Loose Crank Arm Problem

had these for a couple of yrs and no probs yet!

Hi - On Sunday my left crank arm loosened quite dramitically, i couldnt ride it and had to go home and tighten it back up. Also, the plastic extractor has disappeared from the crank bolt...I think this was all due to me not properly tightening it up the first time round!
My question is this, what do i do now, replace the bolts (with the extractor), or can these be left in place as long as they are very tight now?
Thanks

It's unlikely your crank went from fully tight to dramatically loose in the blink of an eye and as such you've probably been riding with it a bit loose for a while. This will have buggered the tapers on the crank arm and it will continually loosen off now. Replacement is the only solution.

The plastic piece is not an extractor, just a finishing piece/dust cap.

Ive only riden the bike twice and that was the second time!!! Im pretty sure my arms aren't buggered, but i will keep an eye on them. Thanks for your reply...
Anyone know where i can get dust caps?

Either from a sufficiently friendly bike shop that has some spare, or by buying new bolts with dustcaps, eg: http://www.jejamescycles.co.uk/ml-shimano-type-8mm-allen-key-crank-bolts-id25133.html

Or just don't worry about it until the crank works loose again and you have to replace the arm as well. Maybe you're lucky, but sadly it takes very little time to bugger up cranks when they're loose.

(Also, check the other side is tight too...)

Cheers - i will hopeful;y not need the new crank arms!

Its my own fault, i didnt properly know how crank bolts / cranks work and just fitted them...and fitted them loosely!! Dildo I am!

(Also, check the other side is tight too...)

I presume it was the left hand crank arm that came loose? (Although I see you've said you fitted them loosely so maybe not)

Forces going through the non-drive side crank arm/bb taper are a lot higher/less supported (rh side is supported by the drivetrain) so it tends to be left hand cranks that work loose.

Riding a mile or two on a loose crank arm is probably enough to knacker the taper.

If the crank arm is buggered though, it won't take anything else with it so ride it to destruction.

Yes the left one came loose... i wasnt even out for 1/2 a mile!

So will it not bugger my bottom bracket?

No. The axle is stronger than the crank arms.

People - thanks for your time and advice...really very appreciative. I will tighten and ride!!!! See what happens!
Thanks again.