I’ll start my in-depth cyclocross series with what is the most important, and often mis-understood, aspect of cyclocross equipment: where the rubber meets the road. Many racers are familiar with either road or mountain bike equipment, but starting from either of these schools of thought can lead you down the wrong path. Additionally, stock cyclocross bikes rarely come with an ideal setup.
Clinchers – I’d say that 90% of racers (across all categories) are racing on clinchers, and most bikes are sold with clincher wheels. Standard, clincher wheels are not the best, but they are perfectly adequate when used properly. I rode clinchers and finished on the lead lap at the USGP Fort Collins in 2011. (I used them because in mostly-dry Colorado, my only mud tires are clinchers).
To maximize performance from your clincher setup, make the most of their primary advantage: Tire selection. Tubeless tires can be changed, but it is messy and not nearly as easy as a simple clincher setup. If you’re not racing under UCI rules, choose a 35mm tire which will also mitigate pinch flatting.
Tubeless – I used a tubeless setup in 2010. I found the performance to be an improvement over tubes, allowing me to run lower pressures. I found it difficult to swap tires due to the messy sealant and tight tire beads. I also found that I really beat up my rims when I would occasionally hit them (once pinching through the entire tire). The tall rim/braking surface is much more prone to bending than on a tubular rim. Another advantage comes from the mandatory use of sealant, if you live in an area prone to thorns.
Even with an ideal rim/tire combination, at race pressure there will always be a risk of a failure in a tubeless system. On dry, sandy courses, sand and debris can be driven into the tire/rim interface and can cause leaks. On rutted or frozen courses, the tires can be pulled off the rim, causing a ‘burp.’
Tubular – This may seem like the ideal setup (it can be), but there are significant downsides. Tires can’t be changed between wheels, so you’ll need to compromise on tires or have multiple sets of wheels. A tubular tire specific to the day’s conditions will always be fastest, but what are the chances you’ll have the right setup on race day?
Personally, I raced tubulars in 2011 and was pretty happy. I used an intermediate tread (Dugast Typhoon), and found it to be useful on most days. However, if you’re not racing UCI races, I’d suggest a 35mm Rhino (or the smaller but more durable Specialized Terra), especially here in Colorado. The aggressive tires aren’t much slower, and most riders will like the smooth ride and grip of a larger, aggressive tubular.
Rim Depth – You may have noticed many riders on deep profile wheels (including myself). These wheels may offer better steering and debris shedding in deep sand, snow, and mud but I think the benefits are minimal. I use deep profile wheels, but only because I only have one pair of tubular wheels for road and cyclocross. Low profile wheels will be lighter, and plenty stiff and durable if they’re built with enough spokes.
Carbon vs Alloy – Carbon wheels will be slightly lighter, but they won’t have the impact resistance of alloy. If you’re using low pressure tubulars properly, you will be hitting the rim occasionally and risking breaking a carbon rim. Carbon also has less than ideal braking performance, especially in the wet.
Size – Like I said above, almost all riders will be happier on bigger tires since they’ll allow a lower pressure, smoother ride, and more grip. One exception may be mud tires. A larger volume tire can ‘float’ on some types of mud. A narrower tire can sometimes sink through and ‘bite’ on the firmer soil below. I use narrower (31mm) mud tires (WTB Crosswolf).
Tread – There are three broad categories of tread. There are ‘file treads’ with almost no knobs, but I’ve never used them (they’re commonly seen on grassy, sandy, and snowy courses). Mud tires have large knobs with a lot of open space between them (so they don’t pack full of mud). Intermediate tires have smaller, more closely spaced knobs and work well in most conditions (but NOT extremely muddy courses).
I’d say the most important thing to have is a dedicated mud tire if you race in wet conditions. Intermediate treads work well in many conditions, but simply will not grip enough when there is a lot of slippery mud. At the 2011 USGP (when I selected my clinchers), I knew quite a few guys on Typhoons and they could hardly even pedal their bikes. Most of the time the finer details of tread patterns don’t matter much, but when there is a lot of mud you must have a specialty tread.
How low can you go? – This is usually the guiding principle of tire pressure for cyclocross. Course conditions, tire type (tubes, tubeless, tubular) and rider weight will dictate the ideal pressure. Keep in mind that many pump gauges are inaccurate, especially at low pressures. Consider always using your own pump to get consistent pressures. Otherwise, carry a quality tire pressure gauge.
On clinchers with tubes, the lowest pressure that avoids pinch flatting is the ideal pressure. Colorado courses frequently feature sections of hardpack dirt with embedded rocks. Keep in mind that the rocks can be easily avoided during warmup, but in the race you may be following closely behind another race and not be able to avoid them. I weigh 160 lb and would probably ride low to mid 30′s for most courses. Tubeless setups have similar constraints due to burping / bead integrity. With my tubeless setup I was able to use pressure just below 30 psi.
Tubular tires are a bit different. If the pressure is too low, the tire will squirm and even fold over in corners (especially on pavement). In some cases, even this can be tolerated if there are only a few paved corners on the course and the rest is extremely bumpy or slippery. On my 33mm Dugast Typhoons, I generally start at around 27/28 psi for my preview lap. In extreme conditions riders will run pressures close to 20 psi in their tubulars!
Personally I’ve got deep carbon tubulars with intermediate tires, which I use for most races, complimented by a set of mud clinchers. It isn’t ideal because I’m risking breaking a nice pair of road wheels, and I can’t use low pressures that increase traction when its muddy.
I think the wheel for most riders in Colorado would be an alloy tubular. You won’t have to switch brake pads every weekend, and can run low pressure with minimal risk to your equipment. A wheelset like this can be custom built for about $400. Used in combination with a higher volume, durable, high quality tubular with an aggressive tread, this wheelset wouldn’t be the sexiest, but it would be versatile, durable, lightweight, and affordable.