Larger Diameter Tires Impact

I'm thinking of dropping width on next set of tires and, adding height. Now have 265/65/17 and, if possible may go to 255/75/17.

Not sure I'm thinking this through properly...would having taller tires reduce the low end "grunt" (that's an off word for this 3.5L)? Takeoffs would become more sluggish?

 

Correct. The word you're looking for is "torque". The torque produced by the engine doesn't change, but the effective torque to the ground is reduced when tires get wider, taller, and heavier. All of it takes more "oomph" from the engine to have the same result spinning the wheels/tires compared to the stock tire size.

Would it be noticeable? That's probably a question better answered by someone with first hand experience with a similar setup. If you kept a similar load range and tire weight, the diameter is only increasing to 32" from 30.6" (~5% increase).

 

Yes. Its the equivalent of starting in a (slightly) higher gear. Also, rotational weight. If two tires weigh the same, the taller one is going to have more rotational momentum, which will effect mileage.

... but it looks bitchin' tho.

 

Use this link to get a visual of the differences along with how it effects the speedometer. You can also calculate the new axle gear ratio by clicking on the "gear ratio calculator"

I'm not sure what gears 3rd gens use, but as long as the final ratio with bigger tires isn't more than about .3 less than where you started you'll probably be OK. You do lose some power, but I don't think that will be enough bigger to justify re-gearing with those sizes.

My truck has 3.73 gears from the factory. With 265/75/16's which are 1" taller I'm effectively 3.61. The difference is barely noticeable, but if the new tire size dropped my effective gearing down into the 3.30 range I'd not be happy with the performance.

 

For what it's worth, I went from 265/70/16 TRD Off Road Goodyears to 265/70/17 Toyo Open Country 3's. In hindsight, I'd probably go with 265/65/17 if I was going to do it again. Even thought the OC 3's are probably some of the lightest A/T tires out there; I feel like I'd be better served with a highway tread at the factory size. That said, I did a couple hundred mile trip from NY to PA and back over the past weekend and with three large humans; I got about 20MPG keeping the speed around 70ish. I didn't really notice any major issues with hills or anything but I also am OTT tuned also.

 

look at the weight, there are 265 70 17 C and D load tires around 45lbs that are lighter than a 255 75 17 in E load. Same with going with a 255 80 17, most are E load but you can find lighter 285 70 17s in C and D load which look better most of the time.

 

in the event you got a flat and had to use the stock spare, would it be OK with the other tires being 255 75 17?