Suspension part 3

The One G Test

The One G Test backs up what we have already done in setting the static sag of the motorcycle, and takes into account the particular weight load that is going to be carried and the way the bike is going to be used. This is the part that most riders listen up!

To be effective, the measurements need to be done with the normal weight load (i.e. the rider) in place. If you are a courier for example and carry a reasonable weight on the back of the bike for a large percentage of the time, or you only ever ride with a pillion in place, it would be a good idea to simulate that situation for the purpose of measuring. If you were planning a touring trip with baggage, but still wanted the bike to handle at it’s best for the roads you plan to ride, you could reset the static sag to suit the weight load carried for that period of time, then change it back to the way it was once the trip is over.

To do this correctly you will need a measuring tape and three helpers. Two to balance the bike with you in place, while a third person measures the sag. First, you need to know how much travel your suspension has by extending it fully and measuring in the direction of travel, just as we did to set the static sag. On the forks this is easy as you simply measure from the top part of the lower fork leg, to the bottom of the triple clamp.

On the rear, you need to pick two points that are at each end of the travel. For example, the grab rail and the axle. Unload the suspension fully by taking the weight off it and measure as shown last issue. This will give you the unloaded distance.

Once you have this measurement, the rider (and any other normal weight load) should be put on the bike as per the pictures shown, with helpers holding the bike front and rear. The rider should then bounce the bike up and down a few times to free up the suspension and put it in the position it would normally sit in with the rider in place. The designated ‘measurer’ should then measure from the same points the first (unloaded) measurements were taken.

The difference between these two figures (the sag) should fall somewhere in the vicinity of 25-35mm front and rear. If you find your bike is either less or more than this, simply adjust the preload either harder or softer using the preload adjuster, until it falls within this range.

Often times bikes that have done a few kilometres will sag way beyond ideal settings, as will new bikes sometimes. As a matter of fact I have measured brand new sport motorcycles that have never been ridden and found they have more than 50mm sag front and rear! As you make adjustments you may find that you get to one end or the other of the existing springs range. If this happens, it means the next spring available (either heavier or softer) is probably going to be on your shopping list.

Often times riders try to make up for a lack in one area of suspension by adjusting another. In this example, if the bike were still too soft after the preload was adjusted fully, you could turn up the compression damping to try and slow the speed of movement downwards. This would begin complications that could severely effect the suspensions ability to function. If you were to arrive at this point, speaking with an expert (as opposed to “pub experts”) is really the only course of action.

Next issue we’ll talk about the final point in getting the springing right in your suspension, and start to figure out what to do with the damping.

Good Luck with your riding...