Another gear problem thread!

[richysgc]

Bike Chain – Google Drive

drive.google.com

Hoping for some advice, as you can see from the video on the link, my chain is jumping off when its on the largest gear.

I have got it booked in at LBS for a service on 21st april, asked them about this gear problem whilst i was booking it in, and they advised it was probably just an adjustment on the barrel adjuster. So after messing about for a while i got it so it was working better than in the video but still jumping off every so often. (Every other gear works fine no issues)

Nothing looks bent or out of place on the hanger, so was thinking it could be an adjustment on the limit screw?? Im sure someone on here will be able to point me in right direction though. Also put the chain checker on and noticed that the chain is at 50% after 90kilometers (all in sloppy shitty conditions but i give my bike a full clean after every ride) First time with an ebike so not sure if that would be classed as normal wear after that distance?

 

[Gyre]

Looks like you have the right idea: Low gear limit screw seems just ever so slightly off. It's hard to eyeball from a side view to say whether it's too much and threatening to jump off the cassette or too little and trying to drop down a gear. Whichever it is, try no more than a half a turn at a time to get it to sit right on the low gear.

 

[richysgc]

Looks like you have the right idea: Low gear limit screw seems just ever so slightly off. It's hard to eyeball from a side view to say whether it's too much and threatening to jump off the cassette or too little and trying to drop down a gear. Whichever it is, try no more than a half a turn at a time to get it to sit right on the low gear.

cheers mate, ive watched videos on youtube, seems straight forward enough, on the videos they have slacked off the gear cable completely, do i need to do that for a small adjustment?

 

[Gyre]

cheers mate, ive watched videos on youtube, seems straight forward enough, on the videos they have slacked off the gear cable completely, do i need to do that for a small adjustment?

That would be a good idea if you were adjusting the high gear limit screw, but on the low gear limit screw you want to do more or less the opposite: gently make sure the derailleur won't pivot any further inboard once you have it dialed in with the limit screw. What that does is make sure your limits are solid so that you don't inadvertently drop the chain off the cassette the next time you make a barrel adjustment or overshift on the thumb shifter.

 

[richysgc]

That would be a good idea if you were adjusting the high gear limit screw, but on the low gear limit screw you want to do more or less the opposite: gently make sure the derailleur won't pivot any further inboard once you have it dialed in with the limit screw. What that does is make sure your limits are solid so that you don't inadvertently drop the chain off the cassette the next time you make a barrel adjustment or overshift on the thumb shifter.

spot on ill give it a bash tomorrow and see how i get on ?

 

[Mikerb]

This has nothing to do with the barrel adjuster ( ie on the shifter). There are 2 possibilities. One, as per posts above, is the limit screw is very slightly out. The top jockey wheel should align with the centre of the largest cog. If it is slightly to the inside ( ie towards the next biggest cog) the chain will lose its wrap with the biggest cog as soon as pressure on the chain is released......and that is exactly what is happening in the video.

There is one other possibility and that is the B tension screw adjustment. The top jockey wheel is at its closest to the cassette cogs when the largest cog is selected. If it is slightly too close it may not be able reliably to select the biggest cog. Less likely than the limit screw so do that first.

The accuracy of the very simple chain checkers .....or lack of it....means there are best used to compare chain wear from one test to the next rather than consider the measure they take as definitive. I have had brand new chains that measure very nearly 0.5 on the simple type chain checker. So you know it measures 0.5 now using your chain checker. Measure again in a few weeks.........unless something is badly out of kilter it will probably read exactly the same!