How Wide Should Your Road Tires Be?

Peter Glassford
by Peter Glassford
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How Wide Should Your Road Tires Be?

With all the talk about fat bikes, gravel bikes, 29-inch mountain bike tires wheels and giant cassettes, it would be easy to assume road tires will also continue to get wider. While top racers used to run 23c or smaller tires, the range now seems to have settled more commonly in the 25–28c range. This upward trend could continue as tubeless and disc-brake technology becomes more prevalent on the road, but there must be a limit, right?

TWO FUNDAMENTAL QUESTIONS

Whenever one of my coaching clients wonders if they should do something, I bring it back to two fundamental questions: Who are you and what do you want to do? As an example, a smaller person who wants to climb fast may not use a wider tire, but a bigger person may find the gains in comfort worth the extra weight.

Andrew Randell, former pro cyclist and co-owner of the Cycling Gym in Toronto, has little desire to get bounced around on the road. “I’ve gone to a 28c tire at 55psi for both racing and training.” This setup prioritizes comfort and control and for someone who is still quite fit, tactical and skilled; it helps to make race and training days much more enjoyable.

ROLLING RESISTANCE

You could be forgiven for thinking wider tires will always be slower than narrower ones, but it is not that simple. Global Cycling Network looked at tire width and found wider tires can actually be faster since there is less tire in contact with the ground (shorter but wider patch) and because there is less vibration on bumpier terrain. This slow progression to wider tires and lower pressures could be compared to what mountain biking went through as disc brakes and tubeless technology became standard and opened up tire options.

BIKE TYPE

The kind of bike you’re riding is one of the reasons I believe we need to be cautious in only guiding our choices by what professional teams use. Since the adoption of disc brakes in the pro peloton is still incomplete, the rim brakes on their bikes limit tire size to around 28c. Similarly, you only have the bike you are currently riding, and that bike determines the range of tire widths you can use.

TERRAIN

The roads you will ride should also be considered. “This season the team will be racing on wider 28mm Continental tires for the cobbled classics, and then we run 25mm tires for most of the races for the rest of the year,” says Leah Kirchmann on how Team Sunweb chooses tire width for different races. “It is especially nice to have those wider tires for better handling and feel when racing on rough terrain,” she says. So if your rides and races happen on bumpy roads, a wider tire offers more comfort and control, but it is still OK to go narrower on smooth roads.

AERODYNAMICS

The Specialized ‘WinTunnel’ compared the aerodynamics of 28c, 32c and 40c tires, and found there actually wasn’t much difference between the tires strictly in terms of aerodynamics. Interestingly, they found a deeper aero rim actually made the most significant difference in aerodynamics. Gutgesell adds another reason to consider a new set of wheels in addition to your tires, “rim width can make a huge difference on the road, a nominal 25c tire can measure anywhere from 23–30mm, depending on rims.”

YOUR GOALS

Your goal in the race should also be considered. If you want fewer flats, you’ll probably prefer a wider and thicker tire. “Almost all of the races I do end up having some sections with terrible roads, and I’ll happily pay a 50–100 gram weight penalty for the extra comfort and insurance when riding in the pack and can’t see what I’m about to hit,” offers Robert Gutgesell, a road racer who has competed for stage races like Tour of the Gila and Redlands. In a very hilly race, Gutgesell would adjust his tires and wheels for weight versus a bias toward reliability and comfort.

THE BOTTOM LINE

With all the tire options it’s easy to get overwhelmed. You can make your decision less complex when you learn what your bike can handle and consider your goals for your training and racing. As with any equipment or technique, it is important to practice in similar conditions and at similar paces to be sure your choice is the best for you.

About the Author

Peter Glassford
Peter Glassford

Peter is a cycling coach and registered kinesiologist from Ontario, Canada. He travels frequently to work with athletes at races, camps and clinics. He also races mountain bikes for Trek Canada and pursues adventure in all types of movement. Follow @peterglassford on Twitter, or check out his online and in-person coaching at www.smartathlete.ca.

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