Lift/tires/performance/mileage

blackout07 · November 6, 2014

Electronic speedometers of today work of a rotary encoder or similar sensor that sends a once per revolution pulse to the ECM. The ECM converts tire rotation frequency into velocity and distance by multiplying the signal by the tire circumference, which is programmed with the factory tire size. The programmed tire size is utilize to calculate both the MPG and odometer change. The only thing required to convert the mileage driven and MPG for an increase in tire size is to multiply the odometer and DIC outputs by (D_new/D_old).

Let's look at an example:

Suppose the DIC on the OP's truck is reporting 160 miles traveled for the last 10 gallons (16MPG). Let's convert that to the total tire revolutions required.

160 miles = 10137600 in and 10137600/(3.14*31.91) = 101125 is how many revolutions the tires made.

taking that many revolutions and finding the new distance traveled with the larger tires.

(33.21*3.14)*101125 = 10550603 in = 166.52 miles and because the fuel consumption is still 10 gallons the new MPG=16.65.

or to simplify things (33.21/31.91)*16 = 16.65 MPG

I'll admit I barely read this post. So by your calculations th mpg increased with larger tires?

Edit: I think i see your point. The 2nd number of 16.65 would be that actual vs reported? I've always found that mileage was reported to be higher by the DIC than it actually was after adding larger tires. Not the other way around.

DanielAcosta · November 8, 2014

Hypertech is great: just correcting for the oversize tires restored better shifting and mileage. I didn't mess with any engine changes, but did experiment with putting in different tire sizes and it definitely affects everything the truck's computer does. Best result (no surprise) was with the tire height that made the speedometer and odometer read perfectly per dual gps calibrations.

My dealer knows about the hypertech, no issues. When I go in for one of the many computer upgrades the 14's have had, I return to stock programming, let the dealer do their thing, then reinstall the hypertech programming afterwards. The 10 minutes it takes to deprogram and then reprogram the hypertech is well worth the improved drivability.

So if you're going to spend a grand on tires, spend a couple hundred extra and add the hypertech. Works great for me. Good luck.

mecwarrior · November 9, 2014

I'm currently driving a 2009 f150 with 6 inch lift, 20s, and 35s. I average 12mpg. Best is 13.5, worst it 8 to 9 towing. I'll hopefully be trading in soon for a 14-15 GMC. If I can average 15 to 16 mpg, I'll be jumping for joy.

blackout07 · November 9, 2014

Good luck.

Spurshot · November 9, 2014

I'm currently driving a 2009 f150 with 6 inch lift, 20s, and 35s. I average 12mpg. Best is 13.5, worst it 8 to 9 towing. I'll hopefully be trading in soon for a 14-15 GMC. If I can average 15 to 16 mpg, I'll be jumping for joy.

I'm running 33x12.50x18 tires on my 5.3L, leveled and get a bit over 15 average for the past 8000 miles with mostly city driving. I don't pussyfoot, but I don't have my foot in it all the time either.

My guess is: If you were to lift my truck 6" and put 35" tires on it, it'd get 12 mpg too.

Prokopchuk_9 · November 9, 2014

Not another one of these threads [emoji23][emoji23]

If you wanted good mileage you should have never put big tires on, you gotta pay to play!

seansharley · November 11, 2014

Thanks for the great suggestions on recalibrating the computer, obviously my mileage wasn't effected as much as I was thinking. Gonna do my homework on exhaust, and intake to go with the software. Prob get into the stereo next

vikingz71 · December 25, 2014

Ok - just did the level and went with 295/60-20 Nitto Terra Grapplers on my '14 crew cab with 5.3 and 3.42 gears.

I understand all the comments posted to date. I was expecting some loss of mileage but I was wondering if any of you felt like the shift points and cylinder shut off were off -- post lift.

Pre-lift - the truck shifted very quickly to top gear and went to V4 mode any time I lifted off the throttle.

Post-lift - just drove it 600 kms and it felt like it was hesitating to go into top gear and only went into V4 mode on steep downhills with no throttle applied. Throttle response still great. At end of trip my rate was 16.0 litres/100km (17.65 miles per imperial gallon or 14.7 miles per US). Not bad but I think that if I got this issue cleared I would improve by at least 10 percent. This calculation does not include the difference for new tire diameter so mileage might even be 4 or 5 percent better than these numbers - these were based on truck calcs only.

Comments - I am thinking the hypertech might be the answer.

A final note - i had '11 ram crew hemi 5 speed auto with level and same tires. It got better mileage than this post lift. Surely this truck can out do that.

hemipowered22z · December 31, 2014

I have a 7 inch and 35s. I lost about 6 mpgs. I put a superchips flashpaq with thier 87 tune in it and got about 2mpgs back.stock other than that. Im ordering my tonno next week but i doubt that will help mpg.

hemipowered22z · December 31, 2014

Ok - just did the level and went with 295/60-20 Nitto Terra Grapplers on my '14 crew cab with 5.3 and 3.42 gears.

