Beadlock
From Wikipedia, the free encyclopedia
A beadlock is a mechanical device that secures the bead of a tire to the wheel.--- First manufactured by Marsh Racing Wheels at Siloam Springs, Arkansas in 1980 but conceived, designed and tested by Marsh Racing Wheels years earlier.[citation needed]
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[edit] Purpose
Air pressure within a tire forces its beads against the wheel rim and normally ensures that the tire and rim rotate as a single unit. In general automotive situations, a tire's air pressure is sufficient to withstand dislodging and rim-slip forces experienced during, respectively, hard cornering and acceleration (including negative acceleration or "braking"). Low tire pressure therefore poses the hazard of enabling sudden loss of air, and loss of control, during hard braking or an evasive maneuver (in addition to generally promoting excessive tire heat and future failure). Modern automotive tires have a soft rubber formulation at the beads, to help maintain good rim contact. Special bead-lock means are not required.
High traction is desired for tires for dirt track racing or for off-road vehicles, and their tread is therefor coarse. Nevertheless, some riders will lower the tire pressure to cause the tread to spread out and create a larger contact patch. This practice can create a safety hazard, as there may not be enough pressure to adequately secure the tire beads to the wheel. Reactive ground forces push a tire to one side or the other, especially the outside rear tire of a racing vehicle when it is turning in a corner of a track. This could cause a bead of the tire to come off the rim completely, or enough to cause partial loss of air. It is also possible for the tire to have more traction on the ground than there is friction between the tire and rim. In this case the wheel would slip around the tire beads without turning the tire. Beadlocks, of one form or another including adhesive, are therefore used to keep the beads of off-road tires firmly seated and prevent slip, even when inflation pressure is low.
[edit] Standard beadlocks
A standard beadlock is designed to clamp the tire bead between an outer and an inner ring. The inner ring may be welded onto a standard wheel increasing wheel width by anywhere from 1 1/2 to 2 inches or may be formed as part of the wheel when the wheel is made in the factory. The outer ring is then bolted onto the inner ring with the bead clamped between them. Anywhere between 16 and 32 bolts at around 10 ft·lbf are used around the circumference of the wheel to keep the clamp tight. The rings and bolts can cause problems with balancing the wheel and tire because all the added weight is on one side. This style is used exclusively for offroad use.
It is important to note that most standard beadlocks clamp only the outside bead. This is fine in most cases because the outside bead is the side that comes unseated most often while off-roading.
 A standard beadlock with tire mounted and bolts tightened. |
 The same wheel with the tire, bolts, and outer ring removed. |
[edit] Internal beadlocks
An internal beadlock is very much like an inner tube within the tire that pushes the bead of the tire tight against the wheel. The internal beadlock is inflated via its own valve stem. The side of the beadlock closest to the tread, the "case", has a layer of thick fabric, generally polyester, which keeps the beadlock from inflating too far up into the tire. This forces the sides into the tire which compresses the bead of the tire against the wheel.
[edit] Streetlocks
Some people want their vehicle to look like it has beadlocks, but don't actually need the benefits of real beadlocks. Many wheels are therefore made to look like beadlocks but they don't actually lock anything. The off-road community generally refers to these as "streetlocks" since the owners typically don't use them for off road use. Streetlocks do improve the structural integrity of the wheel though, and are a good alternative in areas where beadlock wheels are not street legal.
