The Ins and Outs of Cross Bikes

An introduction to a cycling pursuit you may not be familiar with.

By Courtney Johnson

When the road and mountain bike season have ended but the ski hill has more mud and ice than snow comes the time of year called cross season. We have the Belgians to thank for a sport where the worse the weather and the more you suffer, the better for you. The sport is truly gnarly where race day may mean a mixture of perfect fall temps and sun to snow and frozen snot.

While a cross bike resembles a road bike in many ways, there are some significant differences. A cross rig needs to be lightweight enough to carry over the barriers but burly enough to handle mud, sand, rocks and any other obstacles on the course.

This article is intended to talk about the parts of a cross bike, not what a perfect cross bike is. Not all cross bikes are made alike, and there isn’t one bike that is better than the other. The perfect cross bike is the bike that works for you.

Materials

Starting with the largest part of your bike, CX frames are made from a variety of materials. Aluminum is the most popular material because it is lightweight, durable and won’t rust no matter the weather thrown its way. It also is cheaper in price than its counterparts. Steel and titanium do a better job of absorbing the bumps and jolting. But steel is heavy and titanium is very expensive. Carbon frames are becoming more popular as more options are available, and while expensive, the overall cost is coming down.

Geometry and Clearance

Cross bikes typically have a longer wheelbase for more stable handling. Additionally, the bottom bracket is higher for additional clearance of mud, roots, rocks and debris. For better performance and clearance, the front fork and rear triangle are wide. One final touch that cross bikes use is running the shifting and rear brake cable along the top tube. This reduces the amount of abuse the cables take, making them perform better and last longer.

Cranks and Gears

Most bikes come with a cross-specific compact crankset; most common is 46/36 or 46/38 chain ring. This lower gear allows you to power through the sand, mud and grass on the course. Another option is to run a single front ring to lessen the chance of dropping your chain. This limits your gears to nine or ten, but will make the bike lighter and virtually ensure you won’t drop your chain when you add a chain keeper. For the truly hardcore, you can always run a single-speed set up well. Choose your front ring, rear cog combination carefully if you go this route. Because of the low gearing offered by the 46/36 or 38 gearing, a triple chain ring set up is not needed. Converting an old mountain crank by ditching the granny ring is a great option, too. A 12x26 or 12x27 SRAM or Shimano cassette works well and many folks love the low gearing

Brakes

Brakes are typically center-pull cantilever brakes though now disc brakes, which have been lifted from a ban put in place in 2003, are appearing on some high-end bikes. Cantilever style brakes provide more room between the wheel and bicycle frame, allow mud to flow more freely between the tires and the frame. They also offer better clearance for the wide and knobby tires used for better traction on cyclocross bikes. Disc brakes weigh more and require more maintenance but can stop quickly at any speed and in any conditions.

Handle Bars

Drop style handlebars are the consistent choice. Some racers choose to have wider bars by a few centimeters for better leverage, handling and stability. The handle bar tape you use is based on personal preference. Gel inserts can help the hands soften the bumps and tacky ply tape can help with grip.

Saddle and Seat Post

There is nothing different with the saddle although some riders may choose to lower it a bit to make it easier to remount. You want to look for a seat that is more durable versus lightweight.

The seat post also needs to be durable over lightweight to handle the jumping on and off so a non-carbon post is recommended. Some riders choose suspension seat posts for the travel but they are not necessary (Rock-Shox).

Tires

Tires are the most crucial component to how your bike will handle. Cross tires are thinner than mountain bike tires but thicker than the typical road tire. Width choices range from 28 mm (700x28) to 40 mm (700x40) and the one you choose may depend on course conditions. If you are racing a USCF race, you cannot run any tire wider than 33mm.

Many use the standard clincher tire set up and most bikes come with the standard set up. Using the standard rim, tube, tire set up is perfectly fine. The drawback is that you need to run a bit higher psi, 30 and up, to ensure you don’t pinch flat, which is common in ‘cross racing.

The latest push has been to running a tubeless set up. In this setup, the tire sets a strong bead in the rim and creates a seal, thus negating the need for a tube. The advantage to this is that without the tube you have no risk of a pinch flat and can run lower tire pressures, 30psi and under. This is often an advantage as traction is hard to come by. It also makes the tire slightly lighter. To run this set up you will need tubeless compatible wheels and tires, offered by many manufacturers these days. You will want to use a sealant in the tire as that will stop any minor punctures and allow you to keep racing.

Tubular tires have always been the choice of diehard racers. Tubular tires are more expensive and harder to change, but like a tubeless set up won’t pinch flat and are the lightest set up you can have. Like tubeless you can run 30psi or lower.

Tread type and pressure is dependent on course and a major factor in the performance of the bike. The right tire size and tread patter makes all the difference. Small knobby tires are good for grassy and hard pack dirt. In snow and mud larger knobs works best as they don’t get packed with debris. Since many courses have a mix of terrain, there is often no easy decision on which tire is best. Additionally, you may run different tires for the front and rear. As you ride more and get more experience you will become better at learning what tire works for you. Since most races allow you to warm up on the course, try different air pressures and tread patterns to find what works best for you.

Wheels

Cyclocross racing beats up all your gear, especially your equipment. If you want to train and race on a single set, find a 28 or 32 hole box section rim. New on the market are wheels that can be run as a tube or tubeless set up. These wheels offer a nice option for those that get a bit more serious and want to go the tubeless route. The all out racer will choose carbon tubular wheels.

Deep section rims may be best for aerodynamics, but the also drive through sand and mud very well. These types of wheels are expensive, and typically best for racing only.

Pedals and Shoes

Most choose to use mountain bike shoes and pedals for the easy in and out, durability and traction (toe spikes). Pedal choice is also a matter of preference. SPD pedals do a good job keeping mud out. Four sided pedals, like Eggbeaters from Crank Brothers, can release with bumps but are easier to clip into. Whatever you choose, make sure to reduce the tension of your pedals for easier entry and release.

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Courtney Johnson is a freelance sports writer and photographer based just outside Denver. She is always up for adventure from stand up paddle boarding to snowshoeing up the mountain side.