Have you ever had a rear derailleur hanger broken in the moddle of a tour?
 

I was in an LBS the other day, and the guy at the store said that I should buy a spare rear derailleur hanger for my bike before I start my tour. I've read that the hangers will get bent at one point or another (and people were able to bend them back into position, if done carefully), but do they ever snap right off? I figured that if the hanger snaps while I'm touring, at least I can get out a chain breaker and go single speed to the nearest bike shop.

Rear derrailleur hangers are not so expensive nor heavy. If you do not have any sort of accident with your bicycle, the hanger will not snap. Just take a couple of extra hangers in your bag. If they bend, it will be difficult to strait them back without the proper tools. They are easy to replace and do not require rear derrailleur retuning (usually).

On my last tour, the derailleur on my son's bike broke while we were going up a hill. He wasn't shifting or anything. It wasn't the derailleur hanger that broke; it was the aluminum body of the derailleur right where it bolts onto the hanger. I got out the chain tool and converted his bike to a singlespeed, and he rode it that way the rest of the way home, about 20 miles, including some brutal hills.

My sense is that taking an extra part along, such as a derailleur hanger or whatever, will only ensure that a different part of the bike will break. If you bring an extra quick release for the rear wheel, it will be the front one that breaks; and so on. It's Murphy's law, basically. You can't carry spares every part with you; instead, carry some basic tools so you can get the bike functioning again. Then ride to the nearest bike shop.

It would be a really good idea to take a spare if you are doing a tour with a lot of multi-modal transportation (bus/train/plane) or an offroad/mixed offroad tour.

Else, rear panniers do a surprisingly good job at protecting the rear drivetrain when the bike falls over.

Bending a derailer hanger is a rare enough event that you shouldn't worry too much about it. In 30 years of bicycle riding...touring, mountain biking, etc...I've never managed to bend one so far that it wasn't fixable. Even the ones I have bent are so slight that it's more of an annoyance than an actual problem.

If you do happen to bend one, you can straighten it back out by using a 5 or 6 mm allen wrench (depends on what size allen wrench your derailer takes) to leverage the hanger back in place...or at least enough to get you down the road. Even aluminum hangers can stand this treatment as long as they aren't bent too far to begin with.

If you have a replaceable hanger I can (sort of) see the point in carrying a spare, but otherwise you're going to have to find somebody to braze it on for you and make sure it's aligned and that the mounting hole is not distorted. That might be a tall order for a backwoods welder. At that point it's probably best to singlespeed it until you get to civilization and a framebuilder. Actually, you can probably get two or three speeds depending on your cassette and crank. (for example, 33x15 and 22x26 would work with the same length of chain)

Maybe I'm mixing up my threads, but is this the same guy who said to carry a full spare chain?

I agree that it's a bit over the top to carry a spare hanger. In 35 years of touring it has happened to me once and the hanger was part of the frame and not the replaceable type.

hehe...hell no! When it comes to chain, I know I only need to bring a few spare links.

is your hangar the replaceable type? or is it part of your drop out? if its replaceable it really cant hurt to pack an extra. if your packing an adjustable crescant wrench you can always bend it back with that long enough to get to a good bike shop that has the hangar allignment tool or a spare hangar. i had the clamp on my fromt derailleur snap on tour,, spontaniously.. however,, im not about to start packing a spare front derailleur. you obviously cant be prepared for everything but if its a small packable part, you might as well pack it.. nuff said.