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  1. #1
    KevinK
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    Bonking ... not feelin' well cranks skipping recomendations!!!! HELP!!!!

    Recently purchased an Ibis Mojo SL. Took over two months to complete this build, but, it was finally complete. Here are the specs to my bike:

    Rear Derailleur: Sram X.0 med red
    Front Derailleur: XTR
    Headset: Cane Creek IS 110 red
    Cables: Shimano Yumeya SP81
    Cranks: Rotor 3D 2x9 110/74 bcd w/ titanium axle 175mm
    Chainring: Specialties TA 42/30
    Bottom Bracket: Shimano M970 XTR 68mm BSA English thread
    Brakes: Formula R1 w/ 180/160 front/rear
    Shift Levers: Sram X.0 grip shifters
    Cassette: XTR 11-32
    Chain: XTR
    Handlebar: Easton SL, O/S 31.8 x 635mm
    Stem: Ibis 31.8 90mm
    Saddle: Selle SMP Full carbon
    Seatpost Clamp: Ibis 34.9
    Grips: ESI Chunky Grips (Cut for Sram Grip Shifts)
    Seat Post: Thomson Masterpiece 31.6 x 350mm
    Wheels: DT Swiss Tricon XM1550
    Tires: Continental Race King 2.2 UST
    Fork: DT Swiss EXC 150 15TA
    Pedals: CrankBrothers Eggbeaters 2ti w/ titanium spindle
    Sealant: Slime Pro
    Skewers: DT Swiss F/R TA bolts 15TA/ 10TA

    Every time I pedal, in my 30/11-12, when applying some force, it skips every revolution. Some say, chainline, chainring, pedals, BB, Frame, Lopes Link. I don't know what to believe, and how to solve this problem. My LBS said it may be chainline. Pedals are intact, and everything is brand new. Never even hit the dirt yet, just some neighborhood riding trying to get the suspension set up. LBS did one experiment, Took apart the BB and re-assembled it, Skip changed from the Drive side to the non Drive side, took it apart again, and the skip returned the the Drive side. Any Ideas? I hope it's not the frame!!! Could a defective Lopes link be the cause?

    Thanks,

    Kevin



  2. #2
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    You may not have enough chain rap on the small cogs. How close is the upper pulley? There is an adjustment for this on the derailleur. Just a thought.
    milesW

  3. #3
    KevinK
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    Hi Miles, Just returned from the LBS, they added another spacer on the drive side and now I am able to use the #8 cog on the rear without problem. The mech at the LBS said, I shouldn't be crossing over from my 30t chainring to my 11t rear. I thought the cross over problem w/ 3x9 cranks was eliminated w/ the 2x9. Maybe I am wrong!!! The 30t is in the 74bcd spot and the larger, 42t chainring is at the middle 110bcd spot. Mech suggested getting a CK BB as it has three more threads, as opposed to the XTR with I cut the thread count by half. With 3 spacers, I am using approx. 4 threads on the drive side BB and zero spacers and all on the non drive side. CK BB should be in next week. So I guess, I wont be able to use the 30t/11t combo without noise.
    Thanks again,

    Kevin

  4. #4
    www.derbyrims.com
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    Quote Originally Posted by miles wadsworth
    You may not have enough chain rap on the small cogs. How close is the upper pulley? There is an adjustment for this on the derailleur. Just a thought.
    Yes. Try loosening, backing out, the B-tension screw a 2 or 3 turns. The B-tension screw head can be seen looking from the back of the derailleur next to the der hanger.

    This adjustment would allow the whole derailleur to rotate forward and lift the upper cage pulley which will wrap the chain further around the cogs.

    Keep a count of your turns of B-tension screw adjustment. If the adjustment doesn't stop the skipping then re-tighten the B-tension screw in again to the starting place.

    Another possibility is the shift cable barrel adjustment is too tight or loose, but probably not because you would have trouble shifting either into or out of those gears also.

    The BB reinstall test results make no sense unless they changed the spacers. There should be 2 spacers on the right side for correct chainline (unless specifically different for your duel ring cranks).

    This is unusual for new parts. Doing nothing more, I would expect the chain and cogs to break in and stop skipping after a real ride or two. Until then use the big ring for those ratios and those cogs.

  5. #5
    KevinK
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    Thanks Derby, I will check into to the B tension screw, and see if it helps, if not, I will return it to it's original position. Would you stay w/ the three spacers on the drive side and zero on the non drive side, or would you return back to the two spacers on the drive side and one on the non drive side. If I went back to the 2/1 configuration, while in my 30t, I would skip my 11-12, and only use 13-22t. I could then use my 42t for the entire cog, 11-32t. Thoughts...

