In Canada, we use both SAE and Metric. […] However,? cars are all metric, including cars built in the usa.?

When you mix the two, it must be terrible. And yet the US'OM counts wavelengths in meters.

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How do you calculate a surface area when the dimensions are like 27 1/4 inches?

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Strange about cars. At home, I have gardening equipment with Briggs & Stratton engines; they're US screws. In France, they're called "imperial size."

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It's a pain, and even then, when it comes to screws, the choice is limited, but when you use tubes...

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F1AMM

Fran?ois