Catastrophic drivetrain failure

[benb]

@benb is it aluminum? If not, Tim has an adjustable spanner and I have the brute force. All Chas Roberts will use is a fancy bolt and breaker bar to do the dirty deed.

It's steel. I think I'll take it to the framebuilders. It won't be until the new year though.

 

[snailracer]

Sheldon says "When a derailer hanger is bent, it is generally necessary to remove the derailer to straighten it. Bike shops have a special tool, a bar with a sliding gauge on it, that screws into the hole in the hanger in place of the derailer. This tool provides lots of leverage to straighten the hanger with, and has a gauge to judge when it is parallel to the rear wheel...."

From Park Tool:

 

[mickle]

It's steel. I think I'll take it to the framebuilders. It won't be until the new year though.

It really doesn't need a framebuilder - just a competent LBS workshop. I've got a dropout alignment tool languishing in my garage if you'd like to borrow it.

Worst case scenario - the hanger separates from the dropout and you'll need to employ a frame builder to tidy up the edge of the dropout and braze a new hanger tab on to it. But there's a few bends back and forth left in it before that happens

 

[benb]

It really doesn't need a framebuilder - just a competent LBS workshop. I've got a dropout alignment tool languishing in my garage if you'd like to borrow it.

Worst case scenario - the hanger separates from the dropout and you'll need to employ a frame builder to tidy up the edge of the dropout and braze a new hanger tab on to it. But there's a few bends back and forth left in it before that happens

Maybe I'll take it to Pearsons - they know their stuff.

 

[fossyant]

The dropout is steel. Take an adjustable spanner to it and straighten it carefully. Done it myself to a road bike after a crash. Don't get ripped off !

Steel frames don't use replaceable mech hangers as you can bend them back carefully. That's the property of steel. Same can't be said for aluminium.

 

[GrumpyGregry]

Maybe I'll take it to Pearsons - they know their stuff.

That is true. They also know how to make money from people. I realise the quoted ballpark of £200 is probably sight unseen and they are catering for the worst possible starting point, and it may included painting, but it seems like one heck of a lot of money to me for 15 minutes of sweat whilst they set about beating your bike with a metal bar.

The last time I saw an LBS do the job, with the proper tool and everything, they refused payment.

 

[GrumpyGregry]

If you want this not to happen to you:

Clean your drive train

Index your gears properly

Change down on the approach to a hill rather then changing gear going up a hill and please do not change gear when going up the steepest part of the hill and you are up out of the saddle...

and even then be prepared for it to happen to you. Because it will.

 

[mickle]

Re-align hanger and fit new mech and chain: about £20 in our workshop according to the mechanic. Plus t'cost of t'parts. I know it's only York and not That London but still - quite a bit less than £200.

 

[snailracer]

Re-align hanger and fit new mech and chain: about £20 in our workshop according to the mechanic. Plus t'cost of t'parts. I know it's only York and not That London but still - quite a bit less than £200.

One could even buy the Park Tool derailleur tool for a mere £60.

 

[screenman]

http://fagan.co.za/Bikes/Csuck/

Beano1 could you explain to us how chain suck bends a mech, I have seen plenty pulled straight but never bent.

Do you not think that once the loose plate hit the cage this would have stopped your pedaling motion, which in turn would have kicked the freewheel into play.

As someone who works with metal most of my time, I would advise against having a go yourself and bending cold.

 

[mickle]

As someone who works with metal most of my time, I would advise against having a go yourself and bending cold.

So all those derailleur hanger re-alignment tools in the hands of professional bicycle mechanics up and down the country? Designed and manufacturered by many reputable bicycle tool companies all over the world? According to you we shouldn't be using them? Srsly?

 

[screenman]

" professional bicycle mechanics" I believe that you just wrote this.


From Sheldon.
Spoke Protector
A plastic or sheet-metal disc that fits between the cluster and the right-side spokes of a rear wheel. This is intended to prevent the derailer or chain from getting caught in the spokes, possibly causing very extensive/expensive damage/destruction to the wheel, the derailer, and the frame.
A spoke protector is not a necessity on a bike that is well treated, because the derailer can't go into the spokes if it's properly adjusted and if it is not bent. Bicycles which are subjected to rough handling, however, are prone to getting the rear derailer bashed in, and in such a case, the spoke protector can prevent very serious damage.

OK so you take the DIY method, make sure whatever you do that the hanger is straight through all planes.

 

[benb]

That is true. They also know how to make money from people. I realise the quoted ballpark of £200 is probably sight unseen and they are catering for the worst possible starting point, and it may included painting, but it seems like one heck of a lot of money to me for 15 minutes of sweat whilst they set about beating your bike with a metal bar.

The last time I saw an LBS do the job, with the proper tool and everything, they refused payment.

He did say it may be as low as £50. It depends. If the frame is unfixable and he has to cut away part of the chainstay and seatstay and weld new sections in place, then ... £££

I think I'll take it to him and see what the actual quote is, and then decide.

 

[benb]

I was pedalling with some force (albeit on the flat), so I think when the loose chain link caught on the jockey wheel cage, it had enough force to bend it into the spokes. Then the momentum of the wheel pulled it further in and round, bent the frame and then broke the rear mech off completely. At least, that's what I think.

I appreciate the attempts to save me money, but I'd honestly rather get a professional to take a look with something as fundamental to the structure of the bike as this.

 

[screenman]

http://www.pinkbike.com/news/technical-tuesday-straightening-derailleur-hanger-2010.html

The reason I suggested that it might not bend back cold is the amount of bend it has taken, a tweak here and there but that is way more.

benb, I think you are making the right choice, please let us know how you get on as I will happily accept being wrong as it would cost you less.