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Bike chain length

Father JackFather Jack Posts: 3,508
edited May 2016 in The workshop
I've had to change rear derailleur a while back, stock had long and new one is probably medium (I couldn't find long) Also I don't really need a large sprocket on the cassettes so gone more roadie cassettes.

It's obviously too short in small small, and fine in big small, I generally use right gearing so would never use small small

But it's strange when I fitted chain and tested gearing I would have noticed it. Pretty sure it's only just appeared. So is chain too long or something else up? Rear derailleur is pretty new about 6 months of light use.

http://s33.postimg.org/k83l0kedb/bigbig.jpg
http://s33.postimg.org/wdavbdghr/bigsmall.jpg
http://s33.postimg.org/bz5yar5q7/smallbig.jpg
http://s33.postimg.org/amxwjq3zz/smallsmall.jpg

edit when I took out the new chain from the packet I did remove a few links- but perhaps never did account for different cassettes and/or cage length and just kept the same number of links when I had long cage.

Since I'm in 90% middle front then I set gears up for that and just tried all rear sprockets to make sure it's ok (in fact I bet I could switch to single front chainring and be happy with it)
Say... That's a nice bike..
Trax T700 with Lew Racing Pro VT-1 ;-)

Posts

  • gbsahne001gbsahne001 Posts: 1,961
    Everything you need to know about chains "http://www.sheldonbrown.com/chains.html"

    and chain length...
    The best technique for setting chain length is to thread the chain onto the large/large combination, without running it through the rear derailer. Mesh the two ends on to the large chainwheel so that one complete link (one inch, -- one inner and one outer half-link) overlaps. In almost all cases, this will give the optimum length.

    taken from the same source
  • WinNTWinNT Posts: 21
    I hope link provided by gbsahne will help.

    I can add that i looked at the pictures and at bigbig.jpg the chain looks too short and at small-small it is definitely too long.
    I tried to put big-big on my bike and the derailleur was even more extreme, so i think you can make your chain a bit shorted and it still will be ok for big-big and maybe good enough for small-small.

    Also you may try to find information about you derailleur to know what difference in transmission ratio it can deal with.
  • Father JackFather Jack Posts: 3,508
    I've shorted it by one link and it's better. Still not perfect in small small, but I think in large large it may be getting too stretched. I don't use small small anyway or gears around that. I'll take more photos and see, easy enough to shorten it again.
    Say... That's a nice bike..
    Trax T700 with Lew Racing Pro VT-1 ;-)
  • WinNTWinNT Posts: 21
    I've shorted it by one link and it's better. Still not perfect in small small, but I think in large large it may be getting too stretched. I don't use small small anyway or gears around that. I'll take more photos and see, easy enough to shorten it again.
    It is bad for the chain and there is no reason to use small-small and big-big, so now it is not a big issue. But chain still should be in good shape at these positions, so it would be good to find a raeson at least.
  • gbsahne001gbsahne001 Posts: 1,961
    Just looked at the photos ( :oops: ) don't know how I didn't spot them first time round and given it's a triple (8?) then it's crying out for a different rear mech; the one installed appears to be a short cage.

    You should be OK running a 9 or even 10 speed rear mech with your set up, a 9spd unit from the mountain side of shimano should be readily available and work with your set up, if you can't find it in the road side.

    I've just installed a 10spd 105 medium rear mech onto a 9spd drivetrain operating from an XT trigger and it works perfectly well.
  • Father JackFather Jack Posts: 3,508
    That's the only rear derailluer I could find. It's roughly 72mm from center of one jockey pulley to the other. Pretty s

    The groupset is campagnolo, so a Shimano one own't work.
    Say... That's a nice bike..
    Trax T700 with Lew Racing Pro VT-1 ;-)
  • gbsahne001gbsahne001 Posts: 1,961
    I had a quick look and there are some 10s rears for a triple but I don't know the campag range well enough to comment on compatibility with 8 or 9 speed
  • Father JackFather Jack Posts: 3,508
    I'm not buying a new rear derailleur, that one is brand new. Seems to work fine as long as you don't use a bad gear combo like small small.

    In front medium chainring, to any rear sprocket it's fine.
    Say... That's a nice bike..
    Trax T700 with Lew Racing Pro VT-1 ;-)
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