Tyres again.

Hi Folks. Yep it's tyre info required again.

I have a caravan running 15 inch rims and for an upcoming trip I am thinking of making the GU's 265x75R16's interchangable with the vans. To do this I would need to make the rotational size of both the 15 and 16 inch tyres the same (or very similar). I understand the 15 inch rim may not fit on the GU because of disc brake clearance, but what I want is to have 2 spare 265x75R16's for the van (which I have in the shed) and buy two 15 inch tyres to suit my existing 15 inch rims already on the van with a rolling diameter of about 804mm (which is 265x75R16 rolling diameter). This way the vans spares can also be the GU's spares without extra expense of changing rims on the van to 16 inch. I do need the new tyres to have a specific load rating of no less than 112 as the van is very heavy on single axle and I have had history with tyres of less load index going POP.

Can anyone see any flaws in my way of thinking and if not is there a website link that someone can give me to look between brands/sizes and load index all in the one site. Most of the sites I have found do not give specific load index of each tyre.

I have worked out a 265x80R15 and a 32x11.5R15 will have similar rolling diameter to my Gu's 16 inch so working out the prospective sizes is not an issue.

Thanks to anyone who can help.
Trevor.