7900 Dura Ace jumping cogs.
When switching from seated to climbing out of the saddle or quickly pulling away from a standstill on the 53 ring, the chain has has a tendency to jump from either the 4th to 5th or 5th to 6th cog on the cassette. Been to three shops, all of whom say it is adjusted perfectly front and rear. Not a problem performance wise but the clunk it makes sounds like it will soon become expensive, so suggestions as to possible causes will be appreciated.
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If you are sure that the rear mech has been properly adjusted, then I would take out a link from the chain to shorten it a bit. Perhaps there is just a bit too much slack in the chain.
This can be the case if the issue most often occurs when shifting under load, whereby the movement of a slack chain can cause it to slip through the cogs.
Of course could also be worn cassette. I hope your cassette and chain are not also 7900 series. Could become expensive (especially the cassette).0 -
Does it change smoothly otherwise when seated and on inner and outer chain rings? and using the same gears? Go to Parktools.com and learn how to index your own gears, its very simple really.
I d also check for any cable stiction, especially in the loop to the RD - assuming you ve not got DI2 here???? the 7900 drive chain does not like to much cable drag for some reason.
also, Genuine Shimano freehubs as fitted to their own wheels, can make a sound that seems like the wheel is about to explode, its not that is it? obviously that doesnt cause gears to jump.
The original 7900 chains came with a quicklink that wore far quicker than the chain and was replaced with the 7901 chain, which doesnt have this, just replace with a kmc link to prove.
the cassette can be swopped with a Ultegra 6700 one, which is about £45 online and just as good and the 7901 chain is only a few pounds more than a mid range chain from Shamano or use a 6701 or kmc chain.0 -
mamba80 wrote:the cassette can be swopped with a Ultegra 6700 one, which is about £45 online and just as good and the 7901 chain is only a few pounds more than a mid range chain from Shamano or use a 6701 or kmc chain.
Parker International £39.990 -
The whole group set has done less than 1000 miles & was bought as a complete set. The changes are super quick & smooth. Front mech especially is Di2 like in its instantaneous shifting. Cables are smooth and taunt. So everything appears spot on other than it jumping down the middle cogs on the 53. The only fettle left was to remove a chain link, though it appears spot on in length so will probably give that a try. Cheers for the replies!0
