Coil Spring Spacers and Wheel Motion Ratio

69autoXr

Active member
Joined
May 27, 2008
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27
So...I cut my damn Daytona springs too short to be usable. I'm looking at using a spacer under each side so that I can use these springs. I've read that when using a spring spacer it's common to get ride height increase about 3x the thickness of the spacer. A friend when asked commented that it may be due to the suspension motion ratio (perhaps I'm not using the right terms). Any comments from the suspension experts?

Thanks
 
I think It's twice the height of the spacer

My dad put spacers in the from of his 66 that were about 3/4" and it went up like an 1.5"
 
The ride height increase is the result of the spring vs. wheel ratio. What you need to do is measure the distance from cross shaft to spring center and that from cross shaft to outside of wheel. Then you can simply calculate how much ride height you will gain.

V-Twin did the same on his car, the prev. owner cut the springs so short it was scraping and the springs would sit loose (really loose) under droop. Added some urethane spacers that are actually meant to dropa 68-70 mustang by replacing the stock upper rubber donut. Had to profile the sides a bit but otherwise it fits just fine.
 
On a C3 the lower control arm ratio is almost exactly 1.5:1. A 1 inch spring spacer would result in raising the car 1.5 inches
 
...and that from cross shaft to outside of wheel. Then you can simply calculate how much ride height you will gain.

Measure to the outside of the wheel? That means the ratio would change based on which wheels I'm running.

I'll guess I'm looking at a 1.5-2:1 motion ratio, and start with my 3/8" spacers and hope that it's enough to get the height where it needs to be.

Thanks
 
Yes, the smaller the wheel diameter, the larger the wheel to fender gap obviously.
 
I was actuallly referring to wheels of different widths, but the same diameter.
 
Well I used the 3/8" spacers and gained about 3/4" of ride height at the wheel. It's still low, but it handled pretty well at the tracks I ran over the weekend. The spring is still very loose in the A-arm pockets when the suspension is at full droop so I made some droop limiters using steel cable to keep the spring in place when the car is jacked up. I didn't notice any ill-handling from either the new spring rate in front or the droop limiter cables. I posted a few pics of the car under braking and turning in one particular 90* right hander at Waterford Hills road course from Friday's event. The left sidepipe looks real close to the ground in the corner and may have scraped a little going up the hill. I also have some 1/2" spacers I could swap in very easily.

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I have spring rubbers under my springs (Mr Gasket brand I think)...If the hole under the upper a-frame from the rubber bumper is threaded you can use a bolt with a jamb nut as a limiter.....
redvetracr
 
I'll have to take a look at it, I can't see in my head right now which hole you're referring to. But it does sound easier to adjust than my current setup.

Thanks
 
He means the hole in the frame where the bump rubber pushes in. You can easily open up the hole and weld a nut on the underside (inside of frame spring pocket) and then use adjustable bump stops w/ lock nut.
 
as long as my bolt is you can weld a nut on top of the frame.......I will try to get out to the trailer and take a look.....
 
Hmmm...now I think I know why I don't know what you guys are talking about. I'm pretty sure that my car doesn't have the upper bump stops in place-I don't know that it ever has since I've have my car. It seems to me that my suspension droops until the upper A-arm stops on the frame.
 
My shocks limit the down travel for mine

I'm running s10 shocks though and there shorter, they still rub the frame a bit though. And yes they will be getting revalved
 
my "stop" is a 1/2" bolt, there is a nut welded to the top of the frame with a second nut as a lock nut, the bolt head sticks up from the frame about 2.250"
redvetracr
 
As I thought, my car doesn't have the upper bump stops in place. I could also use a bolt with nuts on either side of the frame to lock it in place.
 
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