Newsposted Mar 16, 2012
Tags: General News, How To All Article Tags
Virtually every motorcycle made these days has adjustable suspension of one type or another. Adjusting your suspension for your weight, riding style, comfort and/or performance can be a daunting task. There are knobs and adjusting rings all over the place! What do they all do? Well, that’s a very good question, and one that is a very useful question, because if you don’t know what you are doing, you can very quickly tune yourself into left field, and be stuck with a terrible handling and uncomfortable motorcycle.
Before we get started talking about this, and especially before you pick up any tools, go have a look in your owners manual for a standard suspension setting. If you can find this, you have a baseline you can go back to. If you don’t have this information, we will cover another technique in just a minute.
So what do all those knobs and screws do? Let’s go over a couple of basics. There are three main types of changes you can make to your suspension (some bikes may not have all the adjustments detailed here; see your owner’s manual for specific information):
Spring Preload: Virtually all bikes have adjustable rear spring preload, and many bikes (sport bikes in particular) have adjustable front preload as well. Spring preload primarily affects how the suspension is positioned in its stroke. There is a misconception that spring preload will make the suspension stiffer, but this is not the case. Because all suspension components have a certain amount of static “sag” (the amount the suspension is compressed by the weight of the bike only), increasing the preload will raise the fork and shock in its stroke, the amount of pressure on the spring actually remains the same (unless you run out of sag, of course). Spring preload is mostly useful for problems with bottoming, or not enough of the stroke being used. If you are bottoming your suspension (using the entire suspension stroke), increasing spring preload will keep the fork or shock riding higher, and it will be less prone to bottoming. The opposite goes for not using enough travel, you would decrease the preload.
Compression Damping: Compression damping adjustments influence how the fork will react when it is compressed. More compression damping will make it more resistant to being compressed; less damping will make it less resistant. Compression damping is what most people describe as a fork or shock being “stiff” or “soft”. Changes in compression damping will affect how a fork or shock deals with the front side of bumps that you encounter. As the fork or shock meets the bump the wheel will be moved upward. If there is too much compression damping, the bump force will be translated to the chassis of the bike. Too little compression will make a fork or shock feel mushy, or “wallowy”. Compression damping, from a rider point of view, will mostly provide the proper feel of compliance when adjusted correctly, and reduce the effect of the bumps that are encountered.
Rebound Damping: Rebound is the more mysterious of the two damping adjustments and the more subtle of the two as well. While compression adjustments are almost immediately noticeable, rebound takes a little more thought and experience. As you might imagine, rebound damping controls how fast or slow the fork or shock extends after being compressed. This adjustment is the real “feel” adjustment. When the rebound damping is correct, the suspension will feel controlled, and predictable. If there is too much rebound, the suspension can move too slowly to recover after each bump, and can “pack down”, causing a harsh and out of control feel. It can also not properly follow the back profile of bumps, resulting in a loss of tire contact, and yet more unpredictable feel. Too little rebound can cause a wallowy feel, and in forks, make it feel like the triple clamp is “jumping” up at you. These uncontrolled movements will feed right into the chassis as well, upsetting balance and feel, and also hurting rider confidence.
These are the basics of suspension adjustments. In some sophisticated components there are even low and high speed damping adjustments, but we don’t have the room to cover those details here. Many books have been written about this subject, and if you really want to know about the in depth details of suspension science and engineering, I would suggest you check out a few.
But first, we have to talk about baselines again. I mentioned about stock settings in your owners manual, and those are all fine and good, but your bike might be set up differently than what is in the book. So what we have to do is baseline your suspension first, so we have a home base to go back to, in case an adjustment makes something worse, rather than better. Without a baseline, you can quickly get lost, and make your bike handle worse, not better! Also, make a lot of notes! Write all this information down. Write down the baseline, and write down the changes you make. Then write down what you thought of the change. All of this will help you to keep track of what you are doing, and help you find your way to the best setting possible.
Okay, back to work. Let’s do the spring preload baseline first. Shocks are pretty easy, you can measure where the preload collars are located, and use that as your baseline. On forks that have spring preload, sometimes there are marks on the preload mechanism, but don’t rely on them. You should always count preload in number of turns out from no preload. So turn the preload mechanism out while counting the turns until it is all the way out. That is your baseline preload. Put it back the same number of turns, and we are ready to move on to the next measurement. Damping adjustments are both measured the same way, and they are measured from the adjusters all the way CLOSED, maximum damping. You have to be careful here though. When the adjuster needle touches its seat, you need to stop there, and not apply any pressure to it, or you could damage the needle and its seat. So, from its current location, turn each of the rebound and compression adjusters all the way inwards, until you feel a light resistance. This is the needle touching its seat, and is fully closed. You counted the turns, didn’t you? Some adjusters have a detent, so you can feel “clicks” as you turn the adjuster. This way you just count the clicks, and note that number. Otherwise, count the number of turns. Once you have recorded these numbers, turn them back to the position they were originally in.
In all cases, the next step is to set the rider sag on your bike. There already is a really great article on the Motion Pro website about this subject, you can check it out here.
So now that the sag is set, now what? Well, that’s up to you. Go out for a ride on your bike. What do you like about the way it handles? What don’t you like? Write this stuff down. When you make changes, you want to make sure that you keep the behavior you like, and change the behavior you don’t. Look at the descriptions above about what the various adjustments do, and apply that to your bike. Here are some examples:
Your bike feels stiff over bumps, and particularly kicks back through the seat: This is most likely too much compression damping. Reduce the compression a couple of clicks, more at the back where it seems to be more of a problem. Test ride again…
Your bike feels wallowy under hard braking in a straight line: This is most likely too little compression damping in the fork, allowing the fork to bottom all the way and not work over the bumps you encounter. Interestingly, this also could be too much rebound in the rear, which does not allow the rear wheel to properly track in the back.
Your bike runs wide on the exit of corners on the gas: This could be too little compression in the rear, allowing the rear to squat too much, or too much rebound in the front, not allowing the front wheel to track properly under acceleration.
As you can see, there are a lot of possibilities here, and you may notice that the front can affect the rear, and vice versa. Everything is connected here, and a change in one area can affect many other kinds of behavior. At the risk of repeating myself (this is important though) make lots of notes, and don’t be afraid to experiment, but be aware that changing your settings will change your handling, and so always approach testing changes with caution until you become familiar with what each change will do.
That’s a lot of information, but it’s really just one step out of the door, all things considered. For more information there are a lot of books and publications on the subject of motorcycle suspension, and many people make their living specializing in suspension tuning. If you are really serious about getting the most out of the handling of your motorcycle, you should seek out someone in your area, who can assist you with valving changes, suspension maintenance, and other tasks. Check out their tool boxes first though, and make sure they are using Motion Pro tools, since that is the mark of a true professional…