Bicycle Mechanics - Rear Gear Mechanism --> sudden chain jump/mis-pedal under pressure.

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Archie
10-09-04, 12:03 PM
Hi
New bike, the rear mechanism (Shimano Acera) 'occasionally' causes the chain to suddenly give under force/pressure, do you know what may be causing this please?

Example/scenario:
Changing DOWN to sixth gear at the rear, after a few minutes, when going uphill the chain may give way (one click), as if it just found the correct gear! It runs OK pior to the above effect with no 'obvious' signs (to my untrained eyes anyway). This is a new bike & the set up may not be 100%, but WHAT may be the main cause?

Archie

Indolent58
10-09-04, 12:13 PM
If it's a new bike the most likely explanations are:

If it was always like this, it's poor initial set-up by the LBS

If this problem started after some time riding, the cables are stretching slightly during the break in period. This is normal.

In either case the shop will readjust the cable tension free of charge as part of normal post-sales support.
Archie
10-09-04, 12:27 PM
Indolent58

It started today after bike's first 20 miles or so.

The down-shift at the FRONT is slightly problematic (ie from 2 to 1 at the FRONT) -> re-adjustment/fine tuning is needed of course.

However, the problem with 'chain click/give' at the REAR, started unexpectedly today for the first time.

Thank you for your reply.
Cheers
Archie