rear hub problem.
11-07-21, 11:24 AM
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rear hub problem.
My road bike when I am moving it around off the bike, sometimes the rear hub spins like half a circle backwards, and then when it happens the chain comes off from the front deurailler and gets stuck between the frame and crank. It happens all the time, but doesnt happen when i try to replicate the problem.
It is a mystery to me why this happens. Does anyone else have the same problem?
It is a mystery to me why this happens. Does anyone else have the same problem?
11-08-21, 08:49 AM
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I'm thinking maybe you sometimes shift the front just before you stop from the previous ride and don't pedal enough for the shift to be completed.
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11-08-21, 08:54 AM
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Probably the weight of the pedal/crankarm is turning the crank backward because the chain is partly off.
11-09-21, 01:44 AM
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This might be it. When it spins, it seems it is weighted somehow, and makes half a circle. But I dont know why the chain would be partly off, I dont do anything. Sometimes Im standing still and it happens..
11-09-21, 09:04 AM
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Something wrong with your derailleur adjustments or the chain line is off somehow.
11-10-21, 10:35 AM
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The hub will spin backward by itself if the chain is about to come off any of the crank ring from the bottom.
For the chain to come off from the bottom of the big ring and straight to the frame, skipping the small ring, then you are somehow or something is pushing the chain sideways towards the frame at the bottom while you move the bike around.
By any chance you're carrying the bike with the drive side facing you? Your legs could be pushing the chain in without you noticing it. OR something on the ground is coming into contact with the chain as you move the bike around.
The only time the chain can come off by its own is due to "cross chaining" if the chain is on the big ring and also the biggest sprocket at the back (in terms of physical size). But since you mention the smallest rear ring, it is really weird the chain is getting to the frame instead.
For the chain to come off from the bottom of the big ring and straight to the frame, skipping the small ring, then you are somehow or something is pushing the chain sideways towards the frame at the bottom while you move the bike around.
By any chance you're carrying the bike with the drive side facing you? Your legs could be pushing the chain in without you noticing it. OR something on the ground is coming into contact with the chain as you move the bike around.
The only time the chain can come off by its own is due to "cross chaining" if the chain is on the big ring and also the biggest sprocket at the back (in terms of physical size). But since you mention the smallest rear ring, it is really weird the chain is getting to the frame instead.
But from what you are saying, I was thinking, maybe the front deurailler is pushing itself off because of the gap from the smallest rear cog is too large? is that even possible, if my front deurailler is not adjusted correctly?
11-10-21, 10:46 AM
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How new is this bike? Even if it's over a year old if you bought it from a LBS, they'll probably charge little to nothing if it's only a minor adjustment like the front DR not oriented properly with the rings or a limit screw that wasn't properly adjusted when they sold it.
11-10-21, 08:15 PM
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How new is this bike? Even if it's over a year old if you bought it from a LBS, they'll probably charge little to nothing if it's only a minor adjustment like the front DR not oriented properly with the rings or a limit screw that wasn't properly adjusted when they sold it.
11-11-21, 08:32 AM
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New components or scrounged stuff? If they are Shimano components did you get the tech docs? User instructions (UI), service instructions (SI) and if new enough parts the dealers manuals (DM)? The dealers manuals are everything you'd want a user manual to be. They give the most info about installing, adjusting and any regular maintenance if that part needs such. Shimano has docs for all their stuff online even from the previous Century. Other manufactures seem to take down old documentation or make it hard to find.
Did you mix and match component models and brands or did you use an entire groupset of the same manufacture?
Did you mix and match component models and brands or did you use an entire groupset of the same manufacture?
11-12-21, 03:32 PM
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11-12-21, 04:28 PM
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Am I seeing Di2? Although your description of when you dropped chains didn't sound like the same as mine, when I first got Di2 in March or 2020, I had a rash of chain drops. I finally figured out that as I was getting on and off the bike I was unknowingly pressing the shift levers. Once I taught myself not to do that the chain drops stopped.
