Discussion: Cyclocross Bikes in AR

Why do adventure race rules typically ban the use of cylcocross bikes?

I don't AR, but since you posted this under "Orienteering" --- I figure it's okay to answer anyway.

This 2009 blog has some reasons at least for one race, why cyclo-cross bikes were banned. ---They don't want people finishing too quickly.

...but there are usually no rules saying you can't put cyclocross tires on your (29er) mtb. like anything, it's a risk/reward situation. cx tires can be faster on the road or gravel, but also more prone to flats on singletrack.

Most people including me cant ride cyclocross on really steep or technical single track...so my guess is in some races they dont want people getting in over their heads. I had the same question, because i didn't even have a mb and wanted to do this local AR on my cross bike. but later when i saw the course, i realized i would have been pushing my bike around quite a bit.

One of the local races was gigged when the top two teams finished something like 150 minutes before the cut off time...in a seven hour race!...yet almost two thirds couldn't clear the course. And that was with e'erybody on mountain bikes. That bottom two thirds are not going to buy a cx bike to be competitive, but the top teams might, creating an even more unmanageable disparity.

It's not unusual for our local races to have three hour time gaps between the first and last teams, and that's for races in which the winning team takes three hours to finish!

How do they define a "cyclocross bike"?

roadish frame, drop bars, cantilever brakes. VS a mountain bike with a full suspension frame, straight bars with bar ends, different gearing and disk brakes.

You know a cross bike or a mountain bike when you see one.

So, my mountain bike has cantilever brakes and only front suspension. If I put drop bars on it, would it be out?

Are cyclocross bikes really that much faster? I want the numbers.

I'd add to Ed's definition that cx bikes have 700c x about 32-38 tires vs the 26 x 2. something tires. You can't put 700c tires on a Mtbframe as the brakes wouldn't fit to the rims.
I guess you could find some narrow 29 or 26 tires which might function like a typical cx tire.

Now that the UCI allows disc brakes on CX bikes, the distinction is getting fuzzier and fuzzier. This seems like a stupid rule. But UCI won't allow straight bars in CX races, which is also a stupid rule.

CX bikes are ok if you cover them with tape.

Come to a Canadian adventure race! I've never heard of such a rule.

If speed was of concerns wouldn't smooth tires be excluded, too? I've only done one short AR race for which I specifically bought a used MTB. Slick tires were a huge advantage on the 80% of dirt roads and they did not seem to be an issue on the 20% of single track. For a different race I might have used knobbies ...

Before reading this discussion I thought the prohibition might have had something to do with soil erosion, fat tires being gentler on the trails. What are the rules in big international events?

I have absolutely no experience from adventure races, but couldn't the rule possibly have something to do with the organisers not wanting to "rescue" teams that have run out of spare tubes? Mountainbikes should be sturdier and less prone to breakdowns, right? But from what I've heard, mechanical failures is always a big part of the "adventure" in AR, so I might be wrong...