Were my tires throwing off my fuel logs? Help
 

Hey I was looking at a profile on here where someone said that the tires on their car or whatever it was were 6% bigger then the stