Tyres

 

For cycling on road and cycle paths, smooth tyres will usually give a good compromise between comfort and efficiency (and efficiency means you’re less tired when you arrive).

Smooth beats knobbly

Knobbly tyres, such as those that come fitted to mountain bikes, can be hard work on the road. A simple modification, to make this kind of bike more suitable for day-to-day cycling, is to replace them with smooth tyres (aka slick tyres).

While tyres without tread are a problem on cars, but this is not true for bikes. Sheldon Brown explains why cars are susceptible to aquaplaning while bikes are not. This means you can ignore people who tell you “there’s no tread on your tyres”. Go ahead and fit some slicks.

Buy puncture proof

Puncture proof tyres incorporate a kevlar band beneath the surface. The leading brand is the Schwalbe Marathon. You may see sports cyclists turn up their noses at the Schwalbe Marathon, on the grounds that they offer slightly more rolling resistance; you don’t have to listen to them.

Tyre valve types

There are two types of modern innertube valve: Schrader and Presta. Schrader is also known as ‘car type’ and is more robust. Presta is designed for bicycles and is slightly easier to inflate.
Rolled up innertubes with schraeder valve and presta valve
They are different sizes and wheel rims are drilled for one or the other; Schrader valves are wider and need a larger hole. A rim drilled for a Schrader valve can take a Presta valve, and to fill the gap you can use a special valve nut supplied with some brands of Presta innertube. The nut is stepped and the thinner part acts as a shim. I keep one in my puncture kit so I can use any innertube on my schrader rims.

On old innertubes you may find the Woods valve (known in the USA as the Dunlop valve). Woods valves are also found on some new innertubes in The Netherlands. Woods valves are as wide as a Schrader valve but they are inflated using a screw-on Presta pump.

How wide?

Tyres for road bikes are readily available in 23mm and 25mm widths. Touring bikes, city bikes and hybrids tend to be designed for tyres 28mm wide up to 35mm or slightly wider. Mountain bike tyres are most readily available at 50mm wide, though slimmer and wider are made.

Tyre width in mm will be printed or debossed on the tyre side. It will be the smaller of the two numbers. For instance the tyre shown at the bottom of this page is 35mm wide.

The wider the tyre, the more weight it can take before deforming, all things being equal. So heavier riders and those carrying heavy cargo are better off with wide tyres in order to avoid squashing the tyres right down when riding over bumps. Punctures caused this way are known as pinch flats since the tyre is pinched between the wheel rim and the road.

Narrow tyres are designed to run at high pressures (typically around 100PSI). They allow you to use less pedalling effort, although the ride may be a bit bumpy. Wide tyres are designed to run at low pressures (around 35PSI). They give a plush ride, absorbing more vibration, but there’s more friction to overcome and so you have to work harder. The best tyre for transport cycling is usually somewhere between these two extremes.

It’s best to avoid very narrow tyres on wide rims and vice versa. The acceptable ranges are shown in the table of tyre widths vs rim widths at Sheldon Brown’s webpage on tyre sizing.

Pump it up

The easiest way to make a bike more efficient is inflating the tyres to the correct pressure. Design pressures for tyres are printed on tyre sidewalls. It is usually expressed as a range (e.g. 70 to 100 PSI). They may be expressed in PSI, bars, or both. You should find both these units on a pressure guage on a good quality track pump.

A bike with under-inflated tyres isn’t just exhausting to ride, it’s more susceptible to punctures because glass shards will be able to penetrate easily.

How do you know if a tyre is under-inflated? A rule of thumb is ’15 per cent drop’: if either of your tyres squashes by more than 15 per cent when you sit on the bike, it needs more pressure. You should be able to see 15 per cent tyre deformation when you’re seated on the bike, but it should only just be perceptible. If you’re not sure, you could put a mirror at floor level to check, or set a camera to timer mode, place it on the ground pointing at the bottom of your tyre, then get on the bike.

If you need to top up your tyres when you’re riding in town, remember that bike shops often allow cyclists to inflate their own tyres using the shop’s pump, for no charge. Just ask to use their pump.

More tyre pressure resources

There’s a nice article explaining tyre pressure here at the bicycling.com website. You can find a tyre pressure calculator, which aims to give ideal tyre pressures, using the ’15 per cent drop’ rule, here. It requires figures for rider weight (in pounds), bike weight and weight distribution (front vs rear). If you don’t want to go to all that effort to calculate your ideal tyre pressure, the graphs here (622kb PDF) should get you close enough.

Other bike components


michelin world tour tyre - showing tyre size - on Mavic rim