Chain - coming off on the outside of big ring

[bennydorano]

Last few spins I've been out on I've had at least 2 ocassions on each ride were the chain has come off on the outside of the big ring. That seems strange to me?? It seems to be when I'm going dowhill and dropping into a bigger gear and I reckon it's happened mid cassette on each ocassion. I haven't got a clue what's going on here (or more importanly how to rectify), any ideas? I think I can trace back my mech problems to my 'service' at Halfords

 

[jim55]

yeah ,,adjust the limit screw ,,the cage is obv moving too far and letting the chain jump over the sprocket ,,seek out sheldon browns page to learn about it ,,its not hard

 

[bennydorano]

Cheers Jim, got it up on my newly accquired Lidl bikestand this morning and seem to have rectified it ok, but seem to have lost the use of the smallest 2 sprockets, cant seem to find the balance (assuming loss of the smallest 2 isn't a price I have to pay?). Found something on the 'net, which was going on about 2 screws, I seem to have 3 (Bianchi Ultegra/105 if that makes any difference)

 

[Angelfishsolo]

Cheers Jim, got it up on my newly accquired Lidl bikestand this morning and seem to have rectified it ok, but seem to have lost the use of the smallest 2 sprockets, cant seem to find the balance (assuming loss of the smallest 2 isn't a price I have to pay?). Found something on the 'net, which was going on about 2 screws, I seem to have 3 (Bianchi Ultegra/105 if that makes any difference)

This should make everything clear

 

[bennydorano]

Went a tad pearshaped I'd be happy to take 2 non-working sprockets at the minute. The 2 screws are near worn away with the footering.

 

[Garz]

I adjusted the barrel on the down tube to rectify this at first. The FD after a few chain jams can bend or move out of position, when I started experiencing overthrowing it's time to start tinkering. I guess after 2k+ miles the cable can stretch too.

 

[RecordAceFromNew]

Went a tad pearshaped I'd be happy to take 2 non-working sprockets at the minute. The 2 screws are near worn away with the footering.

It is generally best to adjust those limit screws when the mechs, whether front or back, are not in those gears (although you get immediate feedback if you do). The H/L screws are in compression when the gears are highest/lowest respectively, making it easy to ruin the screw heads.