Beginner Question on tires

[Collect27]

So I have been trying to catalogue the specific code type of my cars and I want to be clear on the tire measurements. For example on the 6c Euclid Dump Truck it lists the tires as 12.5 X 45 So if I'm understanding this correctly the 12.5 is the width of the tire in mm? The 45 would be the number of tread ridges along the outside of the tire? Is this correct? The reason I ask is as I start this I have already identified to vehicles that do not match the code measurements. One is the 6c which if the above is correct is 12.5 X 40. The other vehicle is 4d Dodge Stake Truck which I measure at 12.5 X 45. Any help would certainly be appreciated.

[Idris]

So I have been trying to catalogue the specific code type of my cars and I want to be clear on the tire measurements. For example on the 6c Euclid Dump Truck it lists the tires as 12.5 X 45 So if I'm understanding this correctly the 12.5 is the width of the tire in mm? The 45 would be the number of tread ridges along the outside of the tire? Is this correct?

Yes, you have interpreted the shorthand wheel description correctly (although, in this context, 'diameter' would be a better word than ''width').

[Collect27]

Thank you for the reply, and correction on diameter vs. width. I should post a few pics later of those two.

[johnboy]

I know this will only mean small differences, but it's worth noting that the wheels were made to an imperial measurement (using fractions of an inch). The sizes quoted now are metric (to the nearest half-mm) so there will be some very minor discrepancies because of this. It really only comes into play when the wheels are examined very closely, with a Vernier caliper for example.

[Idris]

I know this will only mean small differences, but it's worth noting that the wheels were made to an imperial measurement (using fractions of an inch).

I think that's almost certainly correct, but were the moulds made to Imperial measurements, or were they oversized (i.e. with an allowance for shrinkage) in order that the actually wheels would be Imperial?

[johnboy]

I know this will only mean small differences, but it's worth noting that the wheels were made to an imperial measurement (using fractions of an inch).

I think that's almost certainly correct, but were the moulds made to Imperial measurements, or were they oversized (i.e. with an allowance for shrinkage) in order that the actually wheels would be Imperial?

A very good question, if anyone has some knowledge in this area it would be interesting to find out more. There was so much effort put into scale modelling that you would assume that this aspect was taken into account somehow in order for the final product to fit the agreed spec. But we also have the same models fitted in production with different size wheels so perhaps things were more relaxed within a certain tolerance?

[kwakers]

If I remember correctly, your country (U.K.) was not using metrics until the U.S. made a move to convince manufacturers to "Standardize" world measurements. I can't tell you exactly when this occurred, but if I remember correctly the U.K. adopted the metric system only very recently for just that reason. Of course the term 'very recently' is relative, I remember it as the late 50s or into the 1960s for this measurement scale change in the U.K. The U.S. then went off track in our thoughts, (Those Da*# Yanks), and we never changed over to metric measurements here in the U.S. at all. In our schools in the early 60s we were forced to learn both measurements as they related to each other, but the inch prevailed in production standards and measurements over here. We yanks are now stuck with both systems over here because most modern autos are now built worldwide using metric measures, threads, etc., while lots of our own products are still based in our "manufacturing Standard" of inch measurements. We yanks have to enjoy owning and packing several tool kits now for even simple household repairs today.
My thoughts are that early metal wheels were sized pretty accurately to scale for each particular model as it was designed. It would seem that the factory may have been so precise in that, the model number was even cast into the side of the early wheels for lots of the early metal wheeled models. The scale of each Lesney toy varied quite a bit back then. The normally huge 6A Euclid Dumper in it's much smaller Lesney toy scale being a prime example of fitting models to their standard size boxes, and not really to any set scale. When Lesney demand exploded in the late 50s and early 60s worldwide, my opinion is that they designed several size plastic wheels to fit the mixture of scales they had used on those early 60s trucks and cars, fitting whatever size seemed most lifelike or 'close enough' on each toy. I am sure shrinkage was factored into their mold size to give a consistent final product diameter for each size in use, but we have found several oddities through the years we cannot explain that are not seen elsewhere in standard Lesney production. Perhaps an early Club publication had related new facts concerning tire usage right from Lesney production designers from the early 60s, but Mike Stannard never touched on any other facts about them in his very informative 1985 Guide to these wheel types and their years of introduction...... kwakers