June 14, 2022
One of the old car magazines I subscribe to has had an ongoing discussion on left-hand- threaded wheel studs. At one time the engineering community was divided on whether the fasteners on the right side of a car needed to be left-hand threads to insure that they did not loosen up on the road. Perhaps this was a carryover from the days of “knock-off” hubs, when wheels had splines in them and a winged nut was hammered to tighten them to the vehicle. It was part of your initiation as a racecar “stooge” to be given a hammer or lug wrench and to be ordered to change the wheels. Many newcomers would whale away on those right-side wing nuts while those in the know quietly laughed. Some kind soul would eventually intervene and school you on the need to “hit them forward” to loosen and “back” to tighten. The same frustration could happen on passenger cars equipped with left-hand wheel studs. A dark and stormy night is no time to learn this. I do not know of any current production car that uses left-hand-threaded wheel studs. Our understanding of how threaded fasteners work and the lack of wheels falling off the cars that never “went left-hand” combined to close out the argument. You can see how similar issues worked themselves out in other products. The longer a problem is “worked,” the more the solutions tend to resemble each other. Spirited discussions on design differences are impossible to maintain when the products are hard to distinguish from each other. The humor in that candy commercial on the perceived differences between the right-hand and left-hand cookies is applicable to almost every consumer product. Industrial gearbox makers once had unique recipes for what made a good design; you had helical gears in some, herringbones in others. Then there were planetaries and different types of bevel gears; today, some product sectors even share mounting dimensions. While these trends are probably good for the end-user, they make advancing gear design difficult.