Issues with Shimano 1x12

[grumpydad]

Bore da pwb,
What I have is shimano deore 1x12, I think it's a 10/51 cassette, and I've recently started having issues with keeping the chain on the single front ring when in the last 2 big cassette cogs, mainly the biggest cog.
The problem appears to be the chain line, there's just no way the chain is going to stay where it's supposed to be, the angle is just too much,
Has anyone one else had this problem or solved the issue, is there a chain guide that I could fit? Not sure if the picture is of any use, it's from the front looking along the chain to the cassette. Any help or ideas appreciated

 

[ianrauk]

Get a dog fang. That should help stop the chain dropping into the BB.
I know it's a 1-12 but can't help but noticing that serious cross chaining to the lowest gear. But perhaps its like that with all 1x gear set ups.

 

[grumpydad]

Cheers bud, I guess it's like that on all 1x's the chain is in line with the front ring when it's on the 4th or 5th cassette ring down from the biggest ring, I've just had a quick internet search and this would appear to be a known issue, it's almost a built-in design fault, very odd.

 

[Sharky]

Do you have a narrow/wide chainring on the front? These are recommended for 1x setups.

 

[wafter]

Interesting pic - that's a bit grotty!

Can't offer any practical help I'm afraid as IMO 1x is fundamentally flawed for this and other reasons. My solution would be to fit a triple

 

[GuyBoden]

Solved my chainline issue with a Dog Fang, a narrow/wide chainring and a shorter BB on my 1x old bloke hill climber.

I preferred the chainline to be more inline when on the larger rear sprocket, I feel it's a better option when putting the power down on steep hills, but not for flat rides on the smallest rear sprocket.

I have Square Taper BB, a better option IMHO for adjusting chainlines.

 

[Ming the Merciless]

Has it only just started doing this, or did it happen from when you bought the bike new?

 

[fossyant]

Worn or dirty chain ring and worn chain won't help

 

[I like Skol]

Looks like the chain is quite elongated to me which is most likely the issue. Appears to be a thick-thin chainring already.

I would start by checking chain wear/length and take it from there. The chains don't last forever.

 

[Deleted member 121159]

If chainline is actually the problem, I believe the proper way of adjusting that is using a longer crank spindle (boost) then using spacers for the BB. Shimano MTB cranks have multiple spindle lengths for this reason. The other way of doing this is getting cranks that take a direct mount chainring. Then get a chainring with chainline adjustment built into it.

 

[grumpydad]

yes, the front ring is a thick and thin, It didn't do it from new only recently started, but I've only done around 200km on the bike so unlikely to be excessive wear, maybe it doesn't take much wear to show up the weakness of the 1x12 design, I would think a smaller cassette would be ok? it's not usually that grubby. Both of my road going bikes are triple's and much easier to deal with. Going by the number of after market chain guides available, this is a common problem, frame manufacturers even came up with ISCG and ISCG 05 to enable after market guides to be fitted.

 

[Jameshow]

Just mount a dummy front mech!🤣🤣🤣

 

[craigwend]

yes, the front ring is a thick and thin, It didn't do it from new only recently started, but I've only done around 200km on the bike so unlikely to be excessive wear, maybe it doesn't take much wear to show up the weakness of the 1x12 design, I would think a smaller cassette would be ok? it's not usually that grubby. Both of my road going bikes are triple's and much easier to deal with. Going by the number of after market chain guides available, this is a common problem, frame manufacturers even came up with ISCG and ISCG 05 to enable after market guides to be fitted.

If only 200km from new, back to the dealer you got it from?

 

[sleuthey]

In terms of chain line angle I've seen worse. It didn't do it when new. It already has a NR chainring. 200km should not cause substantial wear to the chain. I would start with the basics and clean the chain, use a good quality lube and check the BBand chainring bolts are tight. Also, take the chain off and spin the crank and visually check the Chainring isn't buckled/ warped.

 

[chriswoody]

That chain line is perfectly fine. With a 12 speed the cassette will last thousands of kilometres, the trick is to keep an eye on the chain and change it when it gets to 0.75 or there abouts, don't leave it to fully wear out. I generally get through three chains before I change the cassette.

As for your problem, I suspect the clutch on the derailleur has been de-activated. On Shimano derailleurs it's the grey lever towards the front of the derailleur. The clutch needs to be de-activated to remove the wheel, but if it's stays off the derailleur won't have enough tension to keep the chain on.

It's also not a bad idea to get a chain catcher, but the system should work fine without it.