I bought my first mountain bike this year (Specialized Chisel). The uncut bars are 760 mm, but I basically ride with my hands just under and inch from the ends. I could see myself riding them even narrower if I could move the grips for wrist comfort and tree clearance. Should I go ahead and chop 20 mm off each side?
I don’t really know what the normal size for an XC bike is. I’m 5’11”.
Why would you think that in the first place or even mention it when the question is all about handlebar width?
Regardless of those, the Chisel is only available in 29" wheels. It’s never been sold with anything else.
The bars that came with my 29er Camber were 800mm wide. They were hurting my wrists. I cut off 10cm and they are still wider than my last bike!
Similar height to me, I ran 720mm bars for the last few years on 70mm stem, just went to 740mm on 60mm stem.
If you do decide to do I’d recommend getting a pipe cutter which means the ends will be straight and neat, also means instead of taking bars off the bike to clamp in a workbench you only need to remove your grips.
Any trimming IMHO should be done in steps, my bars started at 780mm but are now at 750mm, I did it in 5mm cuts and had a few rides before the next trimming. Much better to be a bit wide than have to fork out a big chunk of cash as you’ve made them too narrow.
I don’t understand the wide bar trend on MTB’s….yes, I understand that they supposedly give you more control, but good lord are they uncomfortable. I’ll gladly sacrifice some control for comfort.
I cut the bars on my fat bike as narrow as I could (could not move the shifters / brake levers inward any further and they are still way too wide.
I still miss reasonable width bars and a good set of bar ends.
OK, excuse me now….I have some kids to shoo off my lawn and clouds to yell at. 
Depends on reach length. In general terms for a given rider, slimmer bars work better with longer reach, and wider bars with shorter reach.
I’m 6’1” and 740mm with 80mm stem is perfect for me. I’ve also never understood the wide handlebar craze. It’s personal preference I suppose.
Contrary to what others are saying I’d say stick with wide bars. Not sure what the argument for cutting bars is. Wide bars give you more precise steering input, the bars flex is usually more benign and predictable and crucially, they force you into a more dynamic body position on the downhill with less straight arms, center of gravity closer to the bikes center, more weight over the front axle and you turn your upper body more into the corner.
A long reach combined with wide bars can be uncomfortable, but I’d recommend trying a shorter stem first before cutting your bars back to 2007.
Comfort.
If you are riding with your hands in that far for comfort, I would cut them. I would recommend verifying that it is a comfort thing and not because your grips and controls just happen to land you there. You can experiment with some soft foam grips, you can slide them around pretty easy with some alcohol. You can also cut them to just barely fit your hand and place them in different locations, adjust your brake levers to match the positions, and see what is comfortable for you. Cut to match.
I had 680 on my old XC bike, it was totally acceptable. I ran 720 on another bike and felt it would have been better and considered changing my XC bike to 720. My current XC bike came with 740 and while the control is nice, it feels too wide for bar bashing in a mass start. But they bike is so well built components wise I don’t want to waste my money changing anything.
My trail bike? 800mm. I would consider experimenting with 820 and a slightly shorter stem (came with a 45mm). But the 800 is comfortable and works, so I am not in a rush to change it. And yes, my hands are on the very far edge of the grip.
If you spend much time slicing through narrow XC tree trails, the advantages of slimmer bars becomes apparent pretty quickly.
An option can be to buy a cheaper (or used) set of bars to test out width. Find your favorite, then cut down your fancy bars to match
First ride “upgrading” from my 29er hardtail to a Trek EX, I was descending down a steep rocky trail at about 20mph and shot in between two trees. The heels of both my left and right hands brushed the bark as I went through. Felt a little like Lando Calrissian at the end of the end of Return of the Jedi.
I found my descending handling is much better with 760 bars over something shorter on my XC bike.
Wider bars and shorter stem make the handling tighter, vice versa for longer stem and shorter bars. There isn’t a way to say “This size is better for this” because it is all relative to what kind of riding you are doing. The wide bars and short stem may be good for descending, but for times when you are putting power down, narrower bars and longer stem will be better.
It’s all about goals. I think it is a good place to help even out weak spots, i.e. if your power and climbing are your strong suits, maybe go with a shorter stem and wider bars to help with handling and descending.
I think the synopsis is that bar width is a compromise between comfort and control. You might take the advice to optimize your weakness, but I don’t think everyone will agree with that. Personally, that’s my choice though - on a bell curve I’m a stronger climber than descender so I default to a slightly wider bar. I’ve landed on 770, or 780 depending on the bike. I also think that most people can adapt to different width bars quicker than expected.
You have an opportunity to try wider bars than you’re used to, why not use that? If you do decide to cut them, go 5mm increments (on each side so a total of 1cm per cut) - pipe cutter is OK if you have aluminum bars, but it’s very possible to cut bars on the bike with a cutting guide and proper hack saw.
This is good advice. Bar width seems to also be very particular, i.e. there is no correct choice for everyone. It is very relative to the individual rider, so one rider’s narrow bars might be far too wide for another rider.
I’ve managed to knock out both ESI bar plugs in XC races at 720mm, 750mm and 780mm. After a few rides I’ll always end up on the edge of the trees.
750 just felt perfect to me, I don’t feel any additional comfort from narrower bars that others have described. I have a 50mm stem, keep the stack pretty low and it just seems to work for me for XC racing, 12 hr rides, and all of the other dumb riding I do.
If you are comfortable with this width and you always find your hands in this position then I would probably just leave it. Or maybe start with chopping 10mm off each side. You can always cut more off later but you can’t add that back on.