Lancia Motor Club

Model Technical and Interest => Aprilia, Ardennes and Ardea => Topic started by: BlueSky on 16 December, 2008, 09:06:39 AM

Title: Wheel nut threads
Post by: BlueSky on 16 December, 2008, 09:06:39 AM
This might be a silly question.

Aprilia wheel nuts are left-hand thread, sinistra, and right-hand thread, destra, hence the S & D stamped on the nuts and the end of the wheel studs. I believe that the left ones go on the left side (passenger) and the right on the right side (driver), is this correct?

My car has them the other way around, I only discovered the difference on the weekend when taking the wheel off a friends car. So is the theory that the nuts should do up in the same forward direction that the wheel rotates so they won’t undo themselves? Has anyone ever lost a wheel from the nuts undoing themselves?

I would also guess that most cars the left-hand thread nuts are pretty buggered through repeated tries to undo them the wrong way.


Noel Macwhirter

Title: Re: Wheel nut threads
Post by: GreenB20 on 16 December, 2008, 04:52:23 PM
 :)Yes you are correct, l/hand thread on n/side

Title: Re: Wheel nut threads
Post by: JohnMillham on 16 December, 2008, 09:57:09 PM
I have never understood why they bothered to use left hand threads on bolt - on wheel nuts. I don't think it will make any difference, as they won't tend to come undone of their own accord anyway, whichever thread they have.
It's obvious why left hand threads were employed with with knock - on wheels, where the left hand threaded spinners are on the offside of the car, as they are then doing themselves up when the car is going forwards, which it is assumed to be doing most of the time!
 Regards, John

Title: Re: Wheel nut threads
Post by: Philm on 16 December, 2008, 10:27:49 PM
You only need handed threads with a single, central nut or spinner.

Title: Re: Wheel nut threads
Post by: BlueSky on 17 December, 2008, 12:34:58 AM
You see this is where we got confused. I think most knock-on wheels have the left hand threads on the right side of the car, see the pic of the 1934 SS wheel, or maybe it's just an English thing. And as you say they're not about to come undone and I'm not about to pull the rear hubs apart to change them over quite yet. This was just one of many differences we noticed with the two Aprilias parked next to each other, good fun.
cheers, Noel.

Title: Re: Wheel nut threads
Post by: davidwheeler on 18 December, 2008, 11:17:19 AM
Freyja's 1970 Alfa 1750 spyder is similarly endowed but I cannot remember offhand which way round they are.  My own Aprilia has sinistra on the nearside.  Seems to have been an Italian fad.

Title: Re: Wheel nut threads
Post by: johnturner on 18 December, 2008, 07:02:58 PM
Not so, my old AC (1926) had right and left hand threads on the wheel nuts but I'm buggered if I can remember which way round they were fitted. And it isn't always true that spinners will wind themselves up as the wheel rotates. If the splines are worn, a sharp stab at the brakes can cause the splines to strip, the spinner to unscrew and the whole lot, wheel and all, disappear down the road, as Nevil Buckle once demonstrated in his Lambda.

Title: Re: Wheel nut threads
Post by: davidwheeler on 02 January, 2009, 02:09:43 PM
This happened to me also and without the braking and only on the offside.  I eventually determined that it was due to a thick and spongy layer of powder coating on the cone preventing proper tightening of the nut.  I have cleaned the cones to bare metal and no further troubles though I now wire the nuts on just to be sure  (this really belongs on the Lambda thread!).  Rudge Whitworth's original design had cone roller bearings on to which the nuts bore but it was found I guess that plain metal cones did as well.

Title: Re: Wheel nut threads
Post by: ben on 15 April, 2011, 10:13:56 AM
Hi Noel
         I am sorry it has taken me nearly 2.5 years to answer this query!
         The wheel nuts with left-hand threads should indeed be on the left-hand side of the car for the Aprilia. The mechanism that tends to make them come undone is an epicyclic one. If the wheel is well located by the big central spigot there is no problem as the wheel cannot orbit on its mounting. However if there is any significant clearance at the spigot interface, as the car rolls along the wheel will tend to orbit (because the load vector is rotating relative to the wheel) within this clearance space.
         Modern cars usually have fairly tight fitting location spigots to the extent that it is sometimes quite difficult to remove a wheel even after the nuts or bolts have been taken off. The spigots on the Aprilia ore not usually tight so orbiting can try to occur. This is prevented by the wheel nuts if they are done up tightly but the epicyclic friction forces will be nagging away at them all the time so I would advise you to keep checking them regularly.
          Presumably if it is just the rears that are the wrong way around it was just chance that led to this situation during the previous rebuild of the car back in the UK.If the fronts were wrong as well one might suspect the restorer was familiar with knock off Rudge-Whitworth type hubs and did it deliberately! As has been posted allready these are installed the other way round. This is because the clamping interface between the nut and the wheel is inside out compared to the ordinary wheel nut. For the ordinary nut the conical nut face is the inner or male member and the corresponding face in the wheel hole is the outer or female member. However the design of the knock-on nut is such that the nut forms the female member and the corresponding conical face is
on the outside of the hub and so forms the male member.     

Title: Re: Wheel nut threads
Post by: ben on 15 April, 2011, 10:57:27 AM
       I ran out of space before concluding the previous post where I was going to add that this issue would have been much more significant for many vintage cars with conventional nuts and no location spigots!
       The loosening tendencies of knock- off hubs are exacerbated by loss of location due to wear in the splines which contributes to both orbital and rotational movement. Only once the spinners have become loose do the more obvious inertial effects come into play. That is to say they may lag behind during acceleration and tend to keep spinning when the wheel slows during braking. One or other of these operating phases will cause a loose spinner to fall off whether the thread is left or right handed. I mention this to again emphasise that the thread hand is chosen to combat the epicyclic "creep" arrising from orbital motion at the clamping interface.
      Obviously conventional nuts or studs are not subject to the inertial forces but are vulnerable to the epicyclic creep if they are not protected by a tight spigot.