Wheel Nuts - Right Hand and Left Hand Thread

[scarbs]

Pat Symonds did a detailed explanation in Racetech earlier this year, on loosening wheelnuts and why they a direcitonal fitment.

[xpensive]

Pat Symonds did a detailed explanation in Racetech earlier this year, on loosening wheelnuts and why they a direcitonal fitment.

Most interesting scarbs, having seen images of a Formula One wheel-nut, with that steep trapezoidal-looking thread, even doubled at that, this might play a more important role than anticipated, JT?

[hardingfv32]

When you torque the wheel nuts and send the car on it's way, there will be a fair amount of contact force between the nut and wheel. My understanding of the concept is that under braking, if there's any slop between the wheel and the drive studs that allow the wheel to rotate a bit... there is enough friction between wheel and nut to drag the nut in the direction of rotation and self-tighten it.

This explanation does not represent the situation on street cars and the left hand threads found on one side of many OEM cars. The OEM guys did not do the left hand threads without reason.

Might they be concerned about the effects/drag caused by a wheel bearing failure?

In the case of an F1 car, we would want to note the thread direction of the stub axle retainer collar/nut. And in fact, the Williams F1 titanium front stub axle I have does use left hand threads. I do not know what side of the car this axle is from.

Brian

[hardingfv32]

Pat Symonds did a detailed explanation in Racetech earlier this year, on loosening wheelnuts and why they a direcitonal fitment.

Can you give a brief summary of his statements... WITHOUT infringing on his copyright?

Brian

[Jersey Tom]

This explanation does not represent the situation on street cars and the left hand threads found on one side of many OEM cars.

I think it does. Why wouldn't it?

I assume you are referring to OEM vehicles with single wheel nuts (which I haven't seen on any current production car!). I have not seen or heard of a vehicle using multiple lug nuts per wheel that have LH and RH threads depending on position.

Then again.. OE's do dumb things sometimes.

[piast9]

I am not sure if that has any reference to the thread direction in F1 but in bicycles it has nothing to do with the inertia or friction but the complicated, precession movements that happen when the machinery is working.

Look at the threads in the pedals or in the bottom bracket in your bicycle. Their direction is exactly opposite to what seams reasonable. If you pedal forward and hold the axis of the pedal (exaggerating the friction inside the pedal) it would unscrew itself. But in real life it actually tightens because of the asymmetric load which changes direction and causes the precession of the pedal axis in the hole at the end of the crank.

[strad]

not seen or heard of a vehicle using multiple lug nuts per wheel that have LH and RH threads depending on position.

Told ya..Chrysler did it up until the early 60s.
Wiki says..

Some cars made up to about 1960 used left-hand and right-hand threaded lug nuts for different sides of the vehicle to prevent loosening, until it was realized that the taper seat performed the same function.

[balangproject]

Aha, like over-torqueing the nuts on one side of the car and loosening them on the other due to the rim slipping when braking?

Right. And by flipping the thread direction on one side, you make them ALL tighten under braking. Now you can make the argument that drive torque will want to loosen them, but we can pretty safely believe that aggressive braking events are going to be more severe than driving.

Anyway, there probably isn't much slop between the drive pins and wheels, so I don't think the effect is that great. The positive lock is the more effective thing.

This would seem correct, except the threads are left-handed on the right side and would therefore loosen under braking. The clockwise motion of the wheel on the right side is opposed by an anti-clockwise force on the hub under braking, therefore the slight clearance in the drive pins would make the nut loosen in a clockwise direction (LH thread).

Pat Symonds did a detailed explanation in Racetech earlier this year, on loosening wheelnuts and why they a direcitonal fitment.

Can you give a brief summary of his statements... WITHOUT infringing on his copyright?

Brian

Would be great.

[hardingfv32]

When you torque the wheel nuts and send the car on it's way, there will be a fair amount of contact force between the nut and wheel. My understanding of the concept is that under braking, if there's any slop between the wheel and the drive studs that allow the wheel to rotate a bit... there is enough friction between wheel and nut to drag the nut in the direction of rotation and self-tighten it.

This explanation does not apply to street cars because they almost always attach their wheels with studs and or lug nuts. There is no opportunity for slop.

Your explanation is correct for single nut wheel retention systems.

My reference would be to axle or hub retention systems, so maybe somewhat off point.

Brian

[riff_raff]

Race Tech no.115, p.34-38.

http://issuu.com/thisisnotadrill/docs/rceteh115webpub

[strad]

I was tired after work...summerize please.

[Richard]

Look at the threads in the pedals or in the bottom bracket in your bicycle.

Agreed, bicycle pedal threads are handed so they don't work loose.

A lot of HGVs and buses in the UK now have indicators to show if a wheel nut is coming loose. Most lorries seem to have them nowadays, I'm not sure if it regulation or insurance that is driving their adoption.

http://wheelsure.co.uk/wheelsure/why-wheel-loss-occurs

Here are some visual indicators



While others are interlinked so a loose nut is restrained by its neighbour

[Richard]

I was tired after work...summerize please.

Summary:

It is easier to describe for a road car with wheel bolts.

There is clearance between the bolt and the wheel. The weight of the vehicle pushes the bolt to the bottom of the hole in the wheel. So as the wheel moves forward, the bolt shaft rotates in the clearance hole like a planetary gear.

Of course if the bolt is properly tightened then the contact friction between the wheel and hub will avoid this movement occurring.

Symonds mentions statistical data that shows loose wheel nuts/bolts occur equally on both sides of vehicles, but detached wheels are much more common on the left side, regardless of which side of the road the vehicle uses. Hence one can conclude that loose wheel nuts is a function of poor workmanship or equipment (independent of the side of the vehicle), but if a nut is loose, then it is much more likely to be unwound by the rotation of the wheel on the left side of vehicle.

[SpookTheHamster]

There's an excellent thread already on the fsae forums about single wheel nuts: http://fsae.com/eve/forums/a/tpc/f/1256 ... 4610603711

How are you justifying the need for a single wheel nut and the risk it brings in a series where there are no pit stops to reap the benefit of a fast wheel change?

[Jersey Tom]

Not sure I'd say there's much inherent risk with it. Do a castle nut with a pin and you're set.

When I was doing it, the big advantage was producing a lightweight and simple hub.