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Old 10-15-09, 02:46 PM   #1
H3llM4rine
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Loose Crank Arms

I'll tighten my cranks as much as possible, and those things just won't stay tight. I can re-tighten them once a week. They're square-taper interface.

I'm honestly considering just getting an ISIS BB and crankset. Any suggestions for a cheap pair of those, as well?
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Old 10-15-09, 02:51 PM   #2
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They must be replaced. By riding them when loose, someone has flared the sockets on the arms and they will henceforth and forevermore work themselves loose. Over tightening the bolt will only break it.

Why ISIS? It is only an interface specification and both good and lousy BBs use it.

Since you don't tell us anything about the bike, we can't make a recommendation.

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Old 10-15-09, 02:53 PM   #3
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Time for new cranks. Square taper ones are reasonable priced, and work well. Just make sure the BB taper and crank taper are the same standard.
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Old 10-15-09, 03:25 PM   #4
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Whoops! I meant to say more about the bicycle.
I'm a heavy guy, and I ride a fixed-gear. I'd like very durable cranks.

The cranks are two weeks old. The day I put them on, I put them on very tightly so that this wouldn't happen, but it still is. Could it be the BB bolt?
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Old 10-15-09, 03:30 PM   #5
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Well, either you really didn't tighten them to the proper torque specs, or you overtightened them and stretched/stripped the threads on the bolt or the BB spindle. A torque wrench is your friend.
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Old 10-15-09, 03:34 PM   #6
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I guess I'll just take it to the LBS and have them tighten them up for me. In the mean time, I'll be looking for a torque wrench.

Thanks!
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Old 10-15-09, 03:38 PM   #7
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Even they can't help you now. Once you ride them loose, the square hole in the crank gets rounded out. They are hosed and need to be replaced.
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Old 10-15-09, 04:01 PM   #8
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Well, actually, the looseness is not on that axis. I'm sorry, I'm doing a horrible job being descriptive today.

They become loose side-to-side, not front-to-back. I can feel them move ever so slightly if I stand on the pedal and let it go over the top I can feel it move slightly outwards.
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Old 10-15-09, 05:13 PM   #9
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Quote:
Originally Posted by H3llM4rine View Post
Whoops! I meant to say more about the bicycle.
I'm a heavy guy, and I ride a fixed-gear. I'd like very durable cranks.
What gearing do you need? What size is the hanger tube? (probably 68mm, but one never knows..)

Quote:
The cranks are two weeks old.
Two weeks old to you? Or two weeks out of the shipping box? I suspect they were fubar when installed.
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Old 10-15-09, 05:15 PM   #10
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Quote:
Originally Posted by H3llM4rine View Post
They become loose side-to-side, not front-to-back.
You're right. I don't get it. Cranks go in a circle. Side-to-side and front-to-back are the same thing.

Or do you mean axially vs. radially?


Let's boil it down to this: Do you need to re-tighten the bolt because it worked loose?
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Old 10-15-09, 05:38 PM   #11
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Quote:
Originally Posted by H3llM4rine View Post
Whoops! I meant to say more about the bicycle.
I'm a heavy guy, and I ride a fixed-gear. I'd like very durable cranks.

The cranks are two weeks old. The day I put them on, I put them on very tightly so that this wouldn't happen, but it still is. Could it be the BB bolt?
Exact how tight did you install them? Did you install them on dry spindle? Oiled or greased? Without an exact torque-figure, they could've been put on too tight or too loose; both of which will result in the crankarm falling off later.

Here's a list of common torque-specs from Park Tool. Square-taper cranks typically require 25-33 lb*ft of torque. This is impossible to do with little L-shaped allen-keys and really requires an automotive-style ratchet-wrench and socket. Preferably one with an 18" handle or longer to achieve the required torque.

Don't worry, you're not alone:

Sheared Crank Bolt Nut Removal.....help please
My left crank fell off...again =T
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Loose crank shaft, second time
crankarm coming loose
Bottom Bracket Torque Spec, Need Help
Problems with crank arm - keeps coming loose
Non-drive-side crank coming loose... repeatedly
Crankset removal/installation
rounded out iro crank = wobbly
Out of commission for nearly another week....
Loosening Crank arm
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Left Crank Falling Off
My crank arm fell off while riding
Crank coming loose
Crank Arm Fell off...
Crank arm
Loose crank shaft, second time
Re-torquing a crank arm bolt
Crank arm
Crank arm continually comes loose
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Old 10-15-09, 05:43 PM   #12
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Quote:
Originally Posted by DannoXYZ View Post
Exact how tight did you install them? Did you install them on dry spindle? Oiled or greased? Without an exact torque-figure, they could've been put on too tight or too loose; both of which will result in the crankarm falling off later.

