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Cyclocross is off-road racing on drop-bar bikes, run through the autumn and winter on short laps of 2.5 to 3.5 km. Races are timed rather than a set distance — typically an hour for elites — and courses deliberately include obstacles you have to get off and run, including barriers up to 40 cm high.
Cyclocross is bicycle racing on a short, closed circuit of grass, mud, sand, gravel and whatever else the organiser can find, on a bike that looks very like a road bike. It runs September to February in the northern hemisphere, which is the first thing to understand about it: cross season is winter, on purpose.
It began as something road riders did to stay sharp over the winter, and the character of it has never really changed. The races are short, the conditions are usually appalling, and the whole thing is over in an hour.
That timing is why this page is on a turbo trainer site. The people who race cross are the same people doing their intervals indoors on a Tuesday night in November, because the season demands repeated hard efforts in the cold and the only reliable way to build those is somewhere warm.
This is the rule that confuses everybody arriving from road racing.
A cross race has no set number of laps. The organiser sets a duration — about an hour for elite categories, commonly 30 or 45 minutes for everyone else — and after the first lap or two the officials work out, from the leader's lap time, how many laps will fit. A board goes up telling you how many remain, and from then on it counts down.
So the lap count is a consequence of how fast the leader is going on the day. A dry, fast course might run seven laps; the same course under six inches of mud might run four.
Each lap is 2.5 to 3.5 km under UCI rules, and the course must be at least 3 metres wide throughout. At least 90 per cent of it has to be rideable — which, read the other way round, is an official acknowledgement that up to a tenth of it does not have to be.
The signature image of cross is a rider carrying a bike over a pair of wooden boards.
Under UCI rules a barrier is no more than 40 centimetres high, and no more than two may be placed in succession. Forty centimetres is a deliberately awkward number: low enough that a very good rider can bunny-hop it, high enough that most people are faster getting off. Some organisers put them in pairs or triples specifically to stop the hopping and force everyone to dismount.
The dismount itself is the skill that separates cross riders from everyone else. Done properly it is one movement: right leg through behind the saddle while still rolling, step off, two or three strides with the bike on the shoulder or in the hand, then back on in one hop. Done badly it is a full stop and a scramble, and across six laps the difference is enormous.
This is also why cross is a running sport. Nobody who cannot run is any good at it, and winter cross racers do running training, which road cyclists find faintly offensive.
Beyond the barriers, two features turn up on almost every serious course.
A sand pit is not an obstacle so much as a decision.
You can ride it, if you carry enough speed and commit, and you will gain several seconds on everybody who did not. Or you stall halfway, fall over sideways in front of a crowd that has gathered there for precisely that reason, and lose far more than you would have lost by running. The choice gets made about a dozen metres out and cannot be changed.
A run-up is a bank too steep to ride, often with steps cut into the top.
Everybody runs it, every lap, and by the fourth lap it is the single worst part of the course.
The rest is deliberately varied: off-camber corners where the bike wants to slide down the slope, tight turns that kill your speed, long drags into the wind, and sections of woodland singletrack. A good course changes what it is asking of you every thirty seconds, which is why specialists at any one thing rarely dominate.
Mud does not just slow you down, it adds weight and jams drivetrains. So cross allows something almost no other discipline does: you can swap your entire bike mid-race.
There is a pit — a marked lane, usually on the right, because most riders dismount to the left. You ride in, step off, step onto a clean bike your mechanic is holding, and ride out. Your filthy one gets jet-washed while you do another lap, and is ready when you come round again.
Bigger races use two pits at different points on the lap, so you are never far from a change. The rules are strict about where it can happen: changes must take place inside the pit lane, and if you have passed the end of one with a problem, you have to carry on to the next.
At the top level riders change every single lap regardless of whether anything is wrong, simply because a clean bike is a lighter and faster bike. It is the only cycling discipline where the support crew's jet wash is a tactical asset.
A cross bike looks like a road bike and is not quite one. Drop bars, but more tyre clearance, lower gearing, a slightly taller bottom bracket, stronger wheels, and a shape you can get your shoulder under without fighting it.
The number everybody quotes is the tyre limit. In a UCI race, 33 mm is the maximum width, and it has been a point of argument for as long as the rule has existed, because wider tyres would plainly be better in mud. Domestic racing is often more relaxed — many regional UK events allow 35 or even 38 mm.
Tread patterns are a whole subject of their own, and tyre pressure is where races are quietly won and lost: low enough for grip in the mud, high enough not to roll the tyre off the rim in a hard corner. People who are serious about it run tubulars for exactly this reason.
Here is the connection back to the rest of this site.
A cross race is an hour of repeated maximal efforts. You sprint off the grid, you sprint out of every corner, you sprint back up to speed after every dismount, and you do that perhaps two hundred times in an hour. Physiologically it is far closer to an interval session than to a road race.
You cannot build that on winter club runs. It needs specific, repeatable, hard work, in the dark, in December, when the weather outside is exactly the weather you will be racing in and therefore the last place you want to do your intervals.
So cross riders train indoors, heavily, through the season they are racing. If you are one of them, the sessions that matter are short and brutal: VO2 max intervals of three to five minutes, and over-unders that teach you to keep working while you clear the previous effort.
Our interval session builder will turn your FTP into the watts for either of those, and the cyclocross game on this site is at least an honest simulation of what the barriers do to your heart rate.
It is set as a time rather than a distance. Elite races are usually about an hour; most other categories race 30 or 45 minutes. The number of laps is worked out from the leader’s lap time after the first lap or two, and a board counts them down.
September to February in the northern hemisphere, with the World Cup running October to February. It is deliberately a winter sport: it began as what road riders did to stay sharp out of season.
A maximum of 40 centimetres under UCI rules, and no more than two may be placed in a row. That height is chosen to be awkward — hoppable by the very best, faster to dismount for everyone else.
Because mud adds weight and wrecks drivetrains. Riders swap to a clean bike in the pit while a mechanic jet-washes the dirty one, and at the top level they do it every lap whether anything is wrong or not.
UCI races cap tyre width at 33 mm. Domestic and regional racing is often more relaxed, with 35 or 38 mm allowed. Pressure matters more than most riders expect: low for grip, but high enough not to roll the tyre off the rim in a hard corner.
Yes. Up to a tenth of a UCI course does not have to be rideable, and between barriers, run-ups and deep mud you will be off the bike several times a lap. Serious cross racers do running training.
That is the problem we are actually trying to solve. Turbo Trainer Games turns your watts into the controls of a browser game — your power flies the aircraft, climbs the mountain, pulls the sledge. Nothing to install, and it works with a smart trainer you already own.
It is in closed testing at the moment, so there is nothing to play yet. But you can put your name down.
Ask for early access