Shock refresh

[Pete_vB]

Originally Posted by scotth944

"it might be interesting to try increasing front shock damping to try and gain a little confidence/ stability, and there may be an inexpensive way to test this using some front M3 struts."

Pete, are you suggesting going towards increasing the front dampening instead of decreasing the front spring rate because of high speed or just to get power down at turnout faster (if I am understanding the dynamics correctly)? I was wondering if less front spring with more rear bar wouldn't make for a more stable setup as long as I'm not overly aggressive with the gas on turnouts?

It'd be easier but I wouldn't drop the front spring rate, mainly because I think it would upset balance too much.

My hypothesis is that the rear is relatively, slightly overdamped. Overdamped can lead to the tire not following the road well over bumps, "skipping". If both the front and rear are damped similarly this will lead to the whole car skipping sideways slightly in a turn, which isn't always ideal but is very controllable. But if only the rear is overdamped and skips sideways that leads the back trying to come around.

Reducing front spring rate as you suggest could make the front overdamped as well, but the rear would then be much stiffer both in spring rate and absolute damping forces. This would most probably lead to significant oversteer-I wouldn't recommend it.

Instead I'd suggest either reducing rear (if you want overall softer) or increasing front damping forces while leaving the springs alone. If mismatched damping is the cause of the instability that should improve it. The concern is that it might come with slower turn-in, but for your use that may be preferable? A decent adjustable shock at one end of the car would let you explore, assuming it's matched well enough to what you've already got (how fresh are they?).

[Pete_vB]

Originally Posted by Em/1

Pardon my ignorance, but pronouns are leaving me confused. What is upside down? Are graphs reversed re rebound and compression; my read says compression:rebound is 1:3 instead of 3:1...

It's just that most shock dynos you'll see in the US have compression on top, assuming you're used to looking at them. The labels are correct, rebound is 3x compression.

[timbo_3101]

Originally Posted by Pete_vB

It's certainly fairly easy to set up a car too stiff, and the more bumps the softer you'd want to go. Nissan softened their lap record Nismo GT-R when setting it up for the Nurburgring: shocks, springs and swaybars. A car also tends to get more difficult to drive as it gets stiffer, requiring more and faster driver inputs. If you're having traction issues it sounds likely you do need to soften it up for that track...

Thanks Pete again for the insights.
Aside from aggravating a back injury, the harshness of my suspension setup is a considerable disincentive to driving my vehicle on a regular basis