Balancing Your Motorcycle Wheels & Tires: Part I

Tire imbalance can cause quite a bit of discomfort to the rider and speed up the wear on bearings, tires, and other parts subject to vibration. Motorcycle tires are generally static balanced only, but they may be spin-balanced at a shop that has a strobe-light balancer and that is far preferable.

To static balance a motorcycle tire, first mount the wheel assembly on a wheel-truing stand. If you don't have access to a stand, loosen the brake adjustment, bearing tension, chain, speedometer cable, or other hindrances so the wheel will turn very freely on its own axle when elevated. Simply counterbalance the heavy spot on the wheel with motorcycle wheel weights (available at your cycle shop) attached to the spokes on the opposite side of the wheel until the wheel will remain at rest wherever it is set. Heavy solder wound around the spoke can be substituted when wheel weights are not available. On a small machine, a wheel out of balance can lower the top speed by 5 to 10 miles per hour (8 - 16 kph). On a large machine, poor wheel balance can contribute to high-speed wobble. In either case it pays to have precisely balanced wheels..

Truing Wheels

A "true" wheel is one that is perfectly round with the axle in the center and has no radial run-out, lateral run-out or side wobble. As in balancing, wheels can be trued either on or off the bike. They may also be trued with the tire mounted or dismounted.

Only slight corrections (less than 3/8 inch or .95 cm) should be made with the tire mounted. Greater corrections call for tightening some spokes so much that a spoke end may eventually puncture the tube. Also, it is safer to correct only lateral run-out with the tire mounted. Remove the tire if any significant radial run-out is encountered. The best procedure is:

1. Make sure that the axle is tight, that wheelbearing play is minimal, and that all of the spokes are "snug," not loose.

2. Mark the high spots and low spots with chalk. Also try to indicate the extent or range of the entire "warped" area.

Note that all of the spokes are attached to the center of the rim, but some are attached to the right side or left side of the hub. If the rim needs to be pulled to the left, loosen the right spokes and tighten the left ones a like amount. At the "high spot" loosen the spokes on the high side first, loosening more in the center of the high area. Decrease the amount of loosening as you get to the baseline or true part of the wheel so that you are loosening only one-quarter turn at the last spoke. Tighten the spokes leading to the hub on the low side the same amount you loosened the corresponding high-side spokes. Repeat this procedure until all the spokes are tight and the wheel is true.

Remember, however, for a freshly laced wheel or one that has severe radial and lateral run-out the best approach is to mount the wheel on a truing stand.

The first step is to eliminate radial run-out or "out of roundness." Loosen the "short" -side spokes by using the tapering or graduated technique used for lateral run-out. Then tighten the long-side spokes, again tightening more at the extreme high point and gradually reducing the turns as you approach the "base line." Repeat this procedure until the wheel is perfectly round and all the spokes are tight. Now proceed to a lateral truing sequence. Remember to loosen the high side first and tighten the same amount afterwards on the low side.

After the wheel is perfectly trued, grind off all protruding spoke ends flush with the nipple, clean out the metal filings left from grinding, reinstall the rim strip, and remount the tire.

Replacing a Rim

Replacing a rim can be a very simple, easy job if you follow certain steps to organize your approach to the task. Remember that there are both "inside" and "outside" spokes on each side of every wheel and that some wheels even have long and short inside and outside spokes. Spoke patterns vary according to the size and use of the machine: even spoke diameters vary with the size of the bike.

Before beginning the project, obtain any spokes you might need to replace broken ones. A spoke wrench, a screwdriver modified for spoke work, and some masking tape are also handy.

The most reliable method for relacing a wheel is the "tape the spokes trick." Simply tape the spokes together at their various intersections or crossing points. Remove the nipples and lift the rim off. Replace any broken or damaged spokes and retape them in the proper position. Remember where the valve core hole goes and install the new rim the same way.

Another technique especially useful if you're building up a wheel from scratch is to install all of the inside spokes first.

Continued In Balancing Your Motorcycle Wheels & Tires: Part II

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