djbowen1
09-02-03, 10:01 AM
can i go from a 12-25 to a 11-23 without any giant concerns or should i stick with the same, i have a triple so i would want harder gears.
Bicycle Mechanics - rear cog question
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lotek
09-02-03, 10:17 AM
You should be able to do this with no problem.
The only area of concern might be chain length, the
existing chain might be too long for the lower gearing.
Of course the best bet would be replace chain with new
cogset, and just set it up as you normally would.
Lots of info on chain length (Too many to list here) available
via search.
Marty
The only area of concern might be chain length, the
existing chain might be too long for the lower gearing.
Of course the best bet would be replace chain with new
cogset, and just set it up as you normally would.
Lots of info on chain length (Too many to list here) available
via search.
Marty
roadbuzz
09-02-03, 10:28 AM
I have an Ultegra double, and switch between a 12-27, 12-25, & 12-23 depending on the ride. I size the chain for the 12-27, and it works fine for the rest.
Check that the chain isn't slack in the small-small combination. I doubt you'll have any problem, especially since you've got a long-throw cage... the chain length difference is negligible.
Check that the chain isn't slack in the small-small combination. I doubt you'll have any problem, especially since you've got a long-throw cage... the chain length difference is negligible.
djbowen1
09-02-03, 02:32 PM
so you are saying the chain will be ok? When you buy a new chain how do you figure out the size? Measure it up with the old one.
roadbuzz
09-02-03, 07:20 PM
I'd guess it will be fine. When I went from a 12-25 to a 12-27, my chain was long enough. (Two teeth = 1/2" bigger circumference, less than half of that is in contact with the chain, so roughly, less than a 1/4 " longer chain... heck, you can only adjust chains in 1" increments.) In your case, I'd think the issue to watch out for is too much chain. Check both extremes.
Normally, when buying a new chain, I just make it the same length as the old one was when it was new. I lay them out side by side and line up the links, since the old one will have stretched. If you have to figure out the size, the easiest way is to wrap it around the largest chainring and largest cog, and then add one inner/outer link pair (1") which will give it a little room for the pulleys. There are other techniques, too.
As Marty points out, if you really want to know all about it, there's been some lengthy discussion along with links to other web-sites in this forum. Do a search!
Normally, when buying a new chain, I just make it the same length as the old one was when it was new. I lay them out side by side and line up the links, since the old one will have stretched. If you have to figure out the size, the easiest way is to wrap it around the largest chainring and largest cog, and then add one inner/outer link pair (1") which will give it a little room for the pulleys. There are other techniques, too.
As Marty points out, if you really want to know all about it, there's been some lengthy discussion along with links to other web-sites in this forum. Do a search!
prestonjb
09-02-03, 08:48 PM
Typically a shop will set the chain length to that of the cassette they will sell on the bike.
In reality you can figure out a chain length that you can always use for a given drive train.
For example the Shimano Dura/Ace/Ultegra and such are capable of ranging from 11-27 with a 53x39.
The best way to do this is to mount an 11x27 and measure the chain at the extremes (53x27 and 39x11) and find the length that prevents the chain from rubbing the bottom of the rear-derailleur cage (39x11) and still gives you at least 1/2 inch to 3/4 inch of forward movement of the cage (when in 53x27).
Once you find this size (it varies based on your chain-stay length) you can count the links and when replacing the chain just be sure the new one has the same number of links.
If you do that then you can change the cassette at any time (keeping in mind cassette/chain wear)... And not worry...
I do this when I leave South Florida to go climbing in the Smokey Mountains/Black Mountains and back again (flat land gears to climbing gears and back).
In reality you can figure out a chain length that you can always use for a given drive train.
For example the Shimano Dura/Ace/Ultegra and such are capable of ranging from 11-27 with a 53x39.
The best way to do this is to mount an 11x27 and measure the chain at the extremes (53x27 and 39x11) and find the length that prevents the chain from rubbing the bottom of the rear-derailleur cage (39x11) and still gives you at least 1/2 inch to 3/4 inch of forward movement of the cage (when in 53x27).
Once you find this size (it varies based on your chain-stay length) you can count the links and when replacing the chain just be sure the new one has the same number of links.
If you do that then you can change the cassette at any time (keeping in mind cassette/chain wear)... And not worry...
I do this when I leave South Florida to go climbing in the Smokey Mountains/Black Mountains and back again (flat land gears to climbing gears and back).
mrfix
09-03-03, 04:59 AM
I have an 11 - 21, 12 - 23, 12 - 25 and a 12 - 27, I cut my chain to be the correct lenght for the 12 - 27 and switch the cassets all the time without any problem, Think about it, all of the gears except for the 11 tooth are on the other cassetts, if you don't have trouble when you ride the 39 - 12 combination with the 12 - 23, then why would you have an issue when riding the 39 - 12 combination with the 12 - 27.
prestonjb
09-03-03, 09:24 AM
Exactly!
But don't forget to check the 53x27 position.
I had an old Schwinn.... Way long ago... That I broke the chain. Back then I simply re-linked it and rode off... Never bothered to replace it or check on it again.
As it turns out a few days later I was in the big ring and started shifting the rear gears lower and lower (bigger and bigger) as I climbed this hill...
Eventually I was in the largest gear on the back and the hill was still steep so I decided it was time to go to the small ring in the front....
Well if you havented guessed... I couldn't shift to the small ring... The chain was stuck!!! The shifter wouldn't budge!!!
The chain was too small for the big-ring-big-gear combo... I had to stop the bike and PRY the chain off of the big ring!
Funny enough I continued to ride the bike just like that knowing all of the time never to shift into those two gears! The good ol' stupid days of biking :)
But don't forget to check the 53x27 position.
I had an old Schwinn.... Way long ago... That I broke the chain. Back then I simply re-linked it and rode off... Never bothered to replace it or check on it again.
As it turns out a few days later I was in the big ring and started shifting the rear gears lower and lower (bigger and bigger) as I climbed this hill...
Eventually I was in the largest gear on the back and the hill was still steep so I decided it was time to go to the small ring in the front....
Well if you havented guessed... I couldn't shift to the small ring... The chain was stuck!!! The shifter wouldn't budge!!!
The chain was too small for the big-ring-big-gear combo... I had to stop the bike and PRY the chain off of the big ring!
Funny enough I continued to ride the bike just like that knowing all of the time never to shift into those two gears! The good ol' stupid days of biking :)