I have 225/70/19. 5 on a Ford F550 and a bigger tire wouldn't work because of the wheel offset... . the tires would touch when they bulge... and this quickly causes overheating of the tires and failure...
I've ordered 19. 5" wheels for my 3 trucks... . 04, 04. 5, 05 duallys and will be switching them over when the wheels arrive... I've ordered the same dimension steel wheel, that is the same width, and offset as the stock 17" wheels and followed the guide in the Michelin tire guide for the 19. 5" wheels...
The sample I've tested works well and I'm looking forward to them.....
We're getting over 100 K on the steer axle on new Michelins and we are using the same Bandag (sp) all season tire that UPS uses on the back... and get close to 90K miles on a $100 cap... . the F550 now has 500K in mileage and we've just ordered a new 5500 to replace it... .....
Hope this helps... .