Results 1 to 32 of 32
  1. #1
    mtbr member
    Reputation:
    Join Date
    May 2004
    Posts
    42

    chain skip/pop under load - Mojo SL

    Hey there-

    I'm starting to have some issues. I'm not sure where to start, but the bottom line is that under a load and under suspension impact, both while pedaling, the chain skips out of gear causing a load pop and my pedals to spin fast. Had a pedal spin around and land on my shin the other day to make the point clear! I can pedal hard going up a hill, down a hill with same effect usually more frequent as suspension is active. Also happens when pedaling over roots, larger size mostly.

    It seems like it just started doing this recently. I only have about 300 miles on it now (lightly used by previous frame owner). I assembled my Mojo from parts, some new some old. I have an old SRAM X9 rear on with a < 100mi 11-36 SRAM 990 and same age 991 chain. For the front I have a stock Stylo Team with BB, chainrings have lots of miles on them, probably need replacing. I don't have any spacers on the BB per the install guide recommendations (which is all I had when building). Cables are all newish, as old as the casette, chain.

    I'm a good distance from an LBS, so I'm reaching out for advice. The only real troubleshooting I've done: adjusting the b-tension screw and it kind-of had an effect but I was still able to make it pop when hammering in the driveway. The gears all shift fine, crisp, etc. No stiff links in the chain.

    Could my chain be a little too short? Would it have anything to do with chainline? My testing is in the middle ring, biggest gear

    Thanks...
    Mark

  2. #2
    screamer
    Reputation: budgie's Avatar
    Join Date
    May 2004
    Posts
    1,316
    Loose cassette?
    On heavy rotation: White Lung: Deep Fantasy

  3. #3
    mtbr member
    Reputation:
    Join Date
    Mar 2010
    Posts
    24
    probably the chain ring. put a new middle ring on it and see if that helps.

  4. #4
    mtbr member
    Reputation:
    Join Date
    Jul 2010
    Posts
    74
    Are you running the Lopes link?

  5. #5
    mtbr member
    Reputation: ScottW's Avatar
    Join Date
    Jan 2004
    Posts
    1,260
    Sounds like a worn out chain ring.

  6. #6
    mtbr member
    Reputation:
    Join Date
    Feb 2008
    Posts
    37
    Inspect your chain as well. Mine does the pop slip thing right before my chain breaks. Usually you'll find 1/2 of the link coming off the pin.

  7. #7
    mtbr member
    Reputation: getbusyliving's Avatar
    Join Date
    Mar 2007
    Posts
    417
    Also could be hub/freehub issue. Or possibly bent tooth/teeth on cassette.

  8. #8
    mtbr member
    Reputation: getbusyliving's Avatar
    Join Date
    Mar 2007
    Posts
    417
    Quote Originally Posted by mramend
    I don't have any spacers on the BB per the install guide recommendations (which is all I had when building).
    Maybe I'm misunderstanding you or your situation is different, but I have two BB spacers on drive side and one spacer on non-drive side. I think that is standard for XT BB on Mojo.

  9. #9
    mtbr member
    Reputation:
    Join Date
    May 2004
    Posts
    42
    Thanks for the ideas, folks. I am starting to suspect chainring wear. I can't see anything obvious, but as I was TRYING to make it pop in my driveway, I noticed that it happened when cranking hard on my right pedal. Hmm... I mean, yeah my right leg is strong arghh but..maybe the teeth on that part of the revolution are the problem

    I probably should have replaced my middle and small rings when I did the cassette and chain. I kinda spent all my dough by then, though..;-)

    I do have the Lopes link, ya. And the BB is a Stylo, not an XT. For what it's worth.

    I'll take a lookee at the cassette fit as well, for good measure.

    Thanks again,
    Mark

  10. #10
    Unpredictable
    Reputation: Ridnparadise's Avatar
    Join Date
    Dec 2007
    Posts
    2,108
    Most likely cause is chain growth. 300miles of dust and mud could be enough to end the life of a chain. Could be a worn chainring. I just had the same thing (more like ghost shifting) on my ride yesterday. The entire rear deraileur was loose at the hanger. The hanger bolt was also loose a tiny bit. Tightened and fixed.

