Adjust ODO for new tires?

[ukrkoz]

I have new rubber installed for 2 weeks.
Now, that tires are larger circumference and they cover more distance under same RPM, mpg should go up. No mas.
Is there any way to DIY ODO mpg calculation based on the new tires? Basically, recalibrate it?
07 Tahoe. Stock 20 inch wheels and matching new tires

 

[gooffeyguy]

What size tires do you have?

Only way I've seen to adjust the odo/speedo/trans shifts for different tire size is with a custom tune or an aftermarket tuning device.

 

[ukrkoz]

275/55/20 I believe. Those are stock size, that year had 2 options, 17 and 20. New tires are exect OEM size match, even if my memory gave me wrong number I posted. Tire shop double checked. So ODO is set to that size from the factory, except that for the last few years truck was running on worn out tread, so it's less distance covered by tire at given RPM, than with new tires with full tread.
Sucks. I hoped there's some tinkering that could be done.
What exactly is calculating mpg? Main ECU? BCM? TCM? I could pull consecutive fuses out to reset them.

 

[mb1500]

Not sure what you’re trying to achieve here. Mpg is best calculated by hand.

 

[ukrkoz]

Just peace of mind. It's a bit retarded to go back caveman and calc it by hand, with all the modern electronics built in.

 

[RST Dana]

275/55/20 I believe. Those are stock size, that year had 2 options, 17 and 20. New tires are exect OEM size match, even if my memory gave me wrong number I posted. Tire shop double checked. So ODO is set to that size from the factory, except that for the last few years truck was running on worn out tread, so it's less distance covered by tire at given RPM, than with new tires with full tread.
Sucks. I hoped there's some tinkering that could be done.
What exactly is calculating mpg? Main ECU? BCM? TCM? I could pull consecutive fuses out to reset them.

The mileage is calculated on distance and a guesstimate of fuel used. As long as the tire height is the same as factory, the results will be the same.

 

[gooffeyguy]

I wouldn't think the tread difference between a worn tire and a new tire would effect mpg by anything noticeable. Like maybe 0.5mpg if that.

 

[ukrkoz]

You'll be surprised. Even if it's only few inches - Can't really measure right now but, if I don't forget, I'll measure next weekend, while removing front struts - multiply times say 2000 rpm at HWY speed times yey many hrs of driving... it adds up.
Out of idle knowledge, I had 2 hybrids and, every time I had new tires installed, MPG dropped, in the dash, by about 30% right after. Every time I pulled main ECU fuse and it jumped to better than old tires did.
I'll pull ECM fuses anyway. Just curious.

 

[gooffeyguy]

You can reset/zero the average MPG shown on the DIC by long pressing the check mark button while on that screen.

Mine will very a lot depending on if I'm driving around town or a lot of highway. It's not super accurate, so I don't see how a few more or less revs per mile from the tire tread difference would make much difference.

 

[gooffeyguy]

Just peace of mind. It's a bit retarded to go back caveman and calc it by hand, with all the modern electronics built in.

All these electronics built in are still pretty archaic in a 2007 that's 16 years old and caveman depending on who you talk to. The ECU is just guestimating. To get an accurate milage figure, best to do it old school after a fill-up with fuel used and miles driven.

 

[ukrkoz]

I goofed. Tire - average one - rpm-s 840 revolutions at 60 mph. I'll measure difference used to new next week, when I'll have new off the car. And do some math.
It's not resetting the current mpg, it's resetting ODO calculator "brain" as it is used to smaller/ worn out tire.

 

[Fless]

When your tires wear down a mm or two are you going to remeasure them and adjust for that?

Why not just track your miles by GPS, log them with your fuel fillups, and do the calculations? Simple Excel worksheet makes the math simple, and you'd have empirical history data. You could then compare to the truck computer's readings.

 

[gooffeyguy]

Let's summon the mileage tracker expert to see what his thoughts are on it.... @swathdiver

As for me, I'm not that concerned about what little mpg difference new vs old worn tire treads may cause, at least not enough to put this much thought into it.

Many other factors effect it more, like tire pressures, driving up hill, driving into the wind, driving in the rain, driving with old gunky axle and trans fluids, etc.

 

[Joseph Garcia]

I agree with the above comments regarding tire wear and MPG. There should be a minute difference, and IMO nothing to burn brain cells on.

