How interpret leftside rotational wear at crank pedal eye?

stickman

Depth, marks, debris etc?

couldashouldawoulda

mmm, I rarely post this kind of response, but WTF are you asking?

Is you pedal wearing your crank, your ankle, your knee?

Once again -in a nice way - what are you on about?

stickman

What the pedal on the left side does is microscopically bore it's way through the crank, I don't know if when a certain tightness is reached at fitting it will overcome this? But when it happens the pedal will snap off eventually. Although hopefully the chainring teeth would be worn before then.

Eyon

worried about microscopic boring? I wouldnt worry, really, dont.

desweller

What on earth are you rabbitting on about?

stickman

It's worth knowing what's what. (Not worried though)

rake

are they left threaded italian cranks? buy some shitmano.

balthazar

Because of the inadequate design of the pedal/crank interface, the spindle is permanently in motion, which causes the wear pattern that can be seen in used cranks. Eventually, this wear can cause crank failure. Over-tightening pedals doesn't help and nor do "pedal washers".

Jobst Brandt developed a modification of his own cranks, after many years of cranks failing at the pedal eye. The modification was "milling a 45-degree conical relief in the pedal eye, and then putting a tapered collet-type clamp around the spindle" (quoted from here)

There's a picture here:

http://pardo.net/bike/pic/fail-002/brandt-cranks.jpg

and a discussion here:

http://www.sheldonbrown.com/brandt/breaking-cranks.html

So far so good, apparently.

stickman

Thanks, interesting reading. I'd been thinking of one of my bikes which i've ridden 1000s of miles on, haven't checked it yet. My other bikes have a Stronglight type, they've gone from plain holes, to my last one which has a recess and washer - but you say these are no good!

rake

surely it will happen both sides, why only the left .

stickman

Because of the left hand thread - and if they had a right hand thread they'd unscrew over time.

rake

stickman wrote:

Because of the left hand thread - and if they had a right hand thread they'd unscrew over time.

why does the left hand thread make any difference. its the same as a right hand thread on the opposite side because the axle forces are reversed. its the same situation in reverse.

father_jack

lol at this thread.

stickman

Don't know, i'm dyslexic so that sort of thing confuses me, but I suppose if you rode a fixed gear permanently backwards the right side would have the problem.

father_jack

The right crank has a standard thread.
The left crank has a reverse thread.

So as you pedal, any rotational force on the pedal axle will tighten it further, upto a point where the torque from the rotation is lower than is required to tighten it anymore.

rake

i concur. its the same effect both sides.