New Bus Owners and Stud Piloted Wheels

[luvrbus]

Paul, my new toy has right handed lug nuts all the way around but it is hub piloted and Nascar uses right handed nuts and they are always turning left I just never could figure this one out and over the years I have seen lots of buses and trucks changed over with all right handed stud pilot nuts and never had problems.
I believe all the hub piloted nuts are right handed


good luck

[bevans6]

I just wrote to a friend of mine who worked in engineering for Chrysler back when they had left hand wheel nuts to ask the engineering reason why.  It has to do with the taper of the lug, the fact that the diameter of the taper on the nut is infinitesimally smaller than the taper in the wheel but I really don't understand it.  Since it has to do with taper (that much I do  know), lug nuts that use washers on the wheels won't have a self tightening action.  I think, but I don't  know, that hub centric truck wheels usually don't have a taper seat.

Traditional fastener technology requires a pre-load in the bolt/stud to stretch it so that it's tensile force is what clamps the parts together and keeps the joint tight.  Nascar, modern cars and trucks, just do up the nut tight enough to stretch the stud so that it all stays clamped, doesn't move, and stays together, no magic.  If you torque up a stud past it's yield limit, it will stretch permanently and lose it's clamping force, we've all seen that with over-torqued wheel nuts.

If my friend comes back with an engineering description of how the taper works to self-tighten, I will copy it here.

Brian

[Dreamscape]

It might make sense to make them all the same, so some of the younger shop guys won't try to overtorque when removing!

Can this be done on our oldies? I'm leaving ours alone at least for now!

You brought up a good subject!

[luvrbus]

Paul, when I was a young man my Dad owned a lot of trucks and trailers with the spoke type wheels all of those were right handed nuts on both sides well that is the way I installed them  lol



good luck

[Dreamscape]

Clifford, You're showing your age!

[Busted Knuckle]

Clifford, You're showing your age!

Paul he means "Dayton" hubs (not old time wagon wheels) that had like a 5 spoke hub with studs on them and a wedge and nut went on them to clamp the wheel in.
Had to tighten the wedges just right or they would wobble like crazy.
When I was taught to tighten 'm I was shown to put a coke bottle beside the tire and spin it watching for run out and you'd loosen opposite of that spot and tight at the spot and so on until it turned true!
  BK 
Also hated those lock rings on those split wheels

[Busted Knuckle]

Clifford I'm like you never made since to me either.
My theory has always been someone did it so others did too, because so & so must know something we don't!
  BK 

[Dreamscape]

BK, That is what I was thinking of, just didn't know what they were called.

Thanks for the history lesson!

[gus]

BK,

Jack has it right.

My left hub has right hand threads and my right hub has left hand threads, just the opposite way it was originally. You can believe I always point this out to tire jockeys!

Just before I got the bus it had all new brakes and shocks so the mechanics obviously replaced the hubs reversed.

I had a '67 Barracuda with L and R wheel studs. I had them damaged so many times by air wrench jockeys that I finally just made them all RHT with no apparent problems of any kind.

[bobofthenorth]

I always thought it was so truck drivers just had to remember "tighten toward the front".

[bevans6]

There is a legitimate self-tightening action with right and left hand thread tapered seat wheel nuts that has to do with the rotation direction of the wheel.  I used to know what did it, my engineer friend admits that it is there but also forgets.  It has to do with the way that a taper has different diameters top and bottom, if it loosens there is a small diameter on the nut touching a larger diameter on the  seat in the wheel, gyroscopic precession requires that the smaller diameter touches the larger diameter which is rotating slower than the smaller diameter of the wheel nut and kicks it forward, in this case towards tight rather than loose.  It sounds logical yet hocus-pocus to me, but working on race cars I know that it works on tapered knock-on or center lock wheel nuts, it's an observable phenomenon, but intuitively you would expect a nut on the axis of rotation to have a greater effect than the lug nuts on our wheels that are 5 inches out from the axis of rotation..

I was googling around and found an article that implied lower failure rates on heavy trucks for left hand thread on the left, but it was inconclusive.  MCI states that stud-centric wheels with taper nuts have left hand threads on the left but right hand threads all round for hub-centric wheels with non-tapered nuts.  In my opinion, it is reasonable to conclude that if a tapered or ball seat wheel nut is loose, from fatigue, yield in the stud, or other reasons, left hand thread on the left would probably act to keep the nut on the stud and possibly keep it marginally tight, but not very tight.  In other words, I think that for tapered and ball seat wheel nuts on buses, there is indeed a real reason for left hand thread on the left, but I have only a faint understanding of the physics involved.  I will have to go on trust and yes, I will be re-torquing the inner Budd nuts on the drives before my next trip....

http://www.mcicoach.com/fyiFromMci/maintMatters/0410.htm

cheers, Brian

[kyle4501]

The reason for left hand on the left & right hand on the right is IF the nuts become loose for what ever reason, they will not continue to back off due to the rotating action of the wheel. When going forward, the right side wheels are rotating clockwise from the nut's perspective, on the left side, the wheel is rotating CCW from the nut's perspective.

I had the pleasure of a tire shop leaving 3 nuts loose on the left rear of my car (I did a walk around to be sure they hadn't damaged the painted rims, center caps or trim rings, so I'm sure I'd have noticed a missing nut or 3). Later that day after the 3 nuts had left the studs, the 2 studs that were tight snapped off & let the wheel go its own way. I then checked all the tires & found some loose nuts on the right side, but they were still touching the rim. 

No, I don't think left hand threads on the left side is necessary, but it does provide another level of safety.
So, yeah, I'm a believer that the left handed threads are a good thing on stud piloted rims - even if it is a pain in the neck! 

[busshawg]

That's exactly why I tighten my inside wheels 50 lbs worth of torque more than the outside on these old bud wheels.