Gear changing issue

A worn chain or cassette cogs can slip which can be mistaken for random shifting. It first starts to show when you increase power as you would climbing a hill. If you let it go, after awhile it will happen all of the time. You can check your chain by measuring it. 12 links should measure exactly 12 inches. If it is over this by 1/8 inches or more, you need to replace the chain. If it continues, then you will also need to replace your cassette as it is worn too.

A less likely cause would be that you are flexing the frame when you climb, and this, in turn, is causing the cable run to the RD to change which would pull the RD into a lower gear. This is unlikely unless you get really physical in your climbing.

If your RD is shifting correctly on the flats, then it does not need adjusting.

I had a problem with my commuter bike doing that I finally figured out my chain was dry causing stiff links and auto shifting under load a drop of lube on every roller made it go away.

Martynb said:

Help.

I have been riring mostly on flat terrain, but the last couple of days have headed into the hills. When I try to power up a short hill, I seem to be slipping into different gears at random. Is this a sign of a stretched chain? Or do I just need to get my rear derailer adjusted?

Many thanks

Martynb said:

Help.

I have been riring mostly on flat terrain, but the last couple of days have headed into the hills. When I try to power up a short hill, I seem to be slipping into different gears at random. Is this a sign of a stretched chain? Or do I just need to get my rear derailer adjusted?

Many thanks

A friend was having a similar problem on his Cannondale, it turned out he was putting pressure on his twist grip shifter, and causing a gear change on climbs. An adjustment of the shifter tension cured it.

Thanks for the replies.

I have lubed the chain and slightly adjusted the rear derailer and the problem seems to be gone.