The wheel size is the diameter of the wheel in inches where the beads of the tire sit on the wheel. This measurement does not include the rim flange. Modern road tires have several measurements associated with their size as specified by tire codes like 225/70R14. The first number in the code (e.g., "225") represents the nominal tire width in millimeters. This is followed by the aspect ratio (e.g.,"70"), which is the height of the side wall expressed as a percentage of the nominal width. "R" stands for radial and relates to the tire construction. The final number in the code (e.g.,"14") is the rim size measured in inches. The overall circumference of the tire will increase by increasing any of the tire's specifications. For example increasing the width of the tire will also increase its circumference, because the side wall height is a proportional length. Increasing the aspect ratio will increase the height of the tire and hence the circumference.
Replacing the wheels on a car with larger ones, normally for a perceived improvement in appearance, also involves using tires with a reduced profile number (often as low as 35%) to keep the overall rolling radius within a few per cent of the original tire. If this is not done, gearing and speedometer accuracy are affected. All other things being equal, larger replacement wheels give a harsher ride because of the shorter and stiffer tire sidewall, in exchange for better handling and higher cornering limits due to the lower sidewall flex. In contrast, a car designed to have large wheels from the outset may have a more normal tire profile and gives a smoother ride due to the larger rolling radius of the tire.
Some wheels also have their diameter quoted in mm as opposed to inches ("metric" wheels). An example of a typical tyre size is 160/65r315, where '315' denotes the wheel diameter in mm.
Off-roading tires may use a different measurement scheme: outside diameter times(by) tread width, followed by rim size (all in inches) - for example 31x10.50R15. The size of the disc however is denoted like 8.5" X 20.0". This shall mean that the width (of thickness) of the wheel is 8.5 inches and the diameter is 20 inches.
A dub is a custom wheel that has a wheel size of 20 inches or greater; the term dub is a slang term for twenty. DUBS may have originated as an abbreviation for double-deuces, or 22 in wheels. DUB Magazine, an automotive enthusiasts magazine, takes its name from the term and covers material chiefly pertaining to urban vehicles and the people that own them.
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Famous quotes containing the words wheel and/or size:
“The wheel is come full circle.”
—William Shakespeare (1564–1616)
“Delusions that shrink to the size of a woman’s glove,
Then sicken inclusively outwards:
. . . the incessant recital
Intoned by reality, larded with technical terms,
Each one double-yolked with meaning and meaning’s rebuttal:
For the skirl of that bulletin unpicks the world like a knot....”
—Philip Larkin (1922–1986)