crank arm fell off?

i was ripping it down the road earlier today after just fitting my new DA bottom bracket. and my bloody drive side just fell off and then got rode over my a car. gay i know.

how could this of happened? i have never put on a crank arm so tight because i was trying to get the chain line spot on. could this of happened because after i had tightened the cranks with a bolt i then replaced with a hex key bolt. did i just not tighten this enough?

dont want it to happen again. i cant afford to keep letting my drive side be run over.

thanks

what BB / crank interface?

bottom bracket installed wrong way could lead to the bolt working its way loose... I have that at the moment where every 4 miles im having to tighten it.

square taper..definitely on the right way. put it on the wrong way to begin with but the chain line was way off.

why would chainline affect which way in install it?

your right it dosent. it was just because i didnt know i had to tighten it so much so when i first shoved it in and had a look it seemed way off. but it fact i later found out i just had really tighten it.

Pics or GTFO

You may have fucked the arm taper from overtightening so pics would help. Or you have mixed tapers and fucked the crank arm.

Basically you are supplying a sub-optimal amount of information to diagnose your problem.

try turing the spanner the other direction

What has the fact your crank likes the same sex got to do with it?

square taper..definitely on the right way. put it on the wrong way to begin with but the chain line was way off.

Does not compute. You put the bottom bracket in the wrong way around?

no bb is in the correct way. adjustable on the non drive side. and sorry but there isnt a great deal to be gained from pictures. no striped threads of visible 'fucked tapers'

sorry i cant supply more info. just wanted to see if any body else had the same accident and might be able to report with a useful tip. tbo i think over tightening was the issue here.

thanks to all who tried to help. especially you 'craftybutcher' ...you joker you!

happened to me when i first got my ESB but thats BMX cranks,
due to lack of tighetning crank bolts down

I'd go to the corner shop, buy a packet of custard creams (or chocolate Hobnobs if you're feeling flush) and take said bike to your friendly LBS.

iso/jis?

Irrelevant, if the arm fell off the taper is probably fucked for good.

Pics or GTFO

You may have fucked the arm taper from overtightening so pics would help. Or you have mixed tapers and fucked the crank arm.

Basically you are supplying a sub-optimal amount of information to diagnose your problem.

Yeah.

i have never put on a crank arm so tight because i was trying to get the chain line spot on.
thanks

You do not adjust chainline by tightening or loosening your crank arms.. You tighten the crank arm on properly, and shim the cog/space the hub & dish the wheel. Even shim the chainring if your feeling odd, but don't loosen or crush the crank arm.

Sorry for your loss.
[INDENT]Crank
The arm which connects the pedal to the bottom bracket axle. Sometimes called a "crank arm", but this is redundant and inelegant. Call it a crank, or call it an arm, but please don't call it a "crank arm"
[/INDENT]

You do not adjust chainline by tightening or loosening your crank arms.. You tighten the crank arm on properly, and shim the cog/space the hub & dish the wheel. Even shim the chainring if your feeling odd, but don't loosen or crush the crank arm.

Or just fit the correct bb.

i fitted a dura ace 7600 crank to a 7400 bb. crank being iso and bb being, i think, jis low profile. only just found this out. i though as they where both njs stamped DA they would be compatible. clearly back to the drawing board with this one.

Problem solved!

Praise be bejebus!