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I've just had my road bike at service because of bad shifts respectively noisy gears on small-big ratios (my lowest gears). Of course I tried to adjust it myself first but never got to an acceptable result, either bad shifts on some cogs or noise, indicating something's off here that couldn't be fixed with just a bit more (or less) tension.

See original topic Shimano 105 R5800 - Noise on largest cog?

I thought I got it because everything was fine on a short test ride and on the stand but the next longer ride proved me wrong.

The mechanic quickly found out that my mech hanger was slightly bent (inwards) and got it fixed without any cost and waiting time, which is great. I'm not aware of any impacts or crashes, just a bit of ambitious riding/racing since the last service and the issue just came by itself, from my memory even during a longer ride.

He said that might be related to out-of-the-saddle efforts that could put stress on the rear derailleur (or the hanger as designed weak point).

I'm of course aware that you shouldn't do hard shifts under load and generally back off power when shifting, especially uphill, but I never heard that just out-of-the-saddle riding would contribute to hanger stress (at least that's how I understood it).

Also, I never had any bad hanger damage with this bike, but could it be that the original hanger that came with the bike is weakened after couple of years and replacement on the next service might help?

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I agree with you. I can't see any plausible way to apply a significant sideways force to the hanger just from pedalling.

Indeed, you shouldn't get much force in any direction just from your effort. The hanger has 2 points of contact: the derailleur and the frame. Bending would require a force applied on one of those (the derailleur, taking the frame as a reference). Pedalling force leads to tension on the top line of the chain between the chainring and sprocket. Following the chain backwards, by the time we get to the rear derailleur, the chain isn't under tension from your efforts. That's why the RD is sprung, to provide enough tension in the chain as it returns to the chainring. This is a pretty weak tension - gentle hand force is enough to overcome it when you're removing a wheel.

Even if the chain doesn't move in a plane parallel to the chainrings (it won't, in almost every gear with multiple sprockets to choose from) it will be close. So the fraction of applied force in the sideways direction is small. And it's a small fraction of a small force. This all assumes a constant choice of gear, but single shifts don't change the picture very much.

Even really banging down through the gears shouldn't really apply more side force to the hanger at high efforts compared to low, because the chain tension at the RD is from the weak spring not your strong legs. Forceful or sudden gear changes under load can dramatically change the resistance to your pedalling - not what you want when standing on the pedals, especially if you're rocking from side to side in sync with your pedal strokes. Such abrupt gear changes do cause the chain to jump around, at which point I wouldn't like to bet on it behaving properly, even though the likelihood of it bending anything is still very low.

If you do manage to apply even fairly moderate pedalling effort to the lower chain line, you can definitely bend a hanger, for example if the chain jams in the cage. But it wouldn't happen without you knowing about it. Mine is integrated and made of steel, with a 5×6mm cross section at the narrowest point. When I got something caught in the chain, that bent the hanger very visibly. It also wrecked the chain, the derailleur, and several spokes. That was climbing but fairly gently.

I'd say it's more likely yours took some impact you didn't know about, perhaps in storage. If you don't have one already, you should buy (and carry) a spare hanger. Personally I wouldn't replace it as a precaution, but if it keeps bending, it probably is weakened enough to consider it past its best.

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    One thing with imperfect setup of rear mechs, and even bent axles, is that they can test fine on the stand or a gentle test ride, but a real effort shows up any failings
    – Chris H
    Commented Jun 15, 2023 at 12:43
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    I reckon someone hitting the RD hard enough to bend the hanger while you're riding would result in one or both of you having a hard time staying upright (especially them if it was their front wheel). I'm more suspicious that it got knocked while not being ridden
    – Chris H
    Commented Jun 15, 2023 at 13:01
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    It might be worth seeing if anyone comes up with any reasoning I've missed (and if they manage to explain it, accepting their answer instead). Some of our best experts are in very different timezones. It looks like you can get spare hangers for Ridley online if you want, but if you've you've got a dealer you can get to, and you want to get one made by Ridley, you could wait.
    – Chris H
    Commented Jun 15, 2023 at 13:05
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    Yeah, I've unchecked it and wait for somebody else's spin on the topic. Meanwhile, I'll ride on and will remember to ask for a spare hanger when I get to the shop next time.
    – DoNuT
    Commented Jun 15, 2023 at 13:21
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    Yeah, if ambitious/enthusiastic pedalling could bend the hanger, it would happen all the time to people. Mechanic is totally full of BS. Commented Jun 15, 2023 at 15:54
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Yeah I tend to agree. Can't see pedalling forces being enough to bend a hanger. Especially inwards, at a "big" stretch maybe outwards in combo with an extremely bad chain line.
Pedalling forces would be parallel (or very close to it) to the Hanger, for that reason alone I'm sceptical.

But replace the hanger anyway, maybe it's been a bit weakened over time. It is meant to be a throw away consumable anyway. What harm could it do?

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  • Yeah, that's what I'll take away from it ... swap the hanger, on next service at latest or as first step when the problem crops up again and I'll leave the bike with my trusted mechanic for diagnosis.
    – DoNuT
    Commented Jun 16, 2023 at 5:40
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"bent inward" implies hanger was pushed there from outside. Your bike was hit by something, perhaps when you weren't around.

If the hanger was bent outward, then its possible the chain could have pulled it, but if the chain has some kind of blockage then its more likely to yank the whole derailleur up and around the cassette which tears the hanger off completely.

Most hangers have a "weak" spot, a narrowing in the metal or some deliberately weak bolts so that catastrophic damage does not continue through to the frame. Replacement hangers are cheaper than frames!


It may be possible to lever the hanger back out and continue riding. Steel should unbend okay, but aluminium hangers tend to crack suddenly when unbending. Even if unbending works, this is your warning to buy a spare hanger and get it in your toolbox, or even your on-bike spares.

Could you swap hanger on the roadside with the tools you carry on every ride? If no, then what else do you need to have ?

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    Yeah, random hit is the most likely scenario, the bike was definitely fine before the weekend (since I definitely rode those gears extensively in training rides) and I can't rule out that something happened in storage overnight but I just didn't notice the issue at first. Not sure if a 10°C temperature drop during the race actually does anything to cable tension so that the problem got worse during the ride but I'll take the bend as root cause, indeed.
    – DoNuT
    Commented Jun 16, 2023 at 5:34
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    Thinking further, I'd straighten this one then keep it as an emergency spare, fitting a new one. But I'd do that at the first convenient chance rather than worrying too much, and ride on the straightened one for now.
    – Chris H
    Commented Jun 16, 2023 at 5:48
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    Yeah, but I can definitely afford to buy two fresh ones if needed. My LBS is a Ridley dealer and since all their ~2015-2019 carbon road models used the HAARCERID033 code hanger, I'm pretty sure he has some of them in stock. I think, the RD is a 5mm Allen key and the hanger itself has smaller ones (probably 2mm?) which should both be on my multitool if I ever need to swap it out on the road.
    – DoNuT
    Commented Jun 16, 2023 at 8:07
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    My frugality is partly financial, but it's also a more general desire to get the most out of things. It's become a habit, even on quite small things
    – Chris H
    Commented Jun 16, 2023 at 19:57

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