Road vs. Mountain handlebar width

[gregk]

I have done some searching lately, but I can't find the answer- how does road bar width translate into mountain bar width?

I'm a roadie who is interested in getting into mountain biking this year. I have always been pretty particular with fit, and I am trying to decide on a handlebar width. I ride 42cm center-to-center bars for road... what do you recommend for mountain? It seems that flat bars are typically narrower- why is this the case? What if someone wanted a narrow riser bar? I suppose they could cut it off. Also, what is the difference between, say, having a 0 degree rise stem and a riser bar vs. a 10 degree rise stem with a flat bar? Wouldn't the actual hand position be nearly the same?

It seems that most flat bars are 560-600mm in width and riser bars are anywhere from 620 to 690 or so. Why would someone need such a wide bar for XC riding? Nobody rides 69cm wide road bars!

Here is the best explanation I could find of flat vs riser bars (suprisingly from the Pricepoint.com FAQ):

The advantage to riser bars is the position that it places the rider in. Riser bars put the rider in a more upright position and generally are 2-3 inches wider. By raising the hand position, some of the rider's weight is transferred back. Most people feel more comfortable descending in this position. The wider bars also create a feeling of stability (longer lever means less steering effort at the grip).

The disadvantages of a riser bar are weight, width, and also position. Generally these bars are heavier than straight bars. When the weight is transferred to the rear of the bike, steep climbing can become tricky. As weight is removed from the front of the bike, there is a tendency for the front wheel to want to lift, and wander all over the trail. In most cases this can be countered by transferring weight forward (leaning further forward) while climbing .

 

[gerardbjr]

I am definitely not an expert on this, but here is what I know:
Don't worry about flat vs. riser bar. Ignoring width, there is very little actual difference (I think) because there are many factors that determine final height of hands (such as stem angle). I have found that many people who choose flat bars do so because they prefer the look.
About width: much of what applies to road bars also applies to mountain bars. Wider bars allow for better stability and they also open up your arms for better breathing. Narrow bars give more responsive handling at low speeds (twitchy at high speeds), and they provide better clearance in narrow spaces such as between trees. A wider bar is more preferred by XC riders because they generally do not have to navigate tight spaces, and they ride at faster speeds where more stable and less twitchy steering is preferred. The bars on my mountain bike are the ones that came with it. I do not know what width they are, but they work fine for me (30mm rise).