Bike Tire Pressure - The Essentials
Dialing in your bike’s tire pressure may be the single biggest improvement that you can make to your riding experience. But what should that pressure actually be?
Why does tire pressure matter?
Tire pressure affects how well your bike handles and your comfort as a rider. On top of that, the correct PSI saves damage to your wheels, tires, tubes, and yourself! The right tire pressure also has the potential to extend your e-bike battery life. A perfectly pumped up tire 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 tires 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 tires.
However, there are problems when the air pressure in tires is too low. The greater ground contact may mean better grip, but it can result in greater rolling resistance. This leads to greater tire wear. Under-inflated tires are also more prone to pinch flats. The soft tire 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 tires, in principle at least, offer less rolling resistance. In practice, however, road surfaces are rarely all that smooth and tires 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 badly as under inflated tires.
There are also risks of damage with too much inflation pressure. Tires do burst when significantly over-inflated, either during pumping or, more dangerously, while riding- this is especially pertinent for longer periods of braking on rim brake wheels. You can also damage the valve or the pump.
What should a bike's tire 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: 80-110psi
Mountain bike: 25-35psi
Gravel bike: 25-60psi
Hybrid bike: 40-70psi
Manufacturers usually have a maximum pressure embossed on the wall of the tire. Inflating tires over these maximum pressures is not advised. The optimum pressure, though, is likely to be less than the max shown.
What factors affect optimum tire pressure?
Tire type and size, riding conditions, bike, and rider weight are all factors that affect your recommended bike tire pressure.
Mountain bike tires 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 tires become more important.
Road bikes' narrower wheel rims need a higher tire pressure to maintain rigidity. Thankfully though, road bike tire pressures are no longer expected to be as high as the 160psi once recommended. 100 or 90psi may be fine with 25mm tires.
Tubeless tires 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 tires 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 tire pressures down a little if you are anticipating rough conditions. For example, chip-seal, cobblestone, or a poor-quality road are reasons enough to give yourself some leeway on your road bike’s tire pressure.
Normal bike tire pressure recommendations are based on a rider's weight of 155 pounds and a bike of 25 pounds. Tire pressure for heavy riders will need to be rather higher. You should adjust your optimum pressures by about 1% per 20lb up or down from these base figures. Electric bike tire pressure can be calculated in the same way: the battery usually adds about 20lb.
How do I check tire pressure?
If you have no pressure gauge, some manual tests can help, though they are far from accurate. The tire 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 tires.
The only accurate reading, however, will come from a bike tire pressure gauge. If you are serious about chasing the most accurate pressure reads, 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 dial in tire pressure. They generally have gauges, which may not be quite as accurate as a digital gauge, but are usually consistent. A floor pump (model depending) 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 tires to full inflation with a hand pump, but they are absolutely essential in case of a puncture (along with spare tubes 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 of the valve 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 tire pressure, you can ensure the most comfortable, efficient and safest ride and the best cycling experience.
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