# LEGO Tyre Measurement Guide

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#### It’s well known that LEGO tyres are notoriously difficult to identify, so we set about developing a standard method of measurement that could both identify and describe LEGO tyres.  We hope you’ll find the following Brickbrowser Guide helpful.

 If you have a spare tyre to hand, all you’ll need is a sheet of white paper (for high contrast background) and a ruler or tape measure with millimetre increments.  For difficult to measure balloon tyres like the 54120 pictured on the right, you’ll need to construct a simple measuring tool (using LEGO of course!), but more about that later…

### Simple Tyres:

Let’s start with a straightforward tyre and look at how we’ve named it using our new nomenclature:

60700: NEW Black LEGO Tyre Ø21/12x12mm Wide

If we strip out the standard number and colour info, we’re left with just the tyre measurements of:

Ø21/12x12mm Wide

The dimensions before the ‘x’ describe the Outer/Inner diameters.  The dimension after the ‘x’ pertains to the tyre width, so our 60700 tyre has an outer diameter of 21mm, an inner diameter of 12mm and a width of 12mm as illustrated below:

The camera angle is deceptive, so despite appearances to the contrary, be assured that the inner diameter really is the same as the width for this tyre!

### Complex Tyres:

Unfortunately, not all LEGO tyres are as straightforward as this, so next we’ll look at how to deal with some minor complications, starting with 2346.  Depending upon the side from which this tyre is viewed, the internal diameter measures either 20mm or 17mm as illustrated below:

To take account of this in the nomenclature, we include both sizes within parenthesis, largest diameter first, as follows:

2346: USED Black LEGO Tyre Ø30/(20/17)x11mm Wide
Sometimes, the internal diameter cannot be measured directly because it is recessed, so falls below the tyre wall surface.  Balloon tyre 6579 is a perfect example since it has different left and right side internal diameters, both of which are recessed below the tyre wall surface.  In such cases, the internal diameter is measured across the wall surface since this is the only measurement that is easily achievable.

### Balloon Tyres - External Diameter:

This is virtually impossible to measure by eye using a ruler or tape measure, so we devised a very simple LEGO tool to perform the necessary measurement.  Much like having your feet or height measured, it comprises one fixed end and one sliding end.  As you can see, we just used a random selection of standard bricks, finished off with some roof slopes for ‘good measure’!  We made our tyre measurer large enough to accommodate the biggest balloon tyre we could find (54120: LEGO Tyre Ø95/62x44mm Wide), so you could probably scale yours down for use with more commonly available / smaller tyre sizes.
 Granted, it’s not a precision instrument (as the sharp eyed amongst you will no doubt notice), but it satisfies ‘rule of thumb’ requirements, so that’ll do nicely. This LEGO Tyre Measurement Guide is designed to be read in conjunction with our LEGO Wheel Measurement Guide.
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