Wheel Sizing - Lug Nuts or Bolts

Lug Nuts or Bolts

Wheels must be fitted with the correct type of lug nuts on wheel studs, or bolts. Lug (aka wheel nuts in British English) nuts are usually either flat, tapered (generally at 60 degrees and referred to as conical seat), or ball seats, meaning the mounting surfaces are flat, tapered, or spherical respectively.

Most Mercedes have ball lug seats from the factory while most aftermarket wheels have a tapered lug design. Wrong lug nuts for the wheel will not properly center it and cause wobble. Some manufacturers (e.g. Toyota and Lexus) have used taper lug nuts for steel wheels and flat seated lug nuts for alloy wheels.

Some aftermarket wheels will only fit smaller lug nuts, or not allow an ordinary lug nut to be properly torqued down because a socket will not fit into the lug hole. Tuner lug nuts were created to solve this problem by utilizing a special key to allow removal and installation with standard lug wrench or socket. The design of tuner lug nuts can range from bit style to multisided or spline drive, and are sometimes lightweight for performance purposes.

A variation is the "locking wheel nut", which is almost universally used for alloy wheels in the United Kingdom. One standard lug nut on each wheel is replaced with a nut which requires a special and unique key (typically a computer-designed, rounded star shape) to fit and remove the nut. This helps to discourage theft of wheels. However, universal removal tools are available which grip the head of the locking nut using a hardened left-hand thread. The success of these depends on whether there is room to use it in the lug hole, and whether the manufacturer has incorporated a free-spinning outer casing to the lock. Keeping an appropriate tool to lock and unlock aftermarket nuts, and a spare set of nuts, with the spare tire in the boot of the car is recommended by manufacturers.