Quote:
Originally Posted by Frank Lee
IF loads are light enough to safely use a smaller tire the gain is in the thinner rubber and fewer belts. And as noted if you can air them up enough so that they aren't suffering increased deflection vs original. I doubt going bigger/stronger than stock results in lower r.r.
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If you sort through all the data here:
http://www.energy.ca.gov/transportat...%20Testing.pdf
you'll find that RRC is slightly better for larger capacity tires. (pg 31)
So going larger than stock is directionally better for fuel economy, and using a tire that can barely carry the load is not the best move to make.