Fitted new cassette and chain and now can't back pedal

othello
othello Posts: 578
edited February 2013 in Workshop
I've just fitted a new chain and casette to my son's Islabike Luath 24. Simple job and all went on OK I thought. Testing it on the bike stand, pedalling forwards is fine and the indexing hasn't needed changing. But when back peddaling everything is stiff and the chain derails.

The cassette is an 8 speed and it has a brand new 8 speed KMC chain on there.

The one thing I have changed is the cassette ratio. Previously it was a 11-32 SRAM. I have switched to a 12-26. I wonder if the top jockey wheel is too far from the cassette and that is the problem. But I have unscrewed it as much as possible (see photo).

Any ideas?

IMG_1950.jpg
Blogging about junior road bikes http://junior-road-bikes.tumblr.com

Comments

  • keef66
    keef66 Posts: 13,123
    What photo?

    Did you shorten the chain at all? Is it correctly routed through the rear mech? (I have managed this trick in the past)
  • othello
    othello Posts: 578
    keef66 wrote:
    What photo?

    Did you shorten the chain at all? Is it correctly routed through the rear mech? (I have managed this trick in the past)

    Photo should have loaded in below the text of my post?

    Chain is the same length as originally with the 11-32 cassette, so I've not shortened it. He has a spare set of wheels with the 11-32 on it for cyclocross/hills and didn't want to shorten the chain if I could.

    Maybe I've been doing the b-tension the wrong way around. It might need to go all the way in, so the slant on the parallelogram isn't so steep...
    Blogging about junior road bikes http://junior-road-bikes.tumblr.com
  • keef66
    keef66 Posts: 13,123
    It just says 'Image' beneath your text. Then again, I am at work, so the company net nanny might be blocking it, or it's something to do with our ISP / servers being in Germany.

    I'd have thought the B screw needed to be unscrewed, ie not pushing the mech away so much?
  • Lazybike
    Lazybike Posts: 22
    Had something similar....turned out to be a sticky jockey wheel.
  • nicklouse
    nicklouse Posts: 50,673
    does it free wheel?
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • Monty Dog
    Monty Dog Posts: 20,614
    Turn the cranks backwards and observe how the chain runs, making sure it's not skipping etc. Could also be a sticky freehub.
    Make mine an Italian, with Campagnolo on the side..
  • othello
    othello Posts: 578
    Monty Dog wrote:
    Turn the cranks backwards and observe how the chain runs, making sure it's not skipping etc. Could also be a sticky freehub.

    Turning the cranks backwards makes the chain skip off the current cassette cog and move down the block (from a bigger cog to a smaller one). It is meeting resistance -- I'll take a look at the jockey wheels, freehub etc
    Blogging about junior road bikes http://junior-road-bikes.tumblr.com
  • slowbike
    slowbike Posts: 8,498
    When back pedalling the feed into the cassette is from the top of the chainring - so if it's jumping off it sounds like something is out of alignment - is the wheel fitted properly? Is the cassette fitted properly?
    Does it do this to the other wheel with the old cassette on it?
  • nicklouse
    nicklouse Posts: 50,673
    Now that I can see he picture.

    Did you shorten the chain?

    How many cogs on the front?
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • othello
    othello Posts: 578
    nicklouse wrote:
    Now that I can see he picture.

    Did you shorten the chain?

    How many cogs on the front?

    Brand new chain, but same length as when running 11-32 cassette (I'm keeping the 11-32 cassette on his spare wheels).

    Single ring on the front.
    Blogging about junior road bikes http://junior-road-bikes.tumblr.com
  • nicklouse
    nicklouse Posts: 50,673
    so about the free-wheeling?

    guess that is fine?

    then dont worry the chain will get more flexy as it is used.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • othello
    othello Posts: 578
    With the bike on the workstand you can freewheel, but the wheel doesn't spin for long before stopping (brakes are disconnected). Certainly not spinning as freely as I would think.

    So I took the wheel off. Turning the cassette I don't get any clicking, so sounds like a dodgy freehub body? This is a brand new wheel I've fitted (from Islabikes) so maybe I've got a duff one? That would explain why the peddaling back is meeting resistance?
    Blogging about junior road bikes http://junior-road-bikes.tumblr.com
  • mr_mojo
    mr_mojo Posts: 200
    Did the cassette come with a large thin flat washer? That goes on the freehub before the new cassette. Sounds to me like the cassette lockring is too tight on the hub and needs the washer for spacing.
  • tincaman
    tincaman Posts: 508
    Check the jockey wheels for seizure
  • Yossie
    Yossie Posts: 2,600
    check that you haven't done the cassette up too tight - 40 Nm max
  • smidsy
    smidsy Posts: 5,273
    Check that the cassette stack height is the same as the old one (when fitted including any spacer).

    Also 40Nm is indeed the max, but is often too tight IME. Generally they only need to be about 30Nm.
    Yellow is the new Black.
  • nicklouse
    nicklouse Posts: 50,673
    The lock ring can not effect the bearings as it in not connected to them.

    It can only effect it if it has now cominto contact with something.

    So time to Czech for contact with any dust shields etc...

    Also whst else did you do?

    Cassette and chain is that it?
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • andrew_s
    andrew_s Posts: 2,511
    If the chain is derailing off the cassette sprocket when pedaled backwards, there must be something taking the chain sideways at the top of the sprocket where the chain engages it. The rear mech can have no effect at all.

    I'd guess that it's just that the new chain is fairly stiff laterally, and the chain is running down the cassette until it's nearer to being in line with the chainring. It will probably loosen up quite quickly once you start using it.
  • Yossie
    Yossie Posts: 2,600
    Cassette done up far too tight can cause the issue - a local LBS did it to a friends madone. Have a go and see!

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