Do be aware that TrevorG posted the post you quoted back in January 2022, and he hasn't visited the Forum since April this year, so he might not ever see your post...
Aaand, while there's a very good chance those tires are quite close in their
actual physical sizes, you should also be aware that those "tire conversion calculators" only refer to the '
Nominal Tire Sizes', and not the ACTUAL tire sizes of any specific tires!! So they're a good indicator of the general size relationship between those sizes, but not necessarily such a good indicator of the actual physical size relationship between any two specific tires/tire sizes! :lecturef_smilie:
Only it gets worse, cos while tire manufacturers not only tend to put the '
nearest applicable NOMINAL tire size' on the sidewalls of their tires when they make them, so
most tires generally are usually fairly close in actual size to their Nominal tire size; but also, different tire manufacturers might also use different methods to choose which nominal size they put on a particular tire... Some manufacturers might use the tire casing minus all the tread layers and tread depth as the basis of their nominal tire size choice; while others might use the completed tire including all the tread layers plus the tread depth as the basis for their choice; and there's other methods used too - the point being, there's no standard method for choosing how to assign the nominal tire size, and tires with exactly the same nominal size may have significantly different actual physical sizes, which means somewhat different rolling diameters than those shown on your handy online tire conversion calculators.
You might think that the difference between the 'Nominal/sidewall size' and the 'actual/physical size' might not be all that great, but so far, the largest variation I've found has been 50mm/2" - Yep,
TWO INCHES difference in rolling diameter between the nominal/sidewall size of a tire and its actual/physical size!! And that's one that I personally physically measured myself!! A supposedly (almost) 32" rolling diameter tire going by its nominal/sidewall size that was actually/physically (almost) 34" in rolling diameter - and that was before it'd been inflated!! :shocked:
So while those handy online tire conversion calculators might help you get an idea of the likely difference in tire sizes,
they don't necessarily reflect the ACTUAL PHYSICAL difference in tire sizes - you need to check the manufacturer's physical specifications for the tire, or the Actual Physical size of a tire to be
reasonably SURE of its true size! :lecturef_smilie: