I’ve been counting lugs on wheels on my walks recently. Some tiny cars have only 3, which seems dangerous. I remember learning the noise of the lost lug nut trapped in the hubcap (remember those? remember people stealing them? I’ve seen hubcap shops.) It wasn’t a big problem: put it back on. How far can a car with only 2 out of 3 lug nuts go before the wheel breaks off? I hope they’re carrying spares (I do! never had to use them though) 'cause they don’t have hubcaps.
What is the additional cost/weight of 4? It can’t be much.
Ask the Nascar drivers how dangerous they think 3 lug nuts ate. Nascar had to make a rule that all 5 lug nuts have to be on and tight because pit crews were only putting on 3 per wheel to speed up pit stops. And they are going 200 mph on some straights and with serious side loads in the turns with 3400 pound cars.Also, when putting 3 lug nuts on 5 studs, they are not even, evenly spaced.
Pa;ul Brand, on the local car radio show used to say: “French engineers, who copy no one, and no one copies”.
I’ve got four lugs even on my light trailer. I think though it’s one thing putting three nuts on fresh and driving around the track for an hour compared to putting three nuts on and maybe not looking at it again for a year or two as the car is driven who knows where.
Same with the Ford Maverick. I had a 6 and got tired of how poorly it stopped so I upgraded the front brakes to the larger V8 versions with 5 lugs. Pretty simple since the spindles were the same so just backing plates, drums, shoes, and hardware. I think the wheel cylinders were the same. It was interesting having to carry two spare tires until I got adapter plates for the rear. Took up almost the entire trunk.
There’s a part on many helicopters called the Jesus nut. It’s the nut that fastens the main rotor to the rotor shaft. It’s called the Jesus nut because if the thing comes loose while you’re flying, that’s who you’re about to meet.
For that reason it’s tightened to exacting specs, and there’s a locking pin inserted to make sure it won’t come off, which is why it’s very rare for a helicopter to crash because of it.
In short, it’s not always the quantity of nuts, as it is the qualities of the nut and the quality of its install. Those Jesus nuts are very high quality, and they’re generally installed by highly trained people following specific procedures.
Lugnuts are often installed by an irritated motorist changing a flat on the side of the road. That’s one good reason to have lots of backups with lugnuts, and it’s why I personally set my comfort limit at cars with 4 of them. If you forget to tighten one lugnut, and you only have 3 on there, you’re probably in trouble. With 4, you’ll probably make it home and hopefully notice it when you go out to the car the next day.
Back when Integras were common you could spot a fake Type R because the poseurs just put the sticker and the wing on there, and never changed to the 5 lug hub the real Type R used.
Manufacturers save pennies all over the place and saving labor minutes is even a bigger payback for them. A factory worker in Europe or North America could easily cost an company $1.00 a minute, when you add up salary, benefits, taxes, square feet used, etc. Add in the cost of 4 extra bolts, lug nuts and all and that adds up to a measurable cost savings to go with 3 lugs instead of 4.
Only? A larger fraction of the diameter is loose. The wheel is only so strong. Even if all 3 bolts were strong enough to hold it on alone (say 25mm diameter) it couldn’t go far with only 1 nut left could it? The moment-arm is greater.