My XT M8000 11 speed drivetrain is now 14 months old and I've been relatively diligent with chain wear and putting on new chains to eek out the lifetime. Fourth chain was fitted at beginning of the month and it runs fine on all the rear sprockets except the 42 tooth whooper. I naively hoped that the chain would stretch and run like a dream by the end of the month.
Unfortunately it is still jumping like a bastard on the 42 tooth sprocket. I am loathed to buy a new cassette at £60 and wondered if there was a way of swapping out the worn sprocket? It appears to be riveted on quite firmly!
I am however enjoying the 10 speed life and have climbed up some big lakeland passes without my easiest gear. Not sure I am going to nail the climb from Seathwaite over Walna Scar at the weekend...
Round chainsaw file and re-profile the back of the teeth.
http://singletrackworld.com/forum/topic/replacing-the-big-sprocket-on-a-shimano-11spd-cassette
The short answer is no, there is no economically viable way to swap the big cog. I've switched to a Sunrace cassette to see how it goes, still a silly aluminium big cog, though.
I reckon you're doing pretty well to get 4 chains worth of wear out of a cassette. As well as being softer than the other cogs, the 1x chainline won't be helping.
I've had one chain and 1100 miles out of mine. 42 is definitely a bit "grumbly" since the replacement but serviceable. Although I'm not sure if mine is limiter screw related (I thought I'd solved it but the issue came back after a few rides)
I think it is fair to say I've not got 4 chains of full life from the drivetrain! I was tempted to put the old chain back on as that worked on the worn 42 sprocket.
Off to Coniston tonight and may have a play with a chainsaw file in the Youth Hostel lounge tonight - nothing to looe!
I think I got around 900 miles and one chain out of mine.
Miles is not a measure I use for mountain bike drivetrains as I seem to ride in permanently wet conditions through eternal bogs in the Lakes.
You should consider fitting a smaller chainring so as to avoid so much use of the 42T. Or even, whisper it, go 2x....
I know you like 2x Scotroutes but 1x lops 1lb of weight off my bikes for no effort, and weight's important to me. I end up with a low gear that I can handle with 30/42 as well. And only one of my mountain bikes will actually take a front mech these days.
I have 1x on one bike and it's fine for that application. However I accept that compromises have to be made somewhere and one of them will be accelerated cassette wear. I'm merely offering it up as an alternative.
I can't say I've had a problem with cassette wear until the M8000 cassette, which seems to have a flaw in the quality of the 42t sprocket. I've just moved to another product, which I'm sure will be fine.
Unfortunately I already run a 30 tooth chainring. Perhaps with the next cassette I will grind on much longer in the second 37 toothed sprocket before I bale out and use the 42 toothed soft alloy sprocket.
I think Shimano do have an issue with their alumminium sprockets. Eighteen months ago I installed a 45t one up sprocket onto a new 11-40t XT cassette. From the start there was the slipping down when back pedaling issue from the 40t but not on the one up 45t even though chainline wise the 40t is moved one sprocket outboard. Now after over a year there is more visible wear on the 40t than on the steel sprockets and more importantly more wear than on the alumminium one up 45t sprocket and I make a concious effort to not be on the 40t for to long.
My next cassette is likely to be the Sunn race 11-46.
M8000 here on my two bikes (since Feb 2016) (one has a 48.5mm chain line, other a 49mm). Both won't back pedal in the 42T. The 37T will back pedal all day though. So I bought the Oneup spacer cog set to put the 42T in the 37T position (4mm outbound) and block off 1st gear with the Low Limit screw (going 10s on 11s!). It still derails on the 42T even then. What's happening is the shift ramps are throwing it off - a known fault apparently. I've put 2 chains on both bikes swapping at 250 miles each and only 0.2-0.3 wear. Nowhere near 0.5 even.
At lunch today I slung an old XT10s cassette on and it shifts perfectly with the 11s stuff and if I block off 1st gear with the low limit screw I'll have a much lighter cassette to boot. SuperStar 40T expander cog ordered for £20 today in Black Friday deal so I'll be giving that a go.
Shimano's 11s cassettes are poor IMO. Seems to be something wrong with the alu sprocket design I think.
I can't go SRAM because I'm on 26 inch bikes and freehubs cost quite a bit and my hubs aren't Boost and they're Pro 2 EVO so any freebub bodies won't fit Pro 4 hubs in the future.
I'd get a few year's worth of 10s bits and bobs for the price of switching to SRAM GX at this stage.
I can probably do with 11-36. I only switched to 11s because I injured my knees last winter because my seatpost slipped down slowly without me noticing. That's fixed and I keep an eye on it but now I've become 42T lazy assed. 40T be fine as a test to see if it all works. I can always put the 11s back on and suffer the shitty back-pedal. Don't say don't back-pedal... it's impossible not to need to sometimes and it does my nut in.
Update: I've solved it!
I've set the limit screw on one bike (425mm chain stay / 48.5mm chain line) and put a 10s cassette on. Shifts perfectly with M8000 shifter / mech. That'll get the 40T expander cog when it arrives.
On the other bike with a (436mm chain stay / 49mm chain line) it was never quite as bad but still unacceptable so I've kept the M8000 11-42 but used the [url= http://www.chainreactioncycles.com/oneup-components-1x11-cassette-sprocket/rp-prod148244 ]OneUp kit[/url] to put a 4mm spacer in and 18T instead of 17/19T and set the limit screw to stop at 2nd - bit of B tension adjusted too. That now back-pedals two revolutions at least which is a lot more than it was doing and I can live with that and still get to use up my XT kit.
Hopefully a good muddy test ride at the weekend will test it for me if I can shake this lurgy I've got.
Ive just bought an 11 speed xt groupset and ditched the 42 cassette for a sunrace 46 to give me a better range, not fitted any of it yet but a bargain at £50 free delivery for any one in need.
http://www.laxzo.com/sunrace-mx8-wide-range-mtb-cassette-silver-11-46t---11-speed-mountain-bike-465g-21756-p.asp
Cassettes must be made out of cheese, makes no sense that an infrequently used 42 sprocket wears out before the 30/32/34 etc alloy chainring.
Edit: Scratch that, it does, especially if the B knuckle is screwed right in , the 42 sprocket will have only fraction of the chainwrap of the front ring.
I dont get how you're getting through these cassettes and chains so much.
New bike in March, XT M8k kit, 1300 miles later and the 42t is still going strong coupled alongside a 30t up front, I've changed the chain once to another KMC but only because the last one snapped.
All of that is riding in the Pennines - Calderdale/Kirklees/Peaks/Dales/Lakes, so certainly not easy going on the drivetrain.
Good luck with anything turning up from Laxzo
Yeah put the old chain back on and run it until it's dead.
I usually get two full chain lifes per cassette, which seems reasonable.
Laxzo delivery arrived next day....I did wonder after reading some reviews but couldn't fault em with my first order.