Tire Diameter vs. Wheel/Tire Weight

[CYi5]

Quick question for those in the know..I'm currently running a set of 255/85 Maxxis Bighorns on a set of stock 5 star tacoma Alloys. I originally did this as I did not want to invest in a new set of 16x8 rims and I just had some on hand. This combination comes out to roughly 75 lbs.

Previously, I was running a set of 32x11.5 Dunlop muds on 15x8 Wheeler's black steelies. I don't recall the exact weight but I believe it was around 74 lbs; something very close.

I just regeared to 4.56's and that helped tremendously with the 33.3" tires at highway speeds, but I have not seen too much of a change in mileage. I wouldn't mind picking up a set of 32" A/T's for a planned extended trip to Colorado in the spring and am unsure whether to put a 265/75 back on the alloys, or a 32x11.5 back on the steelies for a wider stance (preferred with a top heavy RTT.)

Question: Does tire diameter affect power/mileage more than overall tire/wheel combo weight?

 

[nickw]

Quick question for those in the know..I'm currently running a set of 255/85 Maxxis Bighorns on a set of stock 5 star tacoma Alloys. I originally did this as I did not want to invest in a new set of 16x8 rims and I just had some on hand. This combination comes out to roughly 75 lbs.

Previously, I was running a set of 32x11.5 Dunlop muds on 15x8 Wheeler's black steelies. I don't recall the exact weight but I believe it was around 74 lbs; something very close.

I just regeared to 4.56's and that helped tremendously with the 33.3" tires at highway speeds, but I have not seen too much of a change in mileage. I wouldn't mind picking up a set of 32" A/T's for a planned extended trip to Colorado in the spring and am unsure whether to put a 265/75 back on the alloys, or a 32x11.5 back on the steelies for a wider stance (preferred with a top heavy RTT.)

Question: Does tire diameter affect power/mileage more than overall tire/wheel combo weight?

The only time weight of a wheel would make a difference is under acceleration. Once you reach a sustained top speed, theoretically, you wouldnt see any difference. I would suspect around town you may see a slight drop, but I highly doubt that, especially if we are only talking 10 lbs.

Without regearing, tire diameter will make or break you. Obviously if you are not in the optimum RPM range your going to see a big hit to MPG.

But of course, theory doesn't match real world statistics 100% of the time. There are other variables such as tread pattern, width, air pressure and other components that may effect mileage more than the wheel weight itself.

 

[Spikepretorius]

The weight does affect it. However you must factor in the new diameter into your mileage calculation. On my vehicles I calculate true speed and work my mileage from that.

I've worked out that on my current vehicle, having gone up from 245/75/15 to 32/11.50/15, and having deducted the change in tyre diameter, the drop in mileage is minimal. My kilometers refected on the clock per tank of juice is depressing but once the error correction is done the difference is not too bad because I'm travelling more kilometers that what the clock is showing me.

 

[CYi5]

I'm thinking the difference would be negligible, probably not worth the price of a new set of tires. Then again, I wouldn't mind picking up a used set of A/T's just for the on road ride quality.