[CMOTD]

I wouldn't trust any slot car manufacturer to be accurate in this respect. I am also intrigued to know why, in the real world, it is necessary to identify which side is which. How would it make any difference and in what way would each side's tyres vary? There are left and right hand corners on all normal circuits so surely both sides need to be the same.

NASCAR and Indycar are, of course, different as banked curves need special set ups with different pressures on each side. Martin Truex  found this out to his cost a few years back when his team got them mixed up in the final race and he had a car which which wanted to turn right instead of left and it ultimately cost him a championship.

[Qman]

As stated earlier it's to differentiate left and right hand thread.

[Top Down]

Correct - the thread on the wheelnuts, although there are asymetric directional tyres too nowadays, it's the thread that's important.

[Top Down]

Never seen wheel/tyre stacks in the pits with the crayon mark on the treads? LF, RF, LR, RR? (Left front, right front, etc.) 

Seen the wheel changes at Bathurst where they only change the left or right sides, not all four?

Or Rallying where they sometimes have a diagonal F/R mix of soft and harder tyres? All marked up ready to install.

[CMOTD]

Thanks for the explanation folks, sorry for being a bit dim on the subject, I get it now.

However, OCD has now kicked in and I have had to go and check all my other slot cars for colours of lug nuts. The only one I have found with it so far is my Revoslot McLaren and that has got the colours the opposite way round with red on the left side and blue on the right. Is there a set standard in the 1:1 world and is it the same in all categories of racing? Mr Google has been distinctly unhelpful on the subject. I am surprised that the rivet counters out there have never raised the issue before as it would seem to be an ideal subject for their deliberations on model accuracy.

Just to muddy the waters even further, I own a set of full size genuine NASCAR lug nuts from one of Tony Stewart's cars and they are yellow! Does the same system apply with multiple nut wheels or only single centre ones?

[Savage GT]

Only single nuts in most cases I imagine. Although I have seen some military vehicles with multiple wheel nuts that were colour coded due the thread handing.
Multiple nuts are less likely to spin undone as they are less affected by wheel rotation, but centrally mounted ones are more at risk of that, hence the left and right threads.
Yes, I would say the colours should be universal where used, so one of the slot cars is wrong.

[Top Down]

Only single centered. 

Not sure what the protocol is re: colours but my MR Slotcar Mclaren F1 has the same detail - coloured centre fastenings.

[Top Down]

In 'the olden days' when some sports and racing cars had two or three eared centre spinners 'directions for use' were actually cast into the face of the spinner. 
   
Nowadays, with pit stops of seconds rather than minutes, I guess colour coding is a quicker and unmistakable visual aid.  

Unless of course slot car manufacturers get it wrong 

[Top Down]

Brightly coloured e.g yellow  - lug nuts makes it easier to spot whether one has not been replaced, or if dropped, where it's gone. Plain steel just 'disappears' on tarmac.

Not sure whether this and coloured centre spinners are mandatory or just something 'right thinking' pit crews have adopted as 'sensible' though?

[Top Down]

" .... rotation of the wheel on the hub under braking will cause the nut to rotate on its thread. If this rotation is in the correct direction — which is ensured by using differently handed threads on either side of the car— then the nut will automatically retighten itself."

Explanation found on the web.