The tread blocks are worn into steps or dips, so the edge of each block is higher on one side than the other. You can feel it by running your hand around the tyre: smooth one way, rough the other way. It is most common on front tyres. It makes a humming noise that changes with speed and can cause vibration in corners. A little cupping is normal on block-pattern tyres; heavy cupping points to low pressure, worn suspension or wheel problems.
Is it safe to ride?
With care. Heavy cupping reduces grip, especially when braking in corners. Fix the cause and replace the tyre if the steps are deep.
Quick checks first
- Check cold pressure. Low front pressure is the most common cause.
- Run your hand round the tread both ways: feel the steps.
- Listen for a hum at steady speed that rises with road speed.
- Push down hard on the front and rear: do they bounce more than once?
Diagnose it step by step
1Is the pressure below your bike's value?
- Yes: set it (Check tyre pressure) and check weekly. Low pressure lets blocks squirm and wear unevenly.
- No: go to step 2.
2Push the front down hard and release. Does it bounce more than once, or leak oil from a fork leg?
- Yes: fork damping is worn. Inspect the front forks, see Front forks feel harsh.
- No: go to step 3.
3Rear tyre cupped? Push the rear down: more than one bounce?
- Yes: Check the rear shock absorbers, see Rear bounces after bumps.
- No: go to step 4.
4Lift the wheel. Any side play or rough feel when spun?
- Yes: Check wheel bearings.
- No: go to step 5.
5Front: does the steering catch or feel notchy in the centre, or clunk under braking?
- Yes: Check the steering head bearings.
- No: go to step 6.
6Is the wheel true and balanced?
- Unsure: Check a wheel for runout and Balance a wheel.
- Yes: the cupping is probably from the tread pattern and hard braking. Monitor it.
7Are the steps deep, or is the tyre near the wear limit?
- Yes: Replace a tyre after fixing the cause, or the new tyre will cup too.
- No: keep riding and check every week.
Causes, most likely first
| Cause | How to confirm | Fix |
|---|---|---|
| Low tyre pressure | Gauge reads low | Set pressure |
| Worn fork or shock damping | More than one bounce, oil leak | Forks, shocks |
| Worn wheel bearing | Side play, rough spin | Wheel bearings |
| Loose or worn steering head bearings | Clunk or notch in steering | Steering bearings |
| Out of balance or bent wheel | Runout or balance check | Runout, balance |
| Tread pattern and braking style | All else good | Monitor; replace when worn |