Dodgy Big Chainwheel

redddraggon
redddraggon Posts: 10,862
edited July 2007 in Road beginners
Hopefully I'll use the correct terms for things, so here we go:

I've had my road bike for 6 weeks, only doing an average of 40miles a week (but increasing slowly), I haven't used the big cog much. Recently I've started to think that I should keep on the big cog and go through the gears from there, but when I tried today it wouldn't shift there easily, and the chain started slipping down towards the smallest rear cog. Also when the chain was on both the big cogs, there was a real grating noise which I think was the chain scrapping along the front derailler, the grating noise get less as I moved to a smaller cog at the rear, but the noise was still obviously there.


Is it a bike fault, or poor bike assembly?
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Comments

  • mercurykev
    mercurykev Posts: 264
    It's best to steer clear of using big front/big rear and little front/little rear gear combinations as the chain angle is too extreme and you can get noises as you have described and also wear out the chain/cassette/chainwheel more quickly. However, if the chain is still scraping on the front mech when you are on big front/little rear and you have problems changing to the big chainwheel, it sounds like your front mech needs adjusting.

    this might help:
    http://www.parktool.com/repair/readhowto.asp?id=75
  • Bronzie
    Bronzie Posts: 4,927
    Probably needs a bit of adjustment is all - but just so you know, it's generally a bad idea to run the chain from big ring (front) to largest sprocket (rear) [or indeed little ring to smallest sprocket] because the chain is forced into quite an angle which increases chain wear.

    As your bike is still fairly new, phone the shop you got it from and ask them if they'll adjust the gears for you - sounds like the front mech needs adjusting - there are 2 small screws on the top of the mech that adjust it's position. As ever, Sheldon Brown's site offers loads of technical information on this sort of thing:
    http://www.sheldonbrown.com/
    It's a Lifestyle! -+-+- Coggan Training Levels
  • alfablue
    alfablue Posts: 8,497
    It sounds like both front and rear mechs are out of adjustment - new cables can stretch and this is one of the reasons bike shops generally offer a free 6 week service. Alternatively it may have never been set up correctly in the first place.

    You can get the shop to put it right or check out Park Tools as mercury suggests, and have a go yourself.

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