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Rear coil over suspension

PostPosted: Sat Sep 08, 2018 9:18 pm
by pbeck
I'm sure there are some of you out there that are running rear coil over shocks. I need some help/information getting my set up right. What rear weight are you running and what # rating are your springs ? I've had a horrible issue trying to get mine right. I've reduced the spring weight 3 times and still the only suspension movement I get is flex in my rear wheel sidewalls. My rear weight is about 1750#, with an overall weight of 3160#, although I don't have any way to check corner weights. What are you running and how does it work ?

Re: Rear coil over suspension

PostPosted: Mon Sep 10, 2018 9:45 am
by Richard Miller
what spring rate are you running right now ? I tried to find stock rate for a corvair but so far no luck ,, I might guess about 350 ,, if your car has 1750 on rear ,, half is 875 what is your motion ratio ,, probably 1:1 if shock attached to trailing arm ,, effectiveness reduced if shock is mounted at an angle ,,and total suspension travel ? lets say 4 inches ,, and your ride height is half of that ,, then 2 inches of compression needs to support 875 pounds ,,so a rate of 450 would compress 2 inches to 900 at 2 inches of travel with no preload ,, softer with some preload would center your travel and give a softer ride ,, so is my WAG ( wild ass guess ) anywhere near what you are running ?

Re: Rear coil over suspension

PostPosted: Mon Sep 10, 2018 10:43 am
by Richard Miller
spent some time trying to find stock rate with no luck ,, looking at some coil over charts in speedway catalog it looks like rates around 300 are common

Re: Rear coil over suspension

PostPosted: Tue Sep 11, 2018 7:53 pm
by pbeck
I've probably tried 4 different weights, currently have 175# springs on QA1 single adjustable shocks. I am running about 20 degrees or a little less angle from the trailing arms to the upper mount. I had it all torn down a couple of weeks ago, switching to the 175's and I did check the axle tire movement with no spring, but only on the right side (the longest) and it had good motion with very little in/out movement on the inner cv joint. I get all my stuff from Speedway but I'm going to check on the QA1 website and see if I can pick up some additional info.

Re: Rear coil over suspension

PostPosted: Tue Sep 11, 2018 9:24 pm
by Richard Miller
wow I see your dilemma ,, 175 # rate isn't high at all .. suspension should be compressing ,, would sag an inch if I leaned on your fender ..good luck and let us all know what you find

Re: Rear coil over suspension

PostPosted: Sun Nov 18, 2018 10:25 pm
by pbeck
After a lot of measuring and watching the movement of the suspension without the springs, I finally determined that my shocks weren't long enough. Where I should have had about 2" of compression travel, I didn't have any. Don't know how that happened since all the measurements were taken with a set of mockups from Speedway Motors. At any rate I ordered another set of shocks, 2" taller ride height. I ordered them with 175# springs, but after installation, decided that they needed a little more. Ordered 200# rating springs and they turned out just right.

One of the things I learned from all the U tube bits I watched was that the spring rating is really pretty simple. If the spring is rated at 200#, that means that for every 200# weight you apply to the spring, the spring will compress 1". The spring rate remains the same all through the compression.

I still don't know or understand very much about suspension, but sometimes I just get lucky !

Re: Rear coil over suspension

PostPosted: Mon Nov 19, 2018 9:19 am
by 66VairV8
Good information. I am converting my car to a C5 diff and C5 suspension and will be going to coil overs. I was able to scale my current Crown setup and the total weight is 2874 (1/2 tank gas without me in the car) LR= 836 and RR=795. This is the base line and will possibly change once the conversion is completed.
Jeff

Re: Rear coil over suspension

PostPosted: Tue Nov 20, 2018 9:49 pm
by pbeck
The closest I could get (with Ag scales) was 3140 total with approximately 1300# front and 1800# rear. That still sets up the rear spring rate at over 400#. Add to that the shocks mount at about an 80 degree angle. I'm still not sure how I got this lucky, but I'll accept it................

Re: Rear coil over suspension

PostPosted: Tue Dec 25, 2018 3:33 pm
by 66VairV8
I had a senior moment and forgot to post all the numbers. FL 608, FR 635, LR 836, RR 795 1243 front, 1631 rear. I currently have Koni adjustable shocks but will go to coil over with the C5 suspension. Qal1 was what I was looking at. Hopping to expand the wheel well to fit a wider tire.
Jeff

Re: Rear coil over suspension

PostPosted: Sat Jan 05, 2019 10:57 pm
by pbeck
If I had it all to do over (the body work) I would install wheel tubs. It would make a much neater installation and I doubt it would have required much more labor.