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or the past few months, I have packed your heads full of suspension basics. Although some racers have more space in their heads than others, it is now time to tie it all together and do some real set-up. This is the good stuff, so read closely. Oh yeah, we’re only about three issues away from the ever-boring topic of horsepower.
Lets begin by doing a baseline damping set-up, starting with the shock rebound adjuster. It is located at the base of your shock (unless you ride a Buell) and will be either a small screw or a knob of some type. Almost every adjuster works like a mixture screw on a carburetor. If you turn it in, oil flow is restricted, and the suspension moves more slowly. If you turn the screw or knob out, there is less restriction, and the suspension will move faster. Almost all racers refer to this as “harder or softer,” and that confuses people. The way to think about it is “faster or slower,” since that is what you are actually trying to accomplish by turning the knobs. Just so you don’t say I tried to mislead you, “faster” does not mean you will go faster. Man, I crack myself up. . . Anyway, turn the knob way in until you can push on the seat (with a friend balancing the bike off of both stands), and watch the back end rise. It should return very slowly. If you can’t get it to rebound slowly enough, then a revalve is in order. There is no Band-Aid for this situation (ala, mount your pogo-stick and ride Cap’n). If it does appear that you have plenty of damping available, then back the screw out until the back end of the bike rises pretty quickly. This is difficult to describe on paper, so I will explain it as well as I possibly can. In real time it should take about a second for it to rise from a hard push. If you can’t make it to “one,” then it is too fast. Again, you should be able to watch it damp, but it should still be fairly quick. If you push lightly on the seat (like leaning on it), you should be able to get some action out of the suspension. If you can’t , then this is a good sign that you have an overly-preloaded spring. If you have the correct sag number and the bike tops out and has no initial plush action, then your spring is too soft (hint, see previous installments). Set your compression knob, which is located on the shock reservoir, to the softest setting. Stand on the left rear of the bike with your left foot on the peg, lean over the bike, and use your left hand on the seat and your right hand on the pipe. This will allow you to really mash the bike. Feel how much resistance, if any, it puts up on the down stroke. Then put the adjuster in the middle of however much adjustment you get. You should feel a difference. If you don’t, then continue on. Set the adjuster to full hard and back it off a click (set Fox to “8”). There should definitely be a difference by now. If there is none, then off to the suspension shop it needs to go. If you have a Fox shock on a GSXR750 or a Honda Hawk these are two popular shocks that work poorly. Current Ohlins GSXR shocks have little or no rebound damping. Not that the units themselves are bad, the valving doesn’t work. This is easy to have fixed by a suspension shop. It’s a definite bummer to have a new $1,000+ shock revalved and resprung before you even use it, though. The real problem here is that when the end user (that’s you) buys an aftermarket shock, they install it and assume that since they have just invested a ton of money that they must have a good working component. If you think your shock doesn’t work better, then let the manufacturer know. That’s the only way that the product will improve. The trick is finding someone who will take you seriously, since they are the manufacturers and you are simply a Novice club racer. Penske wins in the support category, hands down. Penske has the best out-of-the-box valving for road racing motorcycle shocks right now. For your edification, any of these shocks could be valved to work as good as the next. Only a shock-dyno will tell the subtle differences. Your wallet will feel the difference immediately. My pick of the litter for Novice racers is a Gold-Valved stock shock, retailing at $350 with the correct spring. Some models of bikes benefit from a ride height adjuster, and then you may want to buy an aftermarket shock; these bikes are F3s, FZR400s, and definitely Honda Hawks. If you ride a Hawk, don’t get caught in the 900RR stock shock swap, or you will have pissed away money that you could have used to buy a real shock. Those of you shopping for aftermarket shocks have to watch for a couple of other things. Progressive suspension makes O.E.M. replacement shocks that have nothing to do with racing. WP is in some sort of restructuring mode and we’ll have to wait to see what comes of that. Ohlins has passed their distributor rights several times in the past few years and I’ll