Quote:
Originally Posted by Digitalize
The higher the PSI the higher the spring rate. If it's skipping over bumps then it's too stiff, or your dampening doesn't match the spring rate.
Air Lift have recommended pressures front/rear and dampening rates.
35-45 psi with 10/30 dampening for the front.
70 psi with 10/30 dampening for the rear.
So your dampening seems to stiff, and rear pressure is a little high. Try their recommended settings and go from there.
For anything but a perfectly smooth road a softer suspension setup will be faster than a stiff one.
Also worth looking at your tyre pressures, and have you had the car aligned at drive height?
Have you checked the sway bar location when at drive height? Lengthening the links for aired out might be fine but could put the sway bar in the wrong location when at drive height, this probably wouldn't cause your issue though.
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Thanks for that very detailed reply. Lots of great info here.
The stiffer (higher) spring rate makes sense if there is a high PSI value. That would mean it needs more weight to compress, resulting in less spring travel and a more firm ride. However, I'm right around the recommended PSI settings for my bags, and actually under the level for the rears. So, if anything, shouldn't my ride quality be too soft? Even with my damping being set higher than recommended?
Speaking of which, shouldn't damping only affect how the shocks handle the spring travel? Meaning it shouldn't affect how stiff or soft my ride is, merely how long after I hit a bump it takes to level out? A very high damping setting (30/30) would mean there's zero 'bouce' after I hit a bump where a very low setting (0/30) would continue bouncing for too long? If anything, in order to stabilize the car, the damping value would need to increase at the cost of comfortability? I feel my car bounces too much after a bump, and would rather have the car be more stable instead of comfortable.
This leads me to a question about your statement "For anything but a perfectly smooth road a softer suspension setup will be faster than a stiff one." Surely softer suspension would cause more body roll and general instability as opposed to a stiffer-set suspension? Even with the occasional bumps? Is it just a matter of finding a middle ground?
I'm on 19s with 35 and 30 sidewall front/rear. Hankook Ventus V12 Evo2s. Pressure COLD is 35 front/37 rear, just a hair above BMW door card PSI values, and when hot are about 40 front/42 rear. So this would perhaps add to the reasoning for why I might hop or skip over a bump, that being my tires don't absorb as much of the impact and flex enough to compensate.
I had an alignment done after I initially installed the kit. Then a shop did some minor custom front end work (lengthening sway bar end links), but I did not get an alignment after that. It's possible that disconnecting the bottom of the strut from the knuckle and then re-connecting it was enough to get it out of alignment. The sway bar location at ride height undoubtedly changed as a result of this, perhaps rendering it less effective. I will need to get the car on jackstands and jack both of the front wheels up to see where it sits.
So, overall, while keeping my ride height the same, what would be your recommendations for a more sporty/autocross/stable suspension at the cost of comfortability? Also thanks for reading through this ridiculously lengthy post
