Any tips on what to look out for when buying a mountain bike mainly for commuting (but, of course, also off-duty mtb fun)? Experience anyone?

MTB type? Wheel size? Tires? ... Gear?

I commuted for a few years on a hardtail MTB when living in Germany.

I really liked hydraulic disc brakes.

Never ridden a 29er.

Knobby MTB tires make for crappy commuting on pavement. They slow you down and just aren't well suited to pavement.

That's the biggest down side to a MTB as a commuter. There are some others, but that's the biggest one in my opinion. (I did it for a year and bought a a hybrid for commuting)

You can mitigate that by getting smoother tires with less tread for the streets. Basically turn the MTB into a hybrid. And if you want to switch between on and off road stuff regularly get a second set of wheel for the street tries so you can quickly just swap out wheels based on what kind of riding you're doing that day.

This is a good option on a cheaper bike with cheaper wheels. On a pricier bike with nicer wheels that starts getting expensive in a hurry.

I did about 4000km on mine. Didn't have any issue. Frankfurt bike lanes are quite tough compared to most though and the front suspension/knobby tires were quite useful.

+1

My 1997 Nishiki Blazer unsuspended mountain bike was my main commuter until 2015, it is still my winter commuter and utility bike. And I still ride it for variety.

Besides knobby tires, the other challenge was the low top gearing. I fixed that by putting on the biggest front chain ring that would physically fit. Now it has a tremendous gear range, and is fast; heavy, but fast.

Depending on distance. Less than 10 km, not so bad. Much more, not ideal.

Only suggestion I have is that you have some different tires for pavement riding. Maybe a nice wide Schwalbe Marathon. Very puncture resistance, and going wide will made the road feel a lot smoother.

There's a spectrum of mountain bikes.

You are likely shopping on the cheap end and that's a good place for your stated purpose. Just make sure you have a freehub not a freewheel, which usually means 8 speed not 7 speed in the rear.

if you want to upgrade from there, bikepacking or traditional touring rigs are extremely versatile.

A "real" trail bike with air fork and air shock on a complex rear suspension and a dropper seatpost is excellent at steep climbs and fast descents and you should definitely try one, they are fun as heck. But they're not great commuters.

Just that it is comfortable and that you get good smooth treaded tires. I have some mountain bike tires that are faster than any road tire at typical commuting speeds.

Incidentally right now I've got a "sport" mountain bike for sale, a bike I've had since 2002 and has served me well. But after having a dedicated commuter bike for a few years and now a dedicated mountain bike, it's easy to see its shortcomings at both. I now have both the wherewithal and the room to have both (and a tandem, and a C&V, and other family members' bikes).

As a road bike, if you put 1.5" slicks on it, its gearing comes out wrong, and it's not efficient. Better to have a lighter bike that puts you in a position to make steady power. But it takes a rack and luggage like a champ.

As a mountain bike, the biggest problem is the fork isn't up to snuff. Its seating is much like any modern hybrid, but mountain bikes are now sitting up and back a lot more with wider handlebars and more raked-out steering. And rear suspension is now good enough that there's no really great reason to avoid it. It isn't tubeless-ready and it doesn't have thru-axles which IMO are great. The max tire is 2.2.

I have a very short commute (2km to work) and commuted most of the summer on my hard tail mountain bike until last week. My mountain bike was a 2008 Kona Fire Mountain with 26" wheels with good tires for on the road. Road fine and did the job, put a rack on it and worked well. This bike was also used for bike rides with the kids and pulling a 2 seater bike trailer. I ended up having the opportunity of buying a 2016 Kona Dew Deluxe with 700cc wheels and the ride is night and day. Full 1 minute faster (originally only a 6.5-7 minute commute) and much, much easier to maneuver with the skinnier tires and no front shock bobbing around.

My suggestions, get either a 1) hard tail mountain bike with appropriate tires for all of your uses and have a shock with front lockout, 2) get 2 bikes, one for commuting and one for other uses. This way you also won't miss out on commuting or other uses by having one bike down for repairs etc.

