The maximum PSI rating of a tire does not suggest that one PSI more will result in the tire blowing off the rim. It does however, indicates the strength of the bead and also builds in a buffer for pump gauge variance and rider weight.

In recent years we've seen many cyclists push for higher PSI tires thinking that the more pressure means a faster bike. In a fashion they are correct - the greater the PSI the less tire is in contact with the ground which translates to less rolling resistance. However, less tire on the ground also means reduced cornering and braking performance, and reduced comfort. You could argue that being comfortable on the bike might be equal to, if not more important then, the small change in rolling resistance and lets be clear we are talking SMALL.

Where the rubber hits the road

For the average rider it's pretty much whatever PSI they feel comfortable riding at. A rider at 170lbs can choose to run 80 or 90 PSI but also go up to 130 on a tire rated at 120 PSI. The risk is minimal that something will happen ? however that's not to say it's not there. It's just reduced. As the 170lbs rider goes from 80 to 130 PSI they reduce the amount of contact the tire has on the road which will decrease breaking and cornering performance while increasing, slightly, their speed.

For light riders who are at or above the maximum PSI there can been undesirable riding characteristics. Most noticeable will be comfort. The same tire that the 170lbs rider put a little bulge in will stand tall for a light rider of 130lbs and not give to imperfections in the road. In this situation ride quality and brake/cornering performance are reduced. Reducing the PSI so the tire has a slight bulge while ridden will increase comfort and performance.

It becomes a balancing act for those of us at or above the 200lbs range or those wishing to run higher PSI then rated. It is a personal call. There are no hard and fast rules to follow. Going beyond the manufacturer's rating moves you into uncharted waters. One could view the maximum PSI as 100% but even if you believe the tire can be run at 120% the breaking point is unknown. Tire size and rider weight are not the only factors to gauge maximum PSI. That said some heavier riders have the need to run at or slightly above the maximum PSI to reduce pinch flats. See avoiding flats for more on pinch flats.

Something to consider

When you inflate your tire the PSI on the pump gauge does not include your weight. With a rider on the bike the PSI goes up and even spikes when riding. Bumps, pot holes, change in altitude, heat and the occasional bunny hop cause changes in the PSI. One of these in isolation is not likely to cause a problem, but when pushing the limits on the bead they all become factors of failure to consider when inflating your tires over the maximum PSI.

We Keep You Cycling recommends you run at or below the maximum PSI rating for your tire.