Two Places You Can Find Large Wheels
By George Straton
Let’s ponder for a moment two places where you can find Dub-size wheels (having radii 20 inches or greater):
1) A Hummer H2 where each wheel supports about 1600 lbs. Vehicle length 203 inches x vehicle height of 80”. Proportion of vehicle height to wheel diameter = 3.48.
2) A 1,000,000 lb. (fully laden) Airbus A380, where each wheel supports approximately 45,000 lbs. Each 23 inch diameter wheel, weighing 162 lbs. holds a tire 55 inches in total diameter by 22 inches in width. The tires are even heavier at 240 lbs. Tire air pressures are at 175 psi. The aircraft has fuselage height of about 40 feet rising to 78 feet at the tail and nears 240 feet in length. 260 feet of distance from wing tip to wing tip (wingspan).
If an airline wanted to make a real “baller” appearance using the same proportion of vehicle (aircraft fuselage) to wheel diameter as do the “dubbers”, you should arrive at a wheel diameter of 138” or 11.5 feet, or about TWO feet greater the diameter of the fan inlet on a Rolls Royce Trent 900 engine that powers the A380.
It could end up looking just like this caricature of a jumbo-jet that was in a caricature of a film:
Tire tread temperatures on a jumbo-jet can reach 284 degrees F after lift off (fully laden) and aborted take off. Further after landing. Steel brake linings within the landing gear assemblies can exceed 1470 degrees F after landing and taxiing to the gate. The temps reaching the wheel axles can exceed 480 degrees. Nitrogen which is used to inflate the tires can be released by a thermal fuse in the event emergency braking to avoid tire blow-outs. Tires can be re-treaded or replaced once every 200 take-off and landing cycles. Wheels are inspected in similar intervals for thermal and inertial forces exacted on wheels require inspections for flaws in the wheels using electromagnetic induction and dyes.
The entire purpose of wheel/ tire assemblies, whether on road vehicles or aircraft is control. The goal is reduction of unsprung weight to reduce impact wear on the suspension which improves control. 23” diameter wheels and low aspect ratio tires on passenger cars and light trucks “fly in the face” of that goal. We all know that Dubs are a lucrative – $4 billion per year – consumer market in the U.S. Dub-sized or oversized wheels were latched onto the hydraulically-hopping “Purple Jumbo” piloted by Snoop Dogg to elicit low-brow laughs. Therefore how can they be anything near serious automotive accessories on street passenger cars or trucks? Moreover, could history be as kind to the Dub wheel (late 1990-s – ??) as it was to the “Penny Farthing”(1869-1893)?
The trend toward putting oversized wheels and ultra low-profile tires on a passenger car, while apparently on the wane somewhat (after all, at some point, you really do need to have more than a rubber band’s width between the rim and the road surface) is another example of appearance trumping safety and performance – just like lifted pickup trucks. As much as the Airbus A380 needs 23 inch wheels and nitrogen-filled tires, a car buyer concerned about safety, durability, and handling does not need them.
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