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I am considering the purchase of a bicycle for riding off road, and have heard a lot of buzz about 29" mountain bikes. However, I am not particularly interested in technical riding - although I would like to be able to ride through most things, even if I have to do so slowly.

I am leaning to a CX bike because I am familiar with the handle bars and geometry. However, the 29" also ride very smoothly. I can see that the tires, handlebars, suspension, and geometry are different, but what are the consequences of these differences that I need to consider?

Mountain Bike:

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Cyclocross Bike:

enter image description here

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For uninitiated person like me, which one of the bikes in your photos is the MTB and which one is the CX? –  tehnyit Aug 29 '11 at 12:16
    
@tehnyit thanks for the feedback. figure labels added. –  David Aug 29 '11 at 13:28
    
Nice question, David, generating a lot of good answers. –  Neil Fein Aug 29 '11 at 23:25

8 Answers 8

up vote 10 down vote accepted

There are a few very good answers on here already, however, I feel that a few pointers have been overlooked.

Height

I am not sure whether 29-ers suit all riders. Height comes into it, a 29-er imposes a high handlebar and heavier wheels than a 26" MTB. IMHO you need to be 6" or taller for the big wheel to make sense.

Standover height

The distance between you and the top tube is important on a MTB, regardless of your skill level. Most MTB's have a 'compact geometry' with big seat-post. Out the saddle it is useful to not have a 'five bar gate' between your legs, so, if you do go for the MTB, err on the smaller rather than the larger frame. You don't get this with CX bikes as a rule, although I would not be surprised if Giant do make one.

Brakes

Most 29-ers (if not all) come with disc brakes. CX bikes can come with discs but that is the exception rather than the rule. Disc brakes give much better stopping power, with little need for the rims to clean first. This gives you much better control.

History

Cyclo-cross pre-dates MTB-ing by some decades and the bikes for the sport evolved from road bikes. Meanwhile, the MTB evolved from a few Californians wanting to have fun, any notion of competition came along later. They were not tied down by UCI rules and UCI rules have always served to hinder rather than advance bicycle design. CX bikes are essentially a legacy product, for a 'formula' sport, not 'pure evolution'. They were not that popular before the mountain biking boom and have not been subsequently. Meanwhile, the separately evolved MTB is the 'weapon of choice' for many, many cyclists and CX ideas such as drop bars have not lasted long on MTB's (they have been tried by Johnny Tomac and Specialized did make a 'Rock-Combo' model with them, this was short lived). Wisdom of the crowds is that the MTB rocks off-road.

Suspension

For a long time I thought Suspension was a solution looking for a problem. However, there is suspension and there is suspension. A full suspension top end bike by the likes of Cannondale is amazing off road, you can roll over anything without losing speed or control. Cheap suspension is no good at all, i.e. the effort you get on a £300 MTB, perhaps useful for going up a kerb but that is about it. Modern, expensive full-suspension bikes are ridiculously light for how much is going on and a delight to ride. Well worth the investment, unless you are going XC with a bit of road to get to the trail in which case a hard-tail with front lockout is better for the ride as a whole.

Other uses

If you are a road-bike person then you probably carry nothing. Sometimes it is useful to have a bike you can carry stuff with. An MTB is really well suited to putting a rack on the back and carrying stuff. That may be just a trip to the shops or a long distance tour. Whatever your choice - CX or MTB, do look for those magical eyelets on the rear dropout for putting a rack on there. It may not be what you want to do now, but down the line it just might well be.

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I would say 29" in mountain bikes is a buzz word indeed. If this is your first mountain bike, do not make it 29". The selection of bikes, wheels, tires are quite limited comparing to 26".

Decision MTB vs. CX is entirely up to you. All depends on what do you mean by off-road. Off-road can be country roads or Alps singletrack, or downhill trails.

From my experience wheel size is not the major factor in being able to ride off-road. It is all depends on rider technique, bike can only help. If rider is afraid going down the slope, no bike will get him down.

