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For years I thought slow speed compression was for little bump(tree roots, small rocks), and high speed for big bumps.

Then I was told the opposite by some friends last year, and yesterday was told by the bike shop mechanic , that what I initially thought was correct, slow speed compression was for little bump(tree roots, small rocks), and high speed for big bumps.

Finally now I am confused.

Which dial affect small bump? Slow speed or high speed compression?
 

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Elitest thrill junkie
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For years I thought slow speed compression was for little bump(tree roots, small rocks), and high speed for big bumps.

Then I was told the opposite by some friends last year, and yesterday was told by the bike shop mechanic , that what I initially thought was correct, slow speed compression was for little bump(tree roots, small rocks), and high speed for big bumps.

Finally now I am confused.

Which dial affect small bump? Slow speed or high speed compression?
The speed is the speed of the shaft/piston. Not the speed of your bike. Sharp edge bumps force the shafts to move much faster, IE: "high speed". Slower compression like g-outs, loading the bike, pushing down, "smooth" bumps are "low speed". The "transition point" is somewhat arbitrary, so it's a bit in the eye of the beholder, but that's the basic idea.

The other big misnomer is it has nothing specifically to do with the "size" of the bump.

It's important to consider that oil takes the path of least resistance, so leaving low speed compression wide open can allow more oil to flow through there and not activate your high speed circuit, making it feel harsh. By the same token, leaving the high speed completely open could affect your low speed and make it ineffective, but that just comes down to the individual shock. Sometimes you can't back high speed off enough to really get the range of adjustment that would be useful.
 

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The way I visualize it is by the shape of the bump and rating shaft speed on a scale of 0 - 10.

A rolling trail (wavy roller coaster) will affect LSC. This type of bump makes the shaft move from zero to 10 very slow.

A sharp hit will affect HSC. This type of bump makes the shaft move from zero to 10 pretty quick.

Of course this is a very simplistic way of looking at it as there is more to it than that, but its a starting point to understanding it.
 

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LSC effects high speed and low speed events. The same impact that opens the high speed circuit also forces oil through the low speed circuit.

LSC for support, HSC for bottom out, balance for harshness?
 

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Roots, rocks, and square edges are always high speed events unless you're going REALLY slow. Its still a 1-4 inch tall hit. Its close to a square edge, as you're going from flat to a few inches up.

Going full speed on a bike on flat ground, when your wheel encounters that hit, you're going from flat to 2-4 inches of compression in fractions of a second. Just BAM, you're up and over before you know it. Regardless of size, its high speed due to the rate at which your suspension is being asked to fully clear it.

Low speed is body weight shifts, brake dive, or anything that gradually and slowly moves your suspension into full compression, big or small. A flat drop is sort of a mix of both, its really not all that fast of a motion.
 

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It's important to consider that oil takes the path of least resistance, so leaving low speed compression wide open can allow more oil to flow through there and not activate your high speed circuit, making it feel harsh.
That's fascinating, and something that has never occurred to me. I had always figured that the harshness with a fully open LSC was due to packing and/or getting too deep into the travel. Your explanation makes more sense.
 

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Elitest thrill junkie
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That's fascinating, and something that has never occurred to me. I had always figured that the harshness with a fully open LSC was due to packing and/or getting too deep into the travel. Your explanation makes more sense.
The caveat is that it's theoretical and not all products with adjustable LSC/HSC can support it, so you may make things harsher by increasing LSC when the HSC is too restrictive in the stock setup. But due to crappy restrictive HSC circuits, the industry has "programmed" people to think open "blowing through travel" modes are the best for descending.
 

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For years I thought slow speed compression was for little bump(tree roots, small rocks), and high speed for big bumps.

Then I was told the opposite by some friends last year, and yesterday was told by the bike shop mechanic , that what I initially thought was correct, slow speed compression was for little bump(tree roots, small rocks), and high speed for big bumps.

Finally now I am confused.

Which dial affect small bump? Slow speed or high speed compression?
LSC is for bike stability, it affects brake dive, chassis movements and traction.

HSC is for bump control.

But. A lot of suspension have circuits that do not do what they should. Some get stupidly harsh with any extra LSC because the base-tune is wrong. Some have an LSC dial that does nothing for low speed compression events.
 
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