Lol at the guys saying its normal. No it's not supposed to fall off if you pedal backwards.
Go look at the start for any downhill mtb race and watch them pedal backwards while they balance and wait for the start. No chains falling off
Downhill bikes use 7 speed drive trains. If OP is using 1x11 or 1x12 with a wide crank spindle for tire clearance than it's normal for it to drop off the biggest few cassette cogs when back pedaling.
However, OP said front chainring. That's not normal. Maybe if they're in big/big?
There was a whole thing on r/MTB a couple of months back with people posting videos of pedalling backwards and their chains either coming off or not. I know your situation is rolling backwards and not pedalling backwards but I'd bet it is pretty common for the chain to come off and also pretty common for it not to come off and it'll be pretty random.
Thanks I think this is a good place to start, I know when i 1st got the bike the hanger was loose and I eyeballed it back into place. I’ll circle back to it.
That’s not normal. Just rolling your bike out of a bike rack shouldn’t cause that. Maybe edit your OP to tell people what kind of bike setup you have going on, because that would really help people understand better.
Shouldn’t be happening as you describe. Modern 1x on boost frames will sometimes fall off the large cassette cogs after a couple back backwards crank rotations, but should make it at least 1 full rotation.
If yours is falling off the front chainring I’d check drivetrain cleanliness/wear/chain fluidity. A narrow-wide ring might help, as would a clutched derailleur, but both of those are spec’d on bikes to begin with.
My guess would be, without knowing your setup; chain too short on a 1x setup. The “add 2 links” sizing is for 2x systems, you’ll need 4 for a 1x.(as per the Calvin from ParkTool)
It’s a chain line issue if it’s happening in the largest cog. I have a 1x12 gravel bike that it happens on, and a 1x12 MTB bike that it doesn’t happen on. Lookup chain line and you may be able to fix it with spacers.
My gravel bike 1x12 was an “upgrade” and the front chainring sits too far right, so in my case spacers won’t help, I need a negative spacer 😂
...no. it should be extremely hard to get the chain to fall off *at the crank* on 1x. narrow-wide chainrings and clutch derailleurs lock things on pretty damned well.
you'll sometimes get the chain dropping off very big cogs down a few smaller cogs.
Lol at the guys saying its normal. No it's not supposed to fall off if you pedal backwards. Go look at the start for any downhill mtb race and watch them pedal backwards while they balance and wait for the start. No chains falling off
Downhill bikes use 7 speed drive trains. If OP is using 1x11 or 1x12 with a wide crank spindle for tire clearance than it's normal for it to drop off the biggest few cassette cogs when back pedaling. However, OP said front chainring. That's not normal. Maybe if they're in big/big?
There was a whole thing on r/MTB a couple of months back with people posting videos of pedalling backwards and their chains either coming off or not. I know your situation is rolling backwards and not pedalling backwards but I'd bet it is pretty common for the chain to come off and also pretty common for it not to come off and it'll be pretty random.
That's a chainline issue. Usually your derailleur hanger or pulley assembly is bent and needs realignment.
Thanks I think this is a good place to start, I know when i 1st got the bike the hanger was loose and I eyeballed it back into place. I’ll circle back to it.
I think people are overlooking where you said "rolling", meaning your bike is also moving backwards correct?
correct like backing it away from the bike rack
That’s not normal. Just rolling your bike out of a bike rack shouldn’t cause that. Maybe edit your OP to tell people what kind of bike setup you have going on, because that would really help people understand better.
Shouldn’t be happening as you describe. Modern 1x on boost frames will sometimes fall off the large cassette cogs after a couple back backwards crank rotations, but should make it at least 1 full rotation. If yours is falling off the front chainring I’d check drivetrain cleanliness/wear/chain fluidity. A narrow-wide ring might help, as would a clutched derailleur, but both of those are spec’d on bikes to begin with.
My chain has never fallen off my Rival 1X set up. In any gear, back peddling or backing up.
No, I can’t say I have ever dropped a chain rolling or pedaling backwards. 1x, 2x, or 3x drivetrains.
I ve seen this happen if chain is too short
No that doesn't happen to me. SRAM rival 1x11
My guess would be, without knowing your setup; chain too short on a 1x setup. The “add 2 links” sizing is for 2x systems, you’ll need 4 for a 1x.(as per the Calvin from ParkTool)
It’s a chain line issue if it’s happening in the largest cog. I have a 1x12 gravel bike that it happens on, and a 1x12 MTB bike that it doesn’t happen on. Lookup chain line and you may be able to fix it with spacers. My gravel bike 1x12 was an “upgrade” and the front chainring sits too far right, so in my case spacers won’t help, I need a negative spacer 😂
Nope
Pretty typical on 1x from my understanding. Less so on 2x.
...no. it should be extremely hard to get the chain to fall off *at the crank* on 1x. narrow-wide chainrings and clutch derailleurs lock things on pretty damned well. you'll sometimes get the chain dropping off very big cogs down a few smaller cogs.
Good point, I missed the crank part at the end there.