Went from 30’s to 32’s MPG’s went up?

[EveryDayBronco]

before and after.

I love the looks of that thing with those wheels. To my eye the proportions are "just right"!

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[dgorsett]

Can you guys post pics of your 2 door factory bid bend wheeled broncos (non sas)?

There is a thread
Ultimate Big Bend Non-Sasquatch pics thread | Bronco6G - 2021+ Ford Bronco & Bronco Raptor Forum, News, Blog & Owners Community

 

[dgorsett]

I have a Base 2.3 7MT with about 4K on the odometer that I recently swapped the steelies off of for Big Bend wheels and tires. I have calibrated the speedo. What’s throwing me is my mpgs have gone up. Not considerably but I expected to take a small hit. Right now I’m averaging 23.9 according to the computer. That’s up from just under 23 with the steelies. My first thought is the tires are the same width and the alloys from the BB could be lighter than steelies, though I’m not sure. Does all this seem plausible? I’m also assuming because the speedometer has been calibrated than the mpg reporting should be accurate. I filled up a couple of days ago and I said I had 398 miles until E. I’m sorry I just don’t believe it.

So with the MT you have 4.46 gears, which are quite low with 30" tires. By switching to 32" tires you have effectively changed your gear ratio to about 4.2?, probably keeping your engine in the more efficient power band at cruise. I have the BB 2.3 AT with 4.27's and consistently get 23 mpg,

 

[dck82]

Roll resistance of the two tires are likely different.
Roll resistance influenced by rubber compound, tread style, tire width and pressure.

Also, to compare mpg without a wind and speed consideration on a specific stretch makes it hard to ensure you drove the same with both sets....

I would say I’m a creature of habit. I imagine both sets have seen the same action for the most part. My commute Monday through Friday is mostly highway with speeds from 55-70 and my area of the country is as flat as a pancake. Then some putting around town on the weekends.

 

[dck82]

So with the MT you have 4.46 gears, which are quite low with 4.46 gears. By switching to 32" tires you have effectively changed your gear ratio to about 4.2?, probably keeping your engine in the more efficient power band at cruise. I have the BB 2.3 AT with 4.27's and consistently get 23 mpg,

Thank you. That’s helpful in my understanding.

 

[dgorsett]

Thank you. That’s helpful in my understanding.

Yeah, I mada a typo, should have said"...quite low with 30" tires."

 

[EveryDayBronco]

So with the MT you have 4.46 gears, which are quite low with 30" tires. By switching to 32" tires you have effectively changed your gear ratio to about 4.2?, probably keeping your engine in the more efficient power band at cruise. I have the BB 2.3 AT with 4.27's and consistently get 23 mpg,

Switch to 32" and there's the rotational weight of the tire and wheel.

When I get my base model I plan to weigh both wheel. I'm curious 16" steel vs 17" aluminum??

 

[Taltyman]

No bronco here (yet) but when I switched to 35's on our Wrangler I used an app to re-calibrate the speedo. I then went and verified it with a GPS app on my Iphone and also by doing a test drive on the interstate by resetting a trip odometer as I passed a mile marker. Then drove 10+ miles. Both of these tests indicated my speedo was closer to being correct but still off by a couple of MPH. So I tweaked the tire size some in the app and repeated until I was pretty much right on. Even tire wear after a few 1000 miles will cause it to be off a little. No big deal unless you are way off as then shift points, etc can be compromised. I would have said effected but I'm never sure as to when to use effected/affected
what I thought was strange is that the Nav system MPH in the Jeep always matched the speedo. I would have thought it used GPS for MPH.

 

[pmi3]

We put 32" destination at2's on a badlands (37 lbs a piece vs 51 for the k02s). Getting on average ~21 mpg after recalibration. Mostly short in city trips, some long 50-60mph backroads trips at altitude. 2.3 manual with 4.7 gears. Feels much more peppy now.

 

[topcatrw]

There is a table some place on the Forum that shows the 3.73 gears with 33" tires gets the best MPGs without loosing much off road torque.

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