LUC’S TIPS JULY 2013: Motorcycle Brake Rotor Inspection Before Hitting the Twisties
Last Updated: April 1st, 2024
The wheels on the motorcycle go round and round. Round and round. How do we stop those wheels from turning? We use our brakes. For most modern motorcycles, the use of a braking system that includes pads and rotors are common. Before you hit the twisties this summer, you’ll want to make sure your rotors are in good shape.
WHAT IS A BRAKE ROTOR?
The brake rotor is the part of the braking system that literally gets squeezed by the brake pads. In most cases it is mounted to the hub of a wheel. When a rider squeezes the brake lever, hydraulic fluid pushes brake pads to make contact with the spinning brake rotor. The resulting friction from this squeezing process slows us down. Sometimes, after extended, improper, or high performance usage, brake rotors can reach their limits. Some riders will initially notice this by a pulsing of the front end when brakes are applied.
VISUAL INSPECTION
First, before going hands on to inspect your brake rotors, we recommend elevating the end of the motorcycle you’re inspecting so that the wheel can turn freely.
Second, we recommend wearing latex gloves that are free of oil or grease; we don’t want to contaminate our brake rotor!
Third, we want to check both sides of the rotor to make sure both sides are wearing appropriately, are relatively smooth, and free from deep gouges. We can check for the following major issues:
- Excessively deep scoring or grooves (some light scoring or grooves are typical)
- Glazing (glass-like appearance in the surface; typically caused by pads that are lightly and constantly rubbing on the rotor – especially people who “ride” the rear brake by constantly applying a little bit of pressure to the rear brake)
- Blueing (the rotor will turn blue and have a slight rainbow-like tint)
- Hot spots due to excessively high temperatures (hot spots resist friction from the pads, thus braking power is lost)
- Rotor contamination from grease, fork oil, brake fluid, or other contaminants like grease.
- Cracking or breaking of the hub (webbing) where the rotor is mounted to the wheel.
- Excessive wear beyond manufacturer specification (measure rotor thickness with a micrometer at various points to determine if thickness is out of spec.
If any of these symptoms are present, braking power can be compromised, and severe cases may require a replacement of the rotor. If none of these symptoms are found, but pulsing from the front end occurs, measuring brake rotor run out may be necessary.
MEASURING RUN OUT
Measuring run out isn’t something we’d typically do at home; we’d typically see a dealer or reputable repair shop at this point. However, if you’re handy and know how to use a dial gauge, then give it a shot. It is important to note that if the brake rotor measures out of run-out spec, then we don’t want to replace the rotor just yet. There may be an issue with the wheel bearings. Inspect the bearings before replacing the rotors as bearings are much less expensive and may be the actual problem.
ADDITIONAL CONSIDERATIONS
If you carry exceptionally heavy loads, ride two up, ride aggressively, find yourself on the track for track days, or carry a few extra pounds around the midsection, more braking power is needed for stopping, thus the rotor may wear faster and more aggressively. Making sure your brakes pads are well matched to your rotor can reduce wear and enhance stopping power. You may wear out the pads faster (far cheaper than replacing rotors), but it is worth the added stopping safety.
Without a doubt, one system on our motorcycle we don’t ever want to compromise is our braking system. It will take care of you if you take care of it. So where’s the next stop on your ride?
Safe riding,
-LUC
DISCLAIMER: THE VIEWS AND OPINIONS EXPRESSED IN THIS COLUMN ARE NOT NECESSARILY THOSE OF ANY MANUFACTURER. THE CONTENT PROVIDED IS MERELY EDUCATIONAL AND NOT INTENDED AS A REPLACEMENT FOR PROFESSIONAL REPAIR. TEAM ARIZONA, ITS STAFF, AND ITS RIDERCOACHES ARE UNAVAILABLE FOR PRIVATE MOTORCYCLE REPAIR; WE RECOMMEND SEEING YOUR LOCAL DEALERSHIP OR REPAIR SHOP.
