Shimano M520 screwed the wrong way?

[Zviedrs]

Randomly remembered about my first experience with clip pedals. Few years ago I bought my first Shimano MTB pedals (most likely M520, can't confirm it 100%), screwed them in and went on my training rides to prepare for mountain bike marathon. One training, after multiple rides, the pedal just broke loose on the way home (luckily not in the middle). Back at home I inspected the situation and found out that the crank nut thread was messed up half-way in. Ahh, I just went all-in and screwed it back with a hope that such issue won't occur again. And to my surprise it never did, as I completed the 100km+ marathon without any issues after a week or two and afterwards biked for at least 1500-2000 more kilometers before selling the bike.

1) is it possible that I managed to screw-in that pedal the wrong way? Knowing that I might have gone with the same direction as with the other pedal.
2) was it not screwed in tight/strong enough?

Any other possible causes? Interesting to look back at it now, as at that time I did not know much about bike mechanics.

[Joe_W]

(08-08-2019, 06:27 PM)Zviedrs Wrote:  Randomly remembered about my first experience with clip pedals. Few years ago I bought my first Shimano MTB pedals (most likely M520, can't confirm it 100%), screwed them in and went on my training rides to prepare for mountain bike marathon. One training, after multiple rides, the pedal just broke loose on the way home (luckily not in the middle). Back at home I inspected the situation and found out that the crank nut thread was messed up half-way in. Ahh, I just went all-in and screwed it back with a hope that such issue won't occur again. And to my surprise it never did, as I completed the 100km+ marathon without any issues after a week or two and afterwards biked for at least 1500-2000 more kilometers before selling the bike.

1) is it possible that I managed to screw-in that pedal the wrong way? Knowing that I might have gone with the same direction as with the other pedal.
2) was it not screwed in tight/strong enough?

Any other possible causes? Interesting to look back at it now, as at that time I did not know much about bike mechanics.

1) no. The threads are in different directions. It should not be possible (unless with a lot of brute force, I guess) to do that.
2} It sounds like it was cross threaded though. That is relatively easy to do when not paying attention. The damage could fit...

It will hold after a while even with damaged threads due to electro chemical processes, since I doubt you greased the threads...

[Zviedrs]

(08-09-2019, 04:06 PM)Joe_W Wrote:  1) no. The threads are in different directions. It should not be possible (unless with a lot of brute force, I guess) to do that.
2} It sounds like it was cross threaded though. That is relatively easy to do when not paying attention. The damage could fit...

It will hold after a while even with damaged threads due to electro chemical processes, since I doubt you greased the threads...

Yeah, that sounds about right - cross threaded due to sloppiness it was a pretty clean damage as I remember. Although before I still believed there's chance that it might have been the wrong direction because at that point I did not know about the different thread directions for left/right crank. Could have pushed it with quite some force thinking that both sides should be in the same direction.