    Thanks again,

    Kevin

  6. #6
    www.derbyrims.com
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    Quote Originally Posted by KevinK
    Thanks Derby, I will check into to the B tension screw, and see if it helps, if not, I will return it to it's original position. Would you stay w/ the three spacers on the drive side and zero on the non drive side, or would you return back to the two spacers on the drive side and one on the non drive side. If I went back to the 2/1 configuration, while in my 30t, I would skip my 11-12, and only use 13-22t. I could then use my 42t for the entire cog, 11-32t. Thoughts...

    Thanks again,

    Kevin
    K, Seems like the q-factor - the crank width, and feel of handling balance would be a little messed up with 0||3 BB spacers. I think you could save your money and return the CK BB, put the spacers back to 1||2, and stay away from the smaller cogs while in the small ring. When the chain breaks in after a few rides the noise will probably go away and the smallest cogs will most likely stop skipping in the small ring. But it would be better for wear to avoid standing and hammering those small cogs with only a 30 ring even if the chain-line was straight up. Downhill pedaling the smallest cogs in the 30 ring will probably be no problem after a little break in time. Loosening the B-tension screw should not be needed, and is not really desirable for overall chain tension. BTW, nice bike! Enjoy!!
    Last edited by derby; 03-21-2010 at 08:20 AM.

  7. #7
    KevinK
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    Thanks Derby. Great advice. I will return the spacers to 2 drive side and 1 non drive side. Also, cancel my order for the CK BB. One of the reason I purchased the 2x9 was to improve my chainline, and now, I seem to have forgotten my initial goal, and sabotaged myself. Thanks for putting me back on track.

    Kevin

  8. #8
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    Going to set up my Mojo SL similarly, have had the Rotor 3D cranks w steel axle in a box for a while (like 2 months, lazy me), would just need to find the time to install them. Going 2*9 as well, maybe 2*10 at some point later on, let's see.

    Did you get the chainline you want KevinK? Just one thought, could it be that the chain was touching the shifting pins on the larger chainring causing the skipping? If so, maybe you could file the pins a tad to make them stick out less? This might explain why the "rhythm" of the skipping changed when you supposedly removed the chain and then put it back on (depending on how many pins there are and how they are "located")... Also wonder if a 10-speed chain would make a difference by being just a tad narrower...

    I am going to first try a chainring without shifting pins; if it shifts poorly will need to get something with pins... Going 27 Rotor Q-ring/ 36 Gebhardt "normal" chainring.

  9. #9
    KevinK
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    Quote Originally Posted by Roto599
    Going to set up my Mojo SL similarly, have had the Rotor 3D cranks w steel axle in a box for a while (like 2 months, lazy me), would just need to find the time to install them. Going 2*9 as well, maybe 2*10 at some point later on, let's see.

    Did you get the chainline you want KevinK? Just one thought, could it be that the chain was touching the shifting pins on the larger chainring causing the skipping? If so, maybe you could file the pins a tad to make them stick out less? This might explain why the "rhythm" of the skipping changed when you supposedly removed the chain and then put it back on (depending on how many pins there are and how they are "located")... Also wonder if a 10-speed chain would make a difference by being just a tad narrower...

    I am going to first try a chainring without shifting pins; if it shifts poorly will need to get something with pins... Going 27 Rotor Q-ring/ 36 Gebhardt "normal" chainring.
    Hi Roto599, I received quick responses from Rotor in Spain, as well as from Ibis. Both basically said the same thing. I asked Ibis about the cross over w/ the XX 2x9, Scot said Sram doesn't recommend using your small front to small(High gear) rear. Rotor also said I should not be crossing over to my Small to small, and added, what you said, that the shifting pin on the large chainring may be the cause. They suggested using a smaller large chainring. Also, I don't know if you installed your pedals yet, but, it is common for the threads on the cranks for the pedals to need to be chased w/ a 9/16 thread chaser, this inconvenience is common w/ anodized cranks. The thread chasing just makes the thread deeper. My LBS did this and said, the pedals went on like butter.

    Your going to love these cranks, light and STIFF!!!!

    Thanks again,

    Kevin

  10. #10
    mtbr member
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    Why would you want to be in that gear anyway?

