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  1. #1
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    1x11 with 64BCD chainring on inner of 2x SLX crank - shifting issue

    Hi,

    I have an SLX 2x crank and i've put a 30T in the granny position (64BCD) and a bash guard where the big ring (104BCD) would normally go.

    The chain line appears to be dead centre of the the cassette - which i assumed would be great.

    The issue i've got is that on the trail that i ride 2x a week i spend most of my time on the 13T and 11T of the cassette. What's happening is that when i put the power down when on the 13T the chain will slip every now and then (say 8 times over an hour's ride).

    I can fix it with the barrel adjuster but then the chain slips on the other cassette cogs (except the 11T) so that's not an option.

    What i think is happening is that I'm using a narrower chainline than shimano expect - i'm using about 45mm whereas shimano say to use about 50mm(?) - and when the chain is at that extreme angle it's not what the cassette is designed for and the chain i guess is catching on the 15T cog.

    My guess is that the 11T isn't giving me grief because it's bound by the stop screw and not the barrel adjuster.

    Any ideas on what i should do? Prob change to a 34T on the 104BCD but i want to have a crack at making this work because the ratios with the 30T are great on the technical and uphill rides i do.

  2. #2
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    Why don't you put a 30t or a 32t chainring on the 104BCD?
    You can also use a chairing with an outboard offset on the 64BCD.

  3. #3
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    Slipping or skipping gears usually means a bad interface, either worn chain or cog but the fact that you can fix it with the barrel adjuster suggests that it's something else. I'd start with the basics by making sure the hanger is square, cables are good, etc.

    I don't believe your chainline is the issue, Shimano uses 50mm chainline not because it's ideal but because it's necessary to insure that standard sized chainrings will fit on various frames from different manufactures. 45mm is better IMO.
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  4. #4
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    Since you can fix it by adjusting the cable I'd say it's not chainline related. If it was touching another cog or something like that, adjustment wouldn't help. As JB Weld says, I'd go with the basics, hanger alignment etc.

  5. #5
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    Hi all, thanks for replies. I've been trying to figure this out for the last few months but gotten nowhere.. I'm trying to get this bike ready for a couple of races and i've still got this issue.

    To clarify:

    - It's not actually slipping, just making a huge crunching sound
    - It's only ever happened on the 13T
    - It doesn't get fixed by turning barrel adjuster (i only thought it was fixed..)
    - The chain, cassette, derailleur and hanger were all brand new on a new frame (they all now have about 400 miles on them)
    - The 13T on the cassette looks completely fine
    - The hanger looks fine
    - The chain doesn't have any stuck joints from where i joined it
    - The derailleur seems fine

    This is really annoying me.

    I'm at the point where i'm going to start replacing parts until it works. Any advice on what steps i should take?

    Maybe adjusting the clutch on derailleur?

    The single chainring is sitting basically in the center of the cassette, slightly towards the small sprockets.

    Thanks,
    Tim

  6. #6
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    Have you tried to adj the b screw?

    A picture of your setup in that gear would be nice??
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  7. #7
    Bos
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    Before you replace anything else, try cable and housing first. A sticking cable will cause alot of intermittent issues. I'd recommend SP 41 for price and performance.

  8. #8
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    Quote Originally Posted by thefan View Post
    The issue i've got is that on the trail that i ride 2x a week i spend most of my time on the 13T and 11T of the cassette.


    This is a problem^ Maybe or maybe not the cause of your issues but a problem nonetheless because the gears you're spending the most time in are also the ones that wear the quickest. It would be better to use a chainring that allowed you to utilize the center of the cassette most often.
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  9. #9
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    Initial guess based on description is a bent tooth on the 15T cog or a stretched chain. When you put the chain together, sounds like you pushed the pin back in instead of using a quick link. If the link wasn't pushed in just right and flush, it will catch. I'd recommend getting a quick link in principle. Never a bad idea to have one, and it makes taking the chain off for cleaning so much easier.

    As a simple experiment, I'd grab a 32 or 34T oval chainring off amazon for $20 and throw it in the 104BCD spot. (might need a new chain but it's never a bad idea to have an extra chain anyway). This will move the chainline to see if that's really the issue here. It'll also give you more gearing so you're not always in the 12 or 13T cogs. Unless you find yourself severely limited on the low speed gearing for billy goat climbing, sounds like you don't need all the extra low speed gearing you've currently got.
    https://smile.amazon.com/Crankset-Ch.../dp/B019Y702TI
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  10. #10
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    the hanger can "look" right and still be off, did you check it with a tool?

  11. #11
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    Can you take some pictures with chain in 13 cog? Is it FS bike?

