BB Axle Lengths?

mongooseTE17

Hi just wanted to know about axel lengths. I read that the standard length for an ISIS crank 118mm. I just want to make sure. The cranks are Truvativ Blaze ISIS and my BB shell is 68mm.

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nicklouse

standard is 113mm.

but it bepends on the cranks and chain line.

remove the crank arms and measure it.

nick
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extreme__dude

they often say on the bb shell of the old bb

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extreme__dude

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by extreme__dude</i>

they often say on the bb shell of the old bb
EDIT: youl have to take it out to have a look

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mongooseTE17

See the problem is that i havent got the cranks or the BB yet. Im buying them to replace some square taperd suntour's. The chain line with the square tapers is 47.5mm and the square taper axel length is 122.5mm.

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nicklouse

so go onto the sram site and read the online manuals. that will tell you what axel length you need for a 47,5mm chain line.

linky in the sticky above.

nick
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mongooseTE17

Cheers nick, great help as always! I checked it and its a 113mm. [:D]

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bigrud

Please excuse ignorance on this subject, but . . .

How is the chain line measured ?
How do you determine the required chain line ?

Thanks in advance.

<b>BiGRUD</b>

nicklouse

center of the seat tube to the center of the middle cog. what chain line (there are 2 commonly used 47,5 and 50mm) is determined buy the maker of the frame.

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bigrud

Ah ha. Thanks.

Would 2.5mm make much difference though?
Is there any reason for the 2 measurements (e.g. chainstay clearance, rear cassette alignment etc...).

Cheers,

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