Tire sizing odometer modifier?

[BDC]

Adding a percentage modifier to odo readings automatically?

So say you have a car with bigger diameter tires than the car was sold with stock. For example, I have a 205/50/15 tire on one of my cars which was sold with a 185/60/14 wheel from the factory. The overall tire diameter is about 1.5% more than stock. Thus, the vehicle's odometer, being calibrated for the smaller tire, will tell me that I went 1.5% less distance than I actually did.

I understand this is a real simple thing to do with a calculator, but perhaps there is an option to add or subtract a certain percentage of miles from every reading you log on Fuelly. And perhaps a link to a tire size calculator. For some people this can end up being a significant difference and is rarely considered.

[rjhodges12]

My tires make my speedometer off by 7%. I run a Scan Gauge 2 with that percentage programmed in to give me my correct speed. When calculating my tanks for Fuelly, I just add 7% to what my trip meter shows.

[BDC]

Right, I am asking for a way to automatically do that rather than making an extra calculation every time I add a fuel up.

[VWJunky]

Scan Gauge actually adjusts it. My tiress are stock size but my spedometer and odometer are off a little. You have to get a GPS go down the highway and adjust Scan Gauge MPH to the same as the GPS. Now your Scan Gauge will give you how many miles you actually drove. Over a tank full for me my Odometer says about 4 or 5 miles more than my scangauge. I just use the scangauge number for more accurate numbers. Get one you will like it! LOL!

later

erick

[BDC]

OK, so for those of us without OBDII...

[VWJunky]

GPS or pad and paper. My old cars I just have to wing it.

Later

Erick

[bowtieguy]

http://miata.net/garage/tirecalc.html

this won't do it automatically, but it's good for quick calculations.

[Neanderthal]

I took the RPM (revs per mile) posted @ Tire Rack for the OE and replacement tires, which amounts to a 3% difference for the taller replacement tires. I multiply the trip meter reading by 1.03 and divide that by gallons used. Sometimes I even do it by long division, it's not that difficult.

[Neanderthal]

That Miata calculator is not accurate. I've run a few calculations with sizes from TR and it doesn't add up. Kinda blew the easy way.

It would be nice if there was a calculator built into the site here, no way to correct for the 1.03% that my different tires contribute to MPG.

[bowtieguy]

well here's another...http://1010tires.com/TireSizeCalculator.asp or this one...http://www.euroshina.com.ua/calc.php...=13&lng=en