Weekly Cycle Tip: Wheels, Round & Straight
Our bicycle wheels deserve a lot of credit. A good wheel will stay “true” and support literallythousandsof miles of riding. But how often do we devote any time or thought to their care? There are some simple steps that any user can perform to assure that all is well. If your bike is equipped with rim brakes, the inspection process is fairly easy. If you have disk brakes, there is a decent alternative.
The goal in this is to inspect a wheel to confirm it is functioning properly.
A good wheel needs to meet three criteria.
1) It should be “true.” That is to say that the rim should not vary from side to side.
2) It should be round.
3) The hub should be correctly adjusted.
To check a wheel’s “true,” move so that you can line one eye up sighting along the side of the rim and, comparing the gap between the rim and the brake pad, then slowly rotate the wheel. The gap should remain very constant as the wheel is turned. A variation of 1 - 2 mm is acceptable.
“Roundness” is checked by sighting the rim from the side and, using the brake pad as a reverence. The wheel, when slowly turned, should not deviate up or down. A slightvariation, less than 3 mm, is acceptable.
To check hubs, first gently pull the rim from side to side. If the rim moves, the hub bearings are loose. If no “side-play” is present, lift the wheel from contact with the ground, and gently spin it. If it moves freely, all is well. If it requires constant assistance to keep turning, then the hub bearings are likely over tight.
If you have disk brakes: You will need to provide a visual reference to perform the first two checks described above. Hold a screwdriver against the frame, such that the tip is close to the rim. Use the screw driver as a substitute for a rim brake. This will work as a “field expedient” for checking both “true” and “round.”
Disk brakes and hub inspection: An improperly adjusted disk brake can cause drag in a wheel, even if the wheel is not on the ground. To check for this, sight into the slot in the caliper, there should be a small amount of “daylight” on both sides of the rotor, all the way through a full rotation of the wheel.
Cyclists should check wheels frequently. Problems with wheels are usually a lot more repairable if they are caught early.