  11. #11
    Rider of Gnarl
    Reputation: GnarlRider's Avatar
    Join Date
    Jun 2007
    Posts
    28

    Bet it's the chainring

    I had the same problem. ~300 miles on a Truvativ/SRAM crank and the middle ring got worn/started to slip. Replace the ring and you'll be money.

  12. #12
    Dropshot Champ!
    Reputation: redmr2_man's Avatar
    Join Date
    Jun 2008
    Posts
    5,133
    I had the same problem, new middle ring fixed it.

  13. #13
    mtbr member
    Reputation:
    Join Date
    May 2004
    Posts
    42
    update - I just got 2 steel Truvativ replacement rings today and it all seemed to be fine until I pedaled fast while going over some soft but rough ground (bumpy grass patches). I feel the rear suspension has a role in this (+ the drivetrain)..I'm about 165 lbs, running the RP23 at 150psi. Maybe that's just too cushy for aggressive hammering on the Mojo??

  14. #14
    mtbr member
    Reputation: miles wadsworth's Avatar
    Join Date
    Nov 2006
    Posts
    575
    Is it possible the chain may be too long? The suspension shouldn't have a role in it. A lot of these bikes are raced with no issues. Keep us informed and I hope you get it worked out soon, these things can be frustrating.
    milesW

  15. #15
    mtbr member
    Reputation:
    Join Date
    Feb 2006
    Posts
    101
    Quote Originally Posted by mramend
    update - I just got 2 steel Truvativ replacement rings today and it all seemed to be fine until I pedaled fast while going over some soft but rough ground (bumpy grass patches). I feel the rear suspension has a role in this (+ the drivetrain)..I'm about 165 lbs, running the RP23 at 150psi. Maybe that's just too cushy for aggressive hammering on the Mojo??
    what rear hub are you running ? check your hub body and make sure its not loose or your hub internals aren't broken / breaking. also check the rear der. and make sure its tensioned properly and your chain is the right length.

  16. #16
    mtbr member
    Reputation:
    Join Date
    May 2004
    Posts
    42
    Yikes, scary thought. It's a WTB LaserDisc lite (American Classic design from what I'm told). The rear derailleur is an X9 purchased in 2004. I think I have the b-tension set right (with small gap between largest sprocket and pulley cog, a tad away from grinding close-ness). I'll take off the wheel today and check out the casette and hub..

    I think the chain length is alright if on the short side. I think I set it to the largest ring/cog + two links. My memory is foggy. I should write that stuff down! But I'll check that as well. Thanks everyone so far, very helpful.

  17. #17
    mtbr member
    Reputation:
    Join Date
    Jul 2007
    Posts
    351
    How old is that WTB hub? I had one of these and the symptoms you describe is what it would do right before the pawls would break and leave me coasting.

  18. #18
    mtbr member
    Reputation:
    Join Date
    Feb 2006
    Posts
    101
    Quote Originally Posted by mramend
    Yikes, scary thought. It's a WTB LaserDisc lite (American Classic design from what I'm told). The rear derailleur is an X9 purchased in 2004. I think I have the b-tension set right (with small gap between largest sprocket and pulley cog, a tad away from grinding close-ness). I'll take off the wheel today and check out the casette and hub..

    I think the chain length is alright if on the short side. I think I set it to the largest ring/cog + two links. My memory is foggy. I should write that stuff down! But I'll check that as well. Thanks everyone so far, very helpful.
    I would look @ the hub Ive had more than one problem with wtb hubs ( I wont use them any longer) had problems like you describe not long before the hub completely failed. If you think its the hub Talk with WTB they may warranty it or send you new internals for the hub.

