Anyone with 35s compared odometer miles to Google maps

Took a trip today. Google maps states 84mile trip. My odometer showed 75.1mi

Which makes my odometer understated by almost 12%.

When I'm going 70mph(speedometer), Google maps GPS indicates around 76mph. Which makes my speedometer off by 9%.

Toyos 35/12.5/17

 

35/31 = 1.13

 

It's not always that simple not all 35s are the same size. Then truck weight varies and psi varies.

If it was that simple, indicated 70mph should show 79mph on GPS.

 

ummm, yeah that's why you use the manufacturers stated height or measure....BFG ko2 275/65/20's are a little more than 1/8" shorter than Michelins of the same size and at 75 mph that's a notable difference.

 

Your first sentence is accurate. But, tire pressure and vehicle weight don't affect the circumference of the tire.

You also have to factor in the fact that the speedometer is probably inaccurate even with the stock tires. Any vehicle I've actually checked against GPS shows higher than actual speed.

 

I'm on a 2nd gen, but mine is about 12% off with Kenda 35x10.5R17s. If the odo shows 100 miles, my GPS tracker shows 112-ish. Speedo is off by about 8%. If it shows 60 or 70mph, Google Maps will show 65 or 76. This has been consistent over a couple years of intermittent checks. Not sure if the difference between the two has anything to do with being regeared or not.

 

GPS has a margin of error that varies dramatically depending on conditions especially if being jammed by a foreign adversary.

 

Ok. Measure your tires then. The math is simple.

 

In my 3rd gen I used the hypertech programmer to dial in the speedometer by GPS speed and have checked it against multiple radar speed limit signs at 55 mph. My odometer is still under reporting by about 3%. I would rather have my speedometer correct than the odometer. I just know my MPG is a little better than the odometer is reporting but I'm not really worried about MPGs with 35s

 

Same - I have rough country version of the speedometer calibrator, my speed is accurate but my odometer is about 2% off with my 33s.

 

Hypertech here too. Had to program it to 33 or 34's for my BFG 35x12.50R17's to get the speedo to match GPS. Got it within 1 mph too.

 

What about your odometer?

 

Haven't cared enough to check that, ha. I'll take a look today and report back later.

 

If you get 40’s you will keep your truck as a “low mileage” vehicle when decide to sell in the future.

 

Can someone explain to me, how is it possible that there is different speedometer error VS odometer error?

I would have thought that if you have larger or smaller tires, then both speedo and odo would be off by the same percentage

Am I assuming that the baseline data comes from the same source?

 

Speedo and odo are not necessarily the same calculation. They both pull from wheel or trans speed, but that’s it.
Think about it this way, you can travel a mile at 20mph or at 60mph. The odo will increase by a mile either way, but the Speedo will not be the same (obviously) while doing so.

odo error will be the same no matter how many miles or how fats you travel them with big tires. Speedo will get more error as speeds increase.

 

35’s are about 12% larger in circumference than stock tires so that adds up

1-(31/35)= .11 and change x 100 is 11.4%

 

My simple brain can't grasp that.

If my tires are, say 10% bigger, then driving 100 miles will result in 10% reduction in distance shown on odo. But at any speed (other than 0 mph), my displayed speed should also be 10% less.

If that's not the case, why isn't it?

I realize GPS might not be always accurate, but I'm making another assumption here, that it is far closer to real speed than dashboard display.

I also use scan guage in my vehicles, and that can also be calibrated to display a more accurate speed and distance.

Final assumption here: SG is more accurate, as I see it closely matching gps speeds. (as confirmed by police radars, since they never stop me since I started using gps/SG )

 

Odometer is within half a mile. It's fine.

 

The odometer is accurate from the factory while the speedometer is overstating speed by about 2% so when the speedometer said 65 actual speed was a little less than 64.

When I went up one tire size to 265/75R16 the speedometer was just about perfect but then the odometer was under reporting mileage. I would rather have the speedometer correct so I will live with the odometer being off a bit.