  11. #11
    KevinK
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    Quote Originally Posted by Yody
    Why would you want to be in that gear anyway?
    I guess, for me, in the heat of a race, w/ my triple, I am always in my middle chainring, when I come to a flat area after a ascent, I just drop to the highest gear, and pedal, until the next hill. Just something I have to get used to. I just have to use my big chain ring more often. It's so easy to drop 7 cogs w/ gripshifts!

    If it were a fun ride, I would just take my time, and be in the right gear all the time, so, there wouldn't be a problem. Just a learning curve I was unaware of with 2x9/10 configurations.

    Thanks,

    Kevin

  12. #12
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    Quote Originally Posted by KevinK
    I guess, for me, in the heat of a race, w/ my triple, I am always in my middle chainring, when I come to a flat area after a ascent, I just drop to the highest gear, and pedal, until the next hill. Just something I have to get used to. I just have to use my big chain ring more often. It's so easy to drop 7 cogs w/ gripshifts!

    If it were a fun ride, I would just take my time, and be in the right gear all the time, so, there wouldn't be a problem. Just a learning curve I was unaware of with 2x9/10 configurations.

    Thanks,

    Kevin
    Shifting to the bigger ring up front instead of dropping all the way down in the rear is a fundamental skill. Don't blame it on racing, not every ride is a race. When ur on those fun rides start consciously shifting on the left not the right. Program that into your head and it will come mor naturally, the 11 tooth rear sprocket is such a crummy gear I actually limited my rear derailleur so it can't drop that low, and I'm running 2 x 9.

    Read Ned Overands book, he even states that his 44T big ring front and 32T big ring back is one of his favorite gear combos. Going to a bigger ring gives u less chain slack as well which is a huge bonus.

    Take this opportunity and step up your game and start to use ur gear spread more effectively

  13. #13
    KevinK
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    Quote Originally Posted by Yody
    Shifting to the bigger ring up front instead of dropping all the way down in the rear is a fundamental skill. Don't blame it on racing, not every ride is a race. When ur on those fun rides start consciously shifting on the left not the right. Program that into your head and it will come mor naturally, the 11 tooth rear sprocket is such a crummy gear I actually limited my rear derailleur so it can't drop that low, and I'm running 2 x 9.

    Read Ned Overands book, he even states that his 44T big ring front and 32T big ring back is one of his favorite gear combos. Going to a bigger ring gives u less chain slack as well which is a huge bonus.

    Take this opportunity and step up your game and start to use ur gear spread more effectively
    Thanks Yody. I guess I do have some bad habits I was unaware of. I'll try and consciously think more about shifting to the big chainring when running low gears. Think I'll pick up Ned's book too, as he is one of my favorite riders.

    Thanks again,

    Kevin

  14. #14
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    Cool, when I was first starting it was a bit technical but still a great read, now everything makes much more sense. Highly recommended!

  15. #15
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    Correct length of chain?

    KevinK, from your pictures your chain looks a bit too long, the rear derailleur cage looks almost horizontal on the gear combo that you had in the pics and in my opinion it should be pointing downwards a little bit more even on the smallest cog.. Try removing a few links from the chain just make sure that there's still enough length for the big big combo just in case.

    The noise from the chain rubbing on the front derailleur when crossing small to small or big to big may be hard to get rid of, but it definitely should not be skiping at all.

    Hope it helps.

  16. #16
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    Quote Originally Posted by eyderman
    KevinK, from your pictures your chain looks a bit too long, the rear derailleur cage looks almost horizontal on the gear combo that you had in the pics and in my opinion it should be pointing downwards a little bit more even on the smallest cog.. Try removing a few links from the chain just make sure that there's still enough length for the big big combo just in case.

    The noise from the chain rubbing on the front derailleur when crossing small to small or big to big may be hard to get rid of, but it definitely should not be skiping at all.

    Hope it helps.
    Careful, there is only one minimum chain length. If even slightly too short there's a high risk of damage or very rapid wear. With suspension compressed to maximize chain stay length (it grows while compressing), wrap chain around biggest ring and biggest cog and be able to pinch two links together.

  17. #17
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    I dunno I always run my chain as short as possible, I put it in big/big and then try and put the jockey arm at a 45 degree angle or a little more

  18. #18
    KevinK
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    @ eyderman and Yody.

    Old picture, since then, I have had two links removed, however that wasn't the cause of the skipping, but, did add some noise. Now, everything is perfect.

    Good eyes and good catch!!!

    Thanks again,

    Kevin

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