If I had to choose between MTB or CX, I'd go for MTB with the following reasons:

  • Cyclocross bike is not quite road bike and not yet mountain bike.
  • You can put slick/thin tyres on MTB and it'll be rolling better. But you can't put fatter tyres on CX.
  • If you want rougher terrain, MTB can go anywhere, with CX you'll struggle.
  • I guess you already own a road bike, why not try something new?

Hope this helps.

p.s. my opinion is biased towards MTB, as I'm MTB rider for more than 12 years.

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2  
If a CX is half road bike and half MTB (I never thought of it that way), how is it different from a hybrid aside from the drop bars? Higher quality frames? More aggressive geometry? –  Neil Fein Aug 29 '11 at 23:24

With a mountain bike (26" or 29") you've got

Suspension: basically, suspension lets you get into more trouble. There's terrain you'd need to bail on (or crash on) without it.

Flat bars: Beneficial for two things (IMO)—maneuvering and lifting the front wheel to clear obstacles. Wider bars give more leverage, which may be useful on, say, a very rocky trail, and will attenuate small, unintended steering inputs on fast descents, which also may be a good thing.

More upright position: Also good for lifting the front wheel (less weight naturally carried on the handlebars), looking around.

Fatter tires: can handle more varied terrain.

I'm a roadie. I don't ride CX, but as far as I can tell, a CX bike is "road-plus" in terms of its capabilities. Put slicks on it and it is a road bike. For grass and dirt, it's fine. For riding over exposed tree roots and big rocks, not so great. A mountain bike is really better suited to off-road riding if that's where you'll be spending the majority of your time with this bike.

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Here in Belgium the Cyclocross is used a lot. The championship is a very popular winter sport, and is covered live on national television. It is specially suitable for the terrain here. Flat terrain with a lot of mud and sand.

The cyclocross bike cuts through the mud, and rides on the solid undergrond of the mud, where the MTB floats on the mud. The brake system (cantilever) is more capable for dealing with mud as disk brakes. And they are a lot lighter, specially compared to the 29-er.

The MTB has sturdy tires and suspension, and smaller gears. It is more suitable for rocks, climbing and downhill.

On the organized tours (flat and muddy) here you see a lot of MTB-26's, and a few 29-ers, since they are more comfortable to ride. There are about 2% cyclocross bikes. They are mostly a bit faster, but this could be due to the rider.

Even on the terrain that the cyclocrosser is made for, some "pilots" complain about their wrists after 2 hours of cycling, since they have no suspension and more weight on their arms. Tree roots an stones give more punctures.

Conclusion: On sand, grass and mud the cyclocross bike is a bit faster as a 29-er, but not as comfortable. On rock, steep hills or longer off-road rides the cyclocross bike is not that good.

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Comparing a 29'er and CX is like comparing apples to oranges. The 29'er is a special variation of the Mt. Bike. The CX is a completely different beast.

Extending what Traimax said, I think you may have narrowed this down the the wrong choice ( a "false choice".) (And I have ridden a CX bike (my first bike out of college, 18 years ago) and currently have a Mt. Bike (similar to the above) and a road bike (similar frame to your CX above but with very thin tires). I could not easily (and thus never did) ride my CX bike off road. I could have ridden it on a flat, smooth dirt/cinder trail but not on a gravel trail (if the gravel was more than 1" or so deep).

The differene b/t a 26" and 29" is minimal (in my very limited experience riding one a few times) unless you're riding on very rough stuff and then it just means you get over stuff a little easier, but I suspect it won't be the difference b/t being able to do a particular trail or not. However, the difference between skinny and wide tires is enormous. It can easily be the difference between being able to do a trail or now if that trail is muddy or has a lot of gravel.

I'd recommend flat (mt bike) style handle bars and wide(r) tires. I don't think the suspension (of a mt. bike) matters much unless you're riding on rough trails. And you do save some weight and a lot of cost by leaving out the suspension. If the two options you presented are your only options, I'd say go for the Mt. Bike. (It'll cost more but give you more flexibility).

