When you have 5 lug nuts, the nuts do not unscrew as the car goes down the road, no matter which way the threads go. But it DID matter on stage coaches and covered wagons, which had only one nut. Early cars had LH and RH threads because mechanics who worked on both cars and wagons EXPECTED LH and RH threads. As wagons faded out, the practice continued, until there were more people confused by LH threads.
Here’s a great link that describes, with test results, that it was a fail-safe mechanism Chrysler used, which became relevant in cases where lug nuts were not properly tightened.
I was 16 and working in a gas station. The phone rang, I answered it. It was a customer who was furious at us. He began screaming and swearing at me saying: “You guys installed snow tires on my wife’s car two weeks ago. Today I’m replacing a flat tire in our driveway and the lug nuts are so tight that I snapped two of them.” (It was a Chrysler product). I relayed the message to the mechanic on duty, who said: “Ask the guy if he knows which way to turn the lugnuts.” I told that to the customer, and it only made him swear more and get angrier at us.
20 minutes later he called back to apologize.
Not to get too far OT, but left-side bicycle pedals still incorporate reverse threading, for the same reason: using the pedals tends to keep the pedal tight, vs loosening it.
That’s right @meanjoe75green. The same with the crank nut. The bearing race retainer nut on the wheel hubs as well. Wheel lugs on rims don’t need to be as they are not directly affixed to the revolving hub whose rotation can work with or against the nut.
When much younger, I remember casually pedaling backwards while coasting just for the hang of it. My pedal did indeed come off. Lucky I ride with toe clips and it stayed suspended from my foot. A little disconcerting to say the least…
The threaded portion of the flush handle on many toilets has a left-hand threads. The first time I tried to remove a broken flush handle many years ago, I couldn’t understand how they got it on so tight. I decided to “rock” the nut back and forth and when I turned it the opposite direction, it came right off.
Well, Ken, I would say that you are correct. However, there are a lot of “left hand” nuts on things for good reason. So they wont come off being used.
And occasionally for reasons not mechanical…like to prevent propane tanks from being screwed onto things that should not have propane tanks attached…
Joe, you made me laugh. I clearly remember all the problems those Chrysler left-handed lugs caused.
One of my first days on the job at the garage was a tire repair on a Mopar…yep, busted the stud. At least I stopped at one!
One of my first cars was a nice '63 Bonneville with the 8 lug wheels. My dad drove it down to Sears to have a new set of tires put on since he worked right across the street. Sears called him and said that there was a problem and he needed to come over and take a look. One side had new tires on and the other side (left hand thread lugs) had all 16 lugs broken off. My dad knew about the left hand threads and told the manager that Sears would have to pay for the new lugs. His reasoning: Why would you keep breaking off all the lugs after the first one broke? Sears paid for the new lugs and I got my new tires.
My old 1969 Dodge Dart was the only car I ever drove with backwards lug nuts on one side. Luckily, I figured it out without breaking a stud.
One of the most interesting use of left hand threads that I have heard is the light bulbs on the older New York subway cars. People were stealing the light bulbs. Someone came up with the idea of having custom made sockets and light bulbs. Even if the thief did figure out the system, the bulb would be useless to him.
My 52 truck has lh/rh nuts on the wheels. They are marked “R” and “L”.
When I first got it and started doing some brake work, I noticed that the previous owner had swapped the rear drums (which hold the hubs) so I guess it doesn’t make that much difference.
That’s a pretty good trick to come up w/the idea to use left hand light bulbs to prevent light bulb theft! It’s sort of like those special bolts they use in public restrooms, which – if you want to steal the stall door – it can’t be removed w/out a special tool. One thing I’ve always wondered: Why would someone want to steal a public restroom stall door! That’s really a puzzler. Whoever would want to do this, they must have a good story to tell their grandkids anyway.
I’d have never gotten this puzzler about the lug bolts. My idea was that the spare tire was flat, that’s what a bonehead I am! I was completely unaware of this using of left hand thread bolts on older cars. I wasn’t even aware wheels falling off was even a problem if the lug nuts are properly tightened. Maybe wheel bolts didn’t work as good as they do now, or they didn’t have torque wrenches as a common tool back then?
Hey, guess what? For a change, I do think I know the answer to this week’s puzzler. One out of 20 ain’t bad, eh?
I had a 68 Newport that had reverse lugs, and it would outrun anything on the road.
They stopped putting big blocks in Newports in 1966 I think, but mine was a Special order of a “high output” big block 383 and heavy duty 727? transmission. Still had a special build sheet pasted to rear trunk panel.
It was a real sleeper, would pretty much embarrass any car on the road when I had it in the 90’s.
The use of RH and LH threads on multi-lug wheels is irrelevant, since the lugs are not being rotated in either direction, as they are off-axis, and are not subject to the wheel rotation forces. However, it is a factor on more “specialized” wheels.
I own a 1969 Jaguar XKE. This vehicle has true racing-type wire wheels, with a single, large “knock-off” hub in the center. On this, the thread type is critical, and is chosen such that the forward motion of the vehicle, results in the tightening of the single hub. Each side has an arrow on it to note the removal direction. Curiously, in the ever colorful British system of naming things, the hubs on the right side of the car are labeled “OFF” (you would think that it is to take the hub off. Nope.) and the left are labeled “NEAR.” The labels refer to the “nearside” of the car (close to the side of the road) and the “offside” of the car (furthest away from the side of the road). For the UK, that is correct, but here in the US, the labels are wrong: near would be the right, off would be the left. Obviously the fancy knock off hubs were designed for the British home market… everyone else beware.