Crank Removal Problems

[UpWrong]

Thanks

I'd prefer a solid open-jawed spanner over anything adjustable.

But I wouldn't expect to exert more force with a hex key turned by hand than with that 12" spanner.

Jonathan

The adjustable spanner was fine. It didn't slip at all and could turn the extractor tool bolt. The problem was that the crank arm thread distintegrated before the arm came loose.

Think I'll try a 4" gear/bearing puller from ScrewFix for the right crank, and a dremel for the left crank (if the puller won't fit the left as well).

Paul

[GideonReade]

Depending on how much you're planning to keep...

On one of mine, after heat and a hub puller did nowt (no grip on rather curved LH crank back), I got a long nut and a shortish bolt matching the crank bolt thread. Put on so the bolt end touched the axle end. Thus extended the axle. Then rested bike on side, taking the weight on the bolt head, on concrete, blocked up so the axle was vertical.

Then walloped the now upward facing back of the crank. Directly down, in line with axle. Initially with a mallet, but IIRC, a hammer was finally required. I assume I protected the crank arm somewhat.

Brutal, but it worked. I was able to reuse the crank. My objective was to change the BB, so no idea if I damaged it. The frame (Trek, ally) seemed fine.

[UpWrong]

Depending on how much you're planning to keep...

On one of mine, after heat and a hub puller did nowt (no grip on rather curved LH crank back), I got a long nut and a shortish bolt matching the crank bolt thread. Put on so the bolt end touched the axle end. Thus extended the axle. Then rested bike on side, taking the weight on the bolt head, on concrete, blocked up so the axle was vertical.

Then walloped the now upward facing back of the crank. Directly down, in line with axle. Initially with a mallet, but IIRC, a hammer was finally required. I assume I protected the crank arm somewhat.

Brutal, but it worked. I was able to reuse the crank. My objective was to change the BB, so no idea if I damaged it. The frame (Trek, ally) seemed fine.

I dont' want to harm the BB and pedal assist sensor. I don't mind destroying the cranks. Pretty sure I can dremel off the left hand crank. Hoping the gear puller will deal with the right hand crank by pulling on the spider

[slowster]

What is the diameter of the crank extractor's pusher/piston which bears against the end of the bottom bracket axle?

If the crank is wrecked, one way to get it off after removing the crank bolt is to ride the bike until the crank loosens by itself.

[UpWrong]

What is the diameter of the crank extractor's pusher/piston which bears against the end of the bottom bracket axle?

If the crank is wrecked, one way to get it off after removing the crank bolt is to ride the bike until the crank loosens by itself.

It's about 11 mm. It passes through the square aperture and rests against the end of the spindle.

Riding unttil the cranks loosen? No idea how long that might take. If the puller on the right crank doesn't succeed then it might be worth a try.

[UpWrong]

The gear puller didn't work on the right crank. I had to configure it as a 2 legged puller to fit the crank spider. It wasn't stable enough when I tried to tighten the bolt. I decided to try the std crank extractor tool after spraying with an oil penetrant and heating the crank with a hair drier, and it worked . But there's still the left crank to do.

I tried the oil and hair drier on that after screwing in the extractor tool as best as I could into the damaged threads. No joy and the threads are really rogered now. So I tried dremelling the crank off. I've broken 2 cutting wheels in the process and still haven't cut through to the spindle. Tried a hacksaw but there's not enough clearance. The 4" crank puller can't get a grip on the left crank.

I've ordered the Unior taper crank puller, though I don't have great hope now that I've partially destroyed the crank. Thought it worth a go. A 3" crank puller might be able to get a grip, so that's another possibility if the tapered puller doesn't work.

If all else fails I can try bashing it with a drift. Have been avoiding this so as not to damage the BB bearings.

[UpWrong]

I took some good advice on this forum and whenever removing STCs I carefully insert the tool - pinch it up - screw in the extractor and pinch it up tight then hit the end of the puller with a small hammer.

When this fails (which it does very occasionally on very old cranks) and the thread is a gonner, I repeat the process but using a Unior tapered extractor.

