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Originally Posted by AtomicLabMonkey
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Originally Posted by sperry
To be honest, I'm not 100% what's wrong with my suspension. I know that over the small bumps (esp. on the freeway) the car hops around like a biotch. I've tried every which way on the damper adjustment, and the softer I go the more it bounces, so I have to assume it's not overdamped, and I'm actually bouncing on the springs, not the tires.
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What spring rates are you using right now? Did you ever get any shock dyno info on these units?
Does the "bounciness" feel like the entire car is staying level but just moving vertically too much after hitting a bump, or does it feel like the car is pitching - where the back end is still rising as the front is falling?
Is the car noticeably oscillating up & down after hitting the bump (substantially underdamped), does it move & return to ride height within 1 or 2 cycles (somewhere near critical damping), or does it not come back beyond the original ride height point at all after hitting the bump (overdamped)?
Off the top of my head it sounds to me like a shock valving problem. I know we had some problems similar to that in the past with a prototype strut for the Mustangs - too much vertical motion over the regular small bumps in the road, so the car felt like it was jiggling all the time. An adjustment to the low speed damping fixed the problem. |
With the dampers set closer to the soft side of things, the car oscillates on the springs. Small bumps result in the car bouncing a few times, and when those bounces match the ruts in the road at your speed, you quickly run away into rollercoaster land, updownupdownupdownupdownupdownupdown.
Setting the dampers towards the firm side of things, and the car seems to pitch. The front is tossed up by the bump, then as it comes down the rear is tossed up. Match speed with the bumps and it's bucking bronco time! At least in this situation, if the road smooths out a bit, then the car will settle back down. So this is how it's set right now.
What *really* sucks is how the suspension effects steady-state cornering. The car's got great turn in, and very little roll, but I find any little bump in a long corner makes the car oscillate between over- and under-steer. Perhaps that's just the nature of the beast.... I don't really know, since this is my 1st set of coilovers. The fact that the car bounces in steady state cornering does make me think it is valve related, but a new set of dampers from JIC is $260/corner, and I don't see how they'd be different. Springs are like $260 for four, so finding some springs that would better match my driving ability/road conditions to the existing dampers would be more affordable.
Currently the car has 7kg/mm (392lb/in) front springs and 5kg/mm (280lb/in) rears.
If the real solution involves new dampers, then I'm just selling the JICs and getting Nate to build me a custom Koni/Eibach/GC setup.