left hand threads on left hand wheel studs

[Bevans6]

This is a question that I have tried hard to find a legitimate answer for, I hope you can help. It relates to large vehicles with stud centered wheels, where the common practice is to use left hand thread studs on the left had side of the vehicle. The common wisdom is that there is a self-tightening action from having the lug nuts on a counter-clockwise turning wheel tighten in a counter-clockwise direction,, but it is related to the taper (or ball) seating of the lug nut onto the wheel, since washer style lug nuts used with later hub centered wheels use the more common right hand taper all the way around the vehicle.

So the question is - what is the engineering reason for using LH studs on the LH side of the vehicle, and what is is physical phenomenon that is causing a taper seat lug nut to require this while a washer seat lug nut doesn't?

thanks very much, Brian

 

[Alec186]

I have wondered myself why some car makers did this. The Chrysler Valiant (in Oz) was like this - very awkward undoing the wheel nuts if you didn't know they were left-hand threads. Does any company still use this system?

 

[patprimmer]

A whole lot don't do it and they have no serious issues with wheels falling off, so at best it could be seen as an extra expense and complication to solve a non existent problem while creating a new problem for non suspecting owners when the need to change a wheel.

Regards
Pat
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[FoMoCoMoFo]

I suspect it has nothing to do with lug nut type.
Maybe the more modern washer style is just accompanied
by more modern theory,
(that the Coriolis effect is too small to worry about)?

It's definitely more trouble than it's worth.

 

[evelrod]

A few of the pre war theories made it post war. One of which is the left hand thread on the wheel cap screws (Chrysler products in my experience). Like has been posted, my dad told me it was because in the early cars the left side wheels tended to loosen in use. Dunno. Never thought too much about it...just pleased that it's no longer a problem.

However---This is for those of you that have owned and/or raced pre war and post war MG's---They did have a nasty little habit of loosening the left rear axle nut (RHT) allowing the drum to come off, BTDT! Some later Ford/UK cars had problems with the LF nut backing off due primarily to a faulty stamped 'tang' washer and improperly packed wheel bearings, also BTDT!

Of course, on the other hand, a LHT axle nut could have caused the bearings to seize from being overtightened??? Well, maybe not as I never had any problems with right side axle nuts.

Live long enough, own and drive enough miles in old (pardon me, VINTAGE) cars and your sure to find the built in/design flaws. I never had a wheel loosen because of LHT/RHT OEM design, old or newer cars. I just chalk it up to "lack of sufficient knowledge/customary design" of the times. Times when if "X" would probably work okay, then let's go "2X" just to be on the safe side. Bean counters nightmare?

Rod

 

[CoryPad]

Q: What is the engineering reason for using LH studs on the LH side of the vehicle?

A: As you alluded to, it is due to the idea of self-tightening of the threaded fasteners from rotation of the clamped (but almost unclamped) components.

Q: What is is physical phenomenon that is causing a taper seat lug nut to require this while a washer seat lug nut doesn't?

A: None. As FoMoCoMoFo stated, nut-washer assemblies are newer and it has been found over time that left hand threads do not provide enough value/benefit for the effort/cost involved.

 

[theAAman]

As an AA patrol and oncea service manager in the Commercial vehicle sector I have seen a number of vehicles were the wheels have come loose and lost from the left hand rear wheel station. Even with the correct torque setting wheels will still come loose on the left hand side of the vehicle. This esp found on light commercial vehicles ie 3.5t to 7.5 tonne.

 

[RossABQ]

Rod, I had a big Healey that stripped the splines on the LF wire wheel; when I'd put on the brakes, the hub would stop, the wheel would not (it made an "interesting" noise!!!). It had (as I recall) LHT's on the left side of the car. If it didn't, when my spines stripped, the knock-off nut would have unscrewed the first time I put on the brakes.

Could this type of experience be the origin of this practice?

 

[evelrod]

Probably not, Ross. I think I've seen LHT on the lug bolts of a pretty early 20's car...Plymouth/Dodge, maybe?

I did have the LR wheel of my 50 TD come off once. Stopped with the hand brake and walked back to pick up the shoes, springs, etc. Put it all back together and continued on. Ahhhh, the good old days.
In 1962, the Lucas electrics failed on our 58 MGA coupe between Heber and Snowflake AZ (look it up) and taped two flashlights to the roof...and...continued on...Life's little ups and downs, eh?

Rod

 

[RossABQ]

"the Lucas electrics failed on our 58 MGA coupe"

Go on! Not really?! LOL In all fairness, I have to say none of my Brit cars ever had the usual Lucas issues. Brit motorcycles, that's a different story...

 

[WhizzMan]

Maybe the Coriolis effect does work on bolts that aren't tightened enough? You still do see these still in practice on some modern vehicles, but most passenger cars tend to just use a normal thread these days.

Wheel bolts on passenger cars (only thing I tinker on) that come off, usually are because of the wrong torque used, wrong bolts being used (wrong angle for the centering bit, too short thread part) or stripped threads in my experience. People do underestimate the importance of the correct torque being applied on bolts in combination with cast alloy wheels. Deformation of the rim and metal fatigue in the bolts leading to bolts loosening and shearing is probably too complex for car mechanics and owners.

 

[Tmoose]

On the few dozen alloyed wheel vehicles I have known the clamped interface surrounding the bolt/stud is "solid metal." Thus all the "stretch" occurs in the bolt.

Steel wheels on cars often (but not always) have some arch or contour near the bolt that puts the bolt/nut seat on a plateau or mezzanine up in the air, similar to a belleville washer.

http://image.made-in-china.com/2f0j00JMHtmDwdpzcZ/Steel-Wheel.jpg

http://www.hubcaps-wheelcovers.com/photo/img_3070 (2).jpg

So when thing are tightened the arch flattens as the wheel deforms elastically.

Since maintaining preload ( one of my best friends) requires that the amount of stretch far exceeds the potential embedment, etc, alloy wheels would seem to have a much greater chance of becoming loose over time than typical passenger car car steel wheels.

Tire shops often have a standard note on their invoices saying cars with alloy wheels must be returned for re-torquing in XX days/miles. The Sears service writer looked at the sculptured plastic factory hubcaps retained by the lugnuts on my mom's Honda and told me I had to come back for a re-torque, and stamped my receipt accordingly.

http://www.realpolice.net/forums/archive/t-89565.html

http://www.normarkindustries.com/LooseLugNuts6.25Million.htm

 

[evelrod]

Funny thing happened on the way to victory in the Japanese Grand Prix at Suzuka last night...Seems that a couple left rear wheels came off during the race....Hmmmmm !!!

Rod

 

[WhizzMan]

Formula 1 wheel nuts have a locking mechanism and are single centerpiece items. If the mechanism fails, inertia alone would make it possible for them to come undone. True, there are similarities to the multi-bolt setups for passenger cars, but I don't think it's a fair comparison.

 

[Tmoose]

These two reports say Kubica lost his right rear wheel -

http://www.gpupdate.net/en/f1-news/244618/kubica-out-after-losing-wheel-at-suzuka/

http://www.grandprix.com/race/r836racereport.html