Issues with Shimano 1x12

[grumpydad]

Thanks for all the suggestions, I will spend a bit of time later today cleaning everything up, check more closely for signs of wear and hopefully sort the problem out, I will be investing in a seat tube mounted chain guide thingy, it's nice to know that when I need that big ring it's not going to let me down, I believe this type of gadget will do the job

 

[grumpydad]

Just a quick update on the chain dropping issue, I bought the item pictured above in my last post, unfortunately it didn't fit, due to the angle between the seat post and bottom tube being too small, so not enough room for the bracket to fit, so before I spent any more money I spent some time on the interweb and ended up on an american site where they were discussing this very problem, someone suggested that Giant had made a mistake with the specification of the chainring and that instead of zero offset it should be 3mm offset, so I ordered one of these, It's now fitted, and the chain didn't come off while on the work stand, plus the chain line looks much better, I will report back after I've taken the bike out tomorrow

 

[grumpydad]

So it would appear that the problem wasn't caused by a worn chain or cogs, it wasn't a build up of crud, but it looks like Giant have specced the wrong chainring? it would appear that a chainring with a 3mm offset is what is required, I won't be satisfied until I've given it a good blast around the forestry tracks, but so far so good

 

[T4tomo]

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,

I spent some time on the interweb and ended up on an american site where they were discussing this very problem, someone suggested that Giant had made a mistake with the specification of the chainring and that instead of zero offset it should be 3mm offset,

and thus the 3mm offset achieves what GB was aiming at, off centring the chainline to the larger sprockets where its under more strain when climbing (albeit MTB' go uphill in cars or bike park "lifts" dont they?

 

[chriswoody]

Thanks for getting back on this one. It's always interesting to hear what solutions folk have found to problems. Chainline is something I hadn't thought of before in my earlier reply and was something I only had a passing knowledge of until recently. It seems with the new boost spacing of MTB rear ends, along with 1x12 transmissions, bikes are increasingly needing to use off-set chainrings to maintain a reasonable chainline. There's a bit more in depth about why you need off-set chainrings from Wolf tooth components:

https://www.wolftoothcomponents.com/pages/boost-chainline-and-chainrings

I did read another interesting article about various modern chainlines, (Well I found it interesting, but then I love nerding out on details like this!) a couple of months back, but can't seem to find it now.

You'll have to let us know how it works out though and hopefully that solves your issue.

 

[Biker BoB]

Chain line will always be an issue with set ups like this.

 

[grumpydad]

Well, I can report that all is good!! After several very muddy, very wet rides of roughly 20km around forestry tracks and some road work, my chain is still firmly in place, I made full use of all the gears, changing up and down as you do and even when unnecessary I used the 3 biggest cogs on the cassette as this is when the issue was occurring, I've attached a picture of part of one of the routes I ride, there is ongoing logging works in progress.