Good luck

For commuting I use a hybrid. However, I was thinking about a mountain bike for snowy conditions... (+ fun, backup, variety)

Well then by all means try something more off-road and focused, and take a backpack if you want to commute on it.

I think in this case it would be much much easier to just walk.

Since when is walking 2km "much much easier" than biking 2km, let alone the time difference? You are wrong.

I live in the city and use a Giant MTB for commuting. I didn't want to turn it into a pack mule, so I use an Osprey Radial backpack to haul lunch, extra clothes, tools, lock, etc. I changed out the stock knobbies first for a set of Schwalbe Marathons then settled for the Schwalbe Super Moto which is a 27.5 x 2.4" puncture resistant street tire. The only thing I want to do now is change out the crankset from 40-30-22T to 48-36-26T. Where I live it's relatively flat and I was spinning out on the flat roads at about 18 mph. My one-way trip is only about 5 miles. I'm pretty happy with my setup.

Those Super Motos are pretty cool! I like the look of huge slick tires on a 27.5 MTB, it looks meaty without quite being a fat bike. I'm glad there's some huge slicks now other than Hookworms which are kind of a brick and Kojaks which are under 2"

Yeah, they're not exactly light, but I'm not that concerned about weight. I lost a lot of weight in the past year, so it more than compensated for it. I like the "meaty" look and they are very grippy on the street and give my bike a nice stance. They not only are wider, but this particular tire is taller, so it fills out every bit of space between the chainstays and behind the front derailleur.

If the bike will be parked on a parking with lots of bikes piled up, I'd avoid disk brakes - disks could get bent more easily than the wheels accidentally.

For convenience, I'd also avoid any suspension - adds weight, price and doesn't make much (positive) difference for pavement riding.

The most important thing - mudguards. For me at least, they offer a great deal of comfort for commuting - even when it's not raining, riding on a wet pavement without them gets you quite dirty often. Mudguards allow me to ride to work in the jeans I work in, no need for a change of clothes - saves time and hassle. Same for grocery shopping, going to town (cinema etc).

On the other hand, going off road, mudguards can be dangerous - a branch can easily get stuck between a wheel and a mudguard, causing an unexpected crash.

So I'd get a cheap, no suspension, bike for commuting (prefer 28" wheels bikes, though 26" has it's advantages) and another bike for "mountain biking".

I really like '80s and '90s rigid mountain bikes for commuting. You can set them up a million ways, use fat tires, and they're super durable. In Minneapolis on any given day you can find an old mountain bike that could be fixed up and ready to ride for a total expenditure of $100-$150. Here are the two Schwinn mountain bikes I've ridden recently.
IMG_4469 by [url=https://www.flickr.com/photos/53223642@N05/]


bike by [url=https://www.flickr.com/photos/53223642@N05/]


Each was under $100, and they make the best winter bikes!

Lower BB height to be able to put your foot down, comfortably, at stop signs and lights..


Every thing else is interchangeable parts... I have a Pre Suspension fork old MTB & a NL Koga Trekking bike,

Both use 559 (26") wheels

My two cents: I personally don't like to use a MTB for commuting. Nobby tires are one issue but for me it is mainly the geometry. The 26" MTB bikes I own have the correct frame height for my size but the wheel base is much shorter compared to my city/trekking bike.
Great for tight trails but not really comfy on long smooth city commutes. But I have not tried 29" mountain bikes which might be different.
But then you still have noisy uncomfortable tires. Or you switch to road tires and then the bike will be limited to light trails.
This is why I prefer to have a mountain bike for trails and city/trekking bikes for my commute. Quiet tires, fenders, chain guard, racks for panniers. I actually now added two recumbents to my fleet of commuter bikes.

These tires are inexpensive, very long-lasting, and roll pretty well:

Well, geeze, get some winter tires then. I have fun with studded tires in ugly conditions. Any old school hard tail mountain bike will work. New ones are getting too specialized to use for commuting.

A lot of hybrids are basically mountain bikes with skinnier tired 700c wheels.

This. These make great commuter bikes and can be a lot of fun too.