West Berkshire Spokes

Your tyres are amongst the most important components on your bike, since they provide the contact points between you and the road.  Your choice of tyre can have a big impact on how your bike rides and handles, but there is a bewildering range of tyres available in all sorts of types, sizes and tread patterns, so it can be difficult to know where to begin.

Tyre Types – Broadly speaking, there are three main tyre types: tubular, clinchers and tubeless tyres.  Tubular tyres have an inner tube sewn inside and the tyres have to be bonded to a tubular specific rim. This makes them expensive and / or difficult to replace. They are very lightweight and are aimed at pro road cyclists. Clinchers are the traditional tyre that most of us will be familiar with. They have a ridge or ‘bead’ that keeps the tyre in place by pushing against the hook or ‘bead seat’ on the inside of the wheel rim when the inner tube is inflated. Tubeless tyres are similar to clinchers, but as the name suggests, they don’t have an inner tube. Instead, they have a thicker bead and rely on liquid sealant to form an airtight seal. The main advantage of tubeless tyres is that they are more puncture resistant – the lack of an inner tube eliminates pinch flats and the sealant inside the tyre can fill smaller punctures. There is little weight difference between clinchers and tubeless tyres, so the choice is down to personal preference (and how puncture prone you are).

Valve Types – There are two main types of tyre valve. Shraeder valves are wider and have an internal spring to keep the valve closed. They tend to be fitted to kids bikes and some mountain bikes and hybrids. Presta valves are slimmer and are most often found on road bikes. They have a top section that must be screwed down to close the valve. The difference in the widths means that they are generally not interchangeable, since wheel rims generally have holes designed for one particular valve type.

Tyre sizes – Traditionally tyre sizes are denoted using two numbers – the first is the outer diameter of the tyre and the second is the width, with figures in either inches or millimetres. For example a mountain bike might have 26″ x 1.9″ tyres, while a road bike bike tyre might have 700 x 25 mm tyres. Because of inconsistencies between tyres produced by different manufacturers, the International Standards Organisation (ISO) developed a universal tyre sizing system that uses two numbers – the first is the width of the tyre in millimetres and the second is the diameter of the bead seat on the wheel rim. For example, a 700 x 25 C tyre would be classified as a 25-622 tyre using the ISO system.

So what size tyres should you buy? The diameter of the tyre is determined by the diameter of your wheels and is therefore fixed. However, for any given rim width, there will be a range of tyre widths that will fit. Generally speaking, your tyre width should be 1.4 – 2 times the distance between the inside edges of your wheel rim. For example, a touring bike with a rim width of 19 mm would be capable of taking tyres 28- 38 mm wide.

Wider tyres generally run at lower pressures, which means that they are softer and therefore more comfortable. Intuitively, you might think that wider tyres have higher rolling resistance, but rolling road tests have shown that rolling resistance actually decreases on road bikes as you step up from 23mm to 25mm and again when you step up to 28mm. The reason for this is wider tyres deform less at the same pressures. Real-world tests show that the benefits may be negated by increased wind resistance, but unless you are in a race situation, this shouldn’t be an issue. If you do go for wider tyres, just make sure that the bike frame provides the necessary clearance!

Tyre Pressures – Grip, rolling resistance, comfort and safety are all affected by tyre pressure, so it is important to get it right. Every tyre will have a recommended range of pressures, which is shown on the side wall. Road bike tyres typically need 80 to 130 psi (pounds per square inch); hybrid tyres run at 50 to 70 psi; and mountain bike tyres just need 30 to 50 psi. The correct tyre pressure is usually determined by the weight of the rider. Heavier riders need more air in their tyres than lighter ones and should therefore aim for the upper end of the recommended range.

Tread – On normal roads, tyre tread has a minimal influence on riding properties. The grip generated by the tyre on the road is almost exclusively down to the rubber compound. Unlike a car, a bicycle will not aquaplane, since the contact area is so small. However, tyre tread is important in off-road situations, where it forms an interlocking connection with the ground to transmit driving, braking and steering forces. Some tyres will have tread patterns that are designed to work in a particular direction. On these tyres, the direction of rotation will be marked on the side wall. Also, some mountain bike tyres are designed with different tread patterns at the back and front, with the rear tyres optimised to transmit drive forces and the front ones optimised for steering forces.

Puncture Resistance & Wear – Most tyre manufacturers have a range of tyres that offer different characteristics in terms of wear and puncture protection. Race tyres are designed to have low weight and rolling resistance and are made with softer compounds that offer improved grip. However, the downsides include quicker wear rates and reduced puncture protection. At the other end of the spectrum are tyres designed for long-distance touring and commuting, which have excellent wear rates and puncture protection, but are much heavier and have higher rolling resistance. Ultimately, your choice depends on how, where and when you ride and how much you want to spend. Remember that Spokes members get 10% off tyres at local bike shops!