Read the tyre date code and tread wear marker

Two marks on every tyre say when it should be replaced: the wear marker, which shows tread depth, and the date code, which shows its age. Rubber hardens with time even when the tread looks good, so both marks are worth checking when buying a used bike, after storage and at each service.

Safety

• Do this with the bike on a stand or on level ground, engine off.
• Never ride on a tyre with cords showing, bulges or deep cracks. Replace it.

You need

• A clean rag and a torch.
• The tyre-pressure and size information for your bike (Check tyre pressure).

Steps

1. Wipe the sidewall clean. Turn the wheel until you can see a small triangle moulded on the sidewall near the tread edge. There may be several round the tyre.
2. The triangle points to the wear marker, a raised bar in the bottom of the main tread grooves. When the tread is worn level with the bar, the tyre is at its wear limit. Replace it.
3. Check every marker position. Tyres can wear unevenly, so the lowest reading counts.
4. Find the date code. It is moulded into the sidewall, often in an oval or a small box. It ends in four digits.
5. Read the four digits as week then year. The first two are the week of manufacture and the last two are the year. Example: 3902 means week 39 of 2002.
6. Work out how old the tyre is from today's date. Use your tyre maker's or manual's advice on age. Tread depth alone does not show a tyre is fit to ride.
7. Look at the rubber as well. Fine cracks in the sidewall or between tread blocks, a hard feel, or a shiny, glazed surface mean the tyre should be replaced even if the tread is deep.
8. On a new tyre, note that it has a slippery moulding coating at first. Ride gently until it wears off.

Check your work

• You found and read the wear marker on each tyre.
• You know the week and year of each tyre.
• You have a note of any tyre that is worn to the marker, cracked or old.

If it did not fix the problem

• Worn to the marker, or cracked: Replace a tyre.
• Full visual check of tread, sidewall and valve: Inspect a tyre.
• Sidewall cracks: Tyre is cracked.
• Wear only in the centre or in a scalloped pattern: Tyre wears in the centre and Tyre is cupped.