  12. #12
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    Thanks for the awesome responses!

    The bike is a 2016 Scott Spark 930 (100mm full sus) that i bought new. It came with 2 x 10 and i immediately changed to new 1x11 parts (xt shadow+ derailleur, xtr shifter, xt 11-42 cassette, xt chain, absolute black 64BCD 30T chainring).

    Quote Originally Posted by Bordershy View Post
    Have you tried to adj the b screw?

    A picture of your setup in that gear would be nice??
    I think it's adjusted correctly - i basically tuned it to be as close to the 42T sprocket as possible and still be able to smoothly change into the 42T. I've had a free after-sales service by the shop that sold me the bike and I don't think they changed it but i suspect they didn't do much other than check the tightness of a few bolts. I'll get a photo up asap.


    Quote Originally Posted by Bos View Post
    Before you replace anything else, try cable and housing first. A sticking cable will cause alot of intermittent issues. I'd recommend SP 41 for price and performance.
    I used the stock XTR cable that came with the XTR shifter. The housing was new and I'm 90% sure it came with a new 10sp XT shifter from another bike build.

    I made the internal routing holes of the carbon frame slightly bigger so i could run the housing the full length of the cable. The original internal routing was poor at the point where the cable exited the bottom bracket and it caused the cable to become a bit frayed which is apparently common on the XTR cable and not an issue. I have a standard shimano inner cable i can swap it with.

    Quote Originally Posted by J.B. Weld View Post
    This is a problem^ Maybe or maybe not the cause of your issues but a problem nonetheless because the gears you're spending the most time in are also the ones that wear the quickest. It would be better to use a chainring that allowed you to utilize the center of the cassette most often.
    My riding over summer has been:
    - Once a week where i ride a flat forest trail and spend the whole time (approx 1 hour) in 13T and 11T
    - Once a week i ride in the hills (2 hours) where i use down to 37T climbing (about 1300ft) and spend the rest of the time spread over the rest of the cassette.
    - Once a month i'll do a 4hr+ ride where I use the whole cassette (last weekend i had to walk some sections because 42T with 30T chainring wasn't quite low enough)

    The longer races here often have long sections on farm roads/shingle roads where if it's a bit of a downhill i'll spin out on the 11T at about 42km/hr (26mph) at around 112 rpm on the pedals. Same if there is a decent tail wind.

    I'm wondering if i'm a candidate for 2x which will fix any chainline issues and give approx 1 higher and 1 lower gear. I could put the 2x10 back on but i like the 1x and the scott has their suspension lockout remote above the bars and i'm about to buy a dropper that will have it's remote in the spot where the front shifter would normally be.

    Quote Originally Posted by watts888 View Post
    Initial guess based on description is a bent tooth on the 15T cog or a stretched chain. When you put the chain together, sounds like you pushed the pin back in instead of using a quick link. If the link wasn't pushed in just right and flush, it will catch. I'd recommend getting a quick link in principle. Never a bad idea to have one, and it makes taking the chain off for cleaning so much easier.

    As a simple experiment, I'd grab a 32 or 34T oval chainring off amazon for $20 and throw it in the 104BCD spot. (might need a new chain but it's never a bad idea to have an extra chain anyway). This will move the chainline to see if that's really the issue here. It'll also give you more gearing so you're not always in the 12 or 13T cogs. Unless you find yourself severely limited on the low speed gearing for billy goat climbing, sounds like you don't need all the extra low speed gearing you've currently got.
    https://smile.amazon.com/Crankset-Ch.../dp/B019Y702TI
    I took the cassette off and had a really good look at the 13T and it seemed fine. I've checked the chain with park tools CC3.2 chain checker and the chain hasn't reached 0.5% yet. The chain was new when i fitted it and i used the spare pin that shimano supply.

    I'll have a good look at the 15T. The way the chainline is in the middle of the cassette means that the chain is being pulled by the chainring towards the 15T so maybe this is slightly bent and is trying to pull the chain over.

    I have a 104BCD 34T chainring and some spacers so i'm going to try that and set the chainline maybe one cog further outboard. The way i see it is that the chainline should be slightly outboard rather than right in the middle because the chain gets pulled to the center by the chainring which means outboard of center the chain is being pulled into a bigger cog but inboard of center the chain is being pulled to the center but it always clears the smaller cog that it's being pulled in to.

    Quote Originally Posted by ElwoodT View Post
    the hanger can "look" right and still be off, did you check it with a tool?
    Not with a tool. I'll buy a spare hanger and compare asap.


    I've also got sitting next to me a new xt chain and a new 11-46 xt cassette that i can experiment with.

