Bicycle Mechanics - dangitall crank threading stripped
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01-05-06, 04:00 PM
I'm trying to get the second, driveside crank off of an old 80s frame. There's no spideer, just the crank over the shoddily-made chainrings. Unfortunately, the dustcap/crank tool threads have become stripped. What can I do? LBS time? Help help help... :o
01-05-06, 04:02 PM
do you want to keep the cranks? If not then cut a slot in the arm with a dremel tool than whang at it with a cold chisel. The crank will split around the spinde and you can slide that sucker off.
If you want to keep your cranks you could try this:
look at the second tool down.
Either that or try some gentle heating and some persuasive beating from the opposite side.
01-05-06, 04:04 PM
01-05-06, 04:05 PM
edited my post. look up.
01-05-06, 04:07 PM
Okay, thanks. Anything that centers around the idea of "whanging" has a certain visceral appeal, no :D?
01-05-06, 04:20 PM
1. Lay the bike on the side of the bad crank
2. Place a metal dowel/bolt/socket under the crank spindle to support it
3. Using a metal drift tap the back side of the crank arm until it comes loose and falls from the spindle
Works every time, though you may have to "tap" the heck out of the crank arm.
01-05-06, 06:37 PM
We have that tool at the shop. It is great. Shoudn't be expensive for LBS to use it on you cranks.
01-05-06, 06:46 PM
If the bike is still rideable, ride the bike with the crank bolt off. The crank will quickly loosen. Stop, and remove the crank.
Or, bang the crank off with a BFH. [big ****ing hammer]
01-06-06, 11:24 AM
Still not coming off. There's alot of white, crusty stuff around the spindle: really old grease, maybe? I've got the thing on the bike stand, but banging the crank with a hammer's doing nothing but put dents in the crank, and I tried pound the end of a screwdriver on the inside of the crank near the spindle, but that doesn't seem to be doing anything, either, other than chew up the inside rim of the crank. I'd get on it and ride, but one crank's already off (it was broken in half), and I don't really feel like putting the whole thing together just to ride. RRRR. LBS, I guess?
01-07-06, 12:23 AM
Whenever I have to resort to a hammer to get a crank with damaged threads off a bike, I use a trick a veteran mechanic showed me a long time ago. First (and most important), clamp the bike by the seatpost in the repair stand as loosely as possible (if you don't have a repair stand, use a shock cord or an inner tube to dangle the bike from a pipe in the basement or whatever). It's crucial that none of the hammer impact is absorbed by whatever's holding the bike up off the floor.
Next, find something you can use as a drift pin so that you can hammer on the crank spindle (that's right, you're hammering on the spindle the crank is stuck on instead of on the crank). A long, large-diameter bolt from a hardware store works fine (the bigger the bolt diameter the better, as long as the bolt is a little smaller in cross-section than the spindle end).
Finally, grab the bolt, place the bolt end against the spindle end inside the stuck crank, and smack the other end of the bolt with the biggest hammer you can find. If you hit hard and accurately enough, the crank pops right off the spindle.
I don't know why this works, but it does. Tip: hold the bolt in a pair of vice grips (you're going to be swinging the hammer as hard as you can and you don't want to mash every bone in your hand) and take a few practice swings with the hammer before you give it all you've got.
01-07-06, 01:56 AM
Fawk that noise. Just use a hacksaw or dremel to put a slit in that crank next to the spindle. Chisel it out or just put the crank nut back on and torque it until the crank splits off.
01-07-06, 06:02 AM
I've used motorcycle tyre-irons to pry cranks off before. There's usually two ends to the tyre-irons and one usually fits better between the crank and BB-cup depending upon how much clearance there is. Then pry and POP! off it goes... :)
Other idea is to remove the non-drive side crank-arm and adjustable cup. Lay the bike with crank facing up on top of some blocks of wood on the BB-shell to raise the bare spindle-end off the ground. Screw in a sacrificial bolt about half-way into the crank side of spindle. Smack with hammer until spindle is pushed out.
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