  19. #19
    mtbr member
    Reputation: VTmojo's Avatar
    Join Date
    Apr 2007
    Posts
    515
    Quote Originally Posted by getbusyliving
    Maybe I'm misunderstanding you or your situation is different, but I have two BB spacers on drive side and one spacer on non-drive side. I think that is standard for XT BB on Mojo.
    you should fix this, it could be part of your issue. You need two BB spacers on drive side and one spacer on non-drive side.

  20. #20
    mtbr member
    Reputation:
    Join Date
    Nov 2004
    Posts
    292
    Hmmm interesting. I was just thinking of this problem yesterday as my chain skipped about 1 link lenght and a loud crack resonated thru my frame. It's so loud it startled my riding partner behind me. It has done it couple of dozen times maybe, so now you have got me thinking. My mojo is 3 years old. I replaced the cassette last year, the chain and small ring about 2 months ago. I had the freewheel serviced but the middle ring has never been touched. Looks like that is next in line.

    Thanks,
    Straw
    Ease & Flow Where Ever I Go

  21. #21
    mtbr member
    Reputation:
    Join Date
    Feb 2006
    Posts
    101
    Quote Originally Posted by straw
    Hmmm interesting. I was just thinking of this problem yesterday as my chain skipped about 1 link lenght and a loud crack resonated thru my frame. It's so loud it startled my riding partner behind me. It has done it couple of dozen times maybe, so now you have got me thinking. My mojo is 3 years old. I replaced the cassette last year, the chain and small ring about 2 months ago. I had the freewheel serviced but the middle ring has never been touched. Looks like that is next in line.

    Thanks,
    Straw
    generally you should replace the chain and rear cassette at the same time. and the front rings need to be replaced usually 1x for ever 2 chain / cassette replacements. This is only a general rule I try to follow. due to ridding conditions and use that might vary.Chain rings become bent / broken/ worn and certain chain rings last longer than others. You might want to drop your bike by a trusted shop and have them check your drive train and see what they think. After all this skipping have you ever checked your derailleur hanger? easy to overlook but they can be bent slightly and work OK in most gears but skip occasionally due to excessive force / dirt ect ect.Do you clean your cassette ( dirt and buildup between the cog teeth / chain rings) and lube it every ride.make sure your derailleur arm spring isn't to weak - some just get worn and need to be replaced ( easier to replace whole derailleur). You also said the hub was serviced- check that - if to heavy/ thick if grease/ lube or too much was used in the hub body or pawls it can cause certain hubs to stick and or slip- WTB had a few shipped out with the wrong grease weight and they slipped then broke - I happened to go through 3 in a row. No more wtb for me. Anyway your bike shop should be able to sort out your issues they also should have a tool to check your derailleur hanger alignment. sorry lots of info good luck
    Last edited by dbuilt; 10-12-2010 at 01:16 PM.

  22. #22
    mtbr member
    Reputation:
    Join Date
    May 2004
    Posts
    42
    well, oddly enough - after replacing the middle and inner chainrings, and still making the loud pop/slip happen, I kept staring at the derailleur as I compressed the suspension (with my gut on the seat- works well! to a point). I watched the chain pull the derailleur forward when compressed, adding tension to the chain and thought.."I wonder if I still have those links I removed in my toolbox? Maybe the chain is too short?" I was able to add back two links to the chain. I haven't had the problem since. I guess this is why there is the 'set chain length at maximum compression' rule of thumb.. which well..I don't think I followed.

    Needless to say, the chainrings should have been replaced. But in the end, I think the problem may have been a chain that was too short and causing problems under high tension (and possibly moving the rear derailleur)? Thanks everyone for you ideas, glad the conversation meandered and ..am glad I can now get back to enjoying my Mojo!
    -Mark

  23. #23
    mtbr member
    Reputation:
    Join Date
    Apr 2010
    Posts
    49
    I have a mojo sl with full xtr and mine has done this since it was new. it seems like the chain skips when the chain is in the middle gears on the rear casset. I have had several mechanics look at it and havent fould a fix.

