By Bones Bacon

“My shock is too soft. I’ve gone all the way in on compression and it’s still too soft.” The first few times I heard this, I told the riders to bring their shocks back and let me stiffen them up a little. After checking the adjusters, I realized that the high-speed compression adjuster hadn’t been touched and that the low-speed adjuster was all the way in. Almost all current big bike shocks have an adjuster with two settings: a 14mm or 17mm hex nut that adjusts high-speed compression and a brass screwdriver slot in the center of the plate that adjusts low-speed compression. Had the rider turned his high-speed in just a little, it would have solved the problem.

If you are one of the many riders who never touches his high-speed compression adjuster, don’t be afraid to admit it. The fact of the matter is that it is one of the least understood adjusters on a shock and the one that I use the most when making adjustments.

“WHAT DO HIGH-SPEED AND LOW-SPEED COMPRESSION ADJUSTERS DO? THEY DO EXACTLY WHAT THEIR NAMES SAY THEY DO; HOWEVER, THERE IS SOME CONFUSION ABOUT WHAT “HIGH SPEED” AND “LOW SPEED’ REFER TO.”

What do high-speed and low-speed compression adjusters do? They do exactly what their names say they do; however, there is some confusion about what “high speed” and “low speed’ refer to. In the case of a shock absorber, it has nothing to do with how fast the motorcycle is going but rather how fast the shock shaft is moving. The most common sources of different shock shaft speeds are when absorbing big bumps, squatting under acceleration out of a corner, kicking up when hitting a braking bump, sinking in too much on the face of a jump, or deflecting when accelerating through bumps. It’s all common sense. Just think about how fast the shock shaft has to move and you’ve mastered high- and low-speed compression.

Low-speed compression is the easiest adjuster to fiddle with because everyone has a flat-blade screwdriver, or as Alan Cianciarulo, Adam’s father, used to do, you can just grab a dime to turn a flat-head slot. The low-speed adjuster, as the name implies, is used to adjust the compression when the shock shaft is traveling at low speeds. The low-speed compression adjuster controls the free-flowing oil that is metered by a needle-and-seat and is adjusted by turning the screwdriver in or out. Low shock shaft speeds occur when accelerating out of a corner, hitting a gradual jump face, G-ing out in a shallow dip or accelerating off the start. In these situations, “wallowing” is the best word to describe the feeling when the low-speed compression might be too soft. Conversely, if the rear of the bike has a firm feel, won’t settle enough on acceleration to get any traction and feels a little high, that might mean that the low-speed compression is too stiff. When you feel wallowing or stinkbugging, by all means, grab a flat blade or a dime and make some adjustments.

“DON’T BE STINGY WITH THE T-HANDLE. ADJUST THE HIGH-SPEED OFTEN TO LEARN ITS AFFECT ON YOUR SHOCK.
YOU WILL FIND IT TO BE A MUCH MORE USEFUL ADJUSTER THAN YOU EVER THOUGHT.”

High-speed compression is defined by when the shock shaft is forced to move rapidly through its stroke’especially if it has to move a great distance. When you are hammering through a set of big and fast whoops, slamming into a steep jump face, flat landing off a monster jump, G’ing out at the bottom of a fast downhill or hitting a big braking bump at speed, this is when high-speed compression is your friend. In these situations, the rear may feel low or sink in too much and bounce out to indicate the rear is too soft. A high feeling in these situations, or hitting these whoops or bumps and instantly deflecting off them, indicates that your rear suspension is too stiff.

The word “fast” is used a lot here because it is fast high-speed sections for which the adjuster is named. When the shock has to push a lot of oil through the adjuster in a very short time, the flow is impeded by the low-speed needle-and-seat. At this point, the oil is forced through shims on the high-speed side. The shims, in turn, have to push against a coil spring to let the oil flow freely. The amount of tension on the spring is adjusted by the, you guessed it, high-speed adjuster. When you turn the high-speed adjuster’s 14mm or 17mm nut, you make the spring resist the oil (and vice versa). The normal adjustment is in the 1/4- to 1/2-turn range.

Don’t be stingy with the T-handle. Adjust the high-speed often to learn its affect on your shock. You will find it to be a much more useful adjuster than you ever thought. With experience, you may be able to blend the low-speed with the high-speed to really get your shock dialed in. Remember this important fact: the more you close off the low-speed compression adjuster, the more oil is forced through the high-speed circuit (once the maximum low-speed flow has been reached). The two adjusters work hand-in-hand, but, to my way of thinking, a quick turn of the high-speed adjuster may be all you need to get to the finish line first.

If you have a suspension question, send it to [email protected].