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Need to know what size allen wrench to use to get crank arms off

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Need to know what size allen wrench to use to get crank arms off

Old 06-10-09, 11:01 AM
  #1  
whiskyrebellion
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Need to know what size allen wrench to use to get crank arms off

my bottom bracket "unspun" and i need to get them off to fix it. i had an allen wrench that fit but i seemed to have lost it. so i wanna go pick up a new one without having to buy a whole new set. the cranks are single speed FSA's and it's bigger than 6mm if that helps
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Old 06-10-09, 11:17 AM
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griftereck
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8mm
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Old 06-10-09, 11:25 AM
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+1 -- It's 8mm, but if an 8mm key isn't readilly available a 5/16" (7.94mm) will do in a pinch.
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Old 06-13-09, 08:56 AM
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Mine is 10mm
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Old 06-13-09, 09:06 AM
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I'd strongly recommend an Allen socket to use with a torque wrench. Getting cranks up to specified torque is pretty critical from what I've heard (though I've always brought the torque up to spec and never had a problem, so I haven't ever seen insufficient torque kill a crank).

Here's a good unit, assuming that your cranks use 8mm and you have a 3/8" torque wrench (like the bigger Park Tool wrench):

https://www.mcmaster.com/#8367a45/=2aser4

To get the cranks off, you need a crank puller:

https://www.lickbike.com/productpage....=%272430-00%27

Best of luck.
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Old 06-13-09, 10:45 AM
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Originally Posted by Lawrence08648 View Post
Mine is 10mm
Is it an FSA? All of the Shimano cranks I've ever seen are 8 mm but I came across one requiring a 10 mm and, IIRC, it was an FSA.
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Old 06-13-09, 12:09 PM
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Perhaps you can just measure across the hex opening?
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Old 06-13-09, 12:26 PM
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Park Tool makes a nifty tool that they say will take off the bolt on cranks. It is 8mm. Since I bought that tool - I haven't seen a single 8mm bolt on a crankset. Only 10mm. I suggest getting a full set of metric allen-wrenches. I even have a 7mm - though I've never used it!* LOL!


* - inside joke for mechanics
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Old 06-13-09, 12:46 PM
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Jeff Wills
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Originally Posted by Panthers007 View Post
I even have a 7mm - though I've never used it!* LOL!

* - inside joke for mechanics
Ever had to work on the early-90's Campy self-extracting cranks*? That's where the 7mm comes in handy.



* - well, neither have I.
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Old 06-14-09, 09:46 AM
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Word.*

* - I didn't actually buy the 8mm socket individually, I saved myself the aggravation and bought a full set!
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Old 06-14-09, 10:00 AM
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My SRAM cranks use an 8mm. I recommend an 8mm socket allen head. But if you don't want to do that an small pipe or hollowed out lever will help you with an allen key.
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Old 06-22-09, 10:28 AM
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I initially said mine was 10mm. I just changed my crank and bottom bracket this weekend (with the cassette and chain) and I was wrong, it's not 10mm, it's 8mm. It's a Truvativ, both, the old and new.
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