Removing a Crankset With Stripped Thread

oxocube1

As title suggests, no pics needed. Trying to replace a BB on a bike but the thread on a square taper crankset is completely stripped so obviously the extractor has nothing to pull on.

I had a look at the ParkTool website but they suggested a tool i don't have, and ways that will ruin the crankset.

Anybody know of a way to get the crankset off without ruining it? The BB is expendable as that is what is being replaced.

nicklouse

without damaging the crank? why it is scrap.

cut it off and get new cranks and BB

oxocube1

nicklouse wrote:

without damaging the crank? why it is scrap.

cut it off and get new cranks and BB

Yea this is what I told the customer. He dosen't want to spend the money on a new crank so just seeing if their is an alternative. Otherwise I will gladly do this

nicklouse

well you can ride around with the bolt lose but that tends to damage the taper.

if it is for a customer i would not be doing anything other than replacing the whole lot.

oxocube1

nicklouse wrote:

well you can ride around with the bolt lose but that tends to damage the taper.

if it is for a customer i would not be doing anything other than replacing the whole lot.

Yup it's for a customer. That is one of the options on the PT website, I will suggest it to him and try to do as little damage as possible if he wants me to try. Otherwise I'll just have to tell him he has to spend the money or he gets no new BB!

Horton

Assuming that you're talking about the thread in the crank itself and not the thread in the bottom bracket, I have in my former years removed similarly knackered cranks with judicious use of a mallet and block of wood, although it isn't the quickest or easiest method...

Nick, although it's a PITA to remove (and will continue to be so) surely it's still a perfectly functioning crank so if you can remove it without knackering the taper you can just replace the BB and then bolt it back on? I thought the threads in the crankset were literally just for the puller to screw into to get it off.

nicklouse

Horton wrote:

Nick, although it's a PITA to remove (and will continue to be so) surely it's still a perfectly functioning crank so if you can remove it without knackering the taper you can just replace the BB and then bolt it back on? I thought the threads in the crankset were literally just for the puller to screw into to get it off.

yes been there do that seen other people do and fixed the results of it.

peronally a hacksaw though the boss of the crank to release the pressure and then the bin.

and for CUSTOMER were you have a business relation ship i would not suggest any method but i might suggest a few pages to look at. BUT there is no way i would be making suggestions on what to do.

Like i said i have seen the results of people getting it wrong.

not much fun telling someone there frame is scrap.

Horton

not much fun telling someone there frame is scrap.

Fair point, well made.

PashleyRider

I have had to tackle this in the past on a friends bike. Cut the axle off leaving a stub of it inside the crank arm, then thread a bolt (needs to protrude about an inch) into the axle stub left in the crank. Sit the bb end of the crank into a socket for support/over a hole in a work surface and smack the bolt until the axle stub falls through. Sorted

cycleclinic

The last time I saw this I told if you want me to fix it I am cutting the Bb axle with my friend the angle grinder (quicker than a hacksaw and if you have a thin blade and a steady hand you won't harm the frame), and then I will replace the whole lot. It is not worth the time and effort trying to bodge jobs that will only come back and haunt you. If the customer want a bodge they can do that themselves and then bring it you to put right.

oxocube1

thecycleclinic wrote:

The last time I saw this I told if you want me to fix it I am cutting the Bb axle with my friend the angle grinder (quicker than a hacksaw and if you have a thin blade and a steady hand you won't harm the frame), and then I will replace the whole lot. It is not worth the time and effort trying to bodge jobs that will only come back and haunt you. If the customer want a bodge they can do that themselves and then bring it you to put right.

Yea this is a good point. I'm not hiding anything from him, I'll be telling him straight what I am doing/asking him what he wants me to do as it's his bike at the end of the day. New BB and Crankset is the best option me thinks!

cycleclinic

Cyclus also make a tool kit that will destroy the remaining threads and cut a new bigger one. The tooll kit comes with a new larger extractor. This is useful on cherished cranks or really expensive ones. The kit cost £180+VAT at trade I think. I-ride do them.

The Rookie

Why not get some used cranks to replace them, assuming it's square taper, you could get some off ebay or classifieds for around £20 delivered.

In fact I'll offer a Chin Haur (OE fit) BB and Shimano crankset (M3XX I think - rivetted rings) complete to you for £20 delivered.....off a 2009 Voodoo Bantu, some minor scuffs but otherwise all good, just taking up shed space, too good to throw.

nicklouse

brand new M442 on CRC for 19 quid and a chin haur BB for less than 6.

all new for 26.

The Rookie

Cheers Nick! ;-)

stu76

Before you engage in any of the butchery mentioned above, try using a car jack as per my method posted on retrobike a while back......

http://www.retrobike.co.uk/forum/viewto ... 1&t=193271

Should do the trick.

Stu

nicklouse

FFS. can you say bent BB shell.

all i see is bending forces not pushing forces.

Deputy Dawg

I've used a 3 jaw slide hammer before.

Putting the stripped cranks back on will only give you the same problems the next time the BB needs replacing though.

heez29

Angle grinder is your friend.