Here's a list of common torque-specs from Park Tool. Square-taper cranks typically require 25-33 lb*ft of torque. This is impossible to do with little L-shaped allen-keys and really requires an automotive-style ratchet-wrench and socket. Preferably one with an 18" handle or longer to achieve the required torque.

Don't worry, you're not alone:

Sheared Crank Bolt Nut Removal.....help please
My left crank fell off...again =T
Loosening Crank arm
Crankarm bolt keeps coming loose
Loose crank shaft, second time
crankarm coming loose
Bottom Bracket Torque Spec, Need Help
Problems with crank arm - keeps coming loose
Non-drive-side crank coming loose... repeatedly
Crankset removal/installation
rounded out iro crank = wobbly
Out of commission for nearly another week....
Loosening Crank arm
Crank Torque (and other questions)
Left Crank Falling Off
My crank arm fell off while riding
Crank coming loose
Crank Arm Fell off...
Crank arm
Loose crank shaft, second time
Re-torquing a crank arm bolt
Crank arm
Crank arm continually comes loose
You might want to read the entire thread before replying. He's implying that the BB is loose, not the cranks.
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Old 10-15-09, 05:48 PM   #13
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I dunno. This statement seems pretty unambiguous to me:

Quote:
I'll tighten my cranks as much as possible, and those things just won't stay tight. I can re-tighten them once a week.
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Old 10-15-09, 05:50 PM   #14
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Quote:
Originally Posted by H3llM4rine View Post
I'll tighten my cranks as much as possible, and those things just won't stay tight. I can re-tighten them once a week. They're square-taper interface.

I'm honestly considering just getting an ISIS BB and crankset. Any suggestions for a cheap pair of those, as well?
You will be buying yourself a new problem by going ISIS, there are limited crankset choices and there are limited bottom bracket choices. Stick with the square taper or go with external.
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Old 10-15-09, 05:53 PM   #15
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Originally Posted by operator View Post
You might want to read the entire thread before replying. He's implying that the BB is loose, not the cranks.
Maybe... loose crankarm bolts would result in both axial and radial play. I wonder what he's tightening once a week, and how is he doing it.
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Old 10-15-09, 06:06 PM   #16
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Maybe... loose crankarm bolts would result in both axial and radial play. I wonder what he's tightening once a week, and how is he doing it.
I find it frustrating that threads like this is a 0.5 second solve in real life.
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Old 10-15-09, 06:08 PM   #17
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Well, he is taking it to a shop.
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Old 10-15-09, 08:14 PM   #18
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I'm betting on a bb issue, but who knows? Taking it to a shop is a great idea.
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Old 10-15-09, 08:22 PM   #19
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I get this issue all the time, most common cause is improper tightening in the first place
-this loosens them up
-this rounds them off
-this makes them worthless
-this means you need to replace crankarms

...typically
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Old 10-15-09, 09:29 PM   #20
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Quote:
Originally Posted by DMF View Post
You're right. I don't get it. Cranks go in a circle. Side-to-side and front-to-back are the same thing.

Or do you mean axially vs. radially?


Let's boil it down to this: Do you need to re-tighten the bolt because it worked loose?
Sounds to me like the bottom bracket is the issue, not the crank.
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Old 10-15-09, 10:10 PM   #21
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Before you take it to a shop, get some loctite 243(service removable) slather some on the bb spindle and then put some on the bolts... for god's sake don't reef on the bolts, you just want the taper to interface be snug... we're talking 15nm or less..

let the loctite cure overnight, try em out.

P.s. don't use anything stronger otherwise you'll need a hacksaw to get them off!

Last edited by electrik; 10-15-09 at 10:17 PM.
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Old 10-15-09, 10:28 PM   #22
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Before you take it to a shop, get some loctite 243(service removable) slather some on the bb spindle and then put some on the bolts... for god's sake don't reef on the bolts, you just want the taper to interface be snug... we're talking 15nm or less..

let the loctite cure overnight, try em out.

P.s. don't use anything stronger otherwise you'll need a hacksaw to get them off!
Do not do this.

Bolts and spindles do not need loctite. Grease if anything. Taper is debateable, I do because seized cranks are annoying.
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Old 10-15-09, 11:00 PM   #23
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Do not do this.

Bolts and spindles do not need loctite. Grease if anything. Taper is debateable, I do because seized cranks are annoying.
Why shouldn't he? I did it and my crank arm hasn't come off by itself for 8 months...
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Old 10-15-09, 11:11 PM   #24
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Do not do this.

Bolts and spindles do not need loctite. Grease if anything. Taper is debateable, I do because seized cranks are annoying.
Grease on the bolt threads.
RED locktite on the taper.
But his cranks are pooched.
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Old 10-15-09, 11:23 PM   #25
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You can also use brass shim stock and then torque.
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