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I have replaced my wheels with a Shimano Nexus 8-speed internal gear hub set but I may have had the problem before the change. When I push down relatively hard on the crank arm for example starting off quickly or riding uphill fast, the crank arm slips with a jolt. Quite often the chain comes off soon after. I can't really see anything as I'm always obviously riding at the time, and the noise can't be located, but it is very irritating and happens in all gears.

Would anyone be able to tell me what this could be?

  • Did you replace the chain as well? Is the chain sized properly & have enough tension? I doubt the crank arm itself is slipping, it sounds more like the chain perhaps. – renesis May 11 '15 at 20:09
  • I did replace the chain. – Robert Buckley May 12 '15 at 5:47
  • What are you using for chain tension? Horizontal dropouts or a tensioner? Also, you mention a noise. What noise? – jqning Jun 14 '15 at 3:16
  • How old is your chain ring? A new chain on an old ring (with worn teeth) is likely to slip. – JHCL Oct 12 '15 at 6:30
  • How worn is the chainring? Slipping as you describe is often due to a worn chainring. – Daniel R Hicks Oct 12 '15 at 11:53
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I'd start with a new chain as a simple maintenance matter - this should have been done when the new rear cog went on anyway.

Then compare how your new chain lies around the front chainring compared to the old one. It should mesh fairly well over the whole length of contact, not having phased waves of contact and spaces.

Finally, are you positive its the front chainring skipping? Your feet are on the cranks so it can still be the back, and you feel it through the pedals which makes it seem to be the front. Get a friend to ride along side, or try riding on a treadmill or rollers... or even use a gopro and a mount to see what's going on.

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  • Ditto to this; also check the chainline. If the rear sprocket is out of line with the chainring, the chain might jump. It may be correctable by reversing the sprocket (they are usually dished for this purpose). – JHCL Oct 12 '15 at 10:13
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Check your cable. You should have full length housing. The housing should be compressionless. These hubs are accurate solid performers but are VERY susceptible to small maladjustments in the cable.

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  • OP said the issue was happening before the IGH was fitted. You're completely correct of course, but its not an answer to the question. – Criggie Oct 12 '15 at 8:52

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