If I ever suspect that I pushed them by accident when moving the bike around the house, garage or loading on and off the car, then I lift the back wheel and spin the crank a couple turns before I get on it to ride or just simply roll it around... if I think about it. It still catches me every great once-in-awhile.
If I ever suspect that I pushed them by accident when moving the bike around the house, garage or loading on and off the car, then I lift the back wheel and spin the crank a couple turns before I get on it to ride or just simply roll it around... if I think about it. It still catches me every great once-in-awhile.
Last edited by Iride01; 11-12-21 at 04:33 PM.
11-12-21, 04:35 PM
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Short chainstays exacerbate chain deflection, and backward rotation of the wheel facilitates derailment.
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11-12-21, 07:09 PM
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Am I seeing Di2? Although your description of when you dropped chains didn't sound like the same as mine, when I first got Di2 in March or 2020, I had a rash of chain drops. I finally figured out that as I was getting on and off the bike I was unknowingly pressing the shift levers. Once I taught myself not to do that the chain drops stopped.
If I ever suspect that I pushed them by accident when moving the bike around the house, garage or loading on and off the car, then I lift the back wheel and spin the crank a couple turns before I get on it to ride or just simply roll it around... if I think about it. It still catches me every great once-in-awhile.
If I ever suspect that I pushed them by accident when moving the bike around the house, garage or loading on and off the car, then I lift the back wheel and spin the crank a couple turns before I get on it to ride or just simply roll it around... if I think about it. It still catches me every great once-in-awhile.
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11-13-21, 08:34 AM
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When the line the chain takes from the front chainring to whichever rear sprocket is not parallel to the axis of the frame. The further off the frame axis this line is, the more likely it is for the chain to derail. Short chainstays and extreme gear selection (small front to small back, or large front to large back) exacerbate this.
11-14-21, 06:43 PM
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A video from below would make the cause more obvious. As stated above, it seems like you have a combination of a short chainstay and cross-chaining going on. You should be able to see the chain "miss" the big ring and fall onto the small ring. The bike industry wants you to believe that bicycle drivetrains (bicycles in general) are a solved problem but quite frankly, the derailleur system is just a bodge that got really, really out of hand.
What bike do you have, and what's the chainstay length?
What bike do you have, and what's the chainstay length?
11-15-21, 09:26 AM
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Sometimes bad things happen to good people, but if this "happens all the time", I'd be looking for ways to prevent it. Maybe don't leave your bike in the big-big gear when you're not actively pedalling forward. And if you're in the habit of choosing that as a gear for starting, I'd pick a different gear combination. There should be an equivalent gear combination in the small ring that runs the chain straighter.
11-24-21, 05:19 PM
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The hub will spin backward by itself if the chain is about to come off any of the crank ring from the bottom.
For the chain to come off from the bottom of the big ring and straight to the frame, skipping the small ring, then you are somehow or something is pushing the chain sideways towards the frame at the bottom while you move the bike around.
By any chance you're carrying the bike with the drive side facing you? Your legs could be pushing the chain in without you noticing it. OR something on the ground is coming into contact with the chain as you move the bike around.
The only time the chain can come off by its own is due to "cross chaining" if the chain is on the big ring and also the biggest sprocket at the back (in terms of physical size). But since you mention the smallest rear ring, it is really weird the chain is getting to the frame instead.
For the chain to come off from the bottom of the big ring and straight to the frame, skipping the small ring, then you are somehow or something is pushing the chain sideways towards the frame at the bottom while you move the bike around.
By any chance you're carrying the bike with the drive side facing you? Your legs could be pushing the chain in without you noticing it. OR something on the ground is coming into contact with the chain as you move the bike around.
The only time the chain can come off by its own is due to "cross chaining" if the chain is on the big ring and also the biggest sprocket at the back (in terms of physical size). But since you mention the smallest rear ring, it is really weird the chain is getting to the frame instead.
11-24-21, 06:17 PM
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At the very end of each ride I shift onto the small chain ring (34T) and the fourth largest rear cog (19T) to reduce chain tension and maintain a more or less straight chain line before I hang my bike up.
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11-24-21, 08:12 PM
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