In message . com,
Osprey writes
Been trying to understand tyre markings on my trailer tyres. It is
marked as 205 75 R14

That should mean (I think) rim diam is 14", height of tyre is 75mm and
width is 205mm.

Form this you would assume overall diam of Tyre would be 14" (i.e.
355mm) plus 2 x 75mm so overall width of 505mm Yest if I measure it
the overall width is 635mm significantly different.

Anybody know why the discrepancy?

Surprisingly difficult to find good sites with info on tyre wall
markings - KwikFit have a tiny subsection and doesn't address the OPs
query. Dunlop.co.uk also had minimal info.

But, http://www.tyres-online.co.uk/tech.asp (no connection etc.)
provides all the info. you need I think.

--
Si