Removing crank arms

[NotAGolf]

So I attempted to replace the bottom bracket on my bike (Specialized Allez 16 2010) today which obviously meant removing the crank arms. Rather predictably, I ****** things up. I removed the bolts from the crank arms and then tried to pull the crank arms off using the crank extractor tool sold in this toolkit. I'm not sure what I did wrong, but I managed to strip the thread off the crank arm

Here's what the crank looks like (according to the spec the chainset is Shimano 2300, the bottom bracket is Cr-Mo axle, 68mm x 113mm):

I then screwed the green bit of the tool into the crank arm, then tightened it a touch using the blue bit (this screwed in fine and seemed flush). I then tightened the yellow bit which pushed the red bit into the crank. I didn't feel any movement at all until the tool stripped the thread and came loose.

Did I do something wrong? Should I have loosened something else first? Do you have to do a particular crank arm first?

Now that I've messed up the thread, how can I get the crank arm off?

Thanks for any advice.

 

[dazz25]

Does the black (red) bit come off?

I did this once as I left the bit on the end, which is made for a different type of crank, therefore the tool was just pushing against the crank and not the spindle.

I big hammer on the crank is the only option now i'm afraid!

 

[Saytan]

big hammer is a rubbish way

you need a two-legged puller.

edit: from your description, it sounds like you were doing it right. I've done hundreds of these and the odd one will rip the threads out no matter how careful you are, especially on cheaper cranks

 

[Saytan]

Also since the thread is gone, the crank is basically scrap, so if you're not going to put it back on you can just ride round til it falls off.

 

[Vonhelmet]

That sucks. Sounds like you did it right. I took a 2300 crankset off a few months back without issue, but I guess you got unlucky.

On a square taper, assuming you've got the crank bolt out as you have done, all you're left with is an interference fit between the crankset and the bottom bracket. "All" you need to do is find a way to pull it off the bottom bracket. You could hit the back of the crankset with something until it pops off, though that will likely ruin the bottom bracket - little concern, they cost a tenner - but of more worry would be bending the frame. You might be able to loosen it by heating or cooling the spindle/crankset, but if they're the same material that won't do any good. I don't know what a bottom bracket spindle is made of, so that may not work. You could clamp the crankset in a vice and then pull the frame off it, but too much lateral motion could destroy the bottom bracket shell.

That two legged puller thing that saytan has suggested looks like it will do the job.

 

[Saytan]

a BB spindle is made of hardened steel.

In my experience (I am workshop coordinator at a bike recycling charity) the 2-legged puller is the easiest bet.

with a 2 legged puller you can reuse the crank if you're desperate, though I wouldn't recommend this - you'll only face the same problem next time it needs to come off.

 

[Vonhelmet]

So heating the interface may work, as the crank will expand more than the spindle. You can do it with a hair dryer - I've done it when removing stuck pedals.

 

[NotAGolf]

Does the black (red) bit come off?

I did this once as I left the bit on the end, which is made for a different type of crank, therefore the tool was just pushing against the crank and not the spindle.

The black bit does come off, but it doesn't look like it's supposed to as it just exposes the end of the thin thread (the bit between the red and the green).

Thinking about it, I couldn't tell where crank ended and the spindle began, so maybe like you I have the wrong tool and was just pushing against the crank. That would certainly explain why everything felt so flush and correct, yet still stripped the thread. Vonhelmet: Do you remember what type of tool you had seeing as you had the same kit?

One thing I thought about was that between the BB and the left hand crank there's a gap (see here). I can see a spindle or something in there that has squared edges so I could turn this with a spanner. What is this? Should I have loosened this first? Will it help me get the crank off?

I'm not too worried about breaking the BB as I'm replacing it anyway, obviously I don't want to risk breaking the frame though.

 

[Vonhelmet]

The black bit does come off, but it doesn't look like it's supposed to as it just exposes the end of the thin thread (the bit between the red and the green).

Thinking about it, I couldn't tell where crank ended and the spindle began, so maybe like you I have the wrong tool and was just pushing against the crank. That would certainly explain why everything felt so flush and correct, yet still stripped the thread. Vonhelmet: Do you remember what type of tool you had seeing as you had the same kit?

That's the right tool, and it sounds like you used it correctly. I have a similar one (I have the Icetoolz kit, but it's very similar to your PX one) and mine worked fine, so I think you were just unlucky.

One thing I thought about was that between the BB and the left hand crank there's a gap (see here). I can see a spindle or something in there that has squared edges so I could turn this with a spanner. What is this? Should I have loosened this first? Will it help me get the crank off?

That square bit is the bottom bracket spindle. That's the bit that goes into the crank. The way the crank puller works is to attach to the crankset/crank arm with the green thread, then you turn the yellow bit and it screws the red bit in against the spindle and pushes the spindle away from the crank puller, then because the crank puller is attached to the crank, it pushes the crank off the spindle.

I'm not too worried about breaking the BB as I'm replacing it anyway, obviously I don't want to risk breaking the frame though.

Yeah, it's the frame I'd be worried about. BBs cost next to nothing, certainly a square taper for a bike like that - I think the last replacement one I bought cost under a tenner.

If I were you, my next steps would be to use a hairdryer to heat the spindle/crank join, then use a towel or something to hold the crankset and try to pull it off the spindle. It'll be a tight fit, and you may not manage it, and you don't want too much lateral motion when you're doing this or you could potentially damage the bottom bracket shell of the frame, but with a bit of luck it'll come off. You can use some penetrating oil or something to try to loosen it off a bit. It's an interference fit so the crank is held on to the spindle by nothing more than the fact that it's a tight fit and it was originally screwed on with quite a bit of force, so with enough force in the opposite direction you will be able to pull it off - there's no threads or anything in there. The heat and oil will help.

Failing that, it looks like you can get a two legged puller like Saytan has mentioned on ebay for under a tenner.

 

[NotAGolf]

Many thanks Von. I did the hair dryer trick, gave it a bash with a hammer to try and loosen it up, then managed to get the crank tool wedged back on and got the crank off

I managed to get the other crank arm off fine. I did remove the red cap as dazz suggested as after looking at the marks on the crank arm I think the cap was a smidge too big and wasn't quite pushing on the spindle correctly.

£26 to replace the crank arm makes it a fairly expensive mistake, but I did manage to get the BB off and replaced so if that's the only problem I have during the overhaul I'll be happy. I just hope it gets delivered before the weekend so I can get out on it!

 

[matt_fsr]

£26 to replace the crank arm makes it a fairly expensive mistake....

No, no it wasn't.

I have these cranks on my DH bike. (I didn't fit them, previous owner did)

http://www.chainreactioncycles.com/race-face-atlas-crank-arms/rp-prod82853

My bottom made little squeaking sounds as I gently removed them using the in-built crank puller mechanism, in order to fit a new bottom bracket. I'll be re-fitting them again tonight, and then I'll be able to relax!

Glad you were able to sort yours out though!

 

[Jonny69]

Unlucky. Sounds like you did everything correctly, but they sometimes do strip out. Maybe the thread on the tool was a bit undersize, or the thread in the crank was cut a little big.

Also since the thread is gone, the crank is basically scrap, so if you're not going to put it back on you can just ride round til it falls off.

It's not scrap, I stripped one out a while back and just used a hub puller to remove it. Someone on Retro Bike recently made up a little puller that hooked behind the crank and you tightened a bolt in to pull it off. I'll see if I can find the thread because it was quite a simple but effective solution