Copenhagenjunkie

How many miles do I really have?

I bought my truck with 64,000 miles on it. I chucked the 215/75/16's and put on 235/75/16 tires then and still do now. I have 314,000 miles now. According to my GPS, at 70 mph on the speedometer I am actually doing 75. The slower I go the the more accurate my speedometer is. I there anyway to get an accurate answer?

Bored at work waiting for more snow!

Thanks.

mkubacak

If I did this right and my calculations are right:

314,000 - 64,000 = 250,000 -- indicated miles on 235's

28.7 / 29.9 = 95.99% -- difference in diameter between 215's and 235's

250,000 * .9599 = 239,967 -- calculated actual miles on 235's

239,967 + 64,000 = 303,967 -- calculated total miles on truck

The reason that you see the speedo is not as far off the slower you go, is that it is off by about 4%. Therefore the faster you go, the more the speedo is off.

Hope this helps.

Michael

signature600

Shouldn't the miles go up?

A 235 moves you farther in 1 revolution than does a 215, right?

ALSO, he said that GPS shows 75 when truck shows 70.

SO:

250,000 / .9599 = 260,444

260,444 + 64,000 = 324,444

I hope this is right, it's how I've been figuring my mileage for the past year and a half. If it's not, my truck gets terrible mileage
Chris

ChrisM55

When I went from the 235's to 255's I get an avarage 25 less miles on my odometer than on my gps per tankful. So when I calculate my fuel milage I just add 25 miles to each tank. The taller the tires you get the slower the odometer thinks you are going, that is why it shows less miles than you travel


Chris

Copenhagenjunkie

Amazing, you guys posted before Shovelhead.

I wasn't too concerned about fuel mileage but how many actual miles I have on "Old Blue II". Math was never my strong point. Poor girl is not driven nearly as much as she once was.

Thanks Sig 600.

Shovelhead

Busy day at work..............


http://www.1010tires.com/tiresizecalculator.asp

Circumference: 90.13 in 2289.3 mm / Circumference: 93.83 in 2383.2 mm

Revs per Mile: 724.9 / Revs per Mile: 696.3

Speedometer1: 60 mph 100 km/h / Speedometer2: 57.6 mph 96.0 km/h

Speedometer Difference: 4.107% too slow

Diameter Difference: 3.96%

Lil Dog

If you are calculating fuel mileage, then this is a concern.

As far as drive train is concerned, over the land miles don't matter. YUP.. Think about it, all the drive train does so many revolutions to turn the spindles.. After that its all a matter of circumference to get you down the road. The 4% difference affects your mileage, not the life of your running gear. For me the concern is wear and tear on the rotating parts, the land travel is secondary.

IMHO..

J-eh

BigBlue

I figure that since my speedo was about 10% off with my tires, my odo was the same. So I just add in 10% to the figure. Well, I used to. I got it corrected at 66,000 so I only add in 6000 miles. Thus, my odometer says 68,107, I've actually gone 74,107. I may be off a little bit but oh well.

mkubacak

Doh!! Darn math. Divide, multiply, whats the difference? I knew if I had it wrong, someone would get it right.

ChrisM55

plus havingg the bigger tires helps with resale value. You see, you truck is showing 4%less miles than ittruely has when you go to get rid of it!!!

Chris

signature600

Good luck convincing someone of that

I'm just guessing on my mileage, but I would way that the previous owner changed tire sizes after the factory set, so ~200,000 miles with bigger tires = 210,500 mi

Cool --- My truck has 280,000 miles

Chris