tyres

Explain how tyre sizing works?

This is an area that probably gives rise to more everyday cycle shop problems than any other. There is no truly harmonised system for tyre sizing other than the ETRTO number, which expresses the diameter of the bead, or wire portion of the tyre, and the corresponding seat of the rim, and the nominal 'profile' of the tyre. So, given an ETRTO size of 622 -23, we have a bead diameter of 622mm, and a nominal profile of 23mm. This is also described, in more common language, as 700x23 - as the approximate daimeter of the tyre as a whole is 700mm. To cause further confusion, this size is also known as 28x11/8x15/8. Not all '26' inch tyres will fit all '26' inch rims, and the only sure guide here, again is the ETRTO size. If in doubt, when buying new tyres or tubes, either take the tyre or tube to a reputable retailer and ask them to fit the replacements, and to tell you the sizes used.

Are slick tyres better than treaded ones?

If one looks at the footprint of a cycle tyre, and compares it with that of a car tyre, it instantly becomes clear that on a hard surface, a tread serves almost no purpose. A tread, especially a deep one makes it more likely that the tyre will pick up bits of grit or glass that will then work their way through the tyre and cause punctures. Until recently, most slick tyres were aimed at the racing market, and so were light, with very thin rubber. More recently, new generations of slick and semi slick tyres have appeared that are less prone to punctures and hold the road far better than their older counterparts. For most on-road applications, these tyres will give a better, faster, more lively and predictable ride than the heavily treaded tyres of old.

How hard should my tyres be?

A lot of damage is caused to tyres with riders running them too soft. There is certainly a higher incidence of failure as a result of over soft tyres than over hard. Check the pressures that are recommended on the tyre sidewall, and use a pressure gauge to ensure that you tyre pressures fall into the given range. If you are on the heavy side, or are riding the bike loaded, go for a pressure at the high end of the range. Compared to car tyres, cycle tyre pressures are much higher. Be aware of the fact that like car tyres, the recommended pressures are there to give the tyre the right shape in contact with the road, to help it to stay attached to the rim when cornering, and to protect the wheel itself from mechanical damage.

What is the difference between a tub and a clincher?

A tubular tyre, or tub, is an inner tube sewn into the specially designed carcass of a tyre, which is glued to the rim of the wheel as a unit. It allows the lightest possible combination of rim, carcass and tube, and so is favoured by many racing cyclists. A clincher, by contrast, is a tyre that 'hooks' onto the rim with either a flexible or rigid bead, and retains the inner tube under it: hence also being known as a 'cover'. Such tyres require inherently heavier rims than tubulars, but the advances in tyre design that have been made in recent years make them suitable for all but the most exacting applications.

How can I prevent punctures?

There are several things that can be done to prevent punctures. Running tyres at the correct pressure, using tyres without too deep a tread pattern, not riding in the gutter and avoiding debris in the road all spring to mind. In addition to these measures, a 'Tuffy Tape' can be inserted between the tyre and inner tube and kevlar-belted tyres of higher quality can be fitted to lessen the danger of punctures through the tread. Latex or butylised latex tubes will also help. The tubes can be filled with a compound that will harden on contact with the outside air, sealing any punctures that are picked up. A regular check on the condition of the rim tape under the tube will prevent punctures from the tube being forced down into the spoke eyelet wells, or rubbing against the heads of the spoke nipples. Avoiding potholes in the road will help avoid 'snakebite' punctures, and off-road, anti snakebite tubes and tyres are an effective solution if this is a persistent problem.