Fitment Reference Pack

Everything in this pack is computed from the same library that runs the calculators on this site. It is a printable companion, not a paywalled version of the site: nothing in it is hidden from the free pages.

The numbers in it are checked the same way the site's are. A script re-opens the finished file, reads the figures back out of it, and re-derives all 926 of them through the calculation library before the pack is allowed to ship. A figure printed on paper cannot be corrected after the fact, which is exactly why it gets the stricter treatment rather than the looser one.

What is in it

Twelve pages. Every count below was taken by opening the finished file and counting, not from a description of it.

• The size code, annotated. Two full pages — one for metric notation, one for flotation — with seven labelled elements each and, underneath, everything the code resolves to: diameter, section width, sidewall, circumference, revolutions per mile, and the load and speed figures the service description carries.
• The load index table, index 60 to 140. All 81 rows, with kilograms and pounds side by side and the four-tire total worked out on every line.
• The speed symbol table. All 14 symbols in chart order, with the note about why H sits where it does, followed by the six load-range markings that set the reference pressure the index is quoted at.
• A revolutions-per-mile chart. 65 rows, every quarter inch of overall diameter from 24 in to 40 in, with circumference alongside — for checking a manufacturer's published figure against the geometry.
• A speedometer-error chart. Every whole-percent diameter change from −8% to +15%, read across six indicated speeds: 144 figures, so an indicated speed can be corrected without a calculator.
• The full size catalogue. All 127 sizes on this site, ordered by overall diameter rather than by size code, so neighbouring rows are the sizes that are genuinely interchangeable on rotation count.
• Before-and-after worksheets. Two blank copies, 20 fields each, for recording a change: the two size codes, the measured diameters, the placard pressures, the wheel offsets, and the axle ratio, in one place you can photograph.

Why paper

Because the moment you need the load index table is usually the moment you are standing in a shop or under a truck with dirty hands and one bar of signal, and because a sheet taped inside a toolbox lid survives a phone battery.

What it is not

It is not a fitment guide. It contains no statement that any size fits any vehicle, because that depends on clearance, load rating and local rules, none of which are geometry. It is the arithmetic and the standard tables, laid out to be read at arm's length.

Delivery and fulfilment

The pack is delivered as a PDF by email after payment, sent by hand rather than by an automatic system, so allow a little time. If it does not arrive, the contact page reaches a person who can send it again.

Printing it

The pages are US Letter, with a content width that also clears A4, so the file prints unscaled on either stock. It is set in the site's own palette — the gauge-teal and the cool blue-greys — so it is a colour document if you send it to a colour printer. Nothing in it depends on that colour. Every distinction the pages make is carried by position, rule weight, type weight or a label, never by hue, so a greyscale printer, a photocopier and a colour-blind reader all lose nothing. That is the same decision the site makes: the comparison drawings tell their two tires apart by line treatment rather than colour.

The worksheets are designed to be filled in with a pen and photographed, so the fields are large and the labels are unambiguous when the photograph is taken at an angle in bad light.

Why buy it when the site is free

You should not, if the site is enough. Every table in the pack is derived from the same data the free pages render, and nothing has been held back to make the paid version worth having.

What the pack buys is the layout: the tables arranged for reading at arm's length, on one surface, without a screen. That is worth ten dollars to some people and nothing to others, and this page is not going to pretend otherwise.