How to protect rear derailleur while mountain biking?

Question

I am a college students, and I live right next to an amazing rocky area (picture below), I bike every day, and while I am getting much better and more confident I still take a pretty hard fall every so often.

My derailleur has been crushed so many times, and I have been forced to literally pull on it to bend it back into shape on more than one occasion.

I am hoping to replace the derailleur soon, but I would like to know if there is a good way to protect the derailleur during a fall - this will decide how much I spend on a new one!

This is the stuff that is crushing my derailleur every time I fall.

Answer 1

They make bash guards for derailleurs which mount to the frame which protect a derailleur in a crash like

but these are dangerous in that they transmit a hit to the derailleur to the frame (and frame damage is typically less repairable/ more expensive than a derailleur damage).

Usually, what gets damaged in a crash is the derailleur hanger, which can be bent back into shape with a special tool at your bike shop (Park Tool DAG-2 for example). You should never pull the derailleur into shape by the cage (this is the weakest part of the derailleur and can damage it more). On non-steel bikes, this is often a little replaceable part which is designed to deform in a crash so hopefully your derailleur makes it out alright as does your frame (so if you can't bend it back into shape, you can replace it).

Typically the Shimano Deore level is what gives you the best hit taking ability for the price, though it depends on how you fall and how the derailleur gets hit and stuff. The best thing to do is "don't fall". But obviously, compatibility within brands and budget dictate what to buy.

I'm curious as to how the derailleur is "bent", and how you're straightening it though. It would be good if you updated your question with a diagram or picture of your "bent derailleur", along with the type of bike you're riding.

Answer 2

The derailleur is, unfortunately, one of those critical parts that is very hard to protect from damage; without sacrificing another part.

As Batman pointed out, you can purchase small hoops that attach to your frame and offer some protection. As he pointed out though, these types of products might protect the derailleur to some degree, but you risk transferring those damaging forces to the frame in a crash. Besides that, a derailleur is constantly moving and is very exposed to anything that might knock, touch or grab it.

There really isn't a whole lot you can do. It is easier said than done, but try not to fall as much. Pick your lines carefully through rocks and keep an eye out for anything that will snag it. If you lay your bike down on the ground, always make sure to lay it with the brakes facing the ground, in order to not put the weight of the bike on the derailleur.

One thing that I must ask, is if your derailleur has been damaged multiple times; during any of those incidents, did your derailleur hanger suffer damage? If the hanger has not ever been bent or snapped, maybe it is too stiff/strong and not taking any of damaging forces. I have always had bad luck with very soft hangers that snap prematurely. Try to find a lower quality one and use that. Maybe next time the hanger will bend instead of your derailleur.

Another thing that should be mentioned that every time you bend the derailleur back into its correct position, it gets a little weaker. It will bend under pressure that much easier each further time it is put under stress. Parts get fatigued and sometimes must be replaced, even if they still appear to be semi-functioning.

Sometimes it just comes down to luck at the time of an incident. Sometimes you take a spill and come out of it with zero broken parts. Other times, you can be looking at major damage to something (even from the most innocent of crashes).

Answer 3

Go Singlespeed or use an Internally geared hub to avoid the problem entirely. May need an eccentric bottom bracket or a bike with horizontal dropouts to pull this off without adding dangly bits like a chain tensioner. However, chain tensioner a tend to sit a bit further out of the way and are less likely to be damaged.

Answer 4

Maybe you could change the whole drivetrain to sram x4 because it is cheaper then shimano slx, XT. But also it's cheaper to replace the derailleur on sram x4 for around 20 dollars.