Under Pressure
So what tire pressure is optimal? That depends on the width of your tire, the surface on which you'll be riding and your weight. The current trend is to go for a wider tire, which allows you to ride at a lower pressure but achieve the same rolling resistance of a narrower, higher-pressure tire. The main benefit of this is comfort.: the lower the pressure, the more cushion you will have when going over bumps.
However, there is a point at which low pressure can start to decrease speed and increase the risk of pinch flats. Tire manufacturer Schwalble recommends for a 25mm tire, a 130lbs rider should inflate their tires to 85psi, and a 185lb rider should go up to 100psi.
Aero wheel manufacturer Flo suggests for a 160lb rider on 25mm tires, a tire pressure of 92psi is optimal. If you are unsure, check out the recommendations provided by the manufacturer of your tires.
Tire Pressure Rules
While manufacturers provide recommendations for maximum tire pressure, there may be times when you would want to consider changing your regular tire pressure. There are no fixed rules about tire pressure, but there are some helpful tips to consider following. If you're riding in wet conditions or if the road surface is low quality (e.g. milled for repaving), consider dropping tire pressure by five percent. This will add cushion and increase the grip of the tire on the surface. If you are a heavier rider, in general you may want to consider adding five-percent more pressure in your rear tire, up to the tire's recommended maximum inflation limit.
Comfort Considerations
Wider tires can be inflated to lower pressures. This greater volume and lower inflation pressure increases contact with the road but also slightly increases friction—a.k.a. rolling resistance. If you're more comfortable, you'll be able to generate more power for a longer time, making you faster.
Tires with more give are also less fatiguing, making the quality of your ride more enjoyable. If you are looking to do a long ride or lots of gravel and off pave road sections, we recommend going with a wider tire and lower pressure.
Get a Grip
While it is desirable to reduce the rolling resistance for speed, race tires must also have some grip to them. To compensate for the smaller contact patch of a wider tire, manufacturers have created more supple tires with "stickier" tread compounds and supple casings with higher thread counts for improved grip. However, be aware that stickier tires will also pick up bits of stuff on the road, including glass, more easily. If you've invested in great, grippy tires, you may want to test them a few times and then save them for race day.
Avoid Ice Cream Cones
If you're using narrow wheels with wider tires, the result starts to look like ice cream stuffed onto the top of an ice cream cone if you were to view this configuration in profile. Although tasty, this shape is not aerodynamically efficient. Avoid choosing a tire where the width is greater than 105 percent of the external width of the rim where it will be mounted.
Wheel and tire manufacturer Mavic indicates, "widening the rim for aero benefits is really efficient as long as the tire remains narrower than the rim's widest point."
Close Tolerances
Before wrapping your wheels in 28mm-plus tires, ask your local bike mechanic if the inflated tire will fit in your frame. Wider tires are also taller, and you'll not only need clearance under your brake caliper and between your chainstays, but the inflated tire will also need to clear your bike's seat tube. Your bike may just not be made for wide tires. Most often you'll see people on a 23mm or 25mm tire for race day, both of which are excellent choices if your wheels can accommodate them.
Brand Does Matter
When selecting tires for race wheels, it's always a safe bet to go with the manufacturer-recommended tire—and specific width—for optimal performance for the wheel and tire combo. Brands like Specialized, Zipp, Trek/Bontrager and Mavic all specify tires recommendations on what to use with their wheels. This tire-wheel optimization is developed not for marketing but for optimal performance.
Mix and Match
Brands such as Continental, Schwalbe and Vittoria, among others, all make excellent bike tires that work with any wheel brand and provide recommended inflation guides. Some wheel brands recommend various tire brands with specific, optimal operating pressures, but it's still a good idea to factor in your weight and the road conditions on which you'll be riding.
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