How to find the right tire pressure for cyclocross
By James Huang | Saturday, December 8, 2012 8.30am
Tires are everything in cyclocross, but the pressure is just as important as the tread design James Huang/Future Publishing
Cyclocross racing is all about fitness and skill, but it is about the bike, too, with tire pressure playing a critical role. Too much air sacrifices grip, while too little can cause punctures and vague handling. Here, Cannondale-Cyclocrossworld.com team director Stu Thorne tells BikeRadar his tips and tricks for getting it just right.
According to Thorne, choosing the right tread type for a given day is important, but achieving the proper tire pressure is equally critical.
"[The right pressure] can make such a difference," he said. "A lot of people are hesitant to believe or experiment with adjusting the tire pressure by 5psi or two. [A difference of] 10psi on the road makes a huge difference in the way a bike rides. When you take that down to a cyclocross bike, that can dramatically change the way a bike and tire handles.
"More pressure will be faster, typically, so if it's a fairly fast course where the cornering isn't too extreme or there isn't some crazy off-camber thing, or if it's dry, you can run a little bit higher to get the speed," Thorne continued. "But it's not as high as you might think. Running softer pressure will get you just the opposite where you're looking for that handling in a certain corner or off-camber section and you want as much traction as possible."
Tried and tested
Thorne recommends starting with a high benchmark figure – usually 26-28psi for his team's tubular tires – and then pre-riding the course. From there, his riders can let a little air out while on-course until they get the handling characteristics they feel are appropriate for the day.
"Sometimes a rider will come back in and it could be pushing in a corner – it's just not biting enough – so they'll want to drop a psi out," said Thorne. "That's more of a handling issue.
"Then there's the flatting issue, where they'll say, 'I'm feeling the rim way too much and I don't want to run the risk of flatting, so let's just pop another psi or two in there.' You can also get instances where the tire pressure is too low and it almost feels like it wants to roll. It literally is rolling – you're railing it around a corner and it's just on the rim itself. It's pushed all the way over because the casing isn't holding it."
Digital gauges can help dial in exact pressures, but they're not essential
Thorne says his riders can feel differences of as little as 0.5psi, and that typical front/rear pressure differentials are usually only about 1psi, if anything.
"Those guys will ask for 24 or 24.5psi. I think perhaps there are some psychological issues going on there, where they don't want to feel like they're going up to 25, so we'll meet halfway and our gauge will dial in a half psi. We'll often run a little bit more in the rear."
Regardless of preferences, Thorne emphasizes the need to pre-ride the course at race pace: "[Our riders] will do complete laps and, every once in a while, they'll double back and check a section, but they end up going at a pretty hard pace – very close to race pace – so they're doing openers on a Friday afternoon.
"That's when you're really going to find out where all the bumps are, because if you're just noodling around at half-speed you're not going to find anything. It's when you ramp the speeds up to a pace that you're cross-eyed at in the middle of a race, you know what the tire pressure needs to be."
Conversions for clinchers
For amateur riders using tube-type clinchers, Thorne recommends starting with 35-40psi as a safe figure to prevent pinch flats. But he is still adamant on the need to experiment.
"It's the same process – start with a benchmark and then go out and ride. Even as an amateur, you'll feel that rim if you're hitting the bumps pretty hard. And if you're pushing it through the corners you might want to drop a little out. It's hard to say – that's why I say people need to experiment and learn the differences between the changes in pressure."
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Tubular tires can withstand punishment but clinchers are more prone to pinch flats
"I'm sure there are riders who can get away with quite a bit less than that. I know some of the lighter riders and some of the women out there are running in the high-to-mid 20s with a clincher. But it's the same theory."
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