There's Metric, P-std, P-XL, LT, Cargo, Floatation, etc. The load rating is not a reliable measure of sidewall strength by itself. It just tells you how how much weight the tyre can support at its max pressure. A P-std and P-XL is rated to the exact same load up to a certain pressure, but the XL can hold more pressure and therefore support more weight when inflated higher. Plus we tend not to use the P prefix under the ETRTO standard, but the Yanks tend to under T&RA. So somewhat confusing...
But Tombie is quite right in that higher load does tend towards stronger sidewalks. But one 116 can be constructed very differently to another and therefore be significantly more or less puncture resistant through the sidewall.
An LT tyre has a slightly different shape to a P also. By design it has a squarer shoulder and wider tread face.
Legally a tyre needs to have LT moulded in if that's what it has been built to. Simple as that. If it has LT moulded in before or after the size then it is an LT. If not, then it is not. The construction dictates that, not the load rating. All LTs have standardised load ratings for the size and the range. C, D, and E are pretty common in our sizes. Higher is higher. But, for example, all range C LT285/60R18s will have the exact same load rating (118). Where P tyres can vary a fair bit, in comparison.
DiscoClax
'94 D1 3dr Aegean Blue - 300ci stroker RV8, 4HP24 & Compushift, usual bar-work, various APT gear, 235/85 M/Ts, 3deg arms, Detroit lockers, $$$$, etc.
'08 RRS TDV8 Rimini Red - 285/60R18 Falken AT3Ws, Rock slider-steps, APT full under-protection, Mitch Hitch, Tradesman rack, Traxide DBS, Gap IID
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