Losing a pedal? Sort of a survey.

[aicabsolut]

I've seen pedal spindles break, crank arms break, pedals break, and crank arms come loose, but I've never heard of anyone I know have an issue with pedals unscrewing themselves. The reason for the different threading on each side is that the action of pedaling is supposed to tighten the pedal. So you should definitely not have to stop periodically and keep tightening the pedal. Just pedaling should do that for you.
Bizarre. I can't believe it happened with 2 different cranks!

[TrekJeni]

Honey just asked "what cha doing?" and I read him your story. He's been wrenching for more then a decade and is the manager of his family's shop.

He's never told anyone to tighten their pedals five hours into a ride. He says they probably aren't using pedal washers and now even though the pedal still looks good, it's not. He would have demanded all new parts.

Put some new pedals in there and see if the problem goes away.

Hope this helps.

Jeni

[Grog]

Thanks everyone for your detailed answers!

I increasingly think there is a problem with the pedal. The reason we haven't changed it yet is that the other pedal is fused into the other crank, and I don't think we have an identical R pedal sitting around, or even another SPD pedal. Of course we could get another one, but while we're at it I think we'll just change the other crank and get two new pedals.

Now: would you give the new setup a chance or would you change all parts NOW to avoid further troubles?

[aicabsolut]

I would change all parts. He's lucky he hasn't had a bad crash already from losing a pedal.