  13. #13
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    I agree with jbweld in that the smaller cogs have limited chain engagement & aren't the best for extended torque & you might be better to use a larger chainring.

    Your statement about going back to a 2X might work better for you also.

    Decisions, decisions......
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  14. #14
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    Yeah, you should not be spending massive amounts of time at either extreme end of the cassette on a 1x drivetrain. You will get shifting problems if you do, but moreso on the smaller cogs because they'll wear faster (fewer teeth engaged on the chain at any one time, each tooth spends more time being engaged, etc).

    What cassette is on there now? 11-42? 11-40? I'm guessing one of those two since you're just now talking about 11-46. Wider range cassette might work to put you closer to the middle of the cassette for most riding, but it's not necessarily on its own going to address the crunching.

    If you want a better way to fix it, you're going to have to figure out exactly what's going on. You'll have to replicate the sound under more controlled conditions. It might be a chainline issue. Short of identifying the exact cause, changing to a different ring with a different chainline is sortof a shot in the dark.

  15. #15
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    I'm now really thinking hard about going back to 2x10...

    I think the range I'll get from changing to 32T up front and 11-46 at back would be perfect.

    The issue is that with the 1x setup i'm assuming I can spend as much time as i like in all cogs equally whereas you guys are saying that this isn't really the case.

    If i change to 2x10 that came with the bike it's got 36/22 chainrings so instead of being in the 11T and 13T a lot, i'll be in 13T and 15T.

    It basically comes down to chainline... 1x11 is a big comprimise in chainline for my kind of riding..

  16. #16
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    Quote Originally Posted by Harold View Post
    What cassette is on there now? 11-42? 11-40? I'm guessing one of those two since you're just now talking about 11-46. Wider range cassette might work to put you closer to the middle of the cassette for most riding, but it's not necessarily on its own going to address the crunching.
    I've got 11-42 on there now. I could go 11-46 with 32T chainring which would mean i spend more time in the 13T rather than the 11T.

    Quote Originally Posted by Harold View Post
    If you want a better way to fix it, you're going to have to figure out exactly what's going on. You'll have to replicate the sound under more controlled conditions. It might be a chainline issue. Short of identifying the exact cause, changing to a different ring with a different chainline is sortof a shot in the dark.
    It only happens about once every 30min of riding in the 13T. I just can't think of a more controlled way to make it happen. So, yeah, anything i do is a stab in the dark followed by a couple of hours riding to see if it happens again. That's the real issue.

    What can cause a big crunch at the chain that doesn't involve chain slipping and nuts crashing into the stem?

  17. #17
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    Also, i've got a 3 hour race this weekend that i need to get it ready for.

    I could stick with the status quo and accept that it'll make a big noise a couple of times and increase the chance of a broken chain. Regardless of what i do, i'll start the race with a new chain.

  18. #18
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    Quote Originally Posted by arnea View Post
    Can you take some pictures with chain in 13 cog? Is it FS bike?
    This is with chain in 13T:
    1x11 with 64BCD chainring on inner of 2x SLX crank - shifting issue-_13t.jpg

  19. #19
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    Quote Originally Posted by Bordershy View Post
    Have you tried to adj the b screw?

    A picture of your setup in that gear would be nice??
    This shows where the pulley sits relative to the 42T:
    1x11 with 64BCD chainring on inner of 2x SLX crank - shifting issue-_b-42t.jpg

    And this is when on the 13T:
    1x11 with 64BCD chainring on inner of 2x SLX crank - shifting issue-_b-13t.jpg

  20. #20
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    I took the cassette off and here are the 13, 15 and 17T cogs:
    1x11 with 64BCD chainring on inner of 2x SLX crank - shifting issue-_rub.jpg

    I don't think there are any bent or damaged teeth but i do notice that the side of the teeth on the 13T and 15T have rubbing against them from the chain being on a cog next to it. Ie, if chain is on 11T then the chain is rubbing against the side of the 13T.

    Maybe this is the problem - i adjusted the barrel adjuster for shifting but it seems it should have been slightly more outboard to minimise chain rubbing on other cogs.

    It is tricky though, there are such small tollerances between chain and cassette cogs combined with the chain crossing of a 1x drivetrain.

    What do you guys think?

  21. #21
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    That's probably the main cause. Slight manufacturing tolerance. In time, they'll rub down, but for now, they are annoying and can cause mis-shifts.

    Putting a chainring in the 104BCD position will move it outboard, and no additional spacers are needed. That should pull the chainline out enough so the rubbing is reduced. Of course, this will also put you in a larger cog, which is probably a good idea anyway.
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