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Old 02-24-09, 07:03 PM   #1
jtwilson
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Switching to a wider range cassette

My bike currently has a SRAM PG-950 12-26 cassette, and I want some more granny gearing for steep hill climbs. The PG-950 also comes in 11-34, which is what I would like to try, but it's listed as "MTB" - does that mean I need a different derailleur? The bike has a 105 derailleur. What kind of adjustments would need to be made for this to work?

TIA
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Old 02-24-09, 07:09 PM   #2
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you will need a longer chain for one.

your current derailer might work, it might not, it's hard to say without trying.
to play it safe, you need a shimano SGS long cage MTB rear derailer along with a new chain.
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Old 02-24-09, 07:15 PM   #3
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you will need a longer chain for one.

your current derailer might work, it might not, it's hard to say without trying.
to play it safe, you need a shimano SGS long cage MTB rear derailer along with a new chain.
True, but this would be a worst case scenario. It's quite possible that your current setup can work (although less than ideally with that 34 toother) without much modification. All the more so if your able to be careful to avoid the big/big and small/small combination.
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Old 02-24-09, 07:44 PM   #4
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The current crop of Triples from Shimano use a medium cage (75mm) RD. You need a long cage derailluer (90mm) with the 11-34t cassette if you are using a triple but, a medium cage might work on a double front chain ring (need to try). If you have a short cage (60mm) you will not be able to use it for sure. If you are lucky you might be able to find an old 105 triple long cage RD but if you can't the XT RD will work very well with the STI shifters. I swapped out the setup for my neighbor and she has been pleased with the results.
I am running a Campy setup on my bike with a triple, long cage RD (centaur), and an 11-34t SRAM cassette on an after market Shimano cassette hub body. I am using Centaur 10spd ergo shifters with the 9spd cassette and because the spacing is so close I have very smooth shifting. This is for a touring setup that I am going to use for some extended trips. Oh yes, you will need a chain.
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Old 02-24-09, 09:30 PM   #5
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The current crop of Triples from Shimano use a medium cage (75mm) RD. You need a long cage derailluer (90mm) with the 11-34t cassette if you are using a triple but, a medium cage might work on a double front chain ring (need to try). If you have a short cage (60mm) you will not be able to use it for sure. If you are lucky you might be able to find an old 105 triple long cage RD but if you can't the XT RD will work very well with the STI shifters. I swapped out the setup for my neighbor and she has been pleased with the results.
I am running a Campy setup on my bike with a triple, long cage RD (centaur), and an 11-34t SRAM cassette on an after market Shimano cassette hub body. I am using Centaur 10spd ergo shifters with the 9spd cassette and because the spacing is so close I have very smooth shifting. This is for a touring setup that I am going to use for some extended trips. Oh yes, you will need a chain.
Thanks for the detailed info! My bike has the short cage RD, so I will definitely need to replace it. I've found one vendor with a close-out long cage 105 RD, which I might have to snag. Seems like a good deal [$55]. Is it difficult to swap a RD? I haven't done very much intensive bike work, but if it's just a matter of bolting it on and adjusting the three screws, I should be able to handle that.
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Old 02-24-09, 09:40 PM   #6
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Being that we're going to do some bigger climbs this year, we swapped out my cassette for a 11-34 mtb gearing, and the ultegra der. for a Deore long cage. That's about as technical as I can get. Shifting isn't as responsive, but oh well, at least I can crawl up to Crater lake this summer. Dh has the same set up on his bike.
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Old 02-24-09, 09:55 PM   #7
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Do let us know how it works if you try you old derailleur. With many derailleurs being listed as having a maximum cog-size, it's useful to find out the truth from people's own experience. Often times the listed max - teeth given is far from being the actual truth.

Good luck!
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Old 02-24-09, 09:57 PM   #8
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Thanks for the detailed info! My bike has the short cage RD, so I will definitely need to replace it. I've found one vendor with a close-out long cage 105 RD, which I might have to snag. Seems like a good deal [$55]. Is it difficult to swap a RD? I haven't done very much intensive bike work, but if it's just a matter of bolting it on and adjusting the three screws, I should be able to handle that.
If you don't have quick-disconnect chain such as SRAM Powerlink, then you will need to do a little extra work. If you have a chain tool, you can "break" the chain in order to remove the RD. If you don't have a chain tool you will have to disassemble the derailleur cage (allen wrench is all that is needed) of the old RD and the new RD in order to snake the chain through the pulley system.

