The most important factor in the performance of a bike is also the one taken most for granted. Chances are that if you’re not a cycling pro or aficionado, you won’t pay much attention to your tyre pressure unless someone says, “Hey, I think you have a have a flat tyre,” or when you do have a flat tyre.
It’s a fact that bike tyres need to be checked more often than car tyres, and (another fact) narrow tyres need more air pressure than wide ones. Road tyres generally require 80 to 130 PSI (pounds per square inch); the range for mountain tyres is 25 to 40 PSI, and hybrid tyres ride at 40 to 80 PSI.
The more a rider weighs, the higher the pressure needs to be. I have a mountain bike and I weigh 72 kg, so I ride very comfortably at 30 PSI. Someone who weighs 90 kg will probably ride at about 5 PSI higher, while somebody who tips the scales at 60 kg would ride at 25-27 PSI. But whatever you weigh, never ride at above or below the manufacturer’s recommended tyre pressures, which are listed on the sidewall.
But that’s still not everything you have to consider. Road and weather conditions also play a part. It’s widely believed that higher tyre pressure makes for lower rolling resistance because on a smooth road surface hard tyres flex less and create a small contact surface. But no road is perfectly smooth, and tyres that are properly inflated will conform to road imperfections and absorb shocks. Over-inflated tyres, on the other hand, are more sensitive to surface irregularities and so transmit impacts, large and small, making for an uncomfortable ride.
Lower tyre pressure does indeed increase rolling resistance, but several studies using different road tyres have found that the increase is small, just a few watts of power, even at the lowest allowable pressure. In fact, rolling resistance accounts for a very small part of the forces that prevent you from riding like Sam Bennett. Wind resistance, hills and gravity are far more important. So, again, don’t over-inflate.
On new pavement, my tyres might feel great at 25 PSI, but they will roll faster at 35 PSI on a rough road, so be aware of where you are going to ride and adjust your tyres accordingly. When the surface I’m riding on is wet, I’ll take 3 PSI off my tyres for better traction. And when I’m on a trail, I may go down to 25. But everyone will have their own tyre pressure sweet spot. Find it by trial and error. It’s worth it.
One more thing. It’s pretty standard to inflate both front and rear tyres to the same pressure, but a rider’s weight is not balanced 50-50 front to rear depending again on riding style and also on the type of bike you are riding. For road bikes, it’s about 40 per cent front and 60 per cent rear in most cases.
To find the ideal pressure, begin by deflating front and rear, say, 5 per cent each (per cent, not PSI, if the tyres have different pressures). Go on a ride and see how it feels. Then drop it a little more. The best tyre pressure gives you a comfortable ride with a sure feeling in corners. Once the front wheel starts to feel a little soft in hard cornering, put a few PSI back. Measure front and rear and write the results down as a baseline. But remember that the ideal pressure may change according to conditions, terrain, weather, and when you switch tyre sizes or brands.
And remember, too, to check your tyre pressure often, once a week or, as some do it, before every ride. Because tyres leak.