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Coilover spring rates

I have had AGX shocks (two sets - one for springs and one for Ground Control coilovers) on my '94 miata for several years and I like their adjustability. However, I am still looking for the best compromise of spring rates. I had several of standard-type springs and I have also had several sets coilover springs installed and I have never been satisfied that I arrived at the best compromise. The car is driven daily, summer and winter, and occasionally autocrossed in the summer (pavement) and winter (gravel occasionally with snow and ice). The car has suspension braces front and rear. The car has FM rear shock mounts, stock sway bars and urethane bushings. The front suspension brace made the most dramatic improvement in the car but good tires really do matter.

The OEM springs were Front:153lb, Rear:94lb - considerably too soft for any performance driving. The Eibach Pro-Kit springs were Front:228lb, Rear:137lb - too low, poor suspension travel, really harsh particularly in the rear and not particularly compliant. Flying Miata springs were Front:342lb, Rear:228lb - overall not too bad, maybe a bit too firm in rear for racing on gravel and I did not want to lower the car more than 1/2" or

3/4". The coilovers have had 6" long front 400lb and 7" long front 350lb with 7" long rears of 250lb, 200lb and 150lb. I also tried 10" long 125lb rears. The 10" springs are a bit harsh due to preload, but you eventually find that they are too soft. I am reasonably happy with the front 350's. I am about to order another rear set and I am going to try a combination of linear springs with 4" 250lb springs (Eibach No. 0225.250.0250) coupled to 4" 150lb springs (Eibach No. 0225.250.150) on each rear wheel. Hopefully this combination will seem somewhat progressive by being initially quite compliant, firm when driven hard but will not be vulnerable to any bottoming. Then again it might just be another $300 experiment.

Brian Minto, Calgary, Alberta, Canada

Reply to
Brian Minto
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Maximizing performance over that spectrum of surfaces is a tall order, no?

FYI, FM has revised their springs. Current rates are 318 front and 233 rear, with less drop. The goal is to keep the car off the bumpstops. FM prefers Illuminas, but I'm sure with a phone call you can find out how they work with AGX.

Or, if you are willing to spend the money, Keith Tanner did very well in this year's Targa Newfoundland with his AFCO setup.

Reply to
Lanny Chambers

I am not trying to "maximize performance". You may notice that I used the word "compromise". I use AFCO coils on all four corners already. For example, I have had a set of Eibach 350's and I have had a set of AFCO 350's for the front. I use the AFCO's because they begin moving more smoothly. Although they are the same length and same rate, the Eibachs hit the bumps, while the AFCO's absorb the bumps.

Maximizing performance over that spectrum of surfaces is a tall order, no?

FYI, FM has revised their springs. Current rates are 318 front and 233 rear, with less drop. The goal is to keep the car off the bumpstops. FM prefers Illuminas, but I'm sure with a phone call you can find out how they work with AGX.

Or, if you are willing to spend the money, Keith Tanner did very well in this year's Targa Newfoundland with his AFCO setup.

Reply to
Brian Minto

Sorry, I meant AFCO coilover units, not just their springs.

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-16200++STANDARD

Reply to
Lanny Chambers

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