I was on the trainer and all the sudden the bike violently fell. Everything looks intact, but the hanger was ripped off the frame and the screws holding it on were stripped. I can’t find any references to what the cause would be, as I wasn’t putting down crazy power. I had been adjusting the tension to get my shifting dialed in, but that can’t be it. Anyone know the cause of this?
by Unintelligibl
6 Comments
I have to add…the bent QR skewer was from the non drive side and bent as the bike fell
If I had to guess: the QR skewer failed first which is what caused you to fall, and falling snapped the hanger. Did the drive side end of the skewer come completely off the skewer? If that happened I could see the drive side drop out effectively popping off the trainer and then your weight of whichever pedal was down tipping you over and causing you to fall and bend the skewer and the derailleur hanger.
Looks to me like someone needs to learn how to use a quick release correctly.
The frame has quite a bit of wear on the drive side dropout, from here it looks like the skewer nut was sitting only on the hanger screws and slid out because the dropout is so worn. The screws should be recessed however if the aluminum is squashed and worn away enough they will protrude and prevent proper skewer tension. Screws ripped out after wheel came out of dropout.
Looks like the skewer has been overtightened repeatedly.
I am wondering if the freehub in your trainer locked up and the entire inertia of the flywheel went into the endcap that is supposed to be stationary and ripped the hanger off. That is the only thing I can think of that would have enough energy to bend that QR like that. Even if your QR was loose, I cannot imagine it getting bent like it is.
I had a weird thing happen to me a few years where I had a Quarq that used a magnet mounted near my bottom bracket. The magnet became unglued (apparently) stuck to chain, jammed by gears in a way so that the entire momentum of the bike ripped the hanger off my bike and the whole hanger and derailleur assembly swung around and broke my chain stay. Happened in an instant. One second I was riding and the next my wheel was locked up and I was skidding to stop.
It has to be a combination of things. My best guess given the photos and information you posted….
The skewer rattled slightly loose. Just enough for the dropouts to slip out of the trainer.
In addition the two hanger screws backed out and were hanging by two threads, or the threads in the frame/hanger were stripped already.
The bike came off the trainer first, due to a combination of weight shift forward and pedaling torque. Then the loose hanger came off. Had the limit screws been off, the hanger would have stayed on and bent. The skewer does most of the work holding the hanger securely in place. The two screws are only needed when the wheel is off and to keep the hanger from shifting or rotating.
The driveside detached first and you fell or leaned left, correct? This is what bent the skewer.