Derailleur Types For Mountain Bikes

Video Transcript

"Your mountain bike is going to use one of two different types of rear derailleurs. Bunch of subtypes and stuff like that, but the most important think to know, when selecting your derailleur, besides the diameter of the tube, which should be marked, if you have a derailleur on your bike, and you're upgrading, should be marked on the inside. They start at about 24.9 mm and they go up to 31.9 mm. Really depends on the size of this tube and clamp diameter. The other thing that's really important to know, with front derailleurs, is whether it's a bottom-pull or top-pull front derailluer. This bike here is set up to use a top-pull front derailleur. You can tell because there's a cable stop there, that's designed to pull up on a, pull up on a derailleur. On this bike here, I’ve mounted a roller, so you can use a bottom-pull derailleur. And you can see when I push that lever, up on the handle bars. The lever actuates, the cable, the cable pulls the roller, and everything like that. By adding a roller there, it allows me to use the preferred style of rear derailleur that I want, I mean front derailleur that I want, and still have good cable routing. When you have a bottom-pull rear derailleur, it's routed along the bottom of the tube, usually, and comes up under what we call the bottom bracket shell. Which is this area here. And a nice thing about the bottom-pull derailleur is that it's a little bit simpler, because the spring just has to work one way. And it allows you to use a road-style derailleur, instead of a mountain-style derailleur. The one on here is something off a road bike, and the reason I've used this one is because it's a little bit stiffer, and it's better at shifting across two chain-rings and not just three. So on your standard mountain bike crank, you've got a small chain ring mounted, and then, you know, that's mounted here, and then you have a middle and a large chain ring. if you're just using a middle and large chain ring, and no small ring, with a mountain bike derailleur, which has a wider cage, this area here is little bit wider, profiled differently, and the geometry of the parallelogram is different, because I have to shift across an area this wide, versus an area this wide. When you're using two rings, it doesn't work as well. So, if you want to use one or two rings, know what the diameter of your clamp is, know what your pull is, and you should be ok. If you have any further questions, you stop by a bike shop and ask them, they're certainly going to be able to tell you."