MO Wrenching: Adjusting Ride Height To Account For Tire Diameter
One thing that many riders fail to consider when changing brands or models of tires – even those marked as the same size – is that the new tire will often alter the outer diameter of the complete wheel assembly. So, if you’ve meticulously set up your bike’s ride height to tune its handling or if you’ve just been happy with the turning characteristics of your motorcycle with the old tires, you might want to account for the change in tire diameter so that you can maintain the same chassis attitude.
If you stayed awake during geometry class, you know that, if the circumference of a circle increases or decreases, the radius does, too. In the case of motorcycles, the radius is the distance from the axle to the ground. Having the front radius increase while the rear decreases could turn your razor-sharp canyon weapon to a slow-steering dump truck.
While you can measure your tires’ circumference when the wheels are still mounted on the bike, the best time to measure the circumference is when the wheel is on the balancing stand. Wrap a metric measuring tape around the wheel, making sure that the tape stays in the center of the carcass. (A thin tape, like Race Tech’s Sag Master is ideal since it bends much easier than wide tapes do.) To get your baseline measurement, measure the properly inflated tire before you replace it. Then remeasure after you’ve mounted and inflated the new tire. Read more...