If you have other bike options then:

The bigger decisions are:

  • Drop handlebars (style in your CX photo) vs flat (Mt Bike style).

    • I don't think there is much advantage (despire your experience with it) of drop bars unless you're doing a lot of road riding. Even on my road bike, I'm usually not in the drops, I've got my hands on the horizontal bar above it. In fact, most modern Road Bikes I've seen have a style of shifter that is integrated into the brake levers so that you can shift from the drops or the flats, so I think a lot of people spend a lot of time on road bikes on the flat portion of the bars (not in the drops).
    • There are a lot of advantages to the Mt. Bike style handlebar. It gives you much better manuverability, control and levarage. You can pop the front wheel over a rock (or more easily bunny hop over a stream or mud on a trail, or a curb on the road) and your hands are more solidly on the bars.
  • Thin tires or Mt. Bike style wide tires. Thin tires are faster b/c you can inflate them to a higher pressure and thus get less rolling resistance. That is their only advantage and it really only applies on flat pavement. (Might apply on hard packed ground but your reduced traction offsets this, meaning you're going to have to brake in turns. So I'd say the speed advantage is a wash unless its smooth ground with good traction (i.e., paved). Thin (skinny) tires give you less traction and sink into gravel or soft ground. As TrailMax said above, you can always put slicks (smooth tires) that are thinner on the Mt. Bike (although not quite as thin a tire as you could on the CX boke) but you can't put much thicker tires on the CX bike.

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I own a 29" MTB and a Cyclocross and while I use the CX for winter commuting, trips to the zoo and riding through the park, the 29er is basically for singletrails and mountains only. I rode most of the trails I ride on the 29er with my CX, too (pretty hard work though :) ), but I HATE riding the MTB on the road. So basically I would ask myself, do you want your bike strictly for "sport" in the mountains and woods? Go for the MTB then. Or do you want a versatile bike for everything including some mild wood & trails? That would be the CX.
I also think a 29er is a much better choice of MTB if you take longer trips or end up on roads once in a while.
I hope this helps!

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CX bikes are really intended as special purpose bikes (Cyclocross racing), however plenty of people do use them on the road. I would bet very few people use them where mountain bikes typically go. As someone else said, comparing a CX to a MTB is like comparing apples and oranges.

If you could shed some light on where you plan to do most of your riding then the choice might become more clear.

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I am not sure that I can be more specific than what is already in the question: 'I am not particularly interested in technical riding - although I would like to be able to ride through most things, even if I have to do so slowly.' I want to ride on trails, mostly non-technical stuff, and I don't mind going slowly or walking my bike through any technical stuff that I come across because I probably wouldn't attempt it regardless of the bike I am on. –  David Aug 30 '11 at 23:42

I have a cyclocross as my commuter, and a 26" MTB bike. I rode a loaned 29er for a mtb race this year, and while trying it out in the city, I noticed that I could hit the square curbs in the neighborhood and flow over them, much better than the 26" bike. No need to hop the front wheel.

If this will be your only bike, go with the CX. They are usually built with the CX racing in mind, which means running reasonable good when its crufty dirty. Means that you can get away with less maintenance if necessary, compared to a pure road bike. You can put skinny tires on it, and its a road bike. The extra brake handles on top give you more positions for riding comfort. I find that you can feel all the bumps in the pathways (like frost heaves and root bumps). This could be because I have skinny tires at 120psi, and the carbon fiber fork does not absorb much of the bumps. You can catch the front tire in wider cracks, and hitting a root at an angle can be dangerous.

If you have a road bike, and are looking for a second bike, go with the 29er. The wider softer tires, combined with front suspension, makes most bumps disappear. The upright riding position is quite comfortable. If the trails you want to ride have roots or rocks, the skinny tires on the CX require a skill level that you dont need to have on the 29er. The wider tires take more energy to move and keep moving, and the tread will have higher rolling resistance, so it takes more energy to go the same distance.

Final test before you buy. Borrow one from the LBS, and ride it on the trails you are interested in.

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