If MPG is a concern, take the foot off the gas pedal. My 07 gets 10-12 in the city, 14-16 on the highway, and 18 on the highway if my wife is in the truck (passenger seat driver).

For me, MPG is not a concern, otherwise, I would not have acquired a truck with the 6.2 in it.

 

[BlaineBug]

275/55/20 I believe. Those are stock size, that year had 2 options, 17 and 20. New tires are exect OEM size match, even if my memory gave me wrong number I posted. Tire shop double checked. So ODO is set to that size from the factory, except that for the last few years truck was running on worn out tread, so it's less distance covered by tire at given RPM, than with new tires with full tread.
Sucks. I hoped there's some tinkering that could be done.
What exactly is calculating mpg? Main ECU? BCM? TCM? I could pull consecutive fuses out to reset them.

If the NEW tires are the same size as listed in the door then you are OK and there is nothing you should be concerned about adjusting. Even if you change wheel size, say from 18" to 20", so as long as the exterior dimension is the same as the original wheel and tire combo, you are still good to go with no tuning required.

 

[swathdiver]

A 275-50-20 is 30 15/16 tall mounted on the car and will turn 652 rpms when new. Down to the wear bars it will turn 665 rpms. When new the engine will turn 1732 rpms at 70 mph with 3.42 gears and 1768 rpms on the wear bars. Add 10-20 rpms for torque converter slippage. If you have 3.08 gears the spread is even less.

My speedometer seems most accurate when the tires have passed the halfway point.

 

[BlaineBug]

A 275-50-20 is 30 15/16 tall mounted on the car and will turn 652 rpms when new. Down to the wear bars it will turn 665 rpms. When new the engine will turn 1732 rpms at 70 mph with 3.42 gears and 1768 rpms on the wear bars. Add 10-20 rpms for torque converter slippage. If you have 3.08 gears the spread is even less.

My speedometer seems most accurate when the tires have passed the halfway point.

Your speedometer isn't 100% accurate, ever, and as all gauges go they are most accurate at the midpoint - although I'm not sure these modern electronic gauges really follow this same old school thought.

This is a NON ISSUE unless you are changing overall tire diameter intentionally. Even the same size tires from differing tire manufacturers aren't the same exact diameter when they are made. It's just the way it is. I'm an OCD type of guy too and could care less about this honestly.

 

[durbancic]

When your tires wear down a mm or two are you going to remeasure them and adjust for that?

Why not just track your miles by GPS, log them with your fuel fillups, and do the calculations? Simple Excel worksheet makes the math simple, and you'd have empirical history data. You could then compare to the truck computer's readings.

I like to clip all my gas receipts together in the car. Would log them electronically but have not gotten that advanced yet. Newest receipt goes on top of the pile. Always fill up. Write down odometer reading and trip mileage. Write down "calculated" mpg by vehicle and then calculate it myself using miles driven/gallons added. Then reset trip odometer and mpg reading. Then you can get an idea of your actual mpg and how far off the vehicle is calculating it. By putting the receipts in a stack the receipt under the top one is the fueo your burned to achieve that mpg. So if you notice a trend of better mpg with x station you can try to buy their gas more often. But also try to keep in mind the type of driving on that tank - mix of city vs highway, how much idling time, etc.

 

[RST Dana]

I like to clip all my gas receipts together in the car. Would log them electronically but have not gotten that advanced yet. Newest receipt goes on top of the pile. Always fill up. Write down odometer reading and trip mileage. Write down "calculated" mpg by vehicle and then calculate it myself using miles driven/gallons added. Then reset trip odometer and mpg reading. Then you can get an idea of your actual mpg and how far off the vehicle is calculating it. By putting the receipts in a stack the receipt under the top one is the fueo your burned to achieve that mpg. So if you notice a trend of better mpg with x station you can try to buy their gas more often. But also try to keep in mind the type of driving on that tank - mix of city vs highway, how much idling time, etc.

I electronic log every gas falling purchased. Date, time, distance, fuel brand, octane, and gallons purchased. It gives me immediate feedback on mileage for the last tank used. It even asks me what percentage is city vs Highway.

 

[EvergreenZ71]

Google sheets or even Google forms (exported to a sheet) are a super easy way to grab the data and let the spreadsheet do the math.

Edit: and doing it from a phone makes it even easier.