Which crank arm is left hand thread

So occasionally as you are flying along you have to reset the direction to the compass heading. Comment by Austin Blanco — April 28, The elliptical path generated by the rather insignificant space between the mated parts would only serve to allow the effects of cumulative rotation to eventually separate the parts, hence the need for left and right threaded pedals. Just my 2 cents worth…. Comment by Dave — January 22, Comment by Geert — May 30, I wrote to Huffy and they told me this is the industry standard in pedal design..

How freaking hard is it to turn the thread around on the left pedal? Comment by avemaria — April 28, Fuck that stupid ass design…. There is no god. Por quoi?????????? Comment by Jesse — November 7, I like this example to explain its meaning:. Then pen will tend to spin within the loose grip of the 1st hand in a direction opposite the direction the 2nd hand is rotating. Comment by Asks — November 14, That would make the whole subject clearer a bit.

It took me a while to realize that precession takes place between already partially unscrewed outer thread on the pedal spindle and the inner thread in the hole in the crank. Comment by V. Comment by sam — February 6, Comment by Dennis Hevener — August 21, Comment by sam — August 25, Comment by pedal — March 19, If you want them both to tight, then they have to move to opposite directions, so their helicities must be opposite.

I once built a custom bicycle, and used a crank from another bike. I found that the crank's design differed on the donor bike, and thus, would only fit my custom bicycle when installed in the reverse direction.

I saw no other problems with this solution, until one fine Spring morning, while riding my newly fabricated custom bicycle downhill at great speed, the right-hand pedal un-threaded and dropped onto the roadway.

Unfortunately, my right foot followed; as did my right leg. In what seemed to be nearly a full minute of slow-motion events, my entire body followed for a meet-and-greet with the road surface on that fine Spring morning.

I lay crumpled and severely injured, against a metal road sign for an unknown period of time, until a passing motorist stopped and called I was transported to Emergency Central, where surgeons labored for hours to stop the bleeding and to remove my custom bicycle from its painful resting place in my rectum.

Fearing the worst, a priest was summoned by the hospital staff, and my family was notified of my condition.

Fortunately, I pulled through, and am able to operate my wheelchair without assistance, thanks to many months of rehabilitation and therapy. So, to answer your question; it matters little, why the pedals possess a tendency to loosen when a left-hand thread is installed on the right side.

However, for the love of God; it would be in one's best interest to remember to be absolutely certain to place the pedal with right-hand threads on the right-hand side of the bicycle.

Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. Why are bicycle pedal threads' handedness left on the left and right on the right?

Ask Question. Asked 10 years, 8 months ago. Active 7 years, 10 months ago. Precession of right-side BB cups is less obvious because the rotating load is only partial. For this reason, some right BB cups have used right hand threads and some with left hand threads have loosened. The left BB cup, with no significant rotating load has little tendency to turn.

Freewheel cones are more obvious candidates for precession, their load being mainly radial, and rotating continuously in the direction that would unscrew a right hand thread. There are other such but less common threads on bicycles. Precession forces are large enough that no manner of thread-locking glues, short of welding, will arrest them. We know they confer some protection, but there are limits to their protection.

With a hard enough impact, any helmet will fail. The possible association you mentioned between the use of helmet cams and serious crashes is just that: an association. By concluding that helmet cams are responsible you are suggesting to your readers that correlation equals causation. This is the same logic that says that umbrellas cause rain. Maybe riders with helmet cams take more risks and therefore crash more often?

Your writing has always been sensible and grounded in experience. A couple of items overlooked in the past, I thought might be worth sharing with fellow Tech FAQ readers. I first thought one of the housing sections had burrs. The culprit was the end of the return spring where it runs inside a plastic bushing. So now, in addition to lubing all the pivot points, I squirt a couple of drops of Finish Line Teflon Dry Lube in the bushings.

My brakes have never been smoother! I was surprised to find the two mounting bolts had loosened.