12 Speed slipping

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This topic has 10 replies, 6 voices, and was last updated 4 years ago by couchy.

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12 Speed slipping
couchy
Free Member

New bike has a 12 speed cassette, sunrace csmz80 with a Shimano XT M8100 SGS Shadow Plus derailleur. In normal use works and shifts fine. But changing to an easier gear and then putting a lot of force through it makes it slip and drop with lots of crunching. I’m always careful never to change under load and the gear has selected properly and quietly but once in and trying it starts playing up. If I got to an even easier gear and then back to the gear I want it seems to work fine. Bike is new and would normally go back to the shop. Until then is there anything particular to this 12 speed setup I can look at ? Thanks

Posted 4 years ago

aide
Full Member

How new is the bike? Might just be the cable becoming a wee bit slack with use

Posted 4 years ago

martinhutch
Full Member

Shimano 12s chains are directional. Check it’s on the right way around (HG writing pointing out). I assume the Sunrace cassette is supposed to play nicely with everything if it’s been specced on a new bike.

Posted 4 years ago

FGF 701 The Hydrate Or Die Edition

weeksy
Full Member

2 weeks, about 40 miles.

Posted 4 years ago

couchy
Free Member

Yeah about 100 miles now, I’ll check as suggested and take a bit of slack out the cable

Posted 4 years ago

Davesport
Full Member

Obvious things to check. The chain tension is correct IE the arm is keeping the chain tight & you’ve got the B screw adjusted properly.

Posted 4 years ago

weeksy
Full Member

you’ve got the B screw adjusted properly.

Obviously all this B screw malarky is a bit new as it’s only really in 11/12 it was needed, before that it was mostly just fit and forget.

So, how are we measuring and gauging the B screw being ‘correct’ ?

Posted 4 years ago

kelvin
Full Member

Setting the B screw has been vital for good shifting performance since I was a kid.

Posted 4 years ago

martinhutch
Full Member

So, how are we measuring and gauging the B screw being ‘correct’ ?

For Shimano 12s, there is a line on the inside of the mech cage that you line up with the teeth of the biggest sprocket. There’s a plastic tool for SRAM.

Posted 4 years ago

weeksy
Full Member

For Shimano 12s, there is a line on the inside of the mech cage that you line up with the teeth of the biggest sprocket. There’s a plastic tool for SRAM.

Every day is a school day 😀

I’ll look into that. Thank you.

Posted 4 years ago

couchy
Free Member

Best update this, set and reset the derailleur and went for several rides to get to the bottom of it. In normal use fine but put effort in especially at same time as rear suspension compresses and it jumps a gear or try’s too. Shows up when popping the front up for a wheelie too.
Took the decision to order 11 speed kit same as my other bike as it’s been bombproof and it would mean one set of spares too.

Arrived today so set about swapping it all, starting by taking rear wheel out and here’s the first issue it’s loose, axle is out by 2-3mm and can be spun by hand. Wheel moves nicely side to side lol. Hmmm so I tighten it up and reset derailleur and head out and you’ve guessed it everything is fine !. It was new a couple weeks ago and dealer tubeless’d the tyres but ultimately I should have checked it over when I got it.
The 11 speed kit can stay till it’s time to swap through wear .

Posted 4 years ago