Hardtail frame
32T oval chain ring
Garbaruk 10-50 11 speed cassette
Coming off is a KMC chain and an 11 speed XTR mech with a One Up cage. All was working fine for many miles.
Time to replace the chain and rear mech. Chose a SRAM 12 speed XX1 chain and a Shimano XT 12 speed long cage mech.
Given I'm trying to use a 12 speed mech, I have sized the chain following Shimano guidelines for hardtail which is big big plus 4 links (two pairs) plus the quick line.
Trying to set this up and the B tension set up marking on the inside of the cage is nowhere near the cassette.
Trying to work out what I've done wrong (other than not using all Shimano). It should all work in theory.
Double checked the chain length.
Checked the chain is routed correctly through the mech.
Checked the difference made my major and minor chainring diameter (half of ****-all)
Checked the silly little spinny lump that the B tension screw pushes against.
I know it's not a text book setup, but I also know plenty of you run something similar. Any ideas? If I add more links, I'm likely to get a rattling rear mech, slack chain and chain rub on the mech.
I had a similar thing on my HT recently. I'm using a Deore mech, Brand X cassette with an XTR chain.
If I wind the B screw until the cassette tooth is inline with marker on the cage, it shifts badly and won't shift down off the 51.
From what I understand, the cassette tooth should follow the line on the cage when you rotate the cassette. That doesn't happen on mine. It's like the line is pointing in the wrong direction.
I read a few things that suggest the shape of the frame and hanger can mean it won't ever line up. Basically, there are tolerances from Shimano and if a particular hanger or frame is outside of those, you won't be able to set it up per Shimanos recommendation. It why the UDH is meant to be such a good thing. I mean, yeah it great if you've got one but I dont!
That's not to say it won't work on the frame. I've got mine to shift fairly well. It not quite as crisp as the full XT on my FS but I'm using a cheap Deore mech and non shimano cassette so I wasn't expecting it to be perfect.
I've basically moved the guide pulley closer to the cassette which means the cassette now follows the direction of the line (if that makes sense). It was obviously way off because the chain wrap on the cassette looked terrible with the tooth inline with the marker (not enough wrap). I also ended up shortening the chain slightly. I used the same method as you emotion above but found it sagged when I was in the 10t.
I keep meaning to measure the gap between the cassette tooth and the guide pulley bolt. Following the Shimano set up should give you 46mm from the tip of the longest tooth to the centre of the guide pulley.
Just a thought, with an oval chainring, have you tried the b screw adjustment with the oval at different angles? Mines an oval too and although spinning the chainring alters the angle of the cage, it still never lined up properly.
[img] https://ibb.co/hFKLCJBS [/img]
[IMG] https://ibb.co/PzCg3Pkh [/IMG]
There should be some pictures up there. Not the easiest thing to photograph because the lighting is a bit crap and the bike is plastered in mud but hopefully you see what I'm on about.
I've measured it at ~41mm from the tip of the tooth to the centre of the guide pulley. It's shifts pretty well considering it's a mishmash of parts.
It doesn't have to be perfect to Shimanos recommendation. It's nice if it is but if you can't get it there don't worry. Just set it so it shifts as well as possible.
I went for a smaller oval last weekend and had to lose a link out of the chain. Even that threw the shifting off and I had to tweak the B screw again so it's all fairly sensitive.
32T oval chain ring
Say what, now? Sorry, is this coming via a wormhole from 1988? I stopped using Biopace rings after I sold my Stumpjumper, and eventually, Shimano.
They're not Biopace rings @Countzero the oval is at a different angle - they've been en vogue for a good few years.
Personally, I can't tell the difference between them and round chainrings.
Oval Chainrings Explained (Why You Need One!) | Worldwide Cyclery
I'm not sure the chain length math always works. Certainly on a hard tail I'd be setting chain length based on derailleur position in 50t then ensuring there's chain tension when in 10t.
Why are you using a 12spd chain though? Wouldn't 11 make more sense, although irrelevant to the problem you have as far as b tension/position but the shift quality is determined by the ramps on the cassette, the 12 speed chain is narrower than 11 so aren't you asking the chain to move laterally a little more to engage the ramps?
Did you damage the xtr 11 speed? If it's a wear issue then wouldn't chainring be done too?
