Chain length?

[Noodley]

This follows on from a question I posed in Cakestop, but I'll start again to try to make for some level of clarity:

I have a 10 speed chain on my audax bike which has 53/40/30 and 13/29 with long cage.

I am needing a new chain but it appears there is no indication on packaging about what length a new chain is. Are all 10 speed chains the same length when bought? How do I work out what length of chain I need? Does Shledon hold the answer? (I am usually lost by the second line of any Sheldon Brown explanation

 

[bonj2]

You just need to find the right bit. I'm sure he did have an equation on his website which I used once effectively, but now the recommended method seems to be simpler:

"The best technique for setting chain length is to thread the chain onto the large/large combination, without running it through the rear derailer. Mesh the two ends on to the large chainwheel so that they could be connected (outer link meets inner link), then make the chain one complete link (one inch) longer than that. In almost all cases, this will give the optimum length."
i.e. like this

http://sheldonbrown.com/derailer-adjustment.html#chain

 

[bonj2]

if you've already got a chain on your bike and it's the right length, then why don't you just make the new one the same length? ... duh!

 

[Noodley]

if you've already got a chain on your bike and it's the right length, then why don't you just make the new one the same length? ... duh!

Cos I don't think the one I have IS the right length. Duh.

 

[Noodley]

But this is the bit from the link you provided I was needing:

"New chains come longer than they need to be for the vast majority of bicycles. You will almost certainly need to shorten a new chain before installing it on your bicycle. If your large sprocket sizes are anywhere near the maximum your rear derailer can handle, the chain length can be quite critical."

When taken along with the explanation given I should be okay. Thanks

 

[bobbyp]

I seem to remember there's something in the shimano rear mech instructions about setting the chain length. It'll be on the website but its something along the lines of getting the cage vertical in a certain chainring/sprocket combination.

 

[barq]

Cos I don't think the one I have IS the right length. Duh.

Sadly that is quite common. However Sheldon's method is easy and pretty reliable.

 

[bonj2]

But this is the bit from the link you provided I was needing:

"New chains come longer than they need to be for the vast majority of bicycles. ..."

er... well obviously - they're hardly likely to be shorter are they? That wouldn't be much good...

 

[Noodley]

Sadly that is quite common. However Sheldon's method is easy and pretty reliable.

What I think happened is that when the bike was setup it initially had a 12-25 fitted but I asked for it to be changed for a 13-29 (to much eye-rolling and muttering from the mechanic about there not being hills big enough, etc etc. He changed his mind when I asked if he had ever ridden a 400 or 600 and encountered a hill at the end of it .

I imagine the chain was the correct length for the 12-25 but not for the 13-29 and I now intend to remedy this. I have managed to ride 3000km without any problems with it, but want to make sure the chain length is correct as it is something which niggles away at me if I am miles from anywhere half way up a hill.

 

[Tim Bennet.]

Rather disturbingly, bonj is once again the voice of reason!

The rationale for his advice is this; your chain should 'just' be long enough to go onto the 53/29 combination. This might seem odd because you should always avoid using that combination, but it does prevent it all jamming up should you inadvertently choose it by mistake!

When you then switch to the '30' at the front, you will find you only get about 5 usable gears before the rear changer doubles back on itself, but by then there are equal gears available on the middle ring.

So the idea is to try and balance the maximum number of workable gears whilst avoiding possible foul ups.

 

[Noodley]

Rather disturbingly, bonj is once again the voice of reason!

He knows I treat him with respect (outwith Soapbox , as it should be and is most helpful when he can be.

 

[Noodley]

er... well obviously - they're hardly likely to be shorter are they? That wouldn't be much good...

That was actually my concern There have been a few times when I thought things were obvious but turned out not to have been as obvious to Mr Campagnolo and Mr Shimano.

 

[bonj2]

He knows I treat him with respect (outwith Soapbox , as it should be and is most helpful when he can be.

I guess it would be elementary to assume that there are 'standard' chain lengths and that you can buy one the right length for your bike. But if you imagine the amount of different combinations of bottom-bracket-to-rear-axle length, sprocket size, and chain ring size there are - then it's fairly easy to see how there's not really such thing as a 'standard' length.

 

[mickle]

I guess it would be elementary to assume that there are 'standard' chain lengths and that you can buy one the right length for your bike. But if you imagine the amount of different combinations of bottom-bracket-to-rear-axle length, sprocket size, and chain ring size there are - then it's fairly easy to see how there's not really such thing as a 'standard' length.

Bottom-bracket-to-rear-axle-length? Chainstay length shurely?

 

[John Ponting]

Bottom-bracket-to-rear-axle-length? Chainstay length shurely?

+ style and/or length of rear dropout surely?