  24. #24
    mtbr member
    Reputation:
    Join Date
    Feb 2006
    Posts
    101
    Quote Originally Posted by moabjason
    I have a mojo sl with full xtr and mine has done this since it was new. it seems like the chain skips when the chain is in the middle gears on the rear casset. I have had several mechanics look at it and havent fould a fix.
    I would check by looking @ the der hanger make sure its straight. make sure the der. spring still has good tension then check your cog set. also is the chain stretched - are you possibly running a 8sp chain with a 9 speed set up? check and make sure your rear der cable is long enough and not stretching with the bike compresses.

  25. #25
    mtbr member
    Reputation:
    Join Date
    Apr 2010
    Posts
    49
    Bike was brand new with the wtf package. I have checked all the basics and have had several bike shops look at it. Have done several 100 mile races on the bike and no mechanicals just irritating.

  26. #26
    mtbr member
    Reputation:
    Join Date
    Feb 2006
    Posts
    101
    Quote Originally Posted by moabjason
    Bike was brand new with the wtf package. I have checked all the basics and have had several bike shops look at it. Have done several 100 mile races on the bike and no mechanicals just irritating.
    have you checked the chain and made sure there is not a pin that is to tight and has one link a little stiff or worked its way out partially and lifts the chain as it goes around the cog. do you clean the cogs / lube the chain every ride?

  27. #27
    mtbr member
    Reputation:
    Join Date
    Apr 2010
    Posts
    49
    I thought it might have been stiff links and that was the first thing I checked. After every ride I clean the chain and gears. On long rides I bring chain lube. Maybe the rear hub is defective from the factory.

  28. #28
    mtbr member
    Reputation: getbusyliving's Avatar
    Join Date
    Mar 2007
    Posts
    417
    Quote Originally Posted by moabjason
    I thought it might have been stiff links and that was the first thing I checked. After every ride I clean the chain and gears. On long rides I bring chain lube. Maybe the rear hub is defective from the factory.
    There are more than a few people (including me) who have had XTR freehub issues. Mine popped once in a while, and I finally determined that freehub body had a couple hairline cracks. Shimano replaced it for free, and very quickly (impressively sent new FH to my LBS immediately, before even seeing the cracks), and all is well now.

    Take your cassette off and look really closely at your freehub body. Even if you can't find a crack, could still be an internal FH issue (this is what others have reported). But if you don't see a crack, make sure you cover all your other bases before diagnosing it as bad FH. Good luck, that kind of issue can be a PIA.

  29. #29
    mtbr member
    Reputation:
    Join Date
    Feb 2006
    Posts
    101
    Quote Originally Posted by moabjason
    I thought it might have been stiff links and that was the first thing I checked. After every ride I clean the chain and gears. On long rides I bring chain lube. Maybe the rear hub is defective from the factory.
    what type of hub?

  30. #30
    mtbr member
    Reputation:
    Join Date
    Apr 2010
    Posts
    49
    American classic is what came on the bike.

  31. #31
    mtbr member
    Reputation: somemechanic's Avatar
    Join Date
    Jun 2010
    Posts
    114
    Aside from the plethora of suggestions everyone else has mentioned, how about rear der housing length? Especially between the frame and swing arm. If its too short, tension of the der cable will be increased when the suspension is unloaded, and released vice versa. This could cause shifting issues when the suspension is active, like the situations you have described experiencing the problem. Seen it happen man! Good luck!

  32. #32
    mtbr member
    Reputation: chas_martel's Avatar
    Join Date
    May 2006
    Posts
    3,476
    Quote Originally Posted by mramend
    For the front I have a stock Stylo Team with BB, chainrings have lots of miles on them, probably need replacing.
    There's your problem. Seriously, been there done that with a Stylo, replace it with an XT crank-set and viola your problems will disappear.
    Nobody cares...........

Members who have read this thread: 4

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

THE SITE

ABOUT MTBR

VISIT US AT

© Copyright 2019 VerticalScope Inc. All rights reserved.