Blast! Crank bolt rounded...... « Singletrack Forum

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Blast! Crank bolt rounded......

13 posts & 7 voices | Started 1 year ago by ononeorange | Latest reply from ononeorange

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ononeorange - Member

.....I was removing my square taper crank arms to change the dead BB on my Inbred, I got one off no problems but the other (drive-side) bolt head rounded out just as the arm was beginning to move. It's so circular that no Allen key is going to turn it now.

I'm annoyed as the heads seem to be made of cheese (they're Middleburn - I would have thought they'd be made of Stronganium). So - any thoughts of how to remove it without resorting to drills or explosives? Also any tips for more robust crank bolts to replace them with? (I am guessing this is not an unusual problem.....).

Thanks in advance.

Posted 1 year ago #
julianwilson - Member

are they 'self extracting' bolts? (ie do you undo the bolt to take the crank off, or do you undo and remove it, and then use a crank puller tool to get crank off the bb spindle?)

Posted 1 year ago #
ononeorange - Member

Sorry I should have said. Yes, they're self-extractors.

Posted 1 year ago #
Andy R - Member

Remove the threaded ring that makes them "self extracting" and try just getting bolt out. If the crank was starting to move you should be able to tap it back onto the taper, releasing the loading on the bolt.

Posted 1 year ago #
Rusty Mac - Member

Can you get a torx key that is slightly larger than the hex key? if so smack that in the rounded head and undo the bolt. I have done this on various bolts in the past and it works a treat.

Posted 1 year ago #
ononeorange - Member

Thanks for the tips. Will try those at the weekend.

Posted 1 year ago #
Andy R - Member

Yes, and that ^^^^re torx. But take the self extract ring out and give the crank a tap back on first.
I don't like self-extracting crank bolts - I never use them.

Posted 1 year ago #
bigyinn - Member

God, they're still like this? Had a set of Middleburn self extractors 15 yeaqrs ago, great idea, when they work.

Posted 1 year ago #
Speshpaul - Member

Clean assembly and copper slip, been using them for 15 years and never had a problem.

Steel bolt into a steel axle, kept in the crap for X years until the BB is tatered, and its seized in?? what a shocker

Posted 1 year ago #
julianwilson - Member

Not a fan of self extractors. When you see how much thread you could engage using a crank puller instead of 4 or 5 threads of relatively flimsy steel or alloy. Last set I had flared outwards instead of pulling the crank off.

-Normal bolt with coppaslip on threads.
-Nothing at all on square taper bits
-Grease under head of steel crank bolt where it rotates against the inside of the crank as you fasten it.
-Ride for an hour, torque back up again.
-Remove cranks with a good old fashioned crank puller 2 years later when bb dies.

Hurrah!

Posted 1 year ago #
ononeorange - Member

Lesson learnt. Will not be using self-extractors again!

I did use copperslip on the thread when assembled (only a year ago, it was a second hand BB I'd acquired and was "finishing off");

No grease on square taper (tick)

Didn't grease under head. Good point. The head is like cheese, though (in my opinion).

Posted 1 year ago #
Rickos - Member

Get hold of a set of tools that you fit into a drill. They have a sort of coarse reverse thread on them so that they dig into the sides of the rounded allen hole but the drill turns the right way to undo the bolt. I've got a set and they're fantastic for just this thing, but I can't remember what they're officially called!

EDIT - Screw Extractors!
http://www.screwfix.com/prods/18643/Drill-Bits/Specialist-Drill-Bits/Screw-Extractor-Set

Posted 1 year ago #
ononeorange - Member

Thanks Rickos - good tip! On a drill - should be easy then.

Posted 1 year ago #

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