We are often tempted by the latest equipment and technological advances in cycling, clawing for any advantage that can lead to even the smallest incremental increases in performance and comfort. But what if I told you that one of the most important things you can do to enhance both performance and comfort, while at the same time decreasing certain mechanical headaches, can also be free?
Do I have your attention yet? Good. Here is the answer – perhaps as anticlimactic as it is significant: optimize your tire size and pressure. Indeed, one of the most significant changes that you can make to your bike is also one of the simplest. Choosing the optimal tire pressure depends on several factors but once you get it dialed for your weight, tire size, and terrain, you can increase both performance and comfort, while minimizing the frequency of flats.
Over the past couple of years, the trend both in the peloton and among recreational riders has been to get away from the standard 23mm wide road tire and move toward 25’s or even 28’s. I remember my first “real” road bike back in 1988 – a Cannondale SR700 Black Lightning – that was spec’d with 19mm wide tires. Good luck even finding tires that size anymore.
Old-school thought was that a narrower tire and higher pressure translated to lower contact, decreased rolling resistance, and therefore increased speed. As it turns out, there is a lot more to the equation. In fact, the changes to rolling resistance when going from a narrower to a larger-volume tire are relatively small, and are often offset by other benefits of sizing up.
Benefits of moving to a higher-volume tire ridden at lower pressure:
- Increased traction
- Increased aerodynamics (when paired with certain rims)
- Decreased deflection when rolling over imperfect surfaces (the tire better absorbs bumps and maintain forward momentum rather than moving the whole bike/frame/rider up and down)
- Increased comfort due to the associated pneumatic shock absorption
Disadvantages to lower tire pressure:
- Higher rolling resistance (on perfect surfaces)
- Increased contact point so therefore increased chance of punctures due to road debris
- Faster tire wear
- Increased risk of pinch flats (though this is offset with larger tires given the overall increased air volume)
I wish I could give you a definitive chart that lists the optimal tire size and pressure for every person of every weight, but it is just not that simple due to the plethora of variables, from personal preference regarding ride quality, style of riding, and terrain. If you are considering changing your tire size from, say, a 23mm tire to a 25mm tire, I would recommend decreasing the pressure at which you inflate them by 10-15psi, then go for a ride. You just might find that it is both more comfortable and faster.
As you adjust your tire sizes and pressures, here are a few of things to keep in mind:
- Always keep the pressure within the recommended range listed on the sidewall of the tire
- The smaller the tire, the higher the necessary pressure to overcome the relatively smaller volume and avoid pinch flats
- The more you weigh, the higher the pressures you should run
- More rider weight is on the rear tire than is on the front tire (usually approximately 60% on the rear and 40% on the front, though this varies significantly from rider to rider) so it stands to reason that the necessary pressure in the rear tire should be proportionately higher than the front if you are to maintain consistent ride characteristics between the front and rear tires.
- It is usually a good idea to drop tire pressure by about 10psi when riding in wet or otherwise suboptimal conditions, in order to achieve increased contact area and traction
- Remember that tire pressures change over time and it is a good habit to check them regularly. I tend to check pressures before every ride (unless I am running late to meet friends or get to the start of a group ride on time). On most occasions, I end up adding a little air. The rate of air loss from a tire depends on a few factors, including the type of tube (latex loses air faster than butyl tubes or tubeless systems), pressure (the higher the pressure, the faster it is lost), air temperature (more pressure is lost when it is hot outside), and even what you use to inflate the tire (CO2 is more soluble and is lost through the wall of a tube faster than ambient air).
The examples of tire sizes and pressures herein have focused on road bike tires. However, the same general considerations hold true for mountain bikes and, in fact, are often even more significant given the increased tire volume and rougher terrain.
This discussion is only meant to scratch the surface on maximizing tire performance. Stay tuned. We will discuss other considerations, such as the ins and outs of tubeless set ups for both mountain bikes and road bikes, at some point in the future.
Until then…
Happy Riding.
Trent Newcomer is a veterinarian and the franchise owner of Velofix Colorado, a mobile bike shop operation that serves the Front Range, from Fort Collins to the entire Denver metro area. Book a bike service appointment and have them roll up to your home or business at velofix.com
