CX versus mtb for gravel races
 

I just rode the 100K Castell Grind (central Texas). it was brutal. I am starting to question my wisdom riding a CX bike on terrain like this instead of a HT mountain bike. the route has many, many "washboard" sections that will either bring you to a halt or bounce you right off the bike if you're not careful, and a bunch of sand pits that make it impossible to ride in a straight line, if you make it though on your tires at all.

where do you draw the line between terrain for a CX-type bike and mountain bike terrain?

165 pound rider on my steel cx bike with tubeless 35mm tires at 35-40 psi.

i guess it would depend on the riders ability. the terrain would be a factor too. rock gardens are not fun on a cx bike, nor are roots and big jumps.

Where I live a mountain bike will run circles around a CX bike on 99% of the dirt roads and trails.

Try a no suspension 29er or 29+ with dirt drops.

http://nsmb.com/assets/images/A_even...s/_I4I1775.jpg

I think half of the people I saw on this past race were riding CX type bikes and everyone else was on a mtb. I think it was the washboard sections that killed me. 35mm tires at any pressure are just not enough to float over that crap. 2" tires at 25 psi would have taken care of that, maybe even suspension. I saw at least two Cannondale Slates, which would have been perfect.

this photo makes it look easy, but the first few miles had several sand pits and the rest of the route had tons of washboard surfaces that slowed me down a lot.

http://i819.photobucket.com/albums/z...psdtstnub8.jpg

I might try the next one on my mtb with ~2" tires, bar ends, and a rigid fork. there is no way I could get dirt drops to fit on my mountain bike and I don't think tires wider than 42mm would fit on my cx bike.

what's a tubeless-compatible 40-42mm tire with a tight-fitting bead? it has to fit tight because I am using non-TLR rims with Gorilla tape.

I use an upside down north road bar which, with the hands in the drops, is identical to a dirt drop. The advantages are that I can use MTB shifters and MTB hydraulic brakes, and, the drop is shallow so that I can use an ordinary mountain bike stem. No changes to the cable/hose lengths are needed when switching over from a riser bar. I have found, from years of riding rigid, that I can ride much more smoothly with my hands aligned along top tube rather than across like with a riser bar.

There are all kinds of alternatives these days. Surly Open Bar in zero and 40mm rise/drop and Jeff Jones bars.

I got a 29+ a few months ago. It's the ultimate no suspension bike.

PS Pics of my setup.

https://lh3.googleusercontent.com/1I...K=w890-h667-no

Notice how low my handlebar is. More like a road bike than a MTB. I don't have to be concerned with the fork compressing and catapulting me over the bars.

https://lh3.googleusercontent.com/0i...W=w890-h667-no

It looks like a REALLY fat tired path racer. Awesome!

Thank you Justin.

It really is kind of cool. Something like a Salsa Fargo seems like the ideal bike.

A Salsa can only take regular 29er tires. I can run regular 29er tires or 29x3 Plus tires. Also, because of the 135/170 hub spacing and 100mm BB shell I can run 26x4 Fatbike wheels/tires.

Cyclocross Magazine article on the race:

Another Serving of Texas Gravel, The Castell Grind 100k - Race report, Photos and 100k Full Results - Cyclocross Magazine - Cyclocross News, Races, Bikes, Photos, Videos

Looks like it was won by a guy on a cyclocross bike who barely edged out a guy on a Slate(not that that really says anything about what's best for that course.)

The long shot of the lead group in that article shows very nearly all of them on CX bikes, so I would say it tells you everything about what's best for that course. Well, best meaning "fastest," in this case. Other criteria may exist, but in the case of a race, that's what I think of.

I think the average schlub could ride that course faster on a MTB than on a CX bike.

average schlub is probably a closer description of my abilities than those beasts on CX bikes. that is why I am starting to think that a CX bike should not be my choice. I might be faster on my mtb.

Yes, they are beasts, most people aren't. You would have done better on your CX if you had a dirt drop and rode it drops only. Also, hydraulic discs make a huge difference.

not sure if serious.

I barely used my brakes at all during the race and my mechanical discs work fine. dirt drops would require that I had a ridiculously tall stem on top of the already huge spacer stack that I have on my bike. I have Cowbells now, which have a decent amount of flair to them. I ride this bike on most of the singletrack that I usually reserve for mountain biking, so handling is not the problem. getting bucked off the bike by washboards and sand traps is, in addition to the sheer mileage of the course.

I've got years of riding CX/gravel and rigid MTB. The width of a dirt drop really helps. The grip in the drops is unimpeachable. Hydraulic brakes have much finer control. Brake lightly to control bucking and bouncing. The drop of a Woodchipper or Cowchipper is no deeper than a Cowbell. The hoods are suicide on washboard unless you slow way way down.

Should have specified or used better words. Controlling the bike is not the problem. Maintaining momentum when things get bouncy and sandy is what kills me.

What I do is pedal against the brakes, brake AND pedal at the same time, even though I'm not needing to use the brakes. This keeps the bouncing in check and keeps the rear wheel from spinning out.

I would think that on nearly any terrain that a cx bike can roll it would be faster than a mtb/atb. But the rider might feel differently, you may be more comfortable and therefore faster on a mtb.

If that were true there would be no mountain bke races, only cross races.

alternate issue-

rider is 165 pounds
35mm tubeless tires
course has lots of washboards and a few sand pits
tire pressure? I think I had mine too high.

I think the two classes of bikes hide the real differences. Which are tire size and suspension. A cross bike with 50mm tires and an rigid MTB with 50mm tires are pretty equal. Throw in wildly varying tire sizes and suspension and things change pretty quick.

At Southern Cross this year I rode my 26" hardtail and absolutely blasted by some riders on CX bikes during the descents. Once the washboarding gets bad enough and the road gets steep enough the CX bikes just can't keep up with a hardtail/full-suspension MTB.

I'm not a great descender but riding a MTB hides a lot of that and allowed me to ride downhill significantly faster than the previous year. I also found it a lot more fun to descend with a front suspension so even if my placing was slightly lower than it would have been on a CX bike I had significantly more enjoyable experience.

However, it was with much chagrin that I noted most of the narrower-tired CX riders who I passed on the descent caught and passed me quite easily on the flats.

I'm not sold on either one being faster, it really depends on the set-up and the rider. For me, the MTB was faster downhill but slower on the rollers and the flats. It was also kind of a pain to manually lock-out the fork dozens of times.

I have six gravel events left this year. I'll probably ride my MTB for 3 of them that have serious descents and ride my CX bike for the other 3 that are flatter and faster.

If you have a disc 'cross bike, you could try 650b wheels with ~50 mm tires. Maybe that would be the best of both worlds? Adventure/rando bikes like the Elephant NFE are using this setup.

Good comment. Around here there is dirt that is rideable on a CX, but not much, except if you are a spectacular rider, and such riders exist. I know that me, myself, I on a MTB could run circles around me, myself, I on a CXB.
My 29er and my 29+ have no suspension and have drop bars, dirt drops.