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Chain jumping sprockets -Jockey wheel.

by oldmixte
Tue, Dec 24, 2019 11:16
2

Hope this is of use to someone. About a week ago the chain started jumping on the rear lower sprockets, - 10 speed. The chain is only a couple of months old, so I guessed it might be a frayed cable. Not the easiest thing to change on my Cannondale 105. Didn't help. Checked the blogs for advice which suggested checking the alignment of the jockey wheels, they were about 7 mm out because the the outer metal bracket was bent outwards. Don’t know why as I would have expected any damage coming from the bike falling on its side when the bending would have been towards the wheel not away from it. Still didn’t help, fine on the bike stand but as soon as it was on the road under pressure the chain jumped again. It was the first Jockey wheel causing the problem. It was flopping around. Installed two new wheels and after a short test ride all seems well.

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oldmixte | 5 years ago
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Thanks Pilot Pete

The amount of waggle was about 3mm at the edge of the wheel, the lower one had hardly any,  about the same as the new ones and the new ones have cured the problem.

Cheers OM

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Pilot Pete | 5 years ago
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Hmmn,

You do know that the upper jockey wheel is meant to ‘waggle around’ a bit don’t you?

Most likely suspect is a bent derailleur hanger. If your cage was slightly bent then the chances are the hanger is too. I would check it with a hanger alignment tool as just eye balling it is often not enough to see a subtle (mis)alignment issue. That and indexing.

PP

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