A great tool that has never failed me

https://www.cyclestore.co.uk/unior_tape ... qjEALw_wcB

I've re-read this and realise I didn't understand it the first time. You hit the extractor tool bolt to loosen the crank. Make sense when you think about the square taper interface. I'll heat the crank with the hairdrier first before hitting the extractor bolt with the hammer.

[rjb]

Are you loosening off the removal tool extractor bolt before screwing the extractor body fully into the crank. ? I've never had a problem removing cranks but understand that some have if the extractor hasn't been fully inserted before tightening the centre bolt to force the crank off its taper.
I've never hit the centre bolt with a hammer. Doesn't sit well with my experience.

[Jdsk]

A hairdryer isn't going to raise the temperature much. I recommend a small blowtorch: much hotter and much more localised.

NB adjacent plastic components, and usual precautions.

Jonathan

[UpWrong]

Are you loosening off the removal tool extractor bolt before screwing the extractor body fully into the crank. ? I've never had a problem removing cranks but understand that some have if the extractor hasn't been fully inserted before tightening the centre bolt to force the crank off its taper.
I've never hit the centre bolt with a hammer. Doesn't sit well with my experience.

Yes, I unscrewed the extrator bolt first before screwing in the tool body. I did it up finger tight and on reflection it might have gone in another quarter or half turn if I had firmed it up with a spanner.

[UpWrong]

A hairdryer isn't going to raise the temperature much. I recommend a small blowtorch: much hotter and much more localised.

NB adjacent plastic components, and usual precautions.

Jonathan

I don't have blow torch, I might have a hot air gun. Have a vague recollection of a hot air gun dying on me after a couple of uses but maybe that was a previous one. I'll take a look. I agree it would be better than the hair -dryer. Thanks, Paul

[GideonReade]

A hairdryer isn't going to raise the temperature much. I recommend a small blowtorch: much hotter and much more localised.

NB adjacent plastic components, and usual precautions.

Jonathan

I don't have blow torch, I might have a hot air gun. Have a vague recollection of a hot air gun dying on me after a couple of uses but maybe that was a previous one. I'll take a look. I agree it would be better than the hair -dryer. Thanks, Paul

Is the heat to chemically break the bonding ally-steel, or to increase the size of the hole in the ally with respect to the steel axle? If the latter, I guess you want to try to heat only the ally crank arm, not the axle?

[UpWrong]

A hairdryer isn't going to raise the temperature much. I recommend a small blowtorch: much hotter and much more localised.

NB adjacent plastic components, and usual precautions.

Jonathan

I don't have blow torch, I might have a hot air gun. Have a vague recollection of a hot air gun dying on me after a couple of uses but maybe that was a previous one. I'll take a look. I agree it would be better than the hair -dryer. Thanks, Paul

Is the heat to chemically break the bonding ally-steel, or to increase the size of the hole in the ally with respect to the steel axle? If the latter, I guess you want to try to heat only the ally crank arm, not the axle?

Steel and aluminium have different coefficients of thermal expansion. So the crank hole enlarges quicker than the spindle when you heat both.

[Jdsk]

I don't have blow torch, I might have a hot air gun. Have a vague recollection of a hot air gun dying on me after a couple of uses but maybe that was a previous one. I'll take a look. I agree it would be better than the hair -dryer. Thanks, Paul

Is the heat to chemically break the bonding ally-steel, or to increase the size of the hole in the ally with respect to the steel axle? If the latter, I guess you want to try to heat only the ally crank arm, not the axle?

Steel and aluminium have different coefficients of thermal expansion. So the crank hole enlarges quicker than the spindle when you heat both.

Yes.

But heat can also help to undo eg steel bolts from female threads in steel components.

Jonathan

[UpWrong]

An update on this. Success!! However it wasn't by means of the Unior tapered crank puller, which I ordered from 2 places both saying they had it in stock but they didn't , It became clear there weren't any in the UK.

So I carried on with the dremmel, going through 5 cutting discs. I cut two slots, along the edges of the taper opposite the crank. I tried heating the cranks and banging it off with a mallett but it still wasn't shifting. What worked was hammering an old brick chisel into one of the cut slots and the crank hole split.