Wheel Balancing for your Safety

When installing a new tire, it's a good idea to put the rim on a truing stand to measure radial runout. Check lateral runout at the same time to ensure it's within 0.030 inch. Radial runout is up and down variance from concentric. If the rim has, say 0.030 inch or less radial runout, a wire spoke rim needs to be retrued to bring the radial runout within specifications. A cast rim may need replacing depending on how far above 0.030 inch the radial runout actually is.

Most motorcycle manufacturers advice replacement if radial runout exceeds 1/32 inch, which equates to 0.03125 inch. It is easy to instruct this, but not everyone has deep pockets, so compromise may save some money. I do not get antsy when replacing a rim for less fortunate customers until hitting 0.040 inch radial runout. I explain the pros and cons and let the customer decide. However, if it goes higher than 0.040 inch, then it becomes a safety issue in my mind, and I will dig in my heels and refuse to reinstall the rim.

After mounting the tire, check the radial runout once again. If up/down runout goes beyond 0.090 inch (2.30mm), then it's necessary to remount the tire. Tires are not as precise as metal rims. This is why the radial runout measurement climbs from 0.030 inch on a rim to 0.090 inch on a tire. If the tires radial runout stays at 0.090 inch or more, the tire is defective and in need of replacement.

A hopping tire will create vibration. I also check lateral or side-to0side tire runout. Since the rim has already been checked for both radial and lateral trueness and is known to be good within 0.030 inch, the tire should have a maximum lateral runout of 0.080 inch (2mm). If this runout exceeds this amount, then remove and remount the tire. If it's still above 0.080 inch, replace the tire.

Wheel bearing must be in serviceable condition or they may cause adverse handling reactions and vibration. End spacing is crucial for the same reasons. Wheels, tires, and support bearings are all that's between the rider and the unforgiving pavement. Many ignore these safety items at their peril.

Wheel balancing is crucial to good handling, especially at high speeds and light motorcycles. Unbalanced wheels cause lots of vibration. Static balancing is done with the wheel at rest, being hand-turned while in a wheel truing stand or jig.