Tread Casting

By Dewey H.

The molds are 4 feet long and made from aluminum. They must be sprayed with a mold release before casting.

The chemicals to make the rubber must be measured precisely with a digital scale. There is only a 2% error rate allowed before the rubber won't galvanize. The black pigment is added after the chemicals are mixed.

The rubber is poured just enough to cover the ribs of the mold. The molds must then be bounced several times to remove any air bubbles.

After the rubber reaches it's gel time (the point where it is no longer a liquid) nylon cording is placed along the length of the molds.

Silicone pads are then placed on all ends of the molds. These will allow the next attached casting's nylon cording an overlap area.

Rubber is then poured to the level mark once the silicone plugs are in place.

Once the rubber is set (12 to 24 hours) the treads are removed and reset into the mold. This is where the sizing can be varied.

The same procedure is followed as in the first two steps with the nylon cording run also into the areas that the silicone plugs were in. This gives strength to the "butt splice" where the ends meet.

The treads are now complete. They are treated with a rubber preservative before installing. New rubber has a tendancy to be slightly sticky until treated. Full curing takes several days.