Lastly, long cage is for 51t cassette, 50t is smaller so you wouldn't need to get to the stamped line anyway
Last question, was your xtr and hanger a direct mount setup? Have you installed the XT on an "incompatible" hanger type?
The old mech was direct compatible but not used that way. It had the supplied extension piece connected to the clevis. It had run a goat link in the past.
The new chain is 11 speed. I'm just not very good at typing. The chain came from my personal stockpile before anything in the house was 12 speed. Like you say, might impact shifting, but not chain length and mech angles.
Chainring is fairly new and still okay. Chain is okay too and going to a different bike. Mech was on at least it's 3rd bike.
Difference between 51T and 50T is only 2mm. B-tension should be enough to deal with that.
Garbaruk 32T. It's said to vary between 30 and 34T. Thing is when the 30 meets the chain at the top, the 34 is out front and vice versa. The total chain length presented at any one time is fairly consistent. It causes a little wiggle on the mech cage but nothing compared at adding it removing a pair of links.
I think you might be right, it's probably a non-ideal mech hanger. It's a 2018 Transition frame.
If I run the chain "short" the set up mark on the mech cage is clocked about 30° behind where it should be, that's with zero B-tension . And the chain rubs the mech on the 10T
If I add a pair of links, the shift is better and the mark is close but the chain sags on the 10T. Not enough to rub the mech, but enough to flap about.
It's definitely a 1x mech. is it? You can still get 2x12 XT with a max. cog size of 45T.
If I had a quid for every time I've checked this mech, I'd just replace the whole bike. I've checked the box it came in, Ive measure 96mm between jockey wheels and the setup guide marking say 51T. The mech cage also says JAPAN SGS so I'm pretty convinced now. I was wondering for a long time as it would fit the symptoms
See, mines a 2018 frame too. It's an Orange not a Transition but a quick Google suggests that it predates 12sp so the hanger/frame may not be inside the Shimano tolerance.
I'd ignore the mark. Set the chain length so it doesn't sag on the 10t and fiddle the B screw until it shifts reasonably. For me, the biggest issue was not shifting down from the 51t. Once I'd got it adjusted so it would, it behaves fairly well.
Once you got it shifting though, if you end up changing the chain length, you'll have to start again fiddling the b screw again.
You might find some ideas here (some discussion that you might need a newer, 12 speed compatible hanger) -
https://singletrackworld.com/forum/bike-forum/12spd-xt-rear-mech-and-b-tension-adjustment/
Just tried shortening the chain and the shifting goes to pot. Based on what you said about 2018 bikes, I've emailed Transition to ask if the mech hanger has changed over the years.
That thread is useful, thank you. Cable is routed correctly and the stopper plate is in the right position. However, it looks like the above mech hanger theory could be the one. Just about to plough through the pinkbike thread linked on there but it sounds promising.
Might even mean the chain I just cut too short is still actually usable with a new hanger.
Transition confirmed that the mech hanger did change so I've ordered a new one, let's see if that helps. Sods law it will mean the shifter housing and cable will now be too short.
New mech hanger finally arrived after being pissed about by Windwave.
All sorted now. With the mech rotating forward a little more, it needed a couple of links out of the chain. Shifting lovely now.
Used the new hanger as a template to file down the original and the spare so that they might be if some use in the future.
Thanks for all the help.
Good news!
And it's good that Transition have updated things.
I've just had a quick look to see if there was an updated version for my Crush but it looks like all the 12sp equipped bikes were SRAM and the Shimano equipped bikes are 11sp.
Did you try a modified one to see how well it shifts?
I did, yes. It was relatively easy as I had the new one to compare against but essentially it's just filing the tab so that it sits in a more vertical position rather than facing behind the bike.
I started using an 11 speed Garburuk cassette recently and it was horrible with a new 11 speed chain, tried my old 12 speed chain and it was lovely.
I didn’t realise +4 links is a thing. Always done +2, and yes on a HT.
learnt something new. Thanks
I didn’t realise +4 links is a thing.
I stumbled across this on Friday while checking on how to replace a brake line that has been cut too short. (always, always triple check which side of the hose clamp to cut when installing new brakes and then check it 4 more times before cutting it just too short).