Fall is here, which means it’s time to think about cyclocross again. As the Technical
Director for the Broad Street Cycles Off-Road Team, I spend a lot of time thinking about
bike setup for cyclocross and want to share some of that with you. Our focus today will
be on tire choice and tire pressure. Although this will be written from a cyclocross
perspective, you can apply the lessons to all areas of riding.
Cyclocross tires come in two main styles- clincher and tubular. I am going to largely
ignore tubular tires for this article. They are specific to racing, more expensive, but can
be better when set up well. If you have tubular specific questions, please come see me
at the shop.
Clincher tires are defined as any tire which are affixed to the rim pneumatically. The
force of air pushing out on the tire casing causes the bead of the tire to grab on to the
rim. This covers all tube-type and tubeless tires. Tubulars are glued to the rim- air is not
necessary to keep the tread underneath you. Much like with mountain and road bikes,
tubeless tires are popular for cyclocross. However, the low pressures needed, combined
with the narrow (33mm tires), can cause issues with burping tires. As such, tubes,
especially latex tubes, are still a valuable product for cross racing. One product the
team has had great success with are the CX/Gravel Inserts from CushCore. CushCore
adds a foam liner to the tubeless setup, allowing lower pressure without damaging the
rim. Additionally, the insert provides additional sidewall support, allowing for lower
pressure without risking the bead from separating from the rim- what we call burping.
For reference, Liam raced Topaz COTR at 17.5/18.5 PSI front and rear without issue, and in Belgium last year we got down as low as 13/14 PSI F/R during particularly
muddy races. Previously, these pressures were only attainable with tubular tires.
CushCore lets us run low pressure, and still change the tire out should we need a
different tread pattern.
(Check Out cushcore here!)
Speaking of tread patterns, cyclocross tires come in three basic tread patterns. These
are dry condition, mixed condition, and mud tires. They can be described as follows: Dry
tires have knobs on the side and are fairly smooth down the middle. They are used for
dry courses like Topaz, or courses involving a lot of sand. Think Koksijde in Belgium.
Mixed condition tires have knobs across the surface, with larger, low knobs down the
middle. These are our most used tires and are great from everything from wet grass to
loose-over-hard. If you were to buy one tire, this would be what you wanted. They suffer
when it is very sandy, as too many knobs break the sand underneath you, preventing it from packing in.
Additionally, they pack in with mud in extreme conditions, rendering the knobs useless. Knobs are what provide us traction, so packing them in with mud will
lead to a bad time. Finally, you have mud tires. Mud tires are for deep mud. They are
slow everywhere else, but the combination of tall, widely spaced knobs is the only
option when the conditions get super trying. This spacing between the knobs allows the
tires to shed, or throw material out from between them, keeping your tires running clean
longer.
At Broad Street, we recommend the following tires
Dry- Challenge Chicane, Schwalbe X-One RS
Mixed- Challenge Grifo, Maxxis All-Terrain, Schwalbe X-One R
Mud- Challege Limus and Baby Limus
When looking at these tires, you may see they come in a few different styles. Challenge
for example comes in a standard vulcanized, or open tubular design. We can identify
these as those having black sidewalls (vulcanized), versus tan sidewalls (open tubular).
The tan sidewalls generally denote a thinner sidewall and are a higher performance tire.
More supple sidewalls allow the tire to deform more easily, providing a better ride feel at
higher pressure. This allows a bit of a best of both worlds’ sensation. Schwalbe takes
this a step further with their super-race construction, allowing for great ride feel without
significant losses in sidewall stiffness.
This being said, thinner sidewalls come at a cost. They are less durable, and if you also
use your tires for riding in places like Thetis Lake, you will need more sidewall
protection than they provide. If you do a lot of singletrack, and a bit of cross racing, I
recommend a vulcanized tire. A downside to the vulcanization process is the thicker
sidewalls result in a wider overall tire. When racing UCI events (think CX Nationals or
the Pan American Championships), your tires will be blocked, and if they are wider than
33mm, you will not be allowed to start. If you plan on doing these sorts of events, you
will want to go with an open tubular, or super race casing tire. They are narrower though
the block and will measure legal for the UCI. If you have specific questions about tires
or wheels you have, we have blocks at Broad Street downtown and can help you out
there.
Tire pressure is the next thing we must think about. My rule of thumb is to run the lowest
pressure we can while navigating the most trying section of the course. This might be
some rough roots, or it might be a hard ninety-degree corner on and off pavement. In
both cases, too low of pressure will cause issue. With the roots, you might bottom the
tire out on the rim, damaging the tire, rim, or both. In the second example, too low
pressure can cause the tire to fold when executing a hard road corner, resulting in you
losing traction and crashing. At the same time, too high a pressure will lead to more
rolling resistance, lower traction, and a rougher ride.
When setting tire pressure expectations with the team, significant early season testing
goes in to setting rough baselines for where we want to start. You can replicate this by
going out to a local park, dropping tire pressure, and riding some hard corners until your
tires start to feel unstable. From there, add a psi or so and take that as your baseline.
When you arrive at a race venue, part of your pre-ride routine is deciding what tire
pressure to run. As you do your first laps, consider the course, and think about what
obstacle will be hardest on your tires. Ride it a few times and add pressure if needed.
Keep in mind, while lower might be ‘better’, it comes with risks. Finishing is always
better than a mechanical, causing abandonment. If higher pressure lets you race
confidently, do that.
When measuring tire pressure, most of us have a floor pump to do this with.
Unfortunately, most floor pump gauges are inaccurate. Repeatability is the most
important factor to consider. If you have a pump or gauge that always reads 25psi at the
same pressure, that is great. In my experience, stand-alone tire gauges are more
accurate, leading to more consistent results. Furthermore, separate tire pressure
gauges avoid the air chuck issue that many pump heads have, where removing the
chuck lets air escape, further muddying your results.
Personally, I like the Bosch Easy Pump with an SIlca head as my main inflator. It is
accurate enough (within 0.5 psi), and fits in my pocket. For more accurate
measurement, I rely on gauges from Schwalbe, Topeak, and Efficient Velo Tools. The
cost of these items varies greatly, and although you get more accuracy out of the more
expensive options, a cheaper digital gauge will be more accurate than almost any floor
pump.
Finally, record your results. Either on your phone or a notebook, keep track of what you
rode tire wise and pressure wise given the conditions. With time, you will be able to
predict what tires and pressure you need, simplifying your pre-race routine and leading
to consistent results.
Interested in learning more or supporting the team? Check out
www.broadstreetoffroad.ca. What other insights would you like from the world of racing?
Let us know by email or drop by the shop.