Tyre is cracked or old

Small cracks appear in the sidewall or between the tread blocks. Sun, heat, ozone and long standing make rubber dry and hard ("weather cracks"). An old tyre can have deep tread but poor grip, especially in the wet. Bikes that stand for months, or that are often under-inflated, crack sooner.

Is it safe to ride?

With care if the cracks are fine and only in the surface. If cracks are deep, reach the cords (threads inside the rubber), or are in the tread grooves, do not ride: replace the tyre.

Quick checks first

• Look at both sidewalls and in the bottoms of the tread grooves.
• Bend the sidewall gently with your thumb to open the cracks.
• Find the date code: four digits after DOT (week, then year).
• Check the rubber valve stem for the same cracks.

Diagnose it step by step

1Can you see cords, threads or fabric at the bottom of any crack?

• Yes: stop riding on it. Replace a tyre.
• No: go to step 2.

2Are there cracks in the bottoms of the tread grooves, or across the tread?

• Yes: replace soon. These cracks open under load and can grow into tread separation.
• No: go to step 3.

3Are the sidewall cracks deep (they stay open when you release the bend) or long and joined up?

• Yes: plan replacement now and check pressure before each ride.
• No: fine surface crazing. Go to step 4.

4How old is the tyre (date code)? Does the rubber feel hard, and does the bike slide more than before in the wet?

• Old and hard: replace, even with deep tread. Grip matters more than tread depth.
• Not old, grips well: keep riding, check monthly.

5Has the tyre often run low, or the bike stood for long periods?

• Yes: keep pressure correct (Check tyre pressure). For storage, keep the bike out of the sun and off the tyres if possible.
• No: normal ageing.

6Is the rubber valve also cracked?

• Yes: Check and replace a tyre valve. Fit a new valve with every new tubeless tyre.

Causes, most likely first