1 x 9, dropping chain whn shifting to the rear 34t cog ?

[dragbike]

Hi everyone

Just built up a winter beater with a 1 x 9 drivetrain. When I shift into the top rear 34t cog, the chain drops off the front ring(32t). It drops to the inside to where the granny would normally be.

Everything seems fine otherwise.

Front ring is a ramped 9 speed ring. Not using any kind of chain tension device.

thnx for any ideas

[Slash5]

Depending on your bottom bracket, you could try adjusting your chainline inwards.
A single speed chain ring would help.
Shortening the chain might help but it's a long shot.
You could run an old front derailleur or a bashwich.

The usual answers.

[shiggy]

Depending on your bottom bracket, you could try adjusting your chainline inwards.
A single speed chain ring would help.
Shortening the chain might help but it's a long shot.
You could run an old front derailleur or a bashwich.

The usual answers.

I agree with Slash.

The chainline is too far outboard and the ramped ring wants to drop the chain.

[thomllama]

X3 what they both said... move ring in and/or replace it with a none ramped.. mid (or short) cage derailleur and properly lengthed chain,.. issues gone unless you have something else major like a bent frame...

[dragbike]

thanks guys. Kinda what I thought. Bike is literally a hodge-podge of mostly old parts I had in bins/boxes. The front 32t ring actually has a pretty bad bend/wobble in it and I think that might have something to do with it. The BB shell is 68mm and per the BB info I should be using a drive side 2.5 spacer , I THINK .

Anyways I just found a 34t non-ramped ring in another drawer. I'll throw that on and see how she works.

[shiggy]

thanks guys. Kinda what I thought. Bike is literally a hodge-podge of mostly old parts I had in bins/boxes. The front 32t ring actually has a pretty bad bend/wobble in it and I think that might have something to do with it. The BB shell is 68mm and per the BB info I should be using a drive side 2.5 spacer , I THINK .

Anyways I just found a 34t non-ramped ring in another drawer. I'll throw that on and see how she works.

All current crank chainline are WAY too far out, ~5mm too far.
If you have the clearance for the chainring, move the spacer to the non-driveside. The chainline will still be further outboard than ideal, but better.

[flynbryan19]

Had this exact same problem, but w/ the small rear chain ring instead of the large. As others have said, your chain line is off and the bent front ring I'm sure is only making it worse. I was told to use a non ramped front ring and of course some sort of chain guide on the front will help.