That doesn't add up.... both dual tires on the same side of the truck will turn exactly the same rpm no matter the sizes.
The much taller tire in a side by side pair will wear faster because it sees more load and road. If the difference is not great I bet they both wear faster than expected trying to be the same size eventually.


Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-