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Do I need a short cage rear derailleur?

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Do I need a short cage rear derailleur?

Old 03-24-09, 04:14 PM
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Do I need a short cage rear derailleur?

So I switched my bike to a double from a triple, got a double front derailleur but left the original long cage rear derailleur. Around the time I did this I switched out my rear cassette to a new 12-26, got a new chain and also bought a 12-21 cassette I use for crits.

I've been finding ever since I switched that shifting is fine with the 12-26 but on the 12-21 it typically hangs up shifting on the 21 or 20ish gears. I shift and it just hangs there, sometimes it goes after a few seconds other times it seems to need to be shifted again for it to shift.

I've had the derailleur re adjusted and that helped for a few days but then it went back to doing this. Is this a sign I need to get a short cage rear derailleur?
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Old 03-24-09, 04:15 PM
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all i know is short cages look cooler. sorry i can't be of more help.
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Old 03-24-09, 04:25 PM
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Not sure but I thought you'd have to change the derailleur limits when switching from a 12-26 to a 12-21. Also shouldn't the chain be changed as well? I would think this could be a cause of your shifting issues. I might be wrong though.
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Old 03-24-09, 04:28 PM
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Loosen the B screw when you are using the 12-21. That will get the jockey wheel closer to the cogs.

See the Park web site.
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Old 03-24-09, 04:28 PM
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Originally Posted by chrisvu05
Not sure but I thought you'd have to change the derailleur limits when switching from a 12-26 to a 12-21. Also shouldn't the chain be changed as well? I would think this could be a cause of your shifting issues. I might be wrong though.
Well I don't think limits matter because the cassettes are the same width. As far as chain goes that could be a problem I know the reason people rock long cage derailleurs is to have extra chain length for those big rear cassettes and to be able to drop from 53 all the way down to 30 up front. I hope I can run the same chain on a 26 and 21 cassette because I switch them all the time.
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Old 03-24-09, 04:30 PM
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The real answer here is to have a crit bike for your 12-21 and an everything else bike for your 12-26. That's my set up.
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Old 03-24-09, 04:34 PM
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Originally Posted by chrisvu05
Not sure but I thought you'd have to change the derailleur limits when switching from a 12-26 to a 12-21. Also shouldn't the chain be changed as well? I would think this could be a cause of your shifting issues. I might be wrong though.
You don't have to change anything when switching to a higher low gear, as it is already included within the range of your old gearing. When you have a 12-26, at some point you will be on the 21T. It makes no differernce that you have switched to a cassette where that is now the lowest gear.
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Old 03-24-09, 04:37 PM
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Originally Posted by ericm979
Loosen the B screw when you are using the 12-21. That will get the jockey wheel closer to the cogs.

See the Park web site.
I tried that once and it didn't seem to make any change to the derailleur position it was really weird, I looked at it and tried to pick it apart and it seemed like the b screw had no effect.

So I've gotten no answer yet, will a short cage derailleur still work with both cassettes and give crisper shifting. If it's not going to work with both cassettes I'm just going to deal with it.
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Old 03-24-09, 04:40 PM
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The chain length does not need to be changed, but when a new chain is purchased, set it in the little ring and smallest cog. You could reduce the length by one inch, since the RD has excess wrap capacity.

If the hesitating shifts are from larger cog to smaller ones, the problem is cable housing friction. If the shifts hesitate going to larger cogs, you need more cable tension.

Of course, RD alignment is always suspect.
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Old 03-24-09, 04:44 PM
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Originally Posted by DaveSSS
The chain length does not need to be changed, but when a new chain is purchased, set it in the little ring and smallest cog. You could reduce the length by one inch, since the RD has excess wrap capacity.

If the hesitating shifts are from larger cog to smaller ones, the problem is cable housing friction. If the shifts hesitate going to larger cogs, you need more cable tension.

Of course, RD alignment is always suspect.
The housing has about 4000+ miles on it but I don't have this problem with the sram 12-26 so I don't get why I have the problem on the higher end ultegra 12-21. It actually seems to always hang up on the same gear the third one down from the biggest.
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Old 03-24-09, 04:44 PM
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Originally Posted by fauxto nick
I tried that once and it didn't seem to make any change to the derailleur position it was really weird, I looked at it and tried to pick it apart and it seemed like the b screw had no effect.

So I've gotten no answer yet, will a short cage derailleur still work with both cassettes and give crisper shifting. If it's not going to work with both cassettes I'm just going to deal with it.
Ummm, umd gave you an answer.
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Old 03-24-09, 04:47 PM
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Originally Posted by Tulex
Ummm, umd gave you an answer.
No that answers the question posted by another poster asking if I need to change the limiters, not my original post about if switching to a double requires you to go with a short cage rear derailleur for crisper more accurate shifts.
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Old 03-24-09, 04:49 PM
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Originally Posted by fauxto nick
No that answers the question posted by another poster asking if I need to change the limiters, not my original post about if switching to a double requires you to go with a short cage rear derailleur for crisper more accurate shifts.
The answer is NO. Your old cassette probably had a 19-21 shift and it worked fine, didn't it? The long cage RD merely has excess wrap capacity.
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Old 03-24-09, 04:51 PM
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Originally Posted by DaveSSS
The answer is NO. Your old cassette probably had a 19-21 shift and it worked fine, didn't it? The long cage RD merely has excess wrap capacity.
hmm so if it's not the long cage rear derailleur I wonder what's causing the chain to hang up on that 12-21, weird.
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Old 03-24-09, 04:51 PM
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No, he said you don't have to change anything.
And, in you first post, you say it hangs on the 21, or the biggest one, but later, you say it hangs on the 3rd one down. My guess is that there is a small difference in the distance from the seat of the cassette to the first gear between the 2 cassettes.
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Old 03-24-09, 04:54 PM
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Originally Posted by fauxto nick
No that answers the question posted by another poster asking if I need to change the limiters, not my original post about if switching to a double requires you to go with a short cage rear derailleur for crisper more accurate shifts.
Originally Posted by Tulex
No, he said you don't have to change anything.
And, in you first post, you say it hangs on the 21, or the biggest one, but later, you say it hangs on the 3rd one down. My guess is that there is a small difference in the distance from the seat of the cassette to the first gear between the 2 cassettes.
I was replying directly to the other post but I intentionally said anything to be inclusive of the original question. As Dave said, you are left with some unused chain wrap capacity and an uglier and heavier derailer, but functionally it does not matter.
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Old 03-24-09, 04:54 PM
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Cable tension. When the cable slacks it wouldn't shift down to small ring. When it's too tight it won't shift up to the biggest ring. Maybe your barrel adjuster is not holding the tension.
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Old 03-24-09, 04:56 PM
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What a coincidence. I've got an SRAM 12-26 and a long cage derailleur and just ordered an 11-21. I'll let you know how it works out.
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Old 03-24-09, 05:09 PM
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I've got to ask if you're changing the cassette or wheels without making any alteration to the cable tension or limit screws? Different wheels and/or cassettes often need slightly different setting of all three items. It sucks, but it's a fact of life. If you figure out what needs to be changed when the swap is made, it will make the job easier.

Also be sure that you don't have a cassette spacer in the wrong place. I know little about Shimano cassettes, as a Campy-only guy, but some do have non-uniform spacer thicknesses.

Last edited by DaveSSS; 03-25-09 at 07:43 AM.
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Old 03-24-09, 05:37 PM
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Originally Posted by fauxto nick
No that answers the question posted by another poster asking if I need to change the limiters, not my original post about if switching to a double requires you to go with a short cage rear derailleur for crisper more accurate shifts.
Absolutely not.

You can put a long cage for an MTB that can handle an 11/34 on a double chainring with a normal cassette and it will work fine.
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Old 03-24-09, 05:40 PM
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Ok well I'll try and play with it and see exactly what might be catching up and any trends. Honestly I'm trying to throw as little into this bikes 9 speed drive train as possible so I'll just deal with it most likely. It's not the end of the world, but I have to say when I'm trying to handle the yo yo's in a crit or chase down a break and the shift hangs up it's a bit jarring.
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Old 03-24-09, 05:40 PM
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Long cage is for Freds.
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Old 03-24-09, 05:42 PM
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Originally Posted by fauxto nick
Ok well I'll try and play with it and see exactly what might be catching up and any trends. Honestly I'm trying to throw as little into this bikes 9 speed drive train as possible so I'll just deal with it most likely. It's not the end of the world, but I have to say when I'm trying to handle the yo yo's in a crit or chase down a break and the shift hangs up it's a bit jarring.
If it makes you feel any better, Ben, the kid that was travelling with us over the weekend bent his derailer hanger warming up for the RR on Saturday. Raced the RR and the crit with crappy shifting. I think it mostly worked but would not go into all of the gears. Anyway, he got I think 7th in the cat 4 crit. So no excuses Nick!
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Old 03-24-09, 05:51 PM
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In an early post you mentioned 4000 miles on your cables and housings..... Could it be that your housing is toast? Just had to replace mine at the tight bend at the rear derailleur. No more gear hanging now. Just a thought. YMMV
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Old 03-24-09, 05:56 PM
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Originally Posted by kyakdiver
In an early post you mentioned 4000 miles on your cables and housings..... Could it be that your housing is toast? Just had to replace mine at the tight bend at the rear derailleur. No more gear hanging now. Just a thought. YMMV
I'll check it out I did notice on one of my shifting cables there was some cracking in the housing.
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