Wednesday, October 22, 2008

Wheel Glossary

I like the looks of Radir Wheels and Astro Supreme Wheels. This evening I was surfin' the Net pricing sets of both when I ran across the following "Wheel Glossary". I learned a lot reading through it and thought you might learn a thing or two as well.

Wheel Glossary
Backspacing - The measurement from the mounting pad to the inner edge of the wheel.

Bead seat - The position where the tire rests and seals on the inside of the rim.

Bolt Circle/Bolt Pattern - The bolt pattern is comprised of two numbers - the first indicates how many bolt holes are on the wheeland the other describes how far apart they are. A bolt pattern of 5x4 ¾” would mean the wheel has five bolt holes and they are 4 ¾” apart (measured across the center of the wheel).

Center Bore - The hole in the center of the wheel machined to match the hub of specified vehicles with hub-centric wheels and machined to a generic size with lug centric wheels.

Hub Centric - The center bore hole of a wheel matches the hub diameter of the vehicle. This centers the wheel via the center hole rather than the lug nuts.

Load rating - The maximum weight that the wheel is designed to support. To determine load rating requirements take the gross axle weight ration and divide by 2.

Lug Centric - When the wheel is centered by the bolt holes/ lug nuts of the wheelrather than by the center bore. Lug centric wheels should be balanced from the bolt holes.

Mounting Pad - The surface area on the back of the wheel's center that contacts the brake drum or rotor surface.

Negative offset - When the mounting surface is closer to the disk/drum (Inside) of the wheel. Or the mounting pad is behind the centerline of the wheel. This type of wheel is commonly referred to as a deep-dish wheel. This offset is common in older vehicles and many of today's trucks and will bring the wheel/tire combination out away from the vehicle.

Offset - The offset of the wheel is the distance from the mounting pad to the centerline of the wheel.

Positive offset - The mounting pad is forward of the centerline of the wheeltowards the street side of the wheel. This is common in most front wheel drive cars and some newer trucks. Generally speaking a positive offset wheel brings the wheels closer to the center of the vehicle. Plus 1/ plus 2 sizing - A concept to improve handling and performance through the mounting of lower profile tires to wheels that are 1', 2' or even 3' greater in diameter. The overall ride height remains the same.

Rim width - The width of the custom wheelmeasured from bead seat to bead seat not edge to edge.

Rim Diameter - The overall diameter of the wheel's bead seatnot the diameter of the rim edge.

Rim flange - The outermost edge of the wheel's rim that the clip-on weights attach to on most wheels.

Safety bead - The raised area circling the rim of the wheel and located slightly inward from the bead seat.

Torquing - The securing of the wheel/tire assembly to the automobile by the tightening of the wheel's lug nuts to the studs of the vehicle's hub. Custom wheels should always be torqued with a manual torque wrench (not an impact air wrench) to torque rating specifications followed by periodic re-torquing.

Unsprung weight - The total weight of the vehicle not supported by the suspension system. For example wheels and tires.

Wheel weights - Weights that are used to balance the wheel/tire assembly. They are either clippedtapedor self adhered to the inside or outside of the wheel.

Zero offset - The distance from the mounting pad to the centerline of the wheel is 0.