quick chain question (plus gearing)

[davidg]

Ultegra 10 speed

I have just changed my cassette from a 12-25 to 11-28 in anticipation of doing Fred (not that I have been on my bike for 7 weeks because of my knee but that is a dif story!).

I put on a new chain and kept an extra (full) link in it as it seemed about right for the 28 when I was in the big chain ring (the no feed through rear mech and one link overlap method...).

I thought it was fine but checking ALL of the gears the rear mech and chain get caught up when it is in 34-12 and -11. Chances of me EVER being in that combination is zero as I always change up after about 4-5 changes...

on that basis, do you think I will be okay or is it best not to risk it? have already wasted one connector pin!

cheers

(hope this makes sense!)

 

[accountantpete]

You shouldn't ideally use the opposing extremes ( ie big ring/28 or small ring/11) as the chain is probably running at too harsh an angle and will wear the drive components a lot quicker and sounds like it is fouling the rear mech anyway.

Keep it as it is.

 

[adscrim]

Depends what you mean by caught up. If it's likely to cause damage if you changed into one of these gears by accident then I'd change it. While you should avoid extreme chain angles, you should still be able to use the gears.

 

[MartinC]

I would guess the chain is too long. In 34 12 the tensioner in the rear mech can't take up all the slack chain and it's gone right back so that the chain is rubbing on itself. This is noisy and inefficient but unlikely to do any real damage.

As others have mentioned you should avoid the 'crossover' gears ( small sprockets and small chainring, large sprokets and big chainring) because this gives you a chainline that's too out of line causing inefficiency and wear. The real problem is in having the chain too short - if you inadvertently change into the the largest chainring and sprocket there won't be enough chain to go round both and it may break.

On a double setting the chain length by wrapping it round big chainring, big sprocket (without passing it through the mechs) then adding 2 links normally gives you the right length. There are other methods that people use though.

 

[davidg]

I think I am tempted to leave it. chain defo too long that's the problem but dont want to keep braking the chain. I will ride what I have to and change it back to the 25 in a couple of months anyway, so think I will just leave it for now...

I often get to the 50-12 I am afraid to say before changing down to 34, but cant remember ever being in 34 and going that low as I like to get back to the big ring

 

[davidg]

by caught up I mean the rear mech loosens off and relaxes, rotating backwards (and more horizontally) at which point around 12 it starts to touch the chain, so the chains are rubbing together, running along each other. To be it only looks like it would cause noise and wear if I accidentally changed into that combination, hence I will probably take the risk as it is short term.

If anyone knows otherwise, ie it could catch properly then I would consider shortening

 

[byegad]

I wouldn't worry about that. I run 24 40 55 to 11-34 and can select all 27 gears. The Deore mech can be tucked like yours with the chain rubbing itself at one extreme and almost fully forward on 55 34. It's been like that for 5000+ miles with no issues.

 

[davidg]

that is an outstanding spead, byegad!

cheers everyone