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Stock tires were 265/70/17 (BFG Trail), and this winter I went to **** Cepek FCII's, 285/70/17

Aftermarket tire is 3.5% larger, a little heavier, and has a max tire pressure of 65 psi. Load carrying capacity is the same as the E rated stock tire however tire pressure was 75 psi front and 80 psi rear.

So, I won't bother with the actual mileage numbers but with the switch, I consistently get 9.5% less mileage with the aftermarket tires. This is taking into consideration the difference in rotation as well.

That is a combination of highway, bush roads, 4x4 and in 4x2.

Gearing is the 3.55.

So, I am still OK with that as it is still about 8-10% better than my 6.0 leaker in fuel economy but with more power and torque.

Also, the safety factor on the road is huge. I had the tires siped and there is no comparison on all condiditions other than dry pavement. 35-40% of my mileage is on gravel road conditions, mud, ice and snow so I am much more comfortable with the FCII's and more than happy to use a little more fuel.

Anyhow, thought some of you wanting to change tire size would like to know my findings.

Oh, the TPMS's had to be reprogramed for the new PSI's.
 

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^^What HE said^^^

Wider tires = lower MPGs
Deeper lugs = lower MPGs
More noisy = lower MPGs
Lower inflation = lower MPGs
Heavier loads = lower MPGs
Taller tires = lower MPGs (either/or because the vehicle is TALLER and/or not programmed for the current N/V ratio)

Even changing from one MODEL of tire to another in the same BRAND can affect economy, this is significantly due to differences in belt lay-out and compounds.
 
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