I understand all the comments posted to date. I was expecting some loss of mileage but I was wondering if any of you felt like the shift points and cylinder shut off were off -- post lift.

Pre-lift - the truck shifted very quickly to top gear and went to V4 mode any time I lifted off the throttle.

Post-lift - just drove it 600 kms and it felt like it was hesitating to go into top gear and only went into V4 mode on steep downhills with no throttle applied. Throttle response still great. At end of trip my rate was 16.0 litres/100km (17.65 miles per imperial gallon or 14.7 miles per US). Not bad but I think that if I got this issue cleared I would improve by at least 10 percent. This calculation does not include the difference for new tire diameter so mileage might even be 4 or 5 percent better than these numbers - these were based on truck calcs only.

Comments - I am thinking the hypertech might be the answer.

A final note - i had '11 ram crew hemi 5 speed auto with level and same tires. It got better mileage than this post lift. Surely this truck can out do that.

Havent heard much about the hypertechs seems to me like theyve fell to the bottom out of programmers. I personally have always run a superchips and love em. I have heard good things about the diablos and black bears.

WendysOrBust · December 31, 2014

Electronic speedometers of today work of a rotary encoder or similar sensor that sends a once per revolution pulse to the ECM. The ECM converts tire rotation frequency into velocity and distance by multiplying the signal by the tire circumference, which is programmed with the factory tire size. The programmed tire size is utilize to calculate both the MPG and odometer change. The only thing required to convert the mileage driven and MPG for an increase in tire size is to multiply the odometer and DIC outputs by (D_new/D_old).

Let's look at an example:

Suppose the DIC on the OP's truck is reporting 160 miles traveled for the last 10 gallons (16MPG). Let's convert that to the total tire revolutions required.

160 miles = 10137600 in and 10137600/(3.14*31.91) = 101125 is how many revolutions the tires made.

taking that many revolutions and finding the new distance traveled with the larger tires.

(33.21*3.14)*101125 = 10550603 in = 166.52 miles and because the fuel consumption is still 10 gallons the new MPG=16.65.

or to simplify things (33.21/31.91)*16 = 16.65 MPG

Except the way these trucks calculate MPG is based on throttle position/engine load and expected fuel consumption used at said throttle position.

Based on your math I could get some 37" tires and expect an increase in mpg. Which we all know is false. Larger tires equals more weight, more Rollin resistance, and aerodynamic drag all which add to engine load at any given rpm.

Bmotoman · December 31, 2014

Except the way these trucks calculate MPG is based on throttle position/engine load and expected fuel consumption used at said throttle position.

Based on your math I could get some 37" tires and expect an increase in mpg. Which we all know is false. Larger tires equals more weight, more Rollin resistance, and aerodynamic drag all which add to engine load at any given rpm.

Of course the MPG is going to get worse because of the reasons you stated. The calculation is merely to convert the DIC MPG readout for a situation where the tire size was increased but the computer wasn't reset for the larger tires.

There are two pieces to the equation, fuel consumption (computer known/predicted) and distance traveled.

If you converted to a 37" tire that's about 1.15 times the original 32's but the fuel consumption goes up by 25% then the net result is a decrease in MPG of 8% (1.15/1.25 = 0.92).

junkyardz · December 31, 2014

so what's all these guys that are doing 18-20mpg with lift and 33-35s doing this winter for mpg?

so far I've asked 4 friends all with level and 33-34s and 5.3 what they are getting for mpg...worse was 13.3 avg and best was 15.8avg. still haven't been able to prove in person these claims of 18-19avg with lift and tires...hmmm

vikingz71 · December 31, 2014

Thanks for the respomses! My father-in-law heard me talking about this... He wanted to get me xmas present still so long story short, I have a new max energy power programmer from hypertech!

I will report back on impacts when I correct for tire size and make other adjustments using it. It will be late this weekend before I get a chance.

Another note - on the 600 km return trip on Sunday got down to 14.8 litres/100 km (15.9 mpg US) (19.0 mpg imperial) this was in "auto" 4x4 mode in a blinding snow storm for the first 300 kms.

WendysOrBust · December 31, 2014

so what's all these guys that are doing 18-20mpg with lift and 33-35s doing this winter for mpg?

so far I've asked 4 friends all with level and 33-34s and 5.3 what they are getting for mpg...worse was 13.3 avg and best was 15.8avg. still haven't been able to prove in person these claims of 18-19avg with lift and tires...hmmm

My stock, 2wd 5.3 can only average 19mpg or better when its 80% or more highway miles.