Open Hub with Alloy Wheels

What stops the front wheels from dropping off? Don’t panic the cotter pin through the castle nut and the stub axle do!

The Rumblings this month is on Cotter Pins in relation to the front wheels and how the bearings are retained in place on the Stub-axles, when used on an Open Hub as used with Alloy wheels held on by normal wheel nuts.

When you remove the Dust Cover (Photo 1) you shall gain access to the Castle Nut that holds the Wheel Bearings in place at a specific torque (Photo 2). The Cotter Pin that you can see passing through the axle secures the Castle Nut so stopping the nut from rotating on the thread.

On our Mog’s there are two machined holes through the Stub Axle (Photo 3) This allows the Castle Nuts to be rotated to the right or left to maintain the correct torque on the wheel bearings, as it allows for small increments of movement between the castle nut openings and the Stub-axle holes

Photo-3. Shows the two machined holes at 90degrees to each other

You can also find only single machined holes sometimes on parts that are not specifically torque loaded as the movement would be greater, so changing the torque.

Cotter Pin removal

To remove the Cotter Pin you will need to bring the bent ends together (photo 4a). This will allow you to pull-out the pin by the eye top: or to tap-out the Cotter Pin from the Stub Axle with a drift (Photo 4b).

Installation of Cotter Pins


When choosing the correctly sized Cotter Pin you need to ensure a good fit for hole diameter.

If the Cotter Pin is to long it can be trimmed to length with a good set of dyke’s (wire cutters) Photo 5a, 5b

After trimming to length, it is very important to debur the cut edges, to do this use a fine file then emery cloth or sponge and then rinse with Brake Cleaner to remove the debris

Refit the Cotter Pin by tapping back through the Castle Nut and Stub-axle’s proffered machined hole. You now have a choice of locking styles;

The Long Cotter Pin Method

Photos 6 Shows the cotter pin Legs split apart and then tapped to round the castle nut. This is really only possible to great effect with the Open Hub

Photo-6. Long Pin Method

The Short Cotter Pin Method

The cotter pin is installed ready for the long leg to be pulled forward and tapped down to the Stub-axle as shown in Photo 7

Photo-7 Short Pin Method

This is for solid wheels, next month is looking at wire wheels

Note. We are showing the stub-axle in a vice so that the pictures are clearer to understand.