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The cycling and triathlon industry is constantly evolving, and many changes in rim and tire technology in recent years are causing us to rethink some of what we once thought to be true. Although some tires are indeed faster at high pressure than others, there are others that are proven to be faster at lower tire pressures. The paradigm has shifted around many bike parts over the past few years: crank arm length, saddle tilt, aero helmet shape, and what we now consider to be “high” tire pressure. But before we get into the discussion of “what is the best tire pressure?” let’s explore the difference between tubulars, clinchers, and tubeless so we can set the stage for the ultimate answer: It depends!
Tire and Rim Standards: What Should I Know Before Pumping Up?
The original “gold standard” wheel/tire set up for race wheels was tubular tires—a tire was simply a cotton, kevlar, or rubber casing containing a latex inner tube, sewn on the underside. The tire is then stretched to fit and glued to the surface of a rim. Many triathletes and both elite and recreational bike racers still use tubular tires for racing, but for different reasons than the old school racers of the tubular tire’s heyday. Tubulars were originally thought to have their greatest performance advantage because they have an incredibly high-pressure tolerance.
Many time trialists and triathletes alike were known to race upwards of 150psi with the idea that less surface area contacting the tarmac, the less the rolling resistance. (If you raced in the era of tubies, you know this well. And I’d be interested in what you’re currently riding and racing on!) Challenges of tubular tires for recreational riders lie in the fact that they’re especially difficult to change, especially out on the road. Clinchers (or the hook and bead style which we are most familiar with) offer a much easier rider experience when a puncture occurs. They are relatively easy to change, and can be relatively inexpensive. The main issue with riding at lower tire pressures on a clincher is the risk for pinch flatting. A pinch flat is when the tube gets compressed between the tire and rim from a forceful impact, such as hitting a pothole or rock. The key is finding the best tire/tube combination to reduce the hysteresis (the deformations that occur over time within the tire/tube’s materials and causes rolling resistance). This Ask a Gear Guru piece covers just about every tire out there, with some rim guidelines, and their manufacturers’ recommended ranges for tire pressure.
The latest trend in tire/rim advancements is an adoption from cyclocross, mountain, and, historically, motorcycle, and automotive tires. A tubeless tire is one that has no tube, but has a removable valve, sealed with a layer of rim tape or a strip, and a robust bead that forms a tight and secure seal with the rim. Although these can be challenging to install and change on the side of the road, tubeless tires offer a greatly improved ride quality by enabling lower pressure without the same resistance-causing elements of tubed tires. Tubeless technology has changed the way the bicycle tire industry is approaching this debate, and wheel companies are embracing the movement towards a wider internal rim diameter, hookless rims, and wider tires—and they generally support the “lower is smoother and faster” argument.
Generally speaking, lean on the analogy that a wider rim and tire combination should yield a slightly lower pressure on a clincher. A wider rim will produce a higher volume, reducing the risk of having a pinch flat. A wider rim not only widens the tire to the width of the rim bed, but it also forms the tire into the shape of a ‘U’ instead of a narrower rim which makes the tire in the shape of a ‘C’. This more ‘U’ shape reduces deformations in the tire from pressure and friction, and has a greater amount of tread cap that makes contact with the road.
Rim and Tire Combination Suggestions
For riders still on a narrow rim/narrow tire combination, your pressure still might stay in the triple digits. Riding 100psi on a 23mm tire might not be a terrible idea, since your risk of pinch flatting outweighs the benefits of only a small improvement in surface area contact. For more on this, check out Why are Tires and Wheels Getting Wider.
If you are on a slightly wider tire with a narrow or wide rim, experiment by dropping 5-10psi per tire size you increase by. The improvements in your ride quality will be the most noticeable difference, as the drop in pressure should enable the tire to absorb more oscillation in the road, varying textures of pavement, and provide greater surface area for tire tread cap contact. A wide rim combined with a 25 to 28c tire can yield an even lower pressure, while maintaining a relatively low rolling resistance. The risk for friction and hysteresis still remains for lower tire pressures with a tubed tire setup. It would seem that the untapped potential for performance gains from tire pressure lies in a tubeless-ready wheel and tire combination. Industry recommendations are generally between 50-70psi, and due to the increase in volume combined with less material interacting with the road, there is less rolling resistance, reduced vertical oscillation, and overall, a more efficient and enjoyable bike split. As Neil Shirley, from ENVE, said: “As our understanding of what makes something real-world fast has expanded, it’s been interesting to see where some of the biggest performance gains still exist. Since our rim shapes are well refined, it’s looking at what else is left on the table. Rim and tire volume, along with tire pressure, are the areas where we’re able to find notable improvements in rolling resistance and ride quality.”
Pat Casey is a USAT Level 2 certified coach, certified strength and conditioning specialist, bike fitter, and co-founder of Peak State Fit.