let you figure out what that means on your own. Fox, although having good parts availability, has the most embarrassing shipping system in the entire motorcycle industry. They will tell you themselves over the phone, that even if you order next day air, the fastest your stuff will leave the premises is three days! Brenda at Fox is very helpful, but her hands are tied usually. If you decide to invest the duckies and buy an aftermarket shock, I have often referred to the Fox Shock as the 350 Chevy of shocks. It is affordable and simple to maintain, and retails for $595. However, Penske sells a shock that they call “entry level” for $725 that is way more bang for the buck than the Fox. It is upgradeable at any time by changing the reservoir. This allows you to grow into a more technically complex shock as you riding and tuning skills improve. Back to the compression adjustment. What I like to feel here is some sort of definite resistance to compression. If you are unsure about this step, then set it in the middle and ride it. Come in and turn it in full-hard, minus one click, and go ride it again and see if you notice a difference. If your shock is valved correctly and is working properly, then you should definitely notice a difference. For baseline set-up, just think of your compression adjuster as three settings: Slow, medium, and fast. To summarize, a shock should:
This should bring an end to a thoroughly shocking experience. That’s okay, I didn’t laugh at that one either. Now we have reached a fork in the road, I mean frame. Stand to the left side of the bike and use your left hand to push on the left bar. Your fork should have the same initial plush action as the shock with little effort on the bar. It should sag about 15mm under its own weight. If you bike sags more than this, then you probably haven’t changed the stock fork springs. This will put you on the “List” with the three-toed sloth, the iguana, and Frank (it’s a Budweiser radio spot. . .). Stop reading my column and go directly to The Crash Page. Do not collect contingency or trophy. If you have compression adjusters (at the base of the fork), turn them most of the way out and push on the fork. Grab the brake and stroke down firmly on the front end. Try to push it to the bottom with quick, even force. After you push, let the fork rise freely, but just lightly hang on the bars, so that you keep pressure on the brake. The rebound damping on the fork should appear quicker visually on the fork than on the shock. Mike Ciccotto, AMA Pro racer for the Hooters Racing Team has a pretty good tip for a baseline set-up on your fork. If you compress the fork, it should rise, top out, and stop. If it can rebound fast enough to top out, and start back down again, then it is too fast. Conversely, if you can watch it rise to top-out, then it is too slow. Set the compression adjusters to the middle and feel the change. This mental process should go the same as the shock. If you are unsure about this step, then go ride the bike along at about 10 or 15 mph. Snatch the brake and see if the fork slams the bottom. If it does, then dial in compression just until this goes away. Use as little as possible. If you have to turn the screw all the way in and it still hits the bottom hard, then it’s revalve time. Don’t misunderstand me. The fork should dive; it should not hit bottom. There is a definite difference. The above mentioned philosophy should be executed whenever possible with your suspension: “Use as little as possible.” The problem with rebound damping is that it provides a false sense of stability. Race Tech’s Paul Thede warns that you can actually improve the feel of a motorcycle by dialing in rebound damping long after you have passed the point of maximum available traction. Take note that this is particularly dangerous with the fork. Too much rebound damping here will cause “packing,” which means that the suspension compresses, but can’t return quickly enough before encountering the next irregularity in the pavement. This means your suspension is stuck down and you are on struts. This makes you fall down and go boom! You will then have to dig into your spares kit that you have been amassing for these months. You do have a spares kit, don’t you? Movement in your suspension is a good thing. It’s supposed to move, and too many “Expert” racers think that stiff is fast. The most common thing I see racers getting all worked up over is their zip-tie. “My zip-tie is all of the way at the bottom. I need my suspension stiffer.” A zip-tie wrapped around the fork is very commonly used as a travel indicator. It’s pretty much useless information for many reasons. Many forks do not travel the entire length of the visible fork tube. Conversely, some do use all of the travel. If you have a zip tie on this type of fork, and the fork hits bottom, then you will damage the dust seal and potentially the fork seal.
Choose the correct springs for your fork from my Top Secret Traxxion Dynamic Fork Spring Rate Selection Chart. I’m only going to print these numbers once so pay attention. The correct spring for your shock will sag 20-25mm and have 4-5 mm of sag under its own weight. I’ve hinted at this before. If you are smart, you will not forget that I have said this, and that is all I will ever say about this subject. You will not need a zip tie or a stick, because you will have the right springs and it won’t be an issue. If you can feel you fork hit bottom, then it’s time for a change. But if you are using all of the travel, and you can’t feel it hitting bottom, then why would you want to restrict that by stiffening the fork? This is actually optimum. If you are happy with the way the fork works, but can feel it hitting bottom, then you can raise the level of the oil in the fork to stop this. The oil level in the fork controls bottoming resistance and comes into play only in the last portion of the stroke of the fork. Oil is not compressible, but the air above it is. It acts as a second spring in your fork. This is a tuning variable you may never use, however, and is relatively complicated for most racers to perform trackside since most bikes now have cartridge forks. Incidentally, if you have a fork seal that begins to weep, your bike will not do anything dramatic or handle any worse. The bigger concern is that the oil may get onto your brakes. If the thing is puking oil, then I would not ride anymore until it is fixed. Have both seals replaced, because the other is about to go, and this will ensure that you have the same oil type and viscosity in both forks at the same level. Back to travel indicators. There are devices that you can buy and fit to the back of your bike like the Ontario Stick, developed by all around guru-guy Kaz Yoshima. The primary reason they don’t tell you anything useful is that they only record the sharpest hit or greatest compression. Jeff Ryan, General Manager and Technical Director at Penske Racing Socks confirmed this for me. Let’s say that your bike handles totally bitchin’ and you can’t believe that life could get any better. But just before the start/finish line there is a huge pothole, or a jump, or a “g-out” type depression. The indicators on both ends of the bike will be bottomed out and you are going to get off of the track, look at them, and assume that you need higher spring rates. Even worse, you might over-preload your springs and dial in all sorts of compression damping. You will leave the ballpark and be lost in the parking lot. The only way to actually know where your chassis is really working is with a data acquisition system. This is usually beyond the realm of what we are attempting to accomplish within the restraints of a club racer’s budget. As I’ve said before, you are the only sensor we have to work with, so you’ll have to do. If there were a $100 stick that could tell you what spring to put on your bike, I’d knock you over to be the first to buy one, but as of this date, save your money for something less trick, like new tires. Now we have to check for balance. This is the most important thing to strive for in set-up. Most people think of suspension as the front wheel moving over a bump and then the rear wheel moving over a bump. In reality, they work together. Think about a bump moving under your bike at 100 mph. Let’s be extreme and just call it 50 mph. Do some math with me -- 50 mph is 880 in./sec. and that means that on your 53.5-inch-wheelbase bike it takes 0.0607-second for the bump to pass from the front of the bike to the rear of the bike. For all intents and purposes, this minuscule amount of time is irrelevant. To check for balance in a static environment, take your bike off the stands and stand to the left side of it. Put your left hand on the left bar, your right hand on the tank, and your right foot on the left peg. It’s a twister!!! Leave your left foot on the ground, or you may need your spares again. Push down evenly on all three of these points. This will take some practice, and will seem awkward. What you want to be able to feel is the plushness in the bar, and also at the peg. Remember, light pressure should get the suspension to move. Now push lightly on all three points, and if everything is right, it should work very uniformly, down and up. If it passes the soft push test, mash it hard and the results should be the same. Even compression and even rebound. Have a friend stand 10 feet back and watch the action of the suspension. It should look like one bike on one shock, right in the middle. If it doesn’t, then make it so. Fine tune the spring preloads to make the bike balance. Don’t get too worried about changing the sag; it only serves as a starting point and is not to be etched in stone. Tune the damping to get the action to match at both ends. Suzuki TL1000S, TL1000R and most Ducati models have a peg and swingarm pivot arrangement that is not right for this method to work well. The new ZX Kawasakis are a little difficult to feel this way. You will have to feel each end separately. A sure-fire method is to ride the bike along slowly and lift up slightly and bounce on the suspension, like a jockey on a horse. The results should be the same. Balance, Daniel-San, balance. Now, for the first time ever, you are actually ready to go for an enjoyable test-ride. Pay close attention to what your bike does as you ride. Soon we’ll tune out your chatters, wallows and wobbles, just in time for you to win your first National Championship. - Max McAllister |
