Why is rim size the only Imperial unit on an F1 car?

[Predator]

Inches are used simply because it's what punters understand.

Indeed, plus it's so much easier to remember. Tom, Dick and Harry won't know wheel rim size in metric. Imagine us F1 geeks holding a conversation with the general public and stating the rim size as 330mm. They'll think we're crazy.

[zac510]

There are three things in our metric world we still do on inches: rims (from a F1 car up to a kids push bike), televisions/computer screens and vinyl records.
Funny thing is with all of them, any other measurement is done in metric.

Just some leftover from an old system.

Also, imperial measurements are still popular in English daily speech because they're [almost] all single syllable so they roll off the tongue a lot nicer and hence have a bit more impact.

[Jolle]

There are three things in our metric world we still do on inches: rims (from a F1 car up to a kids push bike), televisions/computer screens and vinyl records.
Funny thing is with all of them, any other measurement is done in metric.

Just some leftover from an old system.

Also, imperial measurements are still popular in English daily speech because they're [almost] all single syllable so they roll off the tongue a lot nicer and hence have a bit more impact.

The average mainland European has no idea how much an inch is in metric

[Jolle]

And by the way not just in F1. In metric countries everything about a car is metric except the rims and the satnav screen

[Holm86]

There are three things in our metric world we still do on inches: rims (from a F1 car up to a kids push bike), televisions/computer screens and vinyl records.
Funny thing is with all of them, any other measurement is done in metric.

Just some leftover from an old system.

Also, imperial measurements are still popular in English daily speech because they're [almost] all single syllable so they roll off the tongue a lot nicer and hence have a bit more impact.

The average mainland European has no idea how much an inch is in metric

25,4 mm, it's common knowledge

[PlatinumZealot]

Or do they really use the metric equivalent, and calling them 13 inch rims is just a misnomer?

The things your 13yr old kids ask when inquiring about the cars during testing..

Thirteen inches is just a nominal size.
Like a shoe size. Quite a bit of tolerance is allowed for street cars. For f1 the technical regulations might give you the size in mm.

[3jawchuck]

Or do they really use the metric equivalent, and calling them 13 inch rims is just a misnomer?

The things your 13yr old kids ask when inquiring about the cars during testing..

Thirteen inches is just a nominal size.
Like a shoe size. Quite a bit of tolerance is allowed for street cars. For f1 the technical regulations might give you the size in mm.

These maybe?

12.4.2 Complete wheel diameter must not exceed 670mm when fitted with dry-weather tyres or 680mm when fitted with wet weather tyres.

12.4.4 Wheel dimensions and geometry must comply with the following specifications:
...
f) The outer lip diameter is 358mm (+/-1mm).

[JordanMugen]

Or do they really use the metric equivalent, and calling them 13 inch rims is just a misnomer?

No, they use 13" wheels... Why wouldn't they?

The reason: almost all cars and motorcycles use imperial diameter wheels.

Michelin tried to launch a metric range of tyres in 1973 called the "TRX" range: https://classic.michelin.com/en/Classic-Tyre-range/TRX

Obviously this never caught on and metric diameter wheels are extremely uncommon, and if you have the misfortune to own a car with metric wheels -- mainly a small number of Ferrari and BMW models -- the tyres are horribly expensive. Most owners will convert to standard imperial wheels.

Metric tyres are quite hard to find the only company still making them are Dunlop and even their stock is often limited. Metric sizes no longer feature on new cars and it just as good as the price of an on off size was very expensive. Today drivers that have metric size wheels are stuck and often find it hard to get stock and if they do manage to find some they are paying over the odds for them. The only alternative is to change the rims to standard size rims.

https://www.ctyres.co.uk/general/metric

For example the Ferrari 308 specifies 220/55 R390 for the rear tyres.

Just like a normal tyre, it has a cross-section of 220mm, a profile of 55% [racing tyres are often labelled as the outer diameter instead, 670mm in the case of Formula One], and is designated R for radial tyre. However, the diameter of the wheel is 390mm or 15.35" instead of the more common 15".

It follows (obviously) that a 220/55 R15 tyre with a 381mm inner diameter will not fit on the Ferrari 308's 390mm wheel!

[JordanMugen]

In metric countries everything about a car is metric except the rims and the satnav screen

Most Japanese and European cars use metric sizing for the exhaust: 55mm (2.17"), 60.5mm (2.36"), 70mm (2.75") (outer diameter)

However, trying to find metric exhaust tubing or components in an aftermarket exhaust shop in Australia or USA is virtually impossible. Exhaust shops only stock the imperial tubing (2", 2.25", 2.5", 3") that is used on American cars such as Chevrolet or Ford (Ford USA not Ford Werks GmBH of Germany that is!).

The amount of times American enthusiasts assume the factory exhaust on, say, their Subaru BRZ is 2.25" (it's not, it's 55mm!) is quite comical... it seems people are quick to assume, and slow to measure!

[JordanMugen]

It's funny because every other measurements regarding wheels and tires uses metric values

You say that, yet the Goodyear Eagle F1 tyres were (for example, the 1997 fronts) 25.5"x9.5"--13" ... None of this metric business... because USA!



Goodyear wet tyres for the front axle from 1997 F1 season

Of course the equivalent 2016 front Pirelli tyre was instead a 245/660-R13 (there were no changes in front tyre size rule from the Goodyear era through to the 2016 Pirelli). Around 1998 when Bridgestone came in, I believe Bridgestone increased the front tyre overall diameter from 25.5" (or 248mm) up to the maximum 26" (660mm) that was permitted under the regulations, and from then on the fronts became the same diameter as the rears.

[rscsr]

Also, imperial measurements are still popular in English daily speech because they're [almost] all single syllable so they roll off the tongue a lot nicer and hence have a bit more impact.

The average mainland European has no idea how much an inch is in metric

25,4 mm, it's common knowledge

even in engineering classes most don't know that.
And a limited study in my family showed that only 1 of 8 people knew that.

[Holm86]

The average mainland European has no idea how much an inch is in metric

25,4 mm, it's common knowledge

even in engineering classes most don't know that.
And a limited study in my family showed that only 1 of 8 people knew that.

I thought it was common knowledge, but most of my friends are of a technical education, and into cars, so they know what an inch is

But I would really hop that the united states would jump on the metric bandwagon, as the inch is an irritating unit to work with when we get CAD models from american sub suppliers.

NASA a place of the most brilliant minds in America uses the metric system, that should say it all

[Webber2011]

The one thing that comes to mind here in Aus that still commonly measured in inches is agricultural piping.

Old farmers have passed that on to their descendants, and almost every roll of polly or pvc I have ever seen is still stamped or printed with both the metric and imperial size.

Go out and visit a 70 year old farmer and start talking about his 12mm drip irrigation and he won't have a clue

[strad]

the inch is an irritating unit to work with

That's exactly how imperial users feel about metric. A real pain in the ass.

[gruntguru]

If you grow up learning a particular system of units, it is natural to find the "other" system a pain in the ass. I grew up in Australia before we converted to metric so have experienced the "pain" of converting to a vastly superior system.

It is a pity there are still two systems on the planet - all because the biggest economy on earth won't bite the bullet and go through that pain. The cost of dual measurement systems to the USA (and the rest of the world) runs into the trillions annually. https://nonpartisaneducation.org/Review/Essays/v3n3.htm