Cyclepartsonline carries a selection of tyres in a range of sizes. But what size do you need? Thanks to a series of differing international measurement references, dodgy advertising and manufacturer's stubborness it can be quite difficult to determine what size tyre will fit your wheel. The picture below illustrates the dilemma.

Both tyres are made by the same company (Primo), are the same model (Comet), are both "16 inch" tyres... and are completely different sizes. What are you supposed to do?

Fortunately, there is generally a way round the problem. If you're replacing a tyre look on it for a label in the format xx-yyy, like to one below.

This is the ERTRO size. The first bit (the "xx") is the height of the profile of the tyre - how much rubber pokes out above the rim. It's also generally close to the width of the tyre, but that's just coincidental. The second bit ("yyy") is the diameter across the tyre beads (see the yellow arrow on the first picture). If your old tyre has an ERTRO size stamped on it, your new tyre should at least have the same "yyy" size, even if you're choosing a thinner (smaller "xx") or fatter (larger "xx") size for the new one.

If there is no ERTRO size stamped on the old tyre then measure the bead width yourself, and use that as a guide. Fortunately there are a limited range of size made, so if you measure your tyre at (say) 304mm across, then it's likely a xx-306 tyre is what you're looking for.

This is not a perfect guide unfortunately - if you have a very old tyre (15 years or more), or are riding a custom or handbuilt machine with nonstandard rims then there might be no good match. If this is the case, call us on 0409 986 268 and we'll see what we can work out.

Tyre Diameter Range