Bent Derailure hanger , what cause it

[Smiley]

Never crashed my tandem and only traveled with it. Got my newly rebuilt rear wheel back from Jeremy and just could not get the shifting right today with a new chain and cassette so for the life of me after about 10 on the road adjustments I took it to a shop. Told them it shifted well in the higher gears but not the lower ones, the kid says that due to a bent rear deraileur and I said geez never crashed but let me know. They call back with two options , bend it back or put a new one on. Its a Aluminum frame with a bolt on hanger , I say DON'T try and bend it back just order a new one. So my question is how does this happen , many thanks for the answers.

[Kevan]

Muscal. Don't know your own strength. Ever watch the backend of bike during some not-so-smooth gear shifts? Some serious bouncing goin' on back there. Add frequency and you got the cause. I'm guessing replaceable hangers are more susceptible.

That's my guess and I'm stickin' to it. (Unless someone else has one better.)

[CalfeeFly]

Unless you watch your bike 100 percent of the time it can happen easily if someone bumps it etc. I was doing a mult-day ride and this evidently happened to me when it was in the storage area that night. They bend fairly easily which is why they are not that hard to bend back. Park makes a tool just for that use. They work fine.

[pdxmech13]

During the stamping process most of the hangers
will not be straight anyway. Have them straighten
it and keep the other for a spare. Especially since
it sounds as if it is only slightly bent atmo.

This is a good one that gets the job done btw

[Smiley]

thanks for the good feedback all, I should have known that something was a miss since I could not freely back pedal the cranks without a hang up when the bike was in the stand.

[alancw3]

bolt on replacement type hangers are much more susceptible to bending than say the old one piece ones incorporated into the rear dropout. campy 1010a and 1010b rear dropouts (the benchmark standard for many many years) were made of forged steel which is much stronger than regular stamped steel used in most bolt ons.

[Ginger]

Smiley...the bolt on deraillure hangars are *supposed* to bend...don't bother straightening it unless you just plan to keep it for a spare "just in case." It will bend quicker and easier the second time.

Be like a mountain biker and buy two new ones. Three if you're keeping the bike for a long time.

Be like a trials rider and throw one of the new ones on your key chain...just in case.
:)

You probably just erred when you leaned the bike up against something or perhaps laid it on it's drive side...not that you would do something like that. But it happens to the best of us.