Stripped crank bolt/extractor threads, how to remove????????

Dr.Robotnik

Dr.Robotnik

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Hi guys,

Well I have rescued my Sunn Radical from its place in the shed at home and have started stripping it down.

However, some how over the years I seem to have installed a set of Mavic cranks which have completely stripped extractor threads. I have tried cutting new threads and using a new tool but there is no material there...

Hammering on the cranks has also not done anything.

I would like to save the BB and obviously do not want to mark the frame (chrome), ideally I would like to save the cranks too, but all I can think of is cutting them off.

So retro-gurus what suggestions can you offer?

Please let me know.

Cheers

Ed
 
Bit of heat on em and then try drifting them off from the back of the spider!
Never failed for me.
 
Are the threads damaged on both drive and non-drive sides? If not, remove the crank with the good threads and the corresponding BB cup. Get a large bolt that will pass through the square taper of the crank but not the BB axle. Welly the bolt from the other side and the BB axle will fly out (at high speed!)
There are a few assumptions here: Your BB has removeable cups both sides; Your frame is not fragile enough to be damaged by the crank resting against the BB shell as you welly the bolt through the offending crank taper.
Good luck!
 
If you're friendly with a local garage or have access to one anyway, I've used a three-legged bearing puller such as the one below to good effect.

bearingpuller.jpg
 
Put the bike back together so you can ride it - leave the crank bolts off, go for a few runs (carefull runs!) and this should pop the cranks off.

Works in all but the most extreme cases - just be carefull.
 
D'oh!

It is so obvious when you guys write it. If only I hadn't taken it all to bits. I think I will put some forks and wheels on and bounce about, like you guys said.

Genius.

I will remember for next time, but the BB is a standard 1995 ish Shimano unit and the offending crank arm is the drive side.

BTW, just while you guys are about. How do I identify the parts on the bike I am trying to build? For example you guys all talk Shimano codes. How do I find out what I need e.g. what the codes are? Basically I am after a 1995 Shimano XT and LX catalogue.

Thank you to all for your suggestions.

Cheers

Ed
 
This is one application (unlike most s/post removals) where a bit of heat works really well - as the spindle is likely steel and the crank arm ali (expands at lower temp.). The 'just ride it' trick works, but has its risks... The ball joint splitter gnarls the frame, no?
 
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