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Old 01-05-08, 01:14 PM   #1
Hammertoe
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Swapping a 10 speed crank with 9 speed chainrings...

I would like to get an Ultegra crankset and swap out the 52/39/30 chanrings with 48/38/26...

I am having a hard time finding a new Ultegra 6503 with 170mm cranks...

Would I be able to remove the chainrings off a 10 speed crankset and replace them with 9 speed chainrings...

I need the 9 speed because I run an XT RD and a 11/34 cassette for hillclimb races...

Thanks...
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Old 01-05-08, 01:32 PM   #2
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Are you talking about Road cranks with "Mountain" rings? IF so, they won't fit. The bolt spacing is different.
110MM on Mountain & 130MM on Road.
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Old 01-05-08, 01:47 PM   #3
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No I will be using a standard road triple 130/74 BCD and TA chainrings ...

Mountain has a 4 arm spider while road has 5 arm spider...
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Old 01-05-08, 02:33 PM   #4
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If you have a braze-on type front derailleur you will probably have problem getting the derailleur low enough for rings that small. It it is a clamp on you will be able to get it low enough but shifting performance probably won't be as good as with the standard chainrings. Front derailleurs are designed for specific ring sizes. The farther you get from those sizes the poorer shifting performance becomes. If I were you I'd go with 50-38-30 rings with the cassette you've chosen. You could climb a tree with a 30-34 combination. A 26 granny seems awfully small to go with a 34t big cog, maybe a 28.

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Old 01-05-08, 03:58 PM   #5
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I already have a bike set up with a Deore 48/36/26 and the shifting is fine...

I want to try an Ultegra crank.......

I can not climb Mt. Washington with a 30/34 combination...

I climb some crazy stuff you should come to the Northeast and we can ride...
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Old 01-05-08, 06:06 PM   #6
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A quick, cheap change is to swap the 30T granny for a 26T. I've done this on numerous 7,8 and 9-speed Shimano triple road cranks and it works very well. The shift from 26 back to the 42T middle ring is ok but not super fast but I doubt you would be in a rush for it.
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Old 01-05-08, 06:14 PM   #7
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Quote:
Originally Posted by Hammertoe View Post
I would like to get an Ultegra crankset and swap out the 52/39/30 chanrings with 48/38/26...

I am having a hard time finding a new Ultegra 6503 with 170mm cranks...

Would I be able to remove the chainrings off a 10 speed crankset and replace them with 9 speed chainrings...

I need the 9 speed because I run an XT RD and a 11/34 cassette for hillclimb races...

Thanks...
There's nothing "N-speed" about a crank. There is a teeeeeensy difference in the chainrings for 9-speed vs. 10-speed, but no difference at all in the cranks.

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Old 01-05-08, 06:22 PM   #8
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No such thing as 9-speed vs. 10-speed chainrings. Just marketing hype...
Read Sheldon Brown's site on the subject.

The crown thickness of said rings is the same, I have been running 50-39-28 ("9-speed" Salsa granny wonderfully replaced the original FSA "10-speed" 30T granny) for about an year now.

The jump 39-26 in front in your case may require a "chain watcher" device, otherwise the chain might drop onto the BB shell at rapid downshifting in front.
Since we are talking real low mounting for the "chain watcher" here, due to lowered FD to fit your 48T, the only one which will fit (and it could be a VERY close call) is the N-Gear Jump Stop
HTML Code:
http://www.gvtc.com/~ngear/whatis.html
Only 10 bucks and Nick is great to deal with.
You would have to fine-tune it to avoid the interference with the FD's inner plate, a 2-minute job.

The 3rd Eye "chain watcher" made by Deda won't fit since it would definitely interfere with the BB shell. Don't ask how I know...
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