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Old 07-23-09, 08:35 PM   #1
GusQuevedo
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48/32 crankset...

I want to assemble a double crankset chainring 48/32 for a Touring MTB.

Is it possible to change the chainring of a crankset SLX 36/22 into 48/32 and to use it without bashguard?
Or: Is better to try it with a Crankset XT 48/36/26, removing the small one and changing the middle for 32?... Would need bashguard or chainguide?

In any of the cases: Can use a X.9 front derailleur with a double chainring 48/32?

Thanks in advance.
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Old 07-23-09, 08:51 PM   #2
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A 32/48 is a 16 T spread. That's a big spread for one shift, and may produce dropped chains on downshifting, and difficulty/trouble when upshifting.
You don't want to have a dropped chain while riding - I destroyed 4 spokes and a RD when my chain dropped last year.
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Old 07-23-09, 09:29 PM   #3
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A 16T difference is really not a problem. Compact road cranksets are often 50/34 which is comparable to a 48/32 in tooth drop. If you can locate a 48T and 32T chainring with a 110mm bolt circle diameter, you can use a compact road crankset.
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Old 07-24-09, 02:32 AM   #4
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If you can locate a 48T and 32T chainring with a 110mm bolt circle diameter, you can use a compact road crankset.
You can't, 34t minimum with 110 BCD.
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Old 07-24-09, 08:09 AM   #5
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Get an XT or SLX 22/32/44, drop the granny and replace the 44 with a 48 like one of these http://www.bikeparts.com/search_resu...p?id=BPC348880 . It's not ramped and pinned but it will still work. I have one on my tourer/commuter. My crank is a 5-arm 94/58mm BCD triple with the granny removed and the outer ring replaced with a 46 so I run 46/32 rings. My crank takes a square taper BB so I was able to get a slightly shorter one for better chain line as a double. Not sure if you can do that with a Hollowtech crank, though.

Or you could get this FSA crank and I think you could replace the bashguard with a 48 ring: http://www.universalcycles.com/shopp...s.php?id=30857

Last edited by Gonzo Bob; 07-24-09 at 08:19 AM.
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Old 07-24-09, 09:14 AM   #6
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Get an XT or SLX 22/32/44, drop the granny and replace the 44 with a 48 like one of these http://www.bikeparts.com/search_resu...p?id=BPC348880 . It's not ramped and pinned but it will still work. I have one on my tourer/commuter. My crank is a 5-arm 94/58mm BCD triple with the granny removed and the outer ring replaced with a 46 so I run 46/32 rings. My crank takes a square taper BB so I was able to get a slightly shorter one for better chain line as a double. Not sure if you can do that with a Hollowtech crank, though.

Or you could get this FSA crank and I think you could replace the bashguard with a 48 ring: http://www.universalcycles.com/shopp...s.php?id=30857
A problem exists. I live in Argentina and here it is difficult to obtain some components. But I can obtain any thing made by Shimano, crankset Shimano and chainrings Shimano, but difficultly obtain here a MegaExo Crankset or a Salsa chainring.
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Old 07-24-09, 11:38 AM   #7
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A problem exists. I live in Argentina and here it is difficult to obtain some components. But I can obtain any thing made by Shimano, crankset Shimano and chainrings Shimano, but difficultly obtain here a MegaExo Crankset or a Salsa chainring.
Then go with a Deore or XT 48/36/26, take off the granny and get a new 32 middle ring.
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Old 07-24-09, 11:49 AM   #8
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Then go with a Deore or XT 48/36/26, take off the granny and get a new 32 middle ring.
But Bob, there is no 32t 110 BCD ring. 33t is actually the smallest 110 BCD ring, and TA is the only one who makes them.
If he's limited to Shimano . . . he's gonna have to play the Shimano game. Time for a new crank and who knows what else, depending on his shifting system.

He could however, take off the 48, run it in the middle, and get a 32t 74mm BCD ring. He'd need a longer BB to get a better chainline, and the Q would be larger, but it could be done.

Last edited by Garthr; 07-24-09 at 11:52 AM.
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Old 07-24-09, 12:50 PM   #9
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But Bob, there is no 32t 110 BCD ring. 33t is actually the smallest 110 BCD ring, and TA is the only one who makes them.
The Deore and XT 48/36/26 are 4-arm 104mm/64mm BCD and you can get 32 rings for those.

Last edited by Gonzo Bob; 07-24-09 at 12:55 PM.
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Old 07-24-09, 06:37 PM   #10
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You can't, 34t minimum with 110 BCD.
Wow. I learned something new today. It makes sense now that I've looked at my compact setup. Thanks for correcting me.
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Old 07-24-09, 06:41 PM   #11
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I'm running an XT crank with 48/32/22 and an Ultegra triple FD.
It isn't the quickest shifting arrangement, but it works pretty good.
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Old 07-24-09, 07:29 PM   #12
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I'm running an XT crank with 48/32/22 and an Ultegra triple FD.
It isn't the quickest shifting arrangement, but it works pretty good.
Its sound good... Can I use the same XT/Ultegra setup but removing the chainring 22? Would need chain guide?
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Old 07-24-09, 11:26 PM   #13
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actually the minimum for 110BCD is a 33T, but good luck finding a 33T 110BCD chainring.

the road compacts with 34/50 from shimano/campy/sram work well because the rings are designed for each other. the outer ring has pins and ramps to aid in shifting the huge jump.

shifting is not as good when mixing rings, especially ones with big jumps.
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Old 07-25-09, 06:34 AM   #14
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How about finding a TA Cyclotourist crankset? That's the crank with the greatest ring flexibility out there, but might be hard to find.
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Old 07-26-09, 05:18 AM   #15
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Its sound good... Can I use the same XT/Ultegra setup but removing the chainring 22? Would need chain guide?
Shimano's road FDs (e.g., Ultegra) have a different cable-pull ratio than their MTB FDs. Therefore, if you're using indexed MTB shifters then don't use a road FD. There are some Shimano MTB FD's that are designed for a big ring of up to 48 teeth, but it should also work fine with one that is only designed for a 42-44 tooth big ring.

Definitely put a chain retention device (e.g., Third Eye) on the seat tube to prevent the chain from derailling off the inside.
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