English-unit parts that are international standard, there are a few ! Options

[ArtechnikA]

There are a few car parts that despite the widespread adoption of the Metric system remain sized in English units as international standards.

Think about it - A few of the known parts in the next post...

[Richard Casto]

Interesting topic. I knew about 1, 3 and 4, but never really thought about 2.

This is really a stretch, but what about Wiper blade lengths?

So in addition to what, how about why?

1) Defacto standard? Does anyone today use metric wheel sizes or is the entire world pretty much on the "inch" standard?
2) Off the shelf ATE design? Question is, why would ATE use English vs. Metric?
3) Same as 2.
4) Is this an agreed upon standard?

[ArtechnikA]

So in addition to what, how about why?

1) Defacto standard? Does anyone today use metric wheel sizes or is the entire world pretty much on the "inch" standard?

IIRC Michelin has tried from time to time to introduce various proprietary metric tire flavors throughout the years. They sold Ford on it maybe 20 years ago. TVR? something like that. Extinct.

2)...why would ATE use English vs. Metric?

I believe Bendix patented the now-familiar hydraulic brake system and licensed it to the world. Terms of the license to ensure international commonality, I believe.

4) Is this an agreed upon standard?

I recall (but I could be wrong) that it is an ISO standard, but it could just be a SAE. In any case - the whole world does it and has since the introduction of the seat belt.

Even your 914 :-;