Thread: Rough Ride ( Suspension Help )

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If you have a Heidts Super ride on the front, I would think that Heidts would have selected a spring rate that's not too far off. Heidts has already selected what should be the proper coil-over shock length. That should not have to be changed.

I've been going through this type problem with Ride Tech, but it was Ride Tech that selected the 450 lb/in spring rate for my Oze front suspension, that is a copy of the Super Ride II. I went to their spring calculator program and came up with a much softer rate of only 350 lb/in, using a guestimated 800 lbs on each front wheel. I've sent them an E-mail asking how they came up with such stiff springs for my car. It will rattle your teeth when it hits a small mismatch in the road.

One of issues that I'm dealing with is my shock mounts appear to be set to position the A-arms approximately parallel and horizontal, with a shock length of 11.8 inches. This works for their Shock Wave system, but not with their coil-overs. The 10" spring coil-overs have a ride height in the 12.2-12.6 inch range and the 8 inch model is 11.2-11.6 inches. One is too long and the other too short. I may end up cutting off my upper shock mounts and moving them up .6 inches, to work properly with the 10 inch spring length coil-overs that they recommended. They'll probably tell me to just set the length to 11.8 inches or maybe 12 and live with the reduced amount of available shock compression.

http://www.ridetech.com/tech/spring-rate-calculator/


One interesting thing that I noticed with their spring rate calculator is that changing from a 10 inch spring coil-over to an 8-inch changed the suggested spring rate from 350 to 450 lb/inch, with no other change to the input information.

I used adjustable mock-up bars to figure out the near-perfect shock length of 11.8 inches. If the length is any longer, the upper A-arm angle changes from horizontal to being angled down, at the ball joint end. Any shorter and the upper A-arm angles upward at the ball joint end. When I was driving the car this year, I had the shock length set around 12.6 inches. This caused the upper arm to angled down by 6-8 degrees, and it pinched the ball joint dust boot, noticeably. The springs were so stiff, that the shock length was overly long, even with no preload on the springs.

I've had no luck with the Ride Tech technical help folks. The guy I spoke to had no opinion at all about using a softer spring. If he was familiar at all with the spring rate calculator, he would have been able to tell me how much more preload I'd need with a 350lb/inch spring rate (about 1 inch).

The amount of preload that you're using can tell you something about the spring stiffness. In my case, I know that I've use zero preload and the shock length was not still not down to the perfect 11.8 inch length. If you have that situation, then the springs are too stiff. I'm confident that I can drop the spring rate down to 350 lb/inch and use less than 1 inch of preload to get the height that I need.

At the rear of my car I have 200 lb/in coil-overs at a 70 degree angle. The ride tech calculator says that 175 lb/inch springs will handle 725 lbs at each wheel, so I plan to reduce the rear spring rate, too. I know that I've driven the car with no preload on the springs, when I had the rear set to the lowest height that I ever tried. I didn't realize that I had no preload until I put the car up on my lift and noticed the rear springs were slightly loose. This is not desirable because the springs won't center on the top mount, without some help. You need at least a little preload.