Info you may want to hear

I did the following to my 2017 Limited DC; 2.5" front lift, 2.0" rear lift, went from 30.5" tires(265/60/18) to 32" tires(275/65/18).
What has surprised me is the following; my transmission shifting has improved dramatically. Previously, I had the shifting problems that have been mentioned many times here. Now, it is a pleasure to drive. I don't know why. Does anyone have an opinion?

 

Because you changed the final gear ratio with the tire change. The transmission is no different, but the RPM ranges you use for the way you drive are.

Put your old size back and it will be just like it was before.

 

Does that mean the RPM ranges before were incorrect? or these are just better for the new tires?

 

Down side is you probably took a ~3mpg hit over the life of the vehicle with this tire size and are putting more strain on driveline and steering components with out of whack geometry.

 

No. It just means you found a band aid for a boo boo.

There are a few other threads around similar in nature, so your results aren't totally surprising.

 

You may be right, but after 2 weeks my mpg has only suffered slightly, maybe because it isn't shifting as much. As to the strain on components and out of whack geometry, I feel and hear nothing out of the ordinary....so far.

 

Have you GPS'd your new speedo error rate, then applied that % variance difference to your calculations?

 

It is designed to shift more to accommodate better fuel economy staying in low RPMs. This is annoying, yes but there is a purpose behind it. Now your truck sense a heavier load trying to turn the larger tires and thus will hold gears longer.

 

If your speedometer if off how do you calculate your fuel use? The onboard computer would also read goofy as well as the trip meter.

I swapped tires and checked my speed w/ a GPS, mile markers and a few radar speed signs to verify my speed but wondering how you know you havent really dropped MPG from stock.

 

The extra weight will hurt your mpgs. The taller tire will have the effect of giving you a taller final drive ratio and would improve mpgs.

The taller tire will also trick the computer as it doesn't read mileage correctly anymore. Basically the calibration of the speedometer and odometer is off...... unless they calculate using GPS (which I don't think cars do this yet).

 

my neighbor claimed the same results after lift and bigger tires. said tranny shifts much smoother than it did before.

 

Easy. Use a tire calculator to determine the difference in tire size, then add the applicable difference in miles before dividing my gallons.

https://www.tacomaworld.com/tirecalc

In this case, OP will travel 5.08% more miles than calculated on the odometer. So if the odometer shows 200 miles, he has actually travelled 210.16 miles...

 

In my 4th Gen 4Runner I found the computer estimate was more accurate after I added bigger tires (the computer overestimated at stock).

 

The speedometer and odometer work off of different systems (older cars were tied together). Most modern cars MPH are slightly lower than actual speed. Odometers are pretty accurate, and when they aren't there have been lawsuits.

 

Taller Tire improves MPGs in some conditions but not in others. It will kill you in stop & go situations and city driving. Only way it really helps is say on a long flat stretch doing 55mph. Go too fast (outside the "sweet spot" for the gear and tire ratio) now the engine is pushing harder to keep those babies turning.

 

That's exactly what I calculated!!