Got a crank off eBay with 24t difference.
06-06-11, 09:13 AM
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Got a crank off eBay with 24t difference.
I bought a crankset that has 52/42/28. The seller didn't specify the size of the small ring and the picture showed the middle crank which read 52/42/30. Shimano claims my XT deore sgs long cage RD will only shift a 22t difference, not a 24t. I told the seller that the item was not as described as I have to buy a new chainring to make it work. They basically said too bad. Should i dispute it with paypal or will the RD shift it just fibe?
06-06-11, 09:18 AM
#2
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want a 74 bcd chainring , 30t? I went the other way, to smaller, sizes.
Campag alloy or Shimano steel, ..(pm?)
I use Bar end shifters , no problems..
Campag alloy or Shimano steel, ..(pm?)
I use Bar end shifters , no problems..
Last edited by fietsbob; 06-06-11 at 10:10 AM.
06-06-11, 09:26 AM
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So does what you got have the same sticker as the picture (ie they swapped out chainrings after that bought it)? If that's the case, I think you'd have a hard time disputing it if they didn't actually state tooth number. If it's not exactly what was pictured, then they could be in some trouble. It all depends on how much effort you want to put into dealing with it.
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06-06-11, 09:37 AM
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They stated that they changed the small ring but did not specify what size. The only number I had to go off of was the etching of the original sizes. The condition was used but totally functional. If there isn't a RD capable of shifting it, it's hardly functional is it ?
06-06-11, 10:02 AM
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Your Deore rd will handle the difference with no problem and a 28T granny ring is more useful than a 30T. I've changed many 52/42/30 cranks to 52/42/26 and they work great even if the rd isn't "supposed" to handle it. At worst you can't use the granny ring with the smallest one or two rear cogs which is no loss.
Last edited by HillRider; 06-06-11 at 10:15 AM.
06-06-11, 10:19 AM
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Why does the RD even care how many teeth are on the cranks so long as you don't exceed chain wrap?
06-06-11, 01:09 PM
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Shimano claims the front derailer will only take a 22t difference, but in practice these tolerances are very conservative. you'll probably be fine.
a similar pattern: Shimano road rear derailers are officially rated to 27t large cog, but in practice always work with 28t and often even 30t large cogs.
a similar pattern: Shimano road rear derailers are officially rated to 27t large cog, but in practice always work with 28t and often even 30t large cogs.
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06-06-11, 03:02 PM
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The OP describes it as a XT long cage rear derailleur but then gives a spec that applies to a front derailleur so it is a bit confusing.
If he is indeed asking about a front derailleur his XT is an MTB front derailleur and won't work at all well with a road crank (52/X/X) as the cage curvature is much too tight and intended to match a 44T big ring, not a 52. It would have to be mounted way to high
If he is indeed asking about a front derailleur his XT is an MTB front derailleur and won't work at all well with a road crank (52/X/X) as the cage curvature is much too tight and intended to match a 44T big ring, not a 52. It would have to be mounted way to high
06-06-11, 04:42 PM
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Not knowing any of this, I temporarily put a 13/34 seven speed wheel on my road bike with a 52/42/26 and everything works just fine. FD is Suntour, RD is Sunrace. Friction shifting, of course.
06-06-11, 05:51 PM
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HI,
I try to understand exactly what front changer you have. Also write down the rear casette tooth numbers. My opinion is that the 22 tooths is not the maximum tooths number if you have 3 speeds just between the 1st and 2nd and between the 2nd and 3rd speed. You have to check the total capacity also. For that I ask the exact number of the changers and back tooth wheel numbers. The question is how many speed you can change with it and the answer is 3 speed for that reason what you have is OK.
losi
I try to understand exactly what front changer you have. Also write down the rear casette tooth numbers. My opinion is that the 22 tooths is not the maximum tooths number if you have 3 speeds just between the 1st and 2nd and between the 2nd and 3rd speed. You have to check the total capacity also. For that I ask the exact number of the changers and back tooth wheel numbers. The question is how many speed you can change with it and the answer is 3 speed for that reason what you have is OK.
losi
Last edited by losi; 06-06-11 at 06:22 PM.
06-07-11, 02:40 AM
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That's why the seeming mis-match works. Friction shifting will allow nearly anything to work with nearly anything else.
06-07-11, 07:42 AM
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When's the last time that you used the little/little combination on a triple? I've never ever used any but the largest 2 or 3 rear cogs with my granny chainring. I can't imagine it ever causing a problem in real life.
06-07-11, 10:30 AM
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Going beyond the capacity of the FD or RD, if properly set up, will likely only cause rubbing in the small/small or small/second-small combo. The RD may not take up enough slack when cross chaining and the chain will rub on itself when running through the derailleur. On the front, the chain may touch the bottom of the derailleur cage.
If you are setting up the bike like this, make sure you have enough chain to safely get into the big-big combo - if your chain is too short and you accidentally shift into the big-big you may cause damage.
However, it is likely that your existing derailleurs will work fine.
If you are setting up the bike like this, make sure you have enough chain to safely get into the big-big combo - if your chain is too short and you accidentally shift into the big-big you may cause damage.
However, it is likely that your existing derailleurs will work fine.
