Quote:
Originally Posted by Execut1ve
I'm in the fantasy stage of putting bigger tires on my truck. I'm considering the interaction between tire size and fuel mileage. Currently on the truck the tires are about 29" and I would be stepping up to 31's or 33's if I went bigger.
Pros: lower RPM at cruising speed
Cons: tires weigh more and have greater moment of inertia
Not sure: larger tires act like taller gears, so I would probably experience reduced power and acceleration from a stop. unsure how that would influence fuel econ
Anyone else want to weigh in? Any thoughts on what the overall effect on fuel econ would be? Thanks!
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Probably the only data you are going to see that even hints at the question you are asking is some data Smithers showed to the California Energy Commission. I analyzed that data here:
Barry's Tire Tech
Basically the data says that larger is better. Just be aware that the data is only about RR and not the effect a larger diameter tire has on the engine RPM, etc.
But the data says the effects of tire size are small compared to the effect careful tire selection has. Also, this data is only about passenger car sized tires. Your truck likely came with tires designed to the same system and it would be tempting to go even larger by going to LT metric tires. That is likely the wrong direction as LT metric tires are designed to a different set of standards and part of what comes along is rubber that can withstand higher loading. That rubber is less flexible and not conducive for better RR.
If you are considering going larger, stay with a passenger car size tire and carefully select a tire where LRR is listed as a feature. The problem will be determining if the LRR label is being applied because the tire truly has LRR or that it is just better than comparable tires - meaning same UTQG treadwear rating.