Bike tyre pressure - the essentials
Achieving optimum air pressure in your tyres may be the single biggest improvement that you can make to your bike. But what psi should a bike tyre be?
Why does tyre pressure matter?
Tyre pressure affects how well your bike handles and your comfort as a rider. On top of that, the correct bike tyre pressure saves damage to your wheels, tyres, tubes and yourself! The right tyre pressure also has the potential to extend your e-bike battery life. A perfectly pumped up tyre is less of a drain on the battery power meaning you keep your wheels turning for longer.
While under-inflation is the most common problem, over-inflation can be just as bad. There is a sweet spot and hitting it can seriously improve your ride.
Softer tyres act as suspension on rough roads or off-road trails. They also maintain more contact with the road at any given moment, meaning improved grip and confidence when cornering. Braking, cornering and uphill traction are better on mountain bikes with softer tyres.
However, there are problems when the air pressure in tyres is too low. The greater ground contact may mean better grip, but it also results in greater rolling resistance. This leads to greater tyre wear. Under-inflated tyres are also more prone to pinch flats. The soft tyre deforms when it hits rough ground or potholes, pinching the inner tube against the rim.
Higher pressures have long been the norm for road bikes. Hard tyres, in principle at least, offer less rolling resistance. In practice, however, road surfaces are rarely all that smooth and tyres inflated to the max are likely to be quite unforgiving. Furthermore, on rougher road surfaces and off-road, the additional vibration and jolts are not only uncomfortable, but they will also actually slow you down as much as under-inflated tyres.
There are also risks of damage with too much inflation pressure. Tyres do burst when significantly over-inflated, either during pumping or, more dangerously, when riding. You can also damage the valve or the pump. It is important, then, to discover what the optimum tyre pressure for a bicycle is.
What should a bike's tyre pressure be?
Pressures can vary greatly depending on a number of factors, so it's useful to have some outside parameters. The following is a rough guide:
Road bike: 80-130psi
Mountain bike: 25-60psi
Hybrid bike: 40-70psi
Manufacturers usually have a maximum pressure embossed on the wall of the tyre. Inflating tyres over these maximum pressures is not advised. The optimum pressure, though, is likely to be less than the max shown.
What factors affect optimum tyre pressure?
Tyre type and size, riding conditions, as well as bike and rider weight are all factors that affect your recommended bike tyre pressure.
Mountain bike tyres are fatter than those of road bikes and the wider rims allow you to run lower pressures. They are also intended to be used on rough and loose surfaces, so the greater traction and shock absorption given by slightly softer tyres become more important.
Road bikes' narrower wheel rims need a higher tyre pressure to maintain rigidity. Thankfully though, road bike tyre pressures are no longer expected to be as high as the 160psi once recommended. 100 or 90psi may be fine with 28mm tyres.
Tubeless tyres have risen in popularity over the last few years particularly on road bikes because of their ability to run lower pressures without risking pinch flats. Tubeless tyres are also more puncture resistant saving you time and money in the long run.
For both road and mountain bikes, you may want to adjust your tyre pressures down a little if you are anticipating rough conditions. For example, cobbles or a poor-quality surface for road bikes, or very rough or steep trails for mountain bikes, will be better handles by softer tyres.
Normal bike tyre pressure recommendations are based on a rider's weight of 70kg and a bike of 12kg. Tyre pressure for heavy riders will need to be rather higher. You should adjust your optimum pressures by about 1% per 10kg up or down from these base figures. Electric bike tyre pressure can be calculated in the same way: the battery usually adds about 10kg.
How do I check tyre pressure?
If you have no pressure gauge, some manual tests can help, though they are far from accurate. The tyre should yield only very slightly when firmly pressed. Also, try pressing down with all of your weight on the saddle: there should be little or no deformation of the tyres.
The only accurate reading, however, will come from a bike tyre pressure gauge. If you are serious about refining your tyre pressures, it’s worth investing in a quality digital gauge. To use it, you just place the nozzle over the valve to get a reading.
What About Pumps?
A quality track pump offers the ability to hone your bicycle tyre pressure. They generally have gauges, which may not be quite as accurate as a digital gauge, but are usually consistent. A floor pump will have switchable adapters to fit both Presta and Schrader valve types.
It is also wise to carry a hand pump with you when you're out. It is difficult to pump tyres to full inflation with a hand pump, but they are absolutely essential in case of a puncture (along with spares or a repair kit).
Many pumps these days have a clamping attachment to fit over the head of both Presta and Schrader valves. However, the attachment will need to be swapped or reversed to fit. Some high-quality floor pumps use a screw-on fixing for a more reliable seal. In any case, it is important to ensure a good fit over the valve. When pumping, you should not hear air hissing from the valve.
With Presta valves, it is necessary to loosen the head nut at the end to allow air to enter the valve. You may also need to press it down slightly to release a little air, as the entry point can become stuck.
It's worth experimenting a little, as personal factors do vary. However, with the right tyre pressure, you can ensure the most comfortable, efficient and safest ride and the best cycling experience.