Search eBay for the derailleur. I found a long cage 105 RD for $42 shipped

Last edited by fetad; 02-24-09 at 10:03 PM.
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Old 02-24-09, 10:27 PM   #9
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Along the same lines I want to pair my medium cage 105 RD with an 11-32T or 11-34T cassette. I have a single front 36T chainring and some latitude for chainline adjustment. Anyone have experience with a 1x9 setup like this?
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Old 02-24-09, 10:32 PM   #10
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Thanks for the detailed info! My bike has the short cage RD, so I will definitely need to replace it. I've found one vendor with a close-out long cage 105 RD, which I might have to snag. Seems like a good deal [$55]. Is it difficult to swap a RD? I haven't done very much intensive bike work, but if it's just a matter of bolting it on and adjusting the three screws, I should be able to handle that.
The cage length is only part of the story. A Shimano road bike long cage rear derailleur, including the 105, is rated for no larger than a 27 tooth large cog. In reality it will work with a 28 and possibly as large as a 30 tooth RD. For a 34t large cog you will need a mountain bike rear derailleur. The conversion works well and is easily done.
The down side of a wide range cassette is that the big ratio jumps from cog to cog causes big jumps in crank rpm making it more difficult to maintain an efficient cadence. But do whatever is best for you and your riding conditions.

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Old 02-24-09, 10:34 PM   #11
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Thanks for the tips. I will look on ebay for the long cage 105 RD too. I figured I would have to make use of a chain tool. I can handle that. Didn't know it could be done without one - interesting.

Also, mudmouse, I assume the less responsive shifting was due to the downgrade from ultegra to deore? The wider gear range shouldn't hurt shifting performance in and of itself right? This will be on my do-it-all primary bike and I'd like to keep the current level of shifting response.

I plan to do some touring, a double century hill challenge, and just plain old messing around with my CX tires and steep grassy slopes.
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Old 02-24-09, 10:40 PM   #12
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The cage length is only part of the story. A Shimano road bike long cage rear derailleur, including the 105, is rated for no larger than a 27 tooth large cog. In reality it will work with a 28 and possibly as large as a 30 tooth RD. For a 34t large cog you will need a mountain bike rear derailleur. The conversion works well and is easily done.
The down side of a wide range cassette is that the big ratio jumps from cog to cog causes big jumps in crank rpm making it more difficult to maintain an efficient cadence. But do whatever is best for you and your riding conditions.

Al
I believe you're thinking of the 'GS' mid length cage which is rated to 27. The long cage designation is SGS and they are rated in the 30s. Since I'm having trouble finding them, I assume they are discontinued, and now 'GS' is the 'long cage' for road derailleurs.

I think I can deal with bigger jumps in cadence, so long as the shift itself feels basically as responsive as I have now with the short cage and 12-26. It would be nice to find all the teeth numbers for the 11-34 cassette however. I may end up compromising with the 11-32, or a 12-32 if those are around.
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Old 02-24-09, 10:47 PM   #13
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I believe you're thinking of the 'GS' mid length cage which is rated to 27. The long cage designation is SGS and they are rated in the 30s. Since I'm having trouble finding them, I assume they are discontinued, and now 'GS' is the 'long cage' for road derailleurs.
According to present and previous Shimano specs, the 105 rear derailleur is rated for a maximum 27 teeth:

http://bike.shimano.com/publish/cont.../road/105.html

As stated above, they will accept a somewhat larger cog, but not a 34.

Al
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Old 02-24-09, 11:34 PM   #14
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Yes, that's the GS. Which is mid length cage. There exists, apparently, a model RD-5600-SGS which, like the other SGS length cages, should handle a 34. For the life of me, I can't figure out how I found the one vendor who claims to have one [open box, close out], as subsequent google searches are not bringing it up. I think it has my name on it.
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Old 02-24-09, 11:50 PM   #15
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Have you considered a triple chainring? A bit more expensive a swap assuming you don't have some mechanical interference, by I wouldn't want to change the 11-27 10 spd cassette on my bike (or my wife's). I recently changed her small chainring to 24t and this appears as though it will work fine. Gives here 50-39-24 up front which should be plenty low enough. Yes, I'm going to change my small chainring to 26t.
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Old 02-24-09, 11:52 PM   #16
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Is this the one you're looking for?

http://bikeusa.com/itemdetails.cfm?ID=8471

It has a chain-wrap capacity of 37 teeth. If you have a standard crankset (53-39) and pair it with the 11-34 cassette, you will have reached the maximum 37 tooth chain wrap capacity.
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Old 02-24-09, 11:59 PM   #17
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fetad,

That's the one. I just ordered it. I have a CX crankset [48-39], so I should be safe. 32 tooth wrap.

