Why left hand lug nuts?

FLATBEDFORD · Post by **FLATBEDFORD** » Sat May 13, 2006 11:57 am

Why did they put left hand studs on cars and trucks back in the day? I thought it was because the nuts would loosen with the rotation of the wheels. Why did that become not a problem? My truck has left hand threads on ONLY the left rear. I broke my 1 1/16 socket finding this out the other day. Had to go to Sears to exchange it.

fordman · Post by **fordman** » Sat May 13, 2006 12:00 pm

thats what i thought too. because of looseing lug nuts on the tires.

xxxtina63 · Post by **xxxtina63** » Sat May 13, 2006 12:04 pm

Not sure why on older cars, but the tech is still used on semi's and their trailers. One side has left hand, the other has right to keep them from coming loose.

68F250 · Post by **68F250** » Sat May 13, 2006 3:10 pm

That's a good question. The knock-offs on both my Triumph TR6 and Spitfire had left-hand threads on the left side and right-hand threads on the right. If you accidently put the hub adaptors on the wrong sides of the car, the spinners will eventually come off!

Older cars also had the left and right lug nuts. Maybe the conical lug nut seat and higher fastening torque solved the problem but Chrysler was the last hold-out on these, don't ask me why. When was the last time you saw a wheel come off a car?

FLATBEDFORD · Post by **FLATBEDFORD** » Sat May 13, 2006 3:53 pm

I can understand center spinners needing left hand threads, but not regular studs. What baffles me is that it was once important but isn't anymore. What changed?

68F250 · Post by **68F250** » Sat May 13, 2006 4:20 pm

Well, wheels used to come off cars, hence the left and right lug nuts. Last year for Chrysler was '70 I think. Guess we need some old-timers to respond.

Here's something I found googling, where do you get a wrench like that?

https://www.logsa.army.mil/WEB-PAGE/200 ... -06-07.pdf

bluef250 · Post by **bluef250** » Sat May 13, 2006 4:33 pm

Chrysler used bolts (left and right threaded) then changed to nuts on studs to secure wheels. Chrysler was a great company for doing engineering on products. Since old habits die hard I guess the left and right studs followed suit. Did the other car companies use left and right handed threads on wheels? I know in some critical applications left hand threads are still used. They do not back off with torque associated with the application.

dotcentral · Post by **dotcentral** » Sat May 13, 2006 11:30 pm

I just read an article on this topic, In Hemmings Muscle car I think. It said Buick, Olds, & Pontiac had left handed studs & lug nuts into the 60's.

As far as a car loosing a wheel, This happens from time to time if you take your car into somewhere like Jiffy Lube and get a tire rotation. Happened to one of my relatives a couple years ago. Not the wheel studs fault, but still going to make for a bad day if it happens to you.

Leadfoot · Post by **Leadfoot** » Sun May 14, 2006 4:23 pm

That was my question to may years back.
And after talking to a very old engineer they told me that with the left hand thread on one side and right hand thread on the other it some how rased the strength and load capacity.it was a long drawn out conversation. he told how it worked but I just can't explain its over my head.

All I know is if you work on a one tonne do yourself a favor and remember at the end of the stud there is a L or R that tells the thread direction.

basketcase0302 · Post by **basketcase0302** » Mon May 15, 2006 5:26 am

Leadfoot,

Been there, done that

After breaking 1/2 drive extension, saw the "L" on the end of the stud

Kinda makes it real hard to get some specific "shiny" lug nuts too!

Basketcase

surubet · Post by **surubet** » Mon May 15, 2006 8:57 am

I had a 1970 Dodge Charger Magnum SE that had the lefthand lugs and studs on it. Even in the early 70's, auto shops paid no attention. So they cross threaded righthand nuts onto lefthanded studs and vice-versa. It wasn't long before I discovered the problem. I ordered new studs and nuts from the dealership. Now you would think the lefthand studs and nuts would be in one bag and the righthand in the other, but not so. They shipped me two bags of mixed parts. I checked the first bag and it had a lefthand stud so I replaced all the lefthand studs and opened the next bag to do the righthand. Well I got them all installed and went about putting the wheels back on and found much to my dismay that I had mixtures of righthand and lefthand studs in every wheel.

Never lost a wheel or lugnut and figured the mixture was a fine addition to keep thieves from stealing my wheels and tires.

Also owned Ramblers ... many of those had lefthand studs on one side. I changed them all to righthand studs because the dealer couldn't get the lefthand ones anymore. Never lost a wheel on those either.

But it is interesting about the knockoff spinners. A buddy had an import with those and his spinners were always coming loose on both sides of the vehicle ... bet they were on the wrong sides of the vehicle.

Later,
Steve

Galaxie64 · Post by **Galaxie64** » Mon May 15, 2006 12:38 pm

I never really thought about it but my '56 1 ton has left hand nuts on the drivers side, never thought about why they didn't need them all the sudden.

Leadfoot · Post by **Leadfoot** » Tue May 16, 2006 3:36 am

but Ford put left hand lugs on the high pay load f350's all the way ta like '90. it was really common on the one tonnes duals.

basketcase0302 · Post by **basketcase0302** » Tue May 16, 2006 6:17 am

Could it be because...If the axle is a "traction-lock" type axle with clutch discs in it and the drivers side is the "normally driven axle side"?

All the torque on the one axle shaft under normal conditions?

Basketcase

68F250 · Post by **68F250** » Tue May 16, 2006 1:20 pm

Commercial trucks today still use left & right hand threads on the front and rear wheels.

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