A number of French cars from the 60’s and 70’s also used three.
It’s a heck of a lot easier to replace a broken bolt than to replace a broken lug stud. It’s nothing new, a number of German cars have used bolts rather than studs and nuts for decades. Some designs have a tapered unthreaded stud that goes through an alignment hole in the wheel (between the bolt holes) to eliminate that awkwardness.
Which, according to most automotive engineers, was completely useless. The vague notion was that forward rotation would tend to tighten the lug nuts, but in practice the forces were too small to matter. Witness the hundreds of millions of cars on the road whose left-side lugs do not unscrew themselves on a regular basis…
I think the idea came from the single-nut spinners, which WILL unscrew themselves under hard acceleration etc. unless threaded to tighten against forward torque. My spinner-equipped vehicle has right and left threaded hubs and spinners, and uses safety wires to keep the spinners from backing off more than a short ways.
High performance is relative. I should have said “Vehicle with a racing heritage” since that’s where the single-nut design came from and is most useful.
Not really, no. As pointed out, the Germans have always preferred bolts to lugs with nuts. Ditto for Volvo. I can think of plusses and minuses for both.
The downside (vs center nuts) is that you can’t use a cool-ass hammer to put them on and off.
Fortunately, I haven’t had to change a tire yet. I don’t remember if my hammer is lead, but I think it is. Could have rawhide on one end. I’ll have to remember to look when I uncover it to start it up.
Another option is a wooden knockoff wrench. I don’t have one of these, but it might be nice to get one just in case. You know, 'cause I have all that room in the ‘boot’!
ISTR my first '66 MGB had a brass hammer that originally came with the car.
I had a friend who espoused that wheel nuts were an indicator of national mentality, a moments observation negates it but the theory was fun.
Three = French as that,s all you need, the Gallic engineering shrug.
Four = British, because we want more than the French, but not as much as…
Five = German ruthless efficiency leads them to over do it.
More = American because they want more of everything and they don’t change their own wheels.
That may be true; I am trying to remember what was in the tool kit of the family Mark II. Might have been a rawhide/brass hammer. I’d guess that brass was a compromise between anything harder, and anything less durable.
In any case, a lead hammer is worth having if your car has spinners. It’s the correct tool even if the manufacturer kindly provided a substitute.
The Smart car is the only recently made car that comes to my mind and has 3 nuts per wheel.
Also note that you can’t have too many lug nuts on a small wheel. The holes on the wheel will be too close together and that will compromise material strength. Those cars/trucks that have a 6 or more pattern, have big wheels and the lug nut holes are further appart from each other
Wheel lugs sometimes rust or gall.
If a lug bolt rusts solid and you twist it off, then you have the problem of getting the rusted in place, or galled broken piece out of the threaded hole in the hub. In many cases this will eventually (after gentler measures have failed) involve drilling it out and then heli-coiling the hub, which weakens it a little.
If you twist off a stud, you can press out the remains of the old one, and press in a new one, throw on a fresh lug nut, and you are good-as-new.
Also, hubs are highly loaded pieces and should be forged and heat treated. This means the threads for lug bolts have to be cut before heat treating, and the dimensions change slightly after heat treatment, so the threads have to be a little sloppier than optimal to allow for this. The plain hole for a stud is significantly less machining.
Even when I can hang a wheel on the hub, I have found it is usually a little fussier getting lug bolts started than nuts on studs. The studs usually have a short un-threaded area at the outside end that makes it really easy to start the nuts without cross-threading.
Lower the car a bit so that with the tire on the ground you can get one hole to line up. Start that bolt. Then raise or lower the car so that the other holes line up.
Personally, I think it’s easier than with nuts but it’s not a big difference either way as long as you do it right
A consideration for studs vs bolts. Bolts increase the possibility somebody will lose a high quality tire bolt then replace it with some cheap assed crap bolt. If they do that to too many bolts that tire may well come off one day.
Five is the number of the bolts, and the number of the bolts shall be five. Six bolts shall thou not use; neither shall thou use four, excepting that thou then proceedst to five. Seven is right out.
My father taught me, but it was four bolts (tighten them alternating across from each other) – since we had a Datsun B210. Yeah, that was small.
Imagine the geometry of various tire bolt patterns. Now imagine one bolt/stud broken. Now consider sideways forces on the tire as the car turns etc…
3 with one gone? Shudder. Load on other two gone way up. There is more than a whole “side” that doesn’t have support. Hope another doesn’t go!
4 with one gone? Load on other 3 still up a fair amount. About half of a “side” without support. Another one going now not quite as bad though.
5 with one gone? Load up on other 4 up but not too bad IMO. Now only a small sector with support and not so much a “side”. Yet another going doesn’t give me the willies now.
6 or more? seems pretty safe to me.
IMO, with my eyeball engineering 5 is the number where I start to feel comfortable about failure rates and modes and such.
Also, while 6 would generally be better than 5 it is possible that an odd number might have less problems with it comes to dynamic loads and resonances on the tire rim (though thats probably only a real issue for high speeds and pushing the rims and tires to the engineering limits).
It might be easier in the less-likely event of the lug bolt breaking (unless it breaks off in the holes…then good luck getting the rest of the bolt out), but for the much more common replacement of a tire, it’s a right pain in the ass. I hated putting on my old VW because it used lug bolts rather than nuts. There was only a very slight (maybe 1/4-1/2") metal “lip” that the wheel had to balance on while you inserted the bolts. The worst time was when I got a flat in the winter, at night, and the shoulder was very inclined (not so much a shoulder as it was a ditch.) Took me forever to get the wheel properly balanced on that lip, then line up the holes in the wheel with the holes on the axle, then keep it help perfectly in place while I try to slide the bolt in.
The “Ugly Duckling,” the Renault 2CV, also has three. As mentioned upthread, French cars tend to have 3.
My first car was a 1979 Fiat X1/9. It had four lug bolts. It was the first time I’d seen lug bolts (my dad had GM products).
French cars in general tend to use solutions and approaches not found anywhere else. Sometimes the solution is better or more appropriate - and the French are having the courage to do it right instead of doing it everyone else’s way - but an awful lot of the time it seems to be a deliberate rejection of a tried-and-true solution in favor of Gallic independence.
I’m fond of this quote: “Think of the Citroen as a vehicle designed by a very clever engineer who once had an automobile described to him.”
You need a “wheel pin” - a threaded metal rod that inserts into one of the bolt holes and keeps everything aligned.
http://www.leatherz.com/Merchant2/art/S3wheelpin03.jpg
Some cars used to come with these, but I don’t think any do anymore.
