Rear Derailleur Probs

LiamHowleyLiamHowley Posts: 6
edited August 2007 in MTB beginners
Heya, I'm new to mountain biking and I just got Hardrock Sport 2008 last week and I'm already having probs with it.

Been riding it to work every day and done only a few dirt trails but when im in the 7th and 8th cog the chain often gets guided off the pulleys on the rear derailleur then gets caught up, then gets unstuck and the pedals kinda "slip". I don't feel safe when in those gears as it does it very often, usually every few seconds when pedalling hard. I've cleaned the pulley wheels and adjusted the derailleur so it slides in/out of each cog perfectly, but when pedalling it still "slips".

Every other cog works perfectly though.

Any suggestions on what to do?

Posts

  • supersonicsupersonic Posts: 82,708 Lives Here
    When you say 7 and 8th gear, is that the big cogs or the small ones? What front cog are you using? You shouldnt cross the chain ie use the big/big cog or small/small conbo as this puts the chain at a nasty angle, and these gears are replicated in the middle chainring anyway. As its new, it needs a tune up, your shop should do that for free.
  • Thanks for the quick reply.

    It happens with the smallest cogs and any of the chainrings. I ordered the bike off the internet so i can't get a free tune up. I've already spent a lot of time adjusting the deraillers using the park tools guide to the point that they shift quicker and more silently than when the bike first arrived though

    If i turn the bike upside-down so i can pedal it with my hands and watch, what i notice is then chain coming off the lower guide pulley and getting stuck between it and the cage, then as i continue to pedal it kind of gathers a load of slack in the chain, then lets it all go making the pedals "slip"

    If i can't get it sorted out myself I'll take it to a local shop and see what they can do, but I want to try and do it myself first, I don't have much money to throw around yet. Not until my student loan comes anyway >.<
  • WoodywmbWoodywmb Posts: 888
    You can't check this with the bike upside down. Use a maintenance stand or string up the saddle with rope onto a garage ceiling joist. The indexing is likely to be set for the lower three quarters of the cassette but still requires fine tuning for the smaller cogs. It could also be a stiff chain link or a kink in the gear cable. But these are almost unheard of on new bikes, A trained mechanic can see and hear gear problems in seconds. And fix them in minutes. It might cost you nothing because the shop will want your custom in future - or they might want the mechanic's time paid for, say the price of a couple of pints. Worth it if you can build up rapport or learn from the repair being carried out.
  • nferrarnferrar Posts: 2,511
    Odd for the chain to come off the jockey wheel and get caught up in the cage, sounds like there's a problem with the chain itself for that to happen. Have you checked it for stiff links and twisted/damaged links?
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