Which is the rear derailleur with the longest chainwrap (capacity)
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Which is the rear derailleur with the largest chainwrap (capacity)
I'd like to run a 53-42-24 front and an 11-34 rear on a touring bike I'm putting together. I think that adds to 51 teeth by the usual formula. Will a shimano SGS work or is there another 9 speed with more takeup capacity?
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I'm running 22/32/48 with 11-36 cassettes on two bikes.
That is also 51 teeth.
I use the 9s "Shadow" RD's.
That is also 51 teeth.
I use the 9s "Shadow" RD's.
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With a triple crank, you can exceed the wrap capacity to some extent.
I would suggest having a long enough chain to shift into big/big (use the big/big + 1" method). Even though you shouldn't use this combo, it should shift there just in case.
If this causes the RD to fold up and the chain goes slack in small/small that's okay since there's no reason to ever use this combo either and you'll be able to get out of that combo when the mistake is realized.
That all said, Shimano's SGS (long cage) mountain RDs have all the same wrap capacities, so any will work (with the usual warnings about 10-speed Dina-Sys cable pull ratio incompatibility and Rapid Rise low-normal backward-ness).
I would suggest having a long enough chain to shift into big/big (use the big/big + 1" method). Even though you shouldn't use this combo, it should shift there just in case.
If this causes the RD to fold up and the chain goes slack in small/small that's okay since there's no reason to ever use this combo either and you'll be able to get out of that combo when the mistake is realized.
That all said, Shimano's SGS (long cage) mountain RDs have all the same wrap capacities, so any will work (with the usual warnings about 10-speed Dina-Sys cable pull ratio incompatibility and Rapid Rise low-normal backward-ness).
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I run a 20 43 on the front and a 12 39 on the rear a standard shimano megarange works fine on this setup. https://www.flickr.com/photos/6337399...in/photostream
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A deore or any mountain bike rear works fine. I don't like the latest and greatest because they don't an adjustment screw on the Der..
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With a triple crank, you can exceed the wrap capacity to some extent.
I would suggest having a long enough chain to shift into big/big (use the big/big + 1" method). Even though you shouldn't use this combo, it should shift there just in case.
If this causes the RD to fold up and the chain goes slack in small/small that's okay since there's no reason to ever use this combo either and you'll be able to get out of that combo when the mistake is realized.
That all said, Shimano's SGS (long cage) mountain RDs have all the same wrap capacities, so any will work (with the usual warnings about 10-speed Dina-Sys cable pull ratio incompatibility and Rapid Rise low-normal backward-ness).
I would suggest having a long enough chain to shift into big/big (use the big/big + 1" method). Even though you shouldn't use this combo, it should shift there just in case.
If this causes the RD to fold up and the chain goes slack in small/small that's okay since there's no reason to ever use this combo either and you'll be able to get out of that combo when the mistake is realized.
That all said, Shimano's SGS (long cage) mountain RDs have all the same wrap capacities, so any will work (with the usual warnings about 10-speed Dina-Sys cable pull ratio incompatibility and Rapid Rise low-normal backward-ness).
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With a triple crank, you can exceed the wrap capacity to some extent.
I would suggest having a long enough chain to shift into big/big (use the big/big + 1" method). Even though you shouldn't use this combo, it should shift there just in case.
If this causes the RD to fold up and the chain goes slack in small/small that's okay since there's no reason to ever use this combo either and you'll be able to get out of that combo when the mistake is realized.
I would suggest having a long enough chain to shift into big/big (use the big/big + 1" method). Even though you shouldn't use this combo, it should shift there just in case.
If this causes the RD to fold up and the chain goes slack in small/small that's okay since there's no reason to ever use this combo either and you'll be able to get out of that combo when the mistake is realized.
#9
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I'm going to play curmudgeon and not speak to your original question. I'll leave alone for the moment how much you will use any of the higher gears, although your choice of a 53 large does come into play. Because you went that large you are somewhat forced to go larger on the middle ring. Because you also chose an extremely low range for the granny you then have a huge jump between that and the middle. The effects are this:
You have a 75% jump in gear ratio between the granny and the middle gear. Perhaps that is acceptable to you because you anticipate a lot of steep/difficult climbing, and the granny is typically not used as much.
HOWEVER, because the middle ring is relatively large, the lowest gear combo on it would yield about 9 miles per hour at 90 rpm (8 mph @ 80rpm). If you go any slower than that you will be forced onto the granny. If you are doing fully loaded touring, which I would expect when you are going for such a low granny range, those speeds could be quite common, resulting in too frequent shifting and a lot less enjoyment.
If you are planning a 10 speed cassette it's not nearly as ideal as a 9 speed, but the common 48/38 combo came about for a reason, and I question if the "benefit" of pedaling downhill at 40+ mph rather than tucking down and coasting is worth the cost of messing up the useability of the middle ring.
p.s. On the topic of too frequent shifting, I found out the hard way that there is one decided downside to brifters for touring that I had not anticipated. When I was on a tour in Italy I had a much longer and much hillier day than anticipated (long story). As a result I was using my left brifter very frequently. As the stroke required for a chainwheel shift is fairly long and requires more force than a rear cog I ended up with a sore hand.
You have a 75% jump in gear ratio between the granny and the middle gear. Perhaps that is acceptable to you because you anticipate a lot of steep/difficult climbing, and the granny is typically not used as much.
HOWEVER, because the middle ring is relatively large, the lowest gear combo on it would yield about 9 miles per hour at 90 rpm (8 mph @ 80rpm). If you go any slower than that you will be forced onto the granny. If you are doing fully loaded touring, which I would expect when you are going for such a low granny range, those speeds could be quite common, resulting in too frequent shifting and a lot less enjoyment.
If you are planning a 10 speed cassette it's not nearly as ideal as a 9 speed, but the common 48/38 combo came about for a reason, and I question if the "benefit" of pedaling downhill at 40+ mph rather than tucking down and coasting is worth the cost of messing up the useability of the middle ring.
p.s. On the topic of too frequent shifting, I found out the hard way that there is one decided downside to brifters for touring that I had not anticipated. When I was on a tour in Italy I had a much longer and much hillier day than anticipated (long story). As a result I was using my left brifter very frequently. As the stroke required for a chainwheel shift is fairly long and requires more force than a rear cog I ended up with a sore hand.
Last edited by cny-bikeman; 06-19-12 at 07:35 AM.
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If you are planning a 10 speed cassette it's not nearly as ideal as a 9 speed, but the common 48/38 combo came about for a reason, and I question if the "benefit" of pedaling downhill at 40+ mph rather than tucking down and coasting is worth the cost of messing up the useability of the middle ring.
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I have a top gear of 48/11 on my climbing road bike and my touring bike, and a top gear 53/11 on another road bike. The 53/11 is rarely used, generally only on descents of -9% or more when I feel the need to break 45mph.
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