old spring with new cushions and cups. Also new bolts and cushions for the trailing arms. When I put it back in, the car sat normal. I'm wondering if Jim's situation is the same as mine. Seemed like the only way to get the new spring down to correct ride height was to have the new spring de-arched or fill the gas tank with concrete.

[Steven B.]

Re: Rear Spring Arch

Right Scott, the long bolts do lower the car. They are usually used on competition springs and have "nyloc washer". I have them on one of mine with Guldstrand comp springs. Old race.

[Mike E.]

Re: Rear Spring Arch

Last year Jeff Salz did a video on rear springs. Lots of good information in it.

Mike

[Gary B.]

[Gerald C.]

Re: Rear Spring Arch

Okay. I have two 1963 springs to choose from...... which one to put back in the car. The first one which came on the car and the seemed to sit okay measures 9 7/8" from the center bolt to the straight edged (4 foot carpenter's level). Of course this is before I replace all the cushions, etc. The existing spring I have measures 10 3/8" from the same measurement parameters. Both are in excellent condition and have new liners. Does the 1/2" difference in the two measurements make a difference on the stance (with adjustments) once installed on the car?

Thanks

[Gary B.]

Re: Rear Spring Arch

Gerald,

Can you post a photo of how you’re measuring; from where to where? The free arch is measured from the concave side, next to the center bolt nut, to a line connecting the centers of the two end holes in the main leaf. I believe the GM spec is 10” +/- 1.8”.

Gary

[Gerald C.]

Re: Rear Spring Arch

Rear Spring-1.jpgRear Spring-2.jpg

[Gerald C.]

Re: Rear Spring Arch

Gary,

Hope these pictures help
Jerry

[Gary B.]

Re: Rear Spring Arch

Gerald,

Should be hole center to hole center. Which will reduce both your numbers. The 9 7/8” will then be lower than the low end of the GM spec.

Gary