You ask we answer. Here's the latest in our "Ask a Mechanic" series.
Q: What are the signs of bad bearings especially bad wheel bearing symptoms?
A: A number of bearings help keep your dirt bike moving (literally in some cases) and functioning properly. Bearings either come sealed from the manufacturer, meaning you cannot service them, or unsealed which allows you to clean and lubricate when necessary. Below is a list of bearings along with whether they come sealed or unsealed (however keep in mind manufacturers do vary in terms of providing sealed or unsealed so understand this in general terms not a hard and fast rule!):
- Swingarm (unsealed)
- Linkage (unsealed)
- Steering (sealed)
- Wheel (sealed)
- Rear Suspension or Shock (unsealed)
Bad Bearing Symptoms
When well-maintained, the bearings on a dirt bike generally last quite a while - long enough for many riders to forget about, until they start to fail. Therefore, if you ride regularly and have owned a dirt bike for some time at some point you probably encountered at least one of the symptoms of bad bearings. Regardless of the type of bearings you can always tell when their time is up based on the following signs:
- Grinding sound
- Slop or side-to-side play (wheel)
- Hard to turn (steering)
- Increased rolling resistance (wheel)
- Resistance when pushing seat down (rear suspension)
- Click or popping sound when rear wheel leaves the ground (rear suspension)
Unsealed bearings breakdown from dirt, lack of lubrication and time thus require routine cleaning and lubrication. Riding in dusty conditions or on sand contributes to faster wear and tear. You can't do much with sealed bearings other than service based on manufacturer's suggested life or wait until you hear or feel the bad bearing symptoms described above. But, it's advisable to pack some grease around the outer dust seal for enhanced protection.
Additional bearings reside inside the engine, like crank and transmission bearings, which get lubricated by the transmission or engine oil and usually get replaced when other parts fail. Check you service manual for more information on when to service.