alternative rear springs

Suspension, including wheel, tire and brake.
datzenmike
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Re: alternative rear springs

Postby datzenmike » 31 Mar 2017 21:26

If a coil over spring (link in original post) it's not the same as the stock 510 spring. It will be too small diameter. A 450 pound spring on a shock mount is insanely stiff. 300 is too stiff.

If going in the stock spring location, because of a mechanical leverage advantage, a 450 lb/in spring will actually be 118 lb/in at the wheel.
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Re: alternative rear springs

Postby HP 510 » 01 Apr 2017 15:09

I guess I wasn't clear, I'm looking for alternative springs to run in the stock location. I know I can buy 3" ID springs and cut them but to get the right combination of rate and ride height might take a lot of springs, shims etc. I thought I might be able to use some of the 2 1/2" springs I have on the shelf but that apparently won't work. Has anyone tried to use 5" OD roundy round springs? They're available in rates up to about 1200 lb/in and heights from 8 to 11 inches with both flat and pigtail ends. What is the OD of the stock spring?

datzenmike
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Re: alternative rear springs

Postby datzenmike » 01 Apr 2017 16:29

Alternative, how? Stiffer? What spring rate do you want on the back? What do you have in the fronts?

The stock 510 fronts are about 89 lb/in so I assume the rears are close to that. Because of rear control arm geometry, to get 90 lb/in at the wheel, you need a 350 lb/in coil spring. Rear coil spring diameter is about 3.5"

As Julian stated the Dodge D-50 front coils are a nice reasonable increase. Comes down to what do you want.
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Re: alternative rear springs

Postby HP 510 » 01 Apr 2017 16:47

It will be an SCCA Production car, race only. Currently 275 fronts but I have other springs from 250-350 in 25 lb. increments, rules require the springs be in the stock location. considering the 3.8 to 1 factor for spring to wheel rate I was expecting to run 950-1100 in the rear. I thought the 3.5 diameter rear spring was the ID. I'll be taking the rear suspension (currently coil over) apart next week to check dimensions. Just thought I could get a head start with a little information.

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Re: alternative rear springs

Postby datzenmike » 01 Apr 2017 20:31

Right.
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bertvorgon
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Re: alternative rear springs

Postby bertvorgon » 02 Apr 2017 08:07

You are on the right track for spring rates. We run 300 at the front for Solo and 350# road racing and 1100 to 1200 on the rear.

re-read the "SUSPENSION" thread as it deals with shock control also.

viewtopic.php?f=29&t=1067&start=105

Start on page 8 if you have not already. Obviously track surface conditions will dictate a bit on spring/shock choice

This is a proven combination. I run 300# and 1200# in my car, with a 1 1/8" front solid bar.

Page 16 talks about shocks
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toylet
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Re: alternative rear springs

Postby toylet » 09 May 2017 20:12

datzenmike wrote:If a coil over spring (link in original post) it's not the same as the stock 510 spring. It will be too small diameter. A 450 pound spring on a shock mount is insanely stiff. 300 is too stiff.

If going in the stock spring location, because of a mechanical leverage advantage, a 450 lb/in spring will actually be 118 lb/in at the wheel.



The springs are for coil overs on big lifted trucks. They measure 3" and fit in the rear control arm perfectly.


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