Am I gaining miles or losing miles need math wizard

[jjsgroi]

Replaced base 16 in tires and wheels with big bend 17 inch tires and wheels . didn't recalibrate not worried about miles per hour but am I gaining odometer miles and if so about how much

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[66Fan]

Replaced base 16 in tires and wheels with big bend 17 inch tires and wheels . didn't recalibrate not worried about miles per hour but am I gaining odometer miles and if so about how much

What size were the old tires?
What size are the new tires?

Assume old: 255/70 R16
Assume new: 255/75 R17

You'll net -41.83 revs/mi. and 6.28" circumference gained.

Less miles on odometer. Speedometer will read low.
Speed Comparison old 75MPH = new 80MPH
Speedo/Odometer will be roughly 6.7% low. 1000 miles gained on odometer will be ~1067 actual miles traveled.

 

[Ground_zero298]

Just gps is. Actual vs what is showing. That will tell you where your at with mileage.

 

[Dingbat]

Big bend tires are larger diameter than base.
You will be moving faster than your speedo reads.
You will travel farther than your odometer reads.

Eta: Circumference = Diameter x 3.14

 

[KABQ]

With a larger diameter TIRE (wheel size doesn't matter), you will go farther per revolution than the car thinks you're going. Therefore you will be going faster than the speedometer reads, and you will be going farther than the odometer reads.

As for the percent difference in speed and distance, you can just punch your tire sizes into a tire size calculator like this one:

https://tiresize.com/comparison/

 

[Karl_in_Chicago]

Anyone with children should pin this to show to them if/when some day they complain "when am I EVER going to need to know geometry when I grow up?".

 

[jjsgroi]

Wheel size doesn't matter.
And right off hand, I can't remember what size tire each have, in inches tall... but it should have slowed down the odometer.. which could mean example... if speedo says 55mph, u may be doing 52, which also means ur mileage is slow. Hope I'm correct, and hopefully it helps just a little.

Just for info I went from 31 to32 and I agree that I should be getting less miles on odometer just Looking for support

 

[Mikesmallcrawler21]

Thanks for correcting me guys. I was trying to remember, I was wrong.. you guys are correct. !!!

 

[Tricky Dick]

Just for info I went from 31 to32 and I agree that I should be getting less miles on odometer just Looking for support

It's probably dead nuts on now. They read a little fast from the factory.

 

[jjsgroi]

What size were the old tires?
What size are the new tires?

Assume old: 255/70 R16
Assume new: 255/75 R17

You'll net -41.83 revs/mi. and 6.28" circumference gained.

Less miles on odometer. Speedometer will read low.
Speed Comparison old 75MPH = new 80MPH
Speedo/Odometer will be roughly 6.7% low. 1000 miles gained on odometer will be ~1067 actual miles traveled.

Thank you I need their was a wise math guy out there

 

[Fly by Nite]

What size were the old tires?
What size are the new tires?

Assume old: 255/70 R16
Assume new: 255/75 R17

You'll net -41.83 revs/mi. and 6.28" circumference gained.

Less miles on odometer. Speedometer will read low.
Speed Comparison old 75MPH = new 80MPH
Speedo/Odometer will be roughly 6.7% low. 1000 miles gained on odometer will be ~1067 actual miles traveled.

I get a 6.3 % difference. We likely used different tire diameters.

I used www.tireconverter.com to find the diameters:

255/70-16 = 30.1" diameter
255/75-17 = 32" diameter

I'll give a little lesson here...
Calculate the % change:
= difference divided by the original size
or
Difference = 32" - 30.1" = 1.9"
Then divide by the original diameter of 30.1":
1.9"/30.1" = 0.063
or a 6.3% increase in diameter.

You can apply that 6.3% to most parameters, they're all proportional to that 6.3% difference.
Going from 30.1 to 32" diameter tire:
30.1" diameter + 6.3% = 31.996"
94.5" circumference + 6.3% = 100.45"
670 revs per mile - 6.3% = 627.8 revs/mile
MPH @ (60mph) + 6.3% = 63.78 mph
MPH @ (75mph) +6.3% = 79.73 mph

P.S. It's not Geometry , it's basic math.

 

[66Fan]

I get a 6.3 % difference. We likely used different tire diameters.

Yeah, rounding errors likely the result.
I used metric sizes/ratios all the way across and only converted for the ease of understanding the circumference gained. 6.28" is better received than the 159.5 mm.

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