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Old 02-09-2010, 07:55 PM   #120
Scooby Guru
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Join Date: Sep 2004
Chapter/Region: MWSOC
Location: Delaware County, Ohio
2005 2.5RS Wagon
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Originally Posted by antonch View Post
I mean you do agree that stiffer springs require less stroke, right?
No, I don't.

Or at least, it's nowhere near that simple. A stiffer spring will result in less damper displacement for a given magnitude of impulse. The problem is that there's basically no upper bound on the magnitude of impulses. If you drive faster, the impulses get bigger. If you hit a higher bump, the impulses get bigger. If you hit a steeper bump, the impulses get bigger. Really, no matter how much travel you have, at least occasionally, you're going to use it.

Then you have to consider the flip-side. The stiffer spring (and the stiffer the damping to go along with it) the greater the force applied to upsetting the chassis as the suspension attempts to absorb the impulse. Upsetting the chassis over every bump is also a bad thing. So in trying to patch the travel issue, you created another problem for yourself.

The thing to take away from this is that you want the minimum spring rate that makes your tires happy and then you want enough travel to prevent reaching a mechanical limit over the majority of your use.

Cars w/ lower motion ratios will require significantly LESS stroke.

Or, again, at least not that simple. Because of the change in motion ratio, you need less travel in the damper. However, you still need the same travel at the wheel. So you're not coming up with less suspension travel overall.

You only need enough stroke to be not fully compressed on corners and have enough travel to soak up the bumps.
Correct. It's just that the amount of travel required to do this is way more than you think it is.

You could rig up shocks like these if you think longer (stroke) is better:
And that's fine, except you can't do that in an Impreza chassis without massively altering the suspension geometry. If I could have 22" of suspension travel and a ramp index that would make a rock crawler cry and yet not alter the suspension geometry, I'd do it in a heartbeat.
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williaty is offline   Reply With Quote