Crank removal issues

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dakari-mane
Posts: 70
Joined: 1 Aug 2013, 3:56pm

Crank removal issues

Post by dakari-mane »

Hi,

My first post, am hoping someone can help as I have become bamboozled.

My friends has a not too good mountain bike & the bottom bracket is shot. Being the helpful chap I am I said I'd replace it for her.

Having checked the BB & seeing it was a square taper one I thought it ought not to have been more than a 5 min job. However upon removing the crank bolts I have been met with this:
Image

So nowhere to screw my crank removal tool into & not a crank type I have encountered before. It's the same on both sides & I have no idea how to remove them (other than maybe just finding a screw the right size to fit the brass looking thread & screwing it it?)

Any thoughts or input greatly appreciated.

Regards
DM
Brucey
Posts: 44521
Joined: 4 Jan 2012, 6:25pm

Re: Crank removal issues

Post by Brucey »

I think using a big bolt in the brassy coloured screw thread is what you are meant to do there. But I've not removed one like that myself.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
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531colin
Posts: 16083
Joined: 4 Dec 2009, 6:56pm
Location: North Yorkshire

Re: Crank removal issues

Post by 531colin »

It looks to me like a steel crank with a plastic "overcoat", so that thread may not be too fragile.
Worth a try to put a bolt in and torque it up, if nothing happens, give the bolt head a sharp crack with a one pound hammer.
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cycleruk
Posts: 6065
Joined: 17 Jan 2009, 9:30pm
Location: Lancashire

Re: Crank removal issues

Post by cycleruk »

Brucey wrote:I think using a big bolt in the brassy coloured screw thread is what you are meant to do there. But I've not removed one like that myself.
cheers


Would it need something to press against so as not to damage the axle threads?
Although if the axle is U.S. then probably doesn't matter.
You'll never know if you don't try it.
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Redvee
Posts: 2465
Joined: 8 Mar 2010, 8:58pm

Re: Crank removal issues

Post by Redvee »

That looks like a Thun chainset to me, or one of a similar design. IIRC you need a standard bolt which you screw into the chainset which then pushes against the axle, 15mm springs to mind for the bolt size but I might be wrong.
prm
Posts: 180
Joined: 7 Apr 2009, 11:15pm

Re: Crank removal issues

Post by prm »

Removed cranks where the extractor threads have been stripped by inserting short flat tapered wedges between the arm and BB flange. Insert a scrap bolt into the spindle, apply heat to the crank arm boss and hammer temporary bolt.

Can be awkward inserting wedges if the inner ring is heavily dished.
Caution with the arm inner flange. These can be quite soft material.
Depending on the BB type/design??? Try working from the other side first.


3-leg puller is ideal. You maybe fortunate, space permitting, to use a vehicle forked ball joint separator.

Unable to quite see if the small rectangle recess near the boss, is for removing a protective cover?
Or…. Removing an outer seal…???
dakari-mane
Posts: 70
Joined: 1 Aug 2013, 3:56pm

Re: Crank removal issues

Post by dakari-mane »

Thanks for all the input!

I have dug out a couple of big bolts & shall see if either of them fit the bill. If not then it's a trip to the hardware store for a three-legged puller! (Sounds like some kind of hideous sci-fi beastie!)

Shall keep you all posted.

Cheers
DM :mrgreen:
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