Rear mech hanger breakage

Climbing up Langbar, rear mech got caught in spokes and got torn off frame


I was worried that meant a new frame for a moment, but I think it just means a new rear mech hanger and new rear derailleur.

Biggest potential culprit lower limit screw on rear derailleur not satisfactorily set to prevent changing down into wheel.

Looks like a bent spoke in frame.

To cycle home, I shortened chain a lot. But, it wasn’t great because it kept slipping upwards and then the chain was too stretched. I limped home from the top of Langbar, but it could have been worse. Probably the worst mechanical I’ve had whilst out riding a bike.



Broken hanger


I was surprised at the sudden force which ripped it off. I was just starting to climb a steep section.



Possible replacement hanger for Trek Emonda SLR CNC

D437 CNC gear mech hanger / derailleur hanger / TREK #135464



Cote du Langbar
Cote du Langbar

A nice view from Langbar, though I can’t say I was appreciating it too much.

7 thoughts on “Rear mech hanger breakage”

  1. Hi Tejvan,

    This questions is not very relevant to this post, but it is something that I’d be interested to hear you take on… When losing weight for hill climbs in Sept/Oct is it best to slowly lose weight as you are training, or eat as normal while training then try and lose it in one or two weeks closer to race time.

    I’m a pretty skinny guy, and last year I was 57kg for hill climb season. I’m up around 61kg now, training hard to bring my wattage up and don’t feel like restricting calories while I am training hard.

    What is your experience of this?


    • I tend to stay at 61kg all through year so have no experience of losing weight. But, I would have thought steady loss better than sudden. Also can be hard to lose weight if you cut back on volume of training for hill climb intervals in Oct

    • George – IMO you are wanting to loose body fat during training so cut down on pre-ride fat (including bread, cheese etc) and replace with pure carbs like fruit squash. You should not feel any lower in energy and all body fat burned during your ride will come from your body stores rather than your food intake. A low fat meal after a hard ride will burn more body fat through afterburn. If you spend 2 weeks prior trying to lose weight by dieting and not doing poor quality/no training you could quickly lose the muscle mass and fitness you have built up.

  2. I wonder if the rear mech got bent whilst transporting your bike? Do you put it in the back of your car or on a rack?

    It doesn’t solve it but it maybe something for the future.

  3. Your hanger did it’s job! You may already know that they are designed with inbuilt weakness in order that they snap before your frame is bent out of shape. Imagine if it was made of material as strong as your frame, you would indeed need a new frame or expensive repair job. When my hanger went (bike fell over while resting against a kerb) I had quite a job finding a replacement, good luck with that.

  4. Hangers are designed to break and Trek ones are generally available. Limit screw can cause it, as can bent hanger, both allowing the chain to reach the spokes.

    But just look at the state of your bike Tejvan, congealed grease and muck on the cassette and chain, now all it need is an object off the road, glass, stone, metal debris to get thrown up into the chain/gears and with your power…. bang, one seized up drive chain with ripped out rear mech. I know as I have done this, but my mech smashed into the down stay part of the carbon frame taking a chunk out in the process.


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