Originally Posted by
Tougeep3
5 lug-Star, 4 lug- square.
Biggest advantage to having more lugs per wheel is that by spreading the loads to more points you reduce warping of brake rotors. Through the '80s as cars got smaller and their performance rose, 4 lug cars had terrible problems with rotor warpage esp. if the lugs were unevenly torqued.
Along with being able to reduce bolt size, another reason to have more than 4 lug nuts on a semi is to create more even clamping pressure. Clamping force under a bolt head or lug nut is shaped like a cone and drops off fairly rapidly as you move away from the nut. So to keep from over stressing the wheel in just 3 or 4 places (underneath the nut), more studs are added to more evenly distribute the load. A bigger vehicle with greater torque to the wheels needs more clamping force. An easy way to generate more clamping force, and increase the total shear strength of the studs without upping the size of the lug studs, is to add more studs of the same size.
One (partial) fallacy is that the lugs support the weight of the car. Not so, they hold the wheel in position so the the hubs can carry the weight. The lugs are then only subject to tensile forces for cornering loads and a small shear load for braking and accelleration forces. Yes, some cars are lug-centric (aftermarket wheels without hubcentric rings have this problem), where the wheel is centered by the cone-shaped lug nuts (or bolts) but these are pretty scarce these days. (Most cars have cone shaped lugs but are still hub-centric.)
Not to mention snap a stud on a 5 lug car and you still have 4.
But yes, you'll find more wheels and brake upgrades for the 5 lug..
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