PART 28: SUSPENSION TWEAKS


Stiffer Springs and a Ride Height "Adjustment"

Special barrel shaped springs offer shorter length but longer travel before binding

It’s always the little things that trip me up. The 1/4 inch clearance difference between the S4 and S5 water pump housings for example. Well I had a similar problem with the suspension. I had lowered the car down to approximately the lowest legal limit by trimming one of the front lower spring seats to let the seat spin a few turns lower on the threaded collar. Sure it lowered the ride height of the car but now I had a tire rubbing issue since the lower collar was now in line with the sidewall of the tire...rats! In the short term I slapped on a pair of 8mm front spacers but I’m not keen on the idea of using the spacers even though I run longer hardened wheel studs. I was in need of shorter front springs to raise that lower collar up and out fo the way of the tire sidewall. My current spring length was 7" so I needed a 6" spring. But this raises another issue in that there will not be sufficient spring/suspension travel to preclude binding of the spring...even when using a stiffer spring. In dialogue with the folks at Ground Control apparently this is not an uncommon problem and they had just the spring for me. A 6" spring with a barrel shape to it. The barrel shape allows greater travel than the straight 7" spring I had on there previously. Since I was going to have to replace the springs to deal with the ride height issues and to compensate for the “shorter” springs I decided to go a bit stiffer over all and bump the front spring rate from the 400lb/in front spring and 275lb/in rear spring to a 440lb/in front and 325lb/in rear spring. The 440lb/in is a conversion from a metric spring rate and hence the unusual number. 450lb/in was my target but I’ll settle for the 440lb/in spring. Additionally to get the rear lower spring perch back into a usable position I opted to go with a longer rear spring as well from 7" to 8" length. In summary I shifted from a front 400lb/in x 7" spring to a 440lb/in x 6" spring and a from a rear 275lb/in x 7" spring to a 325lb/in x 8" spring. The cost of the new springs: $280.00. This solved both an tire interference problem and gave me greater flexibility with ride height adjustments. Time will tell if I chose better spring rates


New springs installed. Note the better placmenet of the lower perch both for additional clearence and flexibility with adjustment.

On a side note I've also experimented with using a smaller diameter tire to address both ride height and gearing issues. The pic below shows the relative differences between a 225/45 R15 tire and a 225/50 R15 tire. The 225/45 tire beig considerably shorter!


Tire comparison.

Chapter I: To Begin the Hooptie to Hotrod Saga: Part 1 of the First 16 Installments
Chapter II: The Saga Continues beginning with Part 17 through 21, A Good Rear End: Part 17
Chapter III: Picking up the Pieces. Part 23 (clutch, adjustable proportioning valve + more)
Chapter III: Shift Mad Quick, Yo! Part 24
Chapter III: Getting a License - Racing School No. 2, Part 25
Chapter III: The S5 Decision, Part 26
Chapter III: S4 to S5 Conversion - CRAZYNESS! Part 27
Chapter III: Oil System Upgrades, Part 28


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This page last updated June 10, 2006


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