|> FAQ > Wheel and Tire Terminology|
Wheel and Tire Terms & Diagrams to help you understand
what they are talking about:
1. Diagram with technical terms describing parts of wheels:
Note "Safety Humps" in diagram and picture below
The Safety Hump (AKA Bead Bump) is required by DOT to help hold the bead of the tire against the flange in case of blowout air pressure loss, while the vehicle is decelerating, to decrease the possibility of tire shredding and complete loss of control.
Hubcap and Trim Ring mounting clips are designed to seat into the groove formed by the Safety Hump, marked in red in the pictures below, for increased hold on the wheel.
If the Safety Hump groove is not present, as in some off-road, ATV, riding lawnmower, or cheap wheels imported from India, Brazil, and other sources, hubcaps or trim rings may not hold the wheel as would normally be expected.
2. "Safety Hump" Marked in Red in the pictures below
3. Another Wheel Diagram:
4. Aspect Ratio:
5. Wheel Offset:
Standard Steel Wheel Eight-Spoke Steel Wheel Mini-Mod Steel Wheel
This picture shows a Cut-away Hubcap mounted on a wheel, intended to show how hubcaps are designed to bridge over the space occupied by wheel weights, so that most wheel weights are no problem with most hubcaps.
However, as of 2013, all states will require conversion to Non-Lead Wheel weights, which are made of lighter metals like iron or zinc,
and some of these may be thicker than those shown.