INSIDE TECH L
Front sag AND a few questions
ast month we discussed, in detail, how to set the rear shock’s preload properly to achieve target rider sag. Everyone should do this on every motorcycle! Even the cheapest bikes have facility to adjust the rear preload as rider and passenger or gear weight changes and has a dramatic, and sometimes even dangerous effect on a motorcycle’s handling. We discussed the procedure and I promised that this month we would discuss the front sag and how to adjust the preload properly. As discussed last issue, the first step is to get a ‘front top-up’ number. The easiest reference point to measure front wheel travel is along the shiny chrome fork tube. On an inverted fork where the upper fork tube is larger than the lower tube, we will measure from the fork seal wiper down to the cast aluminum portion of the foot. This number is often the same as the full available wheel travel, but is occasionally more. In our example, let’s say it is the very common 127 mm (strangely close to five inches... lol). On older conventional forks where the smaller male fork tube is up in the triple
50 Inside Motorcycles
By John Sharrard
clamps, we will measure up from the fork wiper to the lower portion of the bottom triple clamp. Now, to extend the suspension fully, the front wheel has to be off the ground. A centre stand is ideal, but you will need to get the rider to lean on the back of the bike as centre stands are usually biased to get the rear wheel off the ground. A gentle push down on the back of the bike will pop the front tire off the ground. If the bike doesn’t have a centre stand, you can carefully pry it left onto the side stand, or use other proper stands to allow the front wheel to dangle freely. Obviously, you cannot use a front stand that goes under the two fork legs; these are common for brake service and checking tire pressures and they are common at racetracks for the installation of tire warmers, but they do not unweight the springs. Now that the front tire is elevated and you are ready to begin, a mistake is often made when doing sags. Yes, we need to measure our top-up reference at this time, but, we need to ensure the forks are fully extended! There are small top-out springs inside your forks that are
