Which pedal reverse thread

This obviously works as you can hand tighten a pedal and a week later the pedals can be quite tight in the crank arm. Dear Lennard, I just wanted to submit a quick correction on your technical FAQ on why pedal threads are threaded the way they are. Instead, due to an effect called precession, the bearings on the spindle will actually exert a torque opposite to the direction that the pedal spins relative to the bearing — that is, if the pedal is spinning counterclockwise relative to the spindle, as would be the case with the right-side crank pedaling forward, the spindle is actually being torqued clockwise.

Pedals could be threaded the way they are in order to self-tighten them, as you suggest, or as a safety measure to prevent injury in the case of frozen bearings. I think a look at history would tend to favor the latter. If you think of the days of penny-farthings, the high-wheeler bicycles that were common from , a frozen pedal that did not unscrew could be fatal. The only way to increase the gear ratio on a direct-drive bike like that is to increase the diameter of the front wheel. This perched a fast rider who had the strength to push a high gear up high over a very tall front wheel sans helmet, of course.

Such incidents often led to serious head injuries and death. There were a number of features installed on penny-farthings to increase safety. So why do pedal makers add this extra complication? If the left pedal had regular, right-hand threads, that pedaling force would cause the pedal to loosen and eventually fall off mid-ride. So by threading the spindles to pull back into the crank as you pedal, they stay firmly in place without any additional bolts.

Then look at the angle of the threads. The threads on a right-side pedal will slope up and to the right, while the left-side pedal threads slope up and to the left. It is also sometimes necessary to remove the pedals for replacement and to service the pedal bearings. It is important to remember that pedal threads are different from left side and right side.

The right side pedal has a right-hand thread removes counterclockwise, installs clockwise. The left side pedal has a left-hand thread removes clockwise, installs counterclockwise. Additionally, the thread will appear to slope up toward its tightening direction. Left hand threads slope up to the left, while right hand threads slope up to the right, as seen below. Some model and makes of pedal do not use a pedal wrench flat. These pedals will typically have a 8mm hex fitting in the back side of the pedal thread.

Use an 8mm hex wrench in this fitting to remove and secure the pedals. When turning the pedals, keep in mind the wrench is on the back side of the pedal.

View the wrench from the orientation of the pedals, standing to the right side of the bike for the right pedal, and the left side of the bike for the left pedal. Turn the wrench accordingly. Rotate the bike as necessary to access the inside of the crank. Left pedals, however, have a left-hand thread, so they go righty-loosey, lefty-tighty. But why? Some say the Wright Brothers were the first to experiment with a left-hand threaded pedal but, whatever the source, prior to its implementation riders often had their trips cut short by runaway left pedals.

The culprit is an action known as precession. Sheldon Brown suggests an easy way to visualize this, just hold a pen loosely in the end of a fist.