My first thought was a triple up front, but I don't want to invest in another crankset, nor do I want to trade out my 39 for something smaller.

Thanks again.

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Old 02-25-09, 12:02 AM   #18
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Buy a mountain sgs der if you since I believe you are running 9 speed you will be gold. As stated above the recommended for gs der (mid cage) is 27t max you can run about a 30t on most setups. Find an XT or LX on clearance you will be good to go. I really like the new SLX stuff it is cheaper than new XT and I think it shifts as well or better.
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Old 02-25-09, 05:40 AM   #19
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Shimano Ultegra's are known to handle 30 - 32T, though they are rated at 27T. Shimano's Max. T is not to be believed. Here is the 6500 for much less than the 105:

http://www.cambriabike.com/shopexd.a...EAR+DERAILLEUR
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Old 02-25-09, 06:34 AM   #20
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Break the chain, measure the new chain so it just fits tight around the largest rear cog, and the largest front chainring (without threading it through the rear derailleur for measuring purposes), and leave two extra links.

Take the cable out of your old rd. Unthread it from the frame (derailleur hanger). Put grease on the threads of your new rd. Thread it into the derailleur hanger. Be sure to get the derailleur angle adjustment screw above the stop that is forged into the derailleur hanger, so it rests on it when you let go.

Thread the cable through your new rd and tighten. Now you put the chain on. Adjust rd stops so its range goes from smallest cog to largest on the cassette. Put the wheel in and check shifting. Twist barrel adjusters for perfect indexing. Get on it and ride!
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Old 02-25-09, 09:42 AM   #21
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Do let us know how it works if you try you old derailleur. With many derailleurs being listed as having a maximum cog-size, it's useful to find out the truth from people's own experience. Often times the listed max - teeth given is far from being the actual truth.

Good luck!
it's not really the derailer, it's the placement of the derailer hangar.

I've got an SGS long cage rated for a 34T which isn't clearing the 34T properly even with the B-tension maxed out, all thanks to the derailer hangar.
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Old 02-25-09, 10:12 AM   #22
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I apologize in advance for piggy-backing on this thread but my questions seemed reasonably topical.

I'm considering a switch to a wider range cassette for some upcoming touring. I'm currently using an ultegra 6500 9sp 12-25 cassette with a dura-ace RD mounted on a vintage campagnolo horizontal dropout. I've already noticed that my shifting performance changes greatly depending on where along the dropout I've positioned my wheel. (Further forward is better. Makes sense as this approximates the positioning of a vertical dropout.) Could the max range I could get for a cassette depend on my wheel placement in the dropout?

What about if I assume that I will never cross chain too badly and never use those lower gears while I'm in my big ring? (53t) Can I get away with using my current short cage RD?

Also, I've seen on Sheldon's website where he built custom cassettes with wider gear ranges. I don't have 100s of dollars to spend on a cassette so I'm wondering if I could assemble my own cassette? I'm thinking the toughest part will be getting the spacing right? I work at a bike co-op and have access to a lot of used parts.
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Old 02-25-09, 06:39 PM   #23
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What about if I assume that I will never cross chain too badly and never use those lower gears while I'm in my big ring? (53t) Can I get away with using my current short cage RD?
Its not chain length thats the problem Ent, its that the rear derailleur doesn't have enough movement to bring the chain to the largest ring without striking it. So you'd be fine in that case if you never shift down to the lowest gears in the rear, but that would defeat the purpose of getting a wider range cassette
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Old 02-25-09, 06:42 PM   #24
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fetad,

That's the one. I just ordered it. I have a CX crankset [48-39], so I should be safe. 32 tooth wrap.

My first thought was a triple up front, but I don't want to invest in another crankset, nor do I want to trade out my 39 for something smaller.
Chain wrap capacity and cog size limit are two different issues. If you want to run a 34 cog you'll need a mountain bike type rear derailleur.
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Old 02-25-09, 07:45 PM   #25
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Its not chain length thats the problem Ent, its that the rear derailleur doesn't have enough movement to bring the chain to the largest ring without striking it. So you'd be fine in that case if you never shift down to the lowest gears in the rear, but that would defeat the purpose of getting a wider range cassette
Thanks for the info. The 27t limit (from previous posts) for my derailleur is assuming a vertical dropout. I'm thinking that I could fit a larger ring (30-32t) if I slide the wheel back in my horizontal dropout since I'm essentially creating more distance between the RD and the cassette. Is my thinking off-track? I was planning on sliding the wheel back anyway to approximate longer chainstays for touring.
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