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What does float do?

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I revavled my 2013 KX450F with Race techs kit.  It is really good I am just wondering so I can learn suspension theory.  If I change NOTHING but change the float what would that do?  I think RT calls for .080 float just say I change it to .120.  What would that do to the forks.

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Opening the float will allow more fluid to flow before substantial damping in the mid starts taking effect.

Closing the float will do the opposite.

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Float just effects the effective "flow area" of the midvalve.  The total effective flow area is the float plus the shim deflection.  For a given shim stack, more float means more flow area and less damping.  If the float is high enough, the stack is no longer a flow restriction, and all that is relevant is the size of the ports.  When this happens depends on a lot of factors, but it occurs in "checked mid" setups, which often have around 2  mm of float.

 

You say that RaceTech recommends 0.080 of float.  Presumably you mean 0.080 INCHES (which would be 2 mm)?  If so, that is effectively a checked mid, in that the shim stack has little to no bearing on the damping behavior of the mid.  Going from 2 mm to 3 mm (0.120 inches) of float would probably do nearly nothing, because the float is already so high as to not be a significant restriction.

 

Motion's answer is good as well, within the normal float boundaries of active midvalves.  We should keep in mind that there is not a black-and-white transition into "mid taking effect."  The mid is always in effect, it's just a matter of the shape of the curve, how progressive it ramps, etc.

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oops, RT recommended .80mm, not inches.  Ok so too much float and the mid stack really isn't doing anything cause there is so much flow it isn't restrictive and doesnt work.

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0.8 mm of float makes more sense.  Still seems like a lot, unless the bike is set up for woods/enduro?

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Float (or free lift) is like a bleed on the mid valve, and the mid valve has a noticeable effect on the very initial part of stroke movement.

 

If you are a rider who likes to often feel feedback from the front tire, then keep the float tight. But if you also ride trails, then you might want to soften the midvalve stack too.   You can have a tight float and still feel very little on massive, fast, hard impacts.

 

If you are a rider who doesn't like much tire feedback, then widen up the float. You probably wont want much spring preload either.

 

If you calc the area of the gap made by having float, you find that those piston bleed hole(s) dont chage much flow oil. I think they exist to change the pressure waves or something like that.

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