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Old 12-29-06, 08:30 PM   #1
Shilun
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Fitting a triple

I'm just installing my first ever triple crank. I notice that the distance between the granny ring and the chainstay is very tight (maybe only a millimeter or so), although it doesn't touch. Is this normal, or does it indicate that the spindle is too short? My current spindle (111mm) was bought separately from the chainrings/cranks, which themselves were made up from an old double plus a newly purchased granny. If I do indeed need a longer spindle, what length would make a noticeable difference - 113mm, 116mm? The current chainline is about 45mm, if that's relevant, and the tubes are regular diameter (this is an old frame from 1982).

Thanks for any help you can give me. I used to swap out doubles all the time in years gone by, but this triple is really giving me a headache!
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Old 12-29-06, 09:34 PM   #2
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Yeah, 1mm is too close, especially if there is any flex in the BB or the cranks.

You may need to go quite a bit wider. Sheldon Brown indicates that for Shimano road triples, 45mm is the chainline, but because you have made up unique crankset you may need to look at a chainline range of 47.5 or slightly more. I suppose doing the calcs, that would mean a spindle of 116mm as you suggest, and moves the granny a total of 3.5mm away from the chainstay.

I know my old road triple set-up on my Fuji had a 118mm BB, and I might be inclined to go that wide to ensure chainstay clearance in your case. But then you might compromise derailleur range and line to the rear cogs.
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Old 12-30-06, 09:03 AM   #3
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Check Sheldon's site for the correct BB spindle length for your triple crank. He's got it all.

http://www.sheldonbrown.com/bbsize.html
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Old 12-30-06, 09:10 AM   #4
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For Shimano Octalink- specced cranks, ISIS splined or standard square tapers, its usually 110-113 for doubles and 118 or so for triples. But, yes, just check the speccs for your crank.

And, kinda crucial, is your BB 68 or 73MM?
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Old 12-30-06, 09:48 AM   #5
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You can use a spacer to give more clearance on the right side if it won't cause the left arm to hit the chainstay. You may not have a problem anyway. I have a single speed mtb with no more than 1mm between the chainring and the stay.
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Old 12-30-06, 08:06 PM   #6
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You can use a bottom bracket spacer to move the crankset out. These are available in various thicknesses, you may only need a 1mm spacer. These work well and are easy to install. My LBS usually keeps a few in stock. I used a 1.5 to correct a chainline problem on my wife's triple.

Al
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Old 12-30-06, 08:08 PM   #7
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Quote:
Originally Posted by Al1943
You can use a bottom bracket spacer to move the crankset out. These are available in various thicknesses, you may only need a 1mm spacer. These work well and are easy to install. My LBS usually keeps a few in stock. I used a 1.5 to correct a chainline problem on my wife's triple.

Al
Why didn't I think of that?
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