Tyres and Rims
Stuff about the 'relatively' big black rubber things that spin around and bits near them...Tyres and Rims
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On the right is the Hankook 31x10.5R15 RT03 that's currently running on the front of the Rodeo (rears use 33x12.5R15's). The tread pattern (unmodified) is mid-range, which works well over the various surfaces encountered during most events. Also pictured is the Champion beadlock rim that the Rodeo runs. 24 bolts sandwich the outer tyre bead between the beadlock plate and the rim, securely retaining it. The beadlock serves two purposes:
Note that the inner bead doesn't generally require a beadlock as the majority of force on a tyre's inside edge occurs when the tyre is unloaded (i.e. the tyre on the inside of a turn). |
Hubs and Studs
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Yep. Big studs on a floating axle alloy hub, complete with a 4-piston CNC caliper. This is the life! A more technical description would include the fact that a 'floating hub' implies using an axle with a spline at both ends; one into the differential center, the other into the hub. The advantage of this setup is that if an axle breaks, the hub (and hence wheel) doesn't fall off. Unfortunately, driving a car offroad with a broken axle is somewhat difficult; what with the back end constantly trying to overtake the front. The small aluminium end-cap (seen between the studs) can be removed to access the axle. However if the axle is broken the same old problems arise when trying to remove the fragment. |
Inner Tubes
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Pictured is the inner tube Schrader valve. The valve (B) is turned clockwise/in to inflate the tube (C), and anti-clockwise/out to inflate the tyre. This allows different pressures to be run in the tube and tyre; the tube high to keep the bead in place, the tyre low to provide more grip. Note the small hole in the bottom of the valve stem (A) to allow air to enter the tyre when the valve is in the correct position (out). The inner tube is a run-flat generally used to prevent blowouts occuring during NASCAR race meets and is standard equipment on selected circuits. The tube forces the tyre bead against the rim, significantly reducing the possibility of rolling the bead off. The actual tube is a Goodyear Racing Lifeguard Air Container. Note that you can really only run tubes if you use beadlocks. The beadlock stops the tyre rotating on the rim; which would otherwise rip the valve from the tube. |
Tyre Mounting and Other Topics
Not all rims are created equal
Some rims have larger bead retainers than others. If possible, select the rim with a larger retainer; the tyre installer may have more trouble, but you're less likely to roll your tyre off the bead.
Bead Stretching
Mounting a tyre on a rim stretches the bead. Taking it off one rim and putting it on another will result in more stretching. Moral; put the tyre on the rim and leave it there (if possible).
Tyre Mounting
Mounting a tyre with a lubricant, often soapy water, does a couple of things:
- ...it puts small amounts of water into the tyre. When the tyre heats up, some of the water will turn into water vapour and increase the pressure in the tyre (beyond the increase due to the rest of the gas in the tyre expanding due to heat). Changing tyre pressure is generally bad because it means you're running at a different pressure to what you wanted. Many race teams run nitrogen simply because the stuff you get from BOC doesn't contain any water (vapour or otherwise); plus it's easy to carry a bottle around for both the tyres and shocks.
- ...it can leave a residue that reduces the friction between the tyre and the rim. This can lead to the tyre spinning on the rim, gradually losing small amounts of air and eventually being rolled due to extremely low pressure.
Anti-seize
If you're running beadlocks, it's a good idea to install the bolts with a generous coating of anti-seize. There's a few of the things on each rim (24 at last count), and removing them can be 'painful' if they are all firmly stuck.
