Frame bend

Pekka

This may be the wrong forum but as the problem is associated with a loaded touring bike, I have decided to post it here. I recently completed End to End on my Dawes Super Galaxy carrying camping gear,etc. The bike performed well with no major problems except that when going uphill the chain jumps between gears making it dificult to maintain speed. This doesn't happen when the bike is unloaded. I suspect that the frame is bending under the load. Is there anything I can do to prevent this?

nicklouse

Not really but i feel it will be just the gears need setting up correctly.

Or you have some conflict between your load and the cables.

xilios

Try a new chain, if its a bit worn it will jump when stressed enough.
I use one of these (http://www.parktool.com/products/detail.asp?cat=5&item=CC%2D3) to measure the chain once in a while.

cpeachey

Even if the frame did bend I don't think it would cause a gear change. Try the above sugestions.
Chris

JHcp

I would very much doubt it is the frame bending and it is almost certainly your rear derailleur that needs adjusting. The reason that it is happening whilst loaded and going up hill is the added torque that you are putting on the drive system.

Have a look at this great video from the BicycleTutor.com site which shows how to adjust the rear derailleur. http://bicycletutor.com/adjust-rear-derailleur/

redddraggon

Autoshifting can happen when the frame flexes,

http://sheldonbrown.com/autoshift.html

Sheldon brown has a small article on it, I don't think there's much you can do when the frame flexes to stop it.

Pekka

Yes, I read Sheldon Brown's article on frame movement. It's funny thatwhen I changed my bar-end shifter to friction mode but there was no difference. It is worst when the chain is on the middle chainring. As soon as I hit a hill and try and select an easier gear, the chain starts bouncing up and down between gears. It isn't until I get to the highest gears does it stop. No problem when I am on the large chainring on small gears or on the small chainring with high gears. The problem only means that I lose all momemtum going uphill.

Harveytile

I had a similar issue where the chain seemed to try and jump when i was in the middle chain ring. I put the bike on my work stand, adjusted gears, checked it on the stand but as soon as there was some decent pressure on the chain, it seemed to jump. The problem (after a lot of changing bits) turned out to be a worn middle chain ring and this was causing chainsuck. Simply changed it and was fine.

Not wanting to teach people to suck eggs but sometimes it's the bits in front of the face that we can't see :oops: .

Hope this helps.