random tyre question...why mm/inches

[steveo3002]

was wondering how tyres got to be mm/inches ...as in 195mm/50/15" bit strange really ?

why not all inches or mm

[littleredrooster]

Michelin TRXs (?) are all metric. They allowed BMW to charge what they liked for replacement tyres for a while in the 90s......c.£500/corner for the boss's 635CSi, IIRC.

[DannyVTS]

because wheels are measured in inches?

[Major Fallout]

Never really thought about that, strange now you mention it.

Its all inches in my old stuff.

[Ozzie Osmond]

Often wondered the same thing myself....

The only thing I can think of is maybe the sheer size (since the very beginning of cars) of the US car market where everything's in miles, feet, pounds, gallons, farenheit ....... and inches!

[kambites]

This came up a while ago. I believe wheels and tyres originally standardised on imperial measurements because of the location of the early big manufacturers, then Michelin (being French) started to grow and wanted to go metric but were tied to old imperial wheel sizes. Then Michelin became quite powerful because they were the first manufacturer to start mass producing radial-ply tyres, so they ended up setting the standard that everyone else followed.