New cassette - chain length issue?
After one ride on my new bike, and after trying a bigger cassette on my winter bike, I decided to change my ultegra 6700 cassette from a 11-25 to a 11-27 (compact chainset). The LBS were happy to swap the cassette but said that I might need a longer chain. I don't want the hassle of taking the bike into the shop to discover that the chain length is fine, so I was wondering what I should be looking for?
Obviously the problem is with the big ring and big sprocket combo. I know I should avoid it when riding, but not everyone is perfect with their gear changes :oops:
How stretched is too stretched for the rear mech/jockey wheels? Does anyone know of a site with good photos? As long as it's possible to go into the Big+big combo (no matter how undesirable), is my chain length OK? Cheers!
Obviously the problem is with the big ring and big sprocket combo. I know I should avoid it when riding, but not everyone is perfect with their gear changes :oops:
How stretched is too stretched for the rear mech/jockey wheels? Does anyone know of a site with good photos? As long as it's possible to go into the Big+big combo (no matter how undesirable), is my chain length OK? Cheers!
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Comments
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With your chain on the largest chainring and largest rear sprocket but not passed through the rear derailleur you should have 2 spare links.0
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You'll have to make the chain longer only if it was close to the limit with the old cassette.
2 extra teeth on the cassette means that the minimum chain length needed to change onto the big/big combo is 1/2" longer than with the old cassette. You can only change chain length in 1" steps, 10/11 speed half links not being available.
So long as you can change on to big/big the chain length is OK.
If you've used the chain with the old cassette for more than about 1000 miles, the new cassette means that you may well need a new chain anyway. If so size from scratch as rothers_bikeo said - shortest length that will join round big/big, plus 2 links (1 inner + 1 outer).
It's easier to check the length with the ends of the chain on the teeth of the big chainring rather than flapping around in the air. Tie the LH crank to the chainstay.0 -
Thanks for the replies. I know about the big ring-big sprocket + 2 links approach,
but really don't want to take my new chain apart. (I'm bound to make a mess of it!!)andrew_s wrote:If you've used the chain with the old cassette for more than about 1000 miles, the new cassette means that you may well need a new chain anyway. If so size from scratch as rothers_bikeo said - shortest length that will join round big/big, plus 2 links (1 inner + 1 outer).
It goes into the big sprocket gear OK, so is probably OK. It will help me learn not to use it anyway!!0 -
I changed my 12-25 for a 12-27 and kept the same chain length.
When I set my rear mech up I followed guidance from a bike book that said when on big big the mech arm should be at about a 45 degree angle (that is an angle drawn from the floor through the 2 jockey wheels)The dissenter is every human being at those moments of his life when he resigns
momentarily from the herd and thinks for himself.0 -
BlueScot
just make sure you do not use the two big rings and you will be fine."Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
Parktools :?:SheldonBrown0 -
On a mildly related issue would you expect to have to change chainlength going from a compact 50T to standard double 53T if the casette doesn't change?0
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This site works well if you want a "scientific" answer:
http://www.machinehead-software.co.uk/b ... hcalc.html
You just need to measure your chainstay length and stick that in with your cog sizes, although I found that it just confirmed what the tips shown above had already told me when I fitted the chain in the first place.0 -
I went from a 12-25 on the back and 39/50 on the front to an 11-28, 30/42/52 without changing chain length. Using the granny ring on the front means I can only really use the biggest three at the back but that is fine. Never tried big ring to big ring, never needed to.
Next time I change the chain I might adjust it.0 -
nicklouse wrote:BlueScot
just make sure you do not use the two big rings and you will be fine.
The reason that the chain-length should be such as to allow big - big is that , with a too-short chain and this combination, this can result in a horrific accident as the transmission totally freezes.
A moment of inattention when the rider is tired and this can easily happen. No responsible Bike workshop would allow the fitting of a too-short chain for this reason even with Public Liability insurance.0 -
skyblue337 wrote:On a mildly related issue would you expect to have to change chainlength going from a compact 50T to standard double 53T if the casette doesn't change?
yes you would or like above a big big combo will cause issues."Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
Parktools :?:SheldonBrown0 -
nicklouse wrote:skyblue337 wrote:On a mildly related issue would you expect to have to change chainlength going from a compact 50T to standard double 53T if the casette doesn't change?
yes you would or like above a big big combo will cause issues.
I guess it would depend on how accurate the chain length is now though. Going from 50T to 53T would probably need one extra link and a lot of chains will be setup to an accuracy of 1 or 2 links anyway. Hence, if you have say 55 links now which was the right number, running with one short on the 53T setup wouldn't be too big a deal (in my experience, although I do avoid big/big). However, if your current length is short already then...0