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Thread: splined cranks

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    cyclist/gearhead/cycli... moxfyre's Avatar
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    splined cranks

    Are splined cranks/BB really better than square taper? I have never had a splined crank, but I am wondering. I've never heard of an adequately tight crank slipping at all, so how would the splines increase stiffness?
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    Senior Member sydney's Avatar
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    Quote Originally Posted by moxfyre
    Are splined cranks/BB really better than square taper? I have never had a splined crank, but I am wondering. I've never heard of an adequately tight crank slipping at all, so how would the splines increase stiffness?
    It's not about slipping. it's alot about marketing.It's the diameter of the spindle. isis or octalink is bigger diameter. Can you actually flex a square taper?

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    cyclist/gearhead/cycli... moxfyre's Avatar
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    Quote Originally Posted by sydney
    It's not about slipping. it's alot about marketing.It's the diameter of the spindle. isis or octalink is bigger diameter. Can you actually flex a square taper?
    Thanks sydney. That's what I suspected, marketing mostly. I definitely cannot flex a square taper spindle. Almost all the pedaling flex I have ever felt came from the crankarms or from the frame itself.
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    The traditional way of losing weight from a square taper spindle was to make it from titanium, and these can get flexy with big riders. Using a pipe makes better use of the material and allows a lighter, stiffer spindle using steel.
    The spline lets you get a more accurate seating. With square taper, you dont know exactly how far onto the taper the crank will fit.
    The disadvantage of pipe spindles is that you have less room for bearings, unless you use a wider diameter bottom bracket shell.

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    cyclist/gearhead/cycli... moxfyre's Avatar
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    Quote Originally Posted by MichaelW
    The traditional way of losing weight from a square taper spindle was to make it from titanium, and these can get flexy with big riders. Using a pipe makes better use of the material and allows a lighter, stiffer spindle using steel.
    The spline lets you get a more accurate seating. With square taper, you dont know exactly how far onto the taper the crank will fit.
    The disadvantage of pipe spindles is that you have less room for bearings, unless you use a wider diameter bottom bracket shell.
    Ah, thanks for the explanation. So if I understand correctly, a hollow spindle wouldn't be strong or practicable to manufacture with a square taper, and that's why splines are used?
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    Senior Member sydney's Avatar
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    Quote Originally Posted by moxfyre
    Ah, thanks for the explanation. So if I understand correctly, a hollow spindle wouldn't be strong or practicable to manufacture with a square taper, and that's why splines are used?
    No...there are steel square taper spindle that are hollow.It was light Ti spindles that were the issue. And a pipe billet spidle like in octalink or isis could have been made with a square taper on the end of it. FWIW, an ultegra octalink BB for a double is listed as 227 grams. The ultegra sq taper double BB with hollow spindle is 255g. The octalink is marketed as stiffer,along with the 'advantages' of the splined interface, but smaller beraings. Hard to find a free lunch.
    Last edited by sydney; 02-24-05 at 11:44 AM.

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    I drink your MILKSHAKE Raiyn's Avatar
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    On the other hand. Truvativ in order to combat the small bearing problem has stuck more races of bearings into thier Gigapipe ISIS bottom brackets. The one that I presently use on my trail bike (Gigapipe Team DH) has two on the drive side and two on the non drive side for a total of four.

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