Tuesday Tip: A Lesson In Suspension—The Two Main Elements

As most of you know, Ross Maeda is the U.S. front man for Kayaba, and the driving force behind Enzo Racing (and as he likes to remind Swap, the older brother) in the Maeda family.

Since Ross really knows his stuff when it comes to suspension, for this week’s tip we asked him to help us all better understand two of the basic components of suspension tuning:

  1. Springs: Proper spring rates and setting sag.
  2. Damping: Adjusting clickers for specific problems.

That’s all it took to get Ross rolling, so we’ll let him take it from here…

“The springs are the coil springs that work in conjunction with the oil level, and the damping consists of the adjustment clickers and the valving.

“You can ride the bike if the valving isn’t quite suited for you, but if the spring rate isn’t correct for your weight, you’re wasting your time. The most important thing about the springs is whether or not you’re in the proper weight category. The exception to the rule would be Supercross, but that doesn’t apply to the general public.

“If you’re at the light end or actually lighter than the target weight range (of the springs your bike is equipped with), you’ll have to get a softer spring. If you’re heavier or toward the end of the spring’s target weight range, or you’re a faster rider, you’ll have to go to a stiffer rate spring.

“If you’re too heavy for the bike and you have the wrong spring for it, that’s the first thing that you have to fix. You cannot compensate for a spring that’s too soft with damping.”

Here’s where things start to get interesting…and more complicated.

Springs are load or position sensitive, but not speed sensitive.

Damping is speed sensitive. We’ll let Ross sort out those statements.

“If you have a hundred pound spring and set a hundred pounds on it, it will compress one inch. If you set two hundred pounds on it, it will go down two inches. However, if you drop a hundred pounds on it the spring will collapse more than an inch, but will return and settle at one inch of compression. In other words, if you add speed to the equation the spring can’t handle it. It can deal with the load but it can’t deal with the speed.

“Damping on the other hand is like water. It’s speed sensitive. The faster you stroke your arms through the water, the more resistance there is. If you stroke your arms slowly, it becomes easier. So that element is speed sensitive, but it is not load sensitive. It’s important that both elements (springs and damping) are working together. So basically speaking, if you don’t have enough of the spring element to hold you up in a proper place on the bike, you’re lost. Therefore, the most important thing initially is to get the proper spring. And to maintain proper balance, it’s important to get front and rear springs together, and not just one or the other.”

Okay, now that you have some of the basics (and understand the importance of having the proper spring rate on each end), it’s time to start tuning. Take it away, Ross.

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“The process of setting the sag is to first put the bike on a stand, un-weighted, with the rear wheel off the ground. Take a measurement from two points. For example, from the edge of the rear fender at a specific point, to possibly the corner of the chain adjusting block or the center point of the axle. Record that measurement. (These are most often measured in millimeters.)

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“Then take the bike off the stand, place it on level ground, and have the rider sit on the bike directly above the footpegs. Take a measurement at the same two points again. Subtract that number from the first figure, and that your sag measurement. In metric units you’re shooting for a measurement between 90 and 110mm. 90mm is a low number but a high sag because the spring is not compressing as far. 110mm is a high sag number but a lower sag because the bike is sitting lower. Anywhere you end up in-between this range is personal preference.

“If you run a low sag number, in which the bike is sitting high (like 90mm), then it may steer a little bit better, but may also tend dive a little bit too much in corners or whoops. Running a higher sag number (like 110mm) would be more suitable for a person that wants a low ride height (i.e. wants the bike to sit a little bit lower).

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“The rule of thumb is 100mm. If you check the sag and it’s a really high measurement like 80mm, you have to reduce the preload by turning the shock’s spring collar counterclockwise, relieving preload. If the sag measurement number is too high, meaning it’s sitting too low, you have to turn the spring collar clockwise to tighten the spring preload.

“The overall importance of setting sag is choosing a stationary preload measurement on a spring. The whole time you’re riding and you’re loading and unloading the suspension, you have to have a starting point.

“Now that you have the scoop on setting the rear shock’s sag, it’s time to get a handle on what the clickers do to change the fork and shock’s damping characteristics. That means it’s back to Ross for the explanation.

“There are two damping adjusters on a front fork. There’s the compression adjuster, which controls how fast the fork goes down (compresses), and a rebound adjuster, which controls how fast the fork rebounds or returns to its extended length. Generally on Kayaba components the rebound adjuster is on the top of the fork and the compression is on the bottom. On Showa components it’s the opposite.

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“On the rear shock the rebound is on the bottom, underneath the swingarm, and the compression is always on the reservoir. There’s a high and a low speed compression adjuster on most shocks.

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“High and low speed compression was originally intended for the different speeds that the shock compresses at. On a dyno test those adjustments will affect those speeds. From a tuning standpoint, it’s better to consider those adjusters as stroke length. A low speed adjuster will affect situations where a shock is making a short stroke, whether it’s at high or low speed. If it’s a situation where you’re using a lot of stroke, either slow or fast, you want to adjust the high-speed adjuster. Basically speaking, what those adjusters are controlling is the amount or the volume of oil that’s being forced from the shock body into the reservoir tank. If you’re taking short hits then it’s just pumping small amounts of oil through, so the high-speed adjuster doesn’t have much play. If you’re using a lot of stroke, even if it’s at slow speeds, you’re moving a large volume of oil from the body to the reservoir, and the high-speed adjuster will make more of a difference.

“Generally speaking, compression adjustments are more important than rebound because the compression speed on a fork or shock is always much higher. How fast the fork or shock compresses is dependant upon how hard you hit something or how hard you come down. Rebound, on the other hand, is basically controlled by the spring. The highest shaft speed that a rebound ever sees is after full bottoming because that’s when the spring has the most energy. That’s the fastest it will ever see. So basically, the rebound damping’s maximum shaft speed is always slower than compression, by quite a bit. Playing with compression a bit more than rebound is common as so many problems we see are due to compression issues.

“Example: You may think that the rear end of the bike is kicking up when going through holes or hitting square edged obstacles, but in actuality what’s happening is the fork or shock may be compressing too far and too quickly. In other words, it’s going down too deep in the stroke and then coming back with a lot of speed. If you were to simply slow down the rebound, the spring would still compress the same distance, but would come back up too slowly and pack. The rear end will still kick up but the tire will be further up into the fender. In this situation you’re better off adjusting compression so that when you hit that bump it only uses half the stroke.”

Of course, that’s just one example. Obviously suspension’s a complicated science and this article could go on forever if we discussed every scenario. But we appreciate Ross filling us in on some of the starting points to understanding how to dial in your suspension.

ion a bit more than rebound is common as so many problems we see are due to compression issues.

“Example: You may think that the rear end of the bike is kicking up when going through holes or hitting square edged obstacles, but in actuality what’s happening is the fork or shock may be compressing too far and too quickly. In other words, it’s going down too deep in the stroke and then coming back with a lot of speed. If you were to simply slow down the rebound, the spring would still compress the same distance, but would come back up too slowly and pack. The rear end will still kick up but the tire will be further up into the fender. In this situation you’re better off adjusting compression so that when you hit that bump it only uses half the stroke.”

Of course, that’s just one example. Obviously suspension’s a complicated science and this article could go on forever if we discussed every scenario. But we appreciate Ross filling us in on some of the starting points to understanding how to dial in your suspension.