Chain Length - too long?

DefUnctUK

Hi,

I know there are a few ways to measure required chain length, i just wanted to get an opinion regarding my current setup. I have attached two photos, with the chain on 2 largest cogs and on 2 smallest. My feeling is it might be a bit longer than needed. Any advice / opinions? I'm trying to sort out a rattling sound i have when i pedal hard with this new chain.

Thanks in advance!

http://imgur.com/V8jGZFu
http://imgur.com/tvq5DrK

mercia_man

Looks like you could perhaps lose one link although I don't think the chain length is the cause of your rattle. However, if it is a bit slack it may rattle on your chainstay due to low tension. A more likely reason could be that you have put a new chain on a worn cassette. It will jump on the most used cogs if the cassette has gone too far.

For measuring chain length, I normally use a method recommended by Shimano - put chain on big ring and smallest cog and the centre of top rear derailleur jockey wheel should be vertically above the lower jockey wheel. If the lower jockey wheel is further back than the top one, the chain is too long.

arlowood

DefUnctUK wrote:

Hi,

I know there are a few ways to measure required chain length, i just wanted to get an opinion regarding my current setup. I have attached two photos, with the chain on 2 largest cogs and on 2 smallest. My feeling is it might be a bit longer than needed. Any advice / opinions? I'm trying to sort out a rattling sound i have when i pedal hard with this new chain.

Thanks in advance!

http://imgur.com/V8jGZFu
http://imgur.com/tvq5DrK

Doesn't look too bad to me. Can't quite see in the small/small image but as long as the chain is not fouling between the long bottom run and where it rounds the top jockey wheel then you should be fine.

If you worried then just shorten it by a link and see how it goes then regarding the rattling sound

jgsi

Count the links and whats the largest cog on the back and what you running on the front?

sungod

the correct way is to follow the instructions for the rear mech that you are using

if there's noise, check indexing, rd adjustment etc.

if the old chain was too far gone it'll have damaged the cassette, usually this results in skipping under load

DefUnctUK

Thanks for all the advice and opinions. I appreciate the rattling might be caused by something else, possibly the cassette and will look into that. Just wanted to ensure the chain was right before i start digging.

I am running a 50/34 at the front and a 12/25 at the back. The initial reason i thought it might be too long is that when on the 34 chainring and the 12 cog, the chain run fouls between the run to the idler and on to the jockey (2nd image). Not that i'd ever ride like that, but it just seems..not quite right - but i could be wrong. I might then remove 1 or 2 links to see what happens.

k-dog

That's too long then - it's a balance between not rubbing like that and not being too tight in 50/25. As you know you shouldn't really use that gear - but if you change into that combo you don't want it to explode.

I would take one link at a time and see what it looks like - easy if you use a quick link. You don't want to have to put links in again - the chain's never the same again IME.

ElectronShepherd

I think it's too long. For me, in the "big to big" picture the rear derailleur is not pulled forward enough, and looks too curled up in the "small to small" picture.

I would suggest that you split the chain, and go with the old standby of running the chain around the largest cog on the back and the largest chain ring on the front, but *not* through the rear derailleur to make a taut loop, and then add one whole link (i.e. one inch of chain length). See http://sheldonbrown.com/derailer-adjustment.html#chain for some handy pictures.

DefUnctUK

Thanks, i'll be shortening it a little. Now just need to find out where to get a new pin for my Yaban YBN-H11 chain....
..will have to use one of their quick links if i cant find one in an eshop somewhere.

I assume pins are not compatible between chains, correct?