Motorcycle Suspension Setup
If you were asked what the most important component was in your suspension I wonder what the answer would be. Well rest easy, I wonít ask Iíll just tell you, itís your spring. Yes thatís right the springs on your bike are the most important item when it comes to good handling, smoothness, road holding, feed back, and control. Contrary to what you may read in advertising or be told by the bloke down the road who has XYZ, revalving is not where most of the improvements are. Sure they do work and can improve both handling, feedback and stability, but if you donít have the correct spring for your weight then all the revalving in the world wonít make the slightest bit of difference, except of course to your bank account.
Last year I was reminded of the importance of finding the right spring with our race bike, a Yamaha R1. At the start of the season it was re valved and sprung but at some point the springs were mixed up and the wrong ones were installed, we finished up with no end of trouble trying to make the bike behave properly. In frustration after that first race meeting I sent all the springs we had away to be tested and marked, it turned out that while we thought we had .9kg springs in the forks we actually had .75kg springs, it doesnít sound like a big difference but in terms of spring rates that is huge. No wonder we couldnít make sense of what was going on at that race meeting. Once the correct spring was installed everything just fell into place, lesson learnt.
A set of springs to suit your weight cost around $190.00 on the front and $180.00 on the rear plus fitting.* Once they are fitted it s very important to set up the sag. Sag is just as important as getting the correct spring, if itís not in the ball park your wasting your time.
A young MX rider who we are helping this year was recently complaining to me that he couldnít hold the throttle tapped out in a straight line without it trying to buck him off.
ďCan you adjust the rebound up so it rebounds slowerĒ he said. I questioned his reasoning as he already had a lot of rebound anyway. As a rule, the less rebound you can get away with the better so I suggested that we see how much sag itís got first. When I measured it up he had 70mm of sag, he should have had about 90-100mm and as a result the suspension was unable to compress enough to soak up all the bumps.
Contrary to what many people believe this is not rocket science or a black art, just plain old common sense and mathematics - what goes up must come down.
Measuring sag is very simple, and should be the first job when ever buying a new bike. You see, it wonít just tell you whether the measurement is right but it will also indicate whether you have got the correct springs installed for your weight. All you need is a tape measure and a couple of mates.
On the end of the swing arm and tailpiece or rear guard make a reference mark to measure between. Get one of your mates to stand in front of the bike and hold it upright while you lift the bike from the tail end taking all the load off the shock so the swingarm is fully extended. Take a measurement at this point. For this example weíll say its 500mm. Now while your mate is holding the bike upright sit on it with your feet on the pegs bounce up a down a couple of times and return to your natural riding position. Get your other mate to take a measurement from the same reference point as before, this measurement should be 25-30 mm less than the 1st measurement, i.e. 470-475 mm, or about one third of the total shock travel. On an MX bike it would be 90-100mm. If this distance measures 485 mm the spring has too much preload and you need to take some off, if itís the other way add some preload.
If you need to wind the spring up more than 2-3 full turns it is very likely that the spring is too soft for your weight. The rear spring should have no more than about 10-12 mm of preload. Do exactly the same on the front, take measurements fully extended and with you sitting on the bike, one third of fork travel should be around about 40 mm.
I am a bit vague on these measurements because it is not a hard and fast rule. Some guys like it a bit firmer and some a bit softer, either way it should be close to these measurements to be on the money.
If this is all a bit too hard then ask for it to be done
the next time youíre in and weíll do it for you, youíll be amazed by the
difference a simple thing like this makes. The best thing of all, its dirt
cheap, everything you need is already there.
*Please check prices.
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