A bit of help understanding suspension tuning
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Joined: Sep 2008
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Not to bring this back from the dead, but I wanted to get some clarification. I have messed with the rebound a bit since I started this thread, but not a ton. I have been reading and trying to learn some more basic aspects of suspension tuning. One thing I am still a little confused by and possibly where my misunderstanding came from is that the adjustment tool does not refer to higher rebound or lower rebound, it simply says Firm and has an arrow indicating the direction of "firm". So am I increasing the rebound by turning it in the "firm" direction or decreasing it? It seems to me that turning towards firm would be reducing rebound and therefore cause a faster return and more "firm" ride?
Joined: Jun 2010
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From: Near Philadelphia
It might help you to think of shocks as what they are....a piston in a viscous liquid. "More" rebound = stiffer rebound = firmer rebound, which all can be imagined as having more viscosity on a piston, since that's exactly what it is.
Imagine you have a disc that you swing around you, or push in front of you, or something. If you do it out in the air, it won't have any resistance to speed. This would be like having no dampers. Now imagine swinging that disc underwater. That would be like having soft dampers. Hopefully you can visualize the difference. Now imagine swinging the disc in a vat of molasses or oil. That'd be like setting them to stiff.
For the next step, imagine the same plate but attached to the end of a spring, all submersed in whatever fluid. Now if you hit said plate with a hammer, simulating a high speed high force event like a 2700 lb piece of metal hitting a harsh bump, you can hopefully envision what happens in each of those cases. In the air one, it bounces pretty far, then bounces back almost as far, then back again, etc. In water, the initial impact will be more harsh on your arms swinging the hammer but at the same time the disc will move slower than it did before, and will ultimately stop bouncing quicker. In oil/molasses/viscous stuff, same thing but even moreso - you'd break your wrists hitting it, but it would move super slow and probably not even undergo one cycle of bouncing before stopping.
Same thing with shocks. Firmer damping means the impacts will be harsher, but the suspension will move slower.
The complicated thing to think about is that even though it is moving slower, it could become settled faster because it doesn't bounce around nearly as much. But that's a little more complicated because more damping doesn't necessarily mean it will settle faster. That's what critical damping is if you've seen that term thrown around - critical damping is the amount of damping that makes the absolute minimum time to settle the suspension. If you are higher than critical damping, then more damping will actually make it take longer to settle since it's moving so crazy slow. But if you're lower than critical damping, more damping will make it take less time to settle since you're lessening how many times it bounces.
Hopefully that helps and doesn't just confuse you further.
Imagine you have a disc that you swing around you, or push in front of you, or something. If you do it out in the air, it won't have any resistance to speed. This would be like having no dampers. Now imagine swinging that disc underwater. That would be like having soft dampers. Hopefully you can visualize the difference. Now imagine swinging the disc in a vat of molasses or oil. That'd be like setting them to stiff.
For the next step, imagine the same plate but attached to the end of a spring, all submersed in whatever fluid. Now if you hit said plate with a hammer, simulating a high speed high force event like a 2700 lb piece of metal hitting a harsh bump, you can hopefully envision what happens in each of those cases. In the air one, it bounces pretty far, then bounces back almost as far, then back again, etc. In water, the initial impact will be more harsh on your arms swinging the hammer but at the same time the disc will move slower than it did before, and will ultimately stop bouncing quicker. In oil/molasses/viscous stuff, same thing but even moreso - you'd break your wrists hitting it, but it would move super slow and probably not even undergo one cycle of bouncing before stopping.
Same thing with shocks. Firmer damping means the impacts will be harsher, but the suspension will move slower.
The complicated thing to think about is that even though it is moving slower, it could become settled faster because it doesn't bounce around nearly as much. But that's a little more complicated because more damping doesn't necessarily mean it will settle faster. That's what critical damping is if you've seen that term thrown around - critical damping is the amount of damping that makes the absolute minimum time to settle the suspension. If you are higher than critical damping, then more damping will actually make it take longer to settle since it's moving so crazy slow. But if you're lower than critical damping, more damping will make it take less time to settle since you're lessening how many times it bounces.
Hopefully that helps and doesn't just confuse you further.
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The papers are a bit dense, but this helped me signifigantly understand the core of suspension tuning and the math and science behind it....
http://www.optimumg.com/technical/technical-papers/
http://www.optimumg.com/technical/technical-papers/
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