Rim locks are primarily used on Dirt and Enduro bikes.

Before you can fully understand how a rim lock works, you need to understand what a rim lock looks like and how it fits onto the wheel rim.

When you are looking at your rim and see a small bolt that sticks out, you are looking at the rim lock. This is sometimes mistaken for a valve stem. Basically, a rim lock is a clamp that holds your tire to the rim.

The rim lock fits between the tube and the tire. There are metal cleats on the bottom of the rim lock that grip the inside of the tire bead.

Rim locks come in varying sizes depending on the size of the rim you are running. Most decent quality rim locks will have their size stamped or marked on the top or bottom of the rim lock.

The stamping will look something like this: 21 x 1.60, 18 x 2.15, or 19 x 2.15.
The first number is the rim diameter and the second number is the internal width of the rim where the bead of the tire seats. This number needs to match the number on your rim lock. You have been warned about it matching!

Why do you need a Rim Lock?

The rim lock stops the tire spinning on the rim under hard acceleration or braking, especially when the tire is being run at low pressure. If the tire was able to spin, it would rip the valve stem out of the inner tube along with a few other nasty issues.

Common Rim Lock Problems

Like any good safety feature, it can sometimes come with a few downsides.

  • Pinched tube
    When an inner tube is pinched by the rim lock, it is usually because the tube is hung up on the rim lock. This will potentially nick or tear the tube. This defeats the purpose of using a rim lock altogether. Make sure that you double-check the tube when installing the rim lock.
  • Bad teeth
    Inspect the teeth, if they are bad, crushed, or missing, the rim lock will not seat correctly in the bead of the tire. Tiem to get a new rim lock.
  • Stud separation
    Before installing the rim lock, make sure the locking stud has not separated from the rubber body of the rim lock. You will need to move the stud side to side to see this.
    Make sure you give it a good inspection, as sometimes the tearing or separation from the rubber is subtle and easily missed.
  • Tire movement
    An easy way to make sure the tire is not moving is mark the rim and tire in a few places with a vertical line using a marker pen. Ride the bike for a while and see if the lines are still all lined up. Some settling in deviation is allowed, but a noticiable difference in the alignment of the marks means you have a problem and might need to replace the rim lock.
  • Mounting hole size issues
    Sometimes the mounting hole in the rim is too big. Time to get a washer or a new rim 🙂
  • Not the right torque
    It’s common to see riders tighten up a rim lock and not use a torque wrench. Make sure you use a torque wrench set to the OEM’s rim lock specs, so you don’t over or under tighten the rim lock, normally this is between 10-13 ft-lbs. Loose rim locks are the number one reason for failed rim locks.

Video

The video gives a good overview of how a Rim Lock works.