Pedal failure: what did I do wrong?

samoff

I replaced my chainset and pedals a few months back. Riding it last weekend, for almost the first time since then (appendix trouble), one pedal came right out of the crank, having stripped the thread completely.
Now I've got to buy a new chainset. Before I do, I'd very grateful if someone could give me a hint as to something I might have done wrong last time.

Did I maybe
a) do it up too tight
b) choose a dodgy chainset (Shimano M442 square taper)
c) use the wrong amount of grease (a smidge of Finish Line, I think)
d) cross the threads (I don't think I did - but if that's the most likely explaination...)
e) use dodgy pedals (Shimano M545)

... or is it just one of them things.

njee20

Almost certainly d)

Or you didn't do them up tightly enough.

Gwaredd

A combination a A, C, & D maybe. Thing is, you know when you've cross threaded something.

supersonic

I'd say F: you do not torque it tight enough.

nicklouse

supersonic wrote:

I'd say F: you do not torque it tight enough.

+1

ThePriory1978

supersonic wrote:

I'd say F: you did not torque it tight enough.

Thats a BINGO.

samoff

Thanks for the tip. I'll be careful to do it up tight enough next time.

allen.coulson

I would have thought that if they were correctly threaded then they would self tighten. The mode of failure for it to both fall out and with stripped threads was probably overtightening whilst mis threaded.

Gwaredd

allen.coulson wrote:

I would have thought that if they were correctly threaded then they would self tighten. The mode of failure for it to both fall out and with stripped threads was probably overtightening whilst mis threaded.

This.

It's why pedal threads are handed - kind of a failsafe. If you greased the threads during install then this would mask the feeling of you cross threading them, or if you didn't cross thread them, the grease on the threads could've masked the feeling of the treads stripping during over- tightening.

*AJ*

did you use a normal open ended spanner to tighten them up or a pedal spanner?

Some pedals have a narrow axle where the spanner flats are, this results in the pedals tightening up against the spanner rather than the crank arm. It means you think they are tight, but once youve removed the spanner they arent at all.

Hope the above makes sense, but ive seen it done a few times!

pugaltitude

Can I have a 50/50 or phone a friend???

blablablacksheep

samoff wrote:

Thanks for the tip. I'll be careful to do it up tight enough next time.

thats also a problem

the right side pedal only needs to be tight enough so that a little force is needed ie not so that you go red in the face trying to tighten..

Right side will tighten by itself as you pedal, while the left is useally the problem side.

dont forget pinch bolts on chainsets as they need to be re-tightened after being installed about 4-6 rides later i have been also told

supersonic

They fall out when not torqued correctly. The reverse threading helps in some cases, but an incorrectly torqued pedal can come loose, and then strip the threads. They do not self tighten. If you don't believe me, do them up finger tight and go for a ride.

cooldad

blablablacksheep wrote:

samoff wrote:

Thanks for the tip. I'll be careful to do it up tight enough next time.

thats also a problem

the right side pedal only needs to be tight enough so that a little force is needed ie not so that you go red in the face trying to tighten..

Right side will tighten by itself as you pedal, while the left is useally the problem side.

dont forget pinch bolts on chainsets as they need to be re-tightened after being installed about 4-6 rides later i have been also told

You are posting nonsense again. The other pedal has a reverse thread, so extending your 'logic' it too will tighten itself.
Just fit them properly and no problems,
And any bolt on a bike that is tightened to the point that you go red in the face, is seriously overtightened.

tri-sexual

clean thread (pedal and inside crankarm) with a rag
lightly grease threads
start by finger tightening, cw for right, acw for left and finish with pedal spanner, 6mm/ 8mm hex (which ever is applicable)
tighten to the correct torque (for your shimano 35Nm), undertightening or overtightening is not recommended esp the latter, overtightened pedals can cause damaged threads and can be a nightmare to remove
wipe off excess grease