Load index, C-type and LT tyres

The load index (a two- or three-digit number after the size) says how much mass the tyre may carry at a reference pressure. Replacing a 91 with an 88 is a downgrade even if the tyre looks wider.

C-type commercial tyres (common on Transits, Trafic, Crafter) and LT-metric tyres are built for higher inflation. Their placards already live in that band. Putting a P-metric passenger tyre on that axle to “ride nicer” can be a load violation.

Load/inflation tables from the big makers map single versus dual, load index and psi. That table is the adult document when you changed size.

Dual-rear vans: inner duals run at the dual rating, which is a different column than single. Guessing is how inner duals fail on the motorway.

Valve stems on high-pressure C-type tyres should be rated for that pressure. A passenger snap-in stem at 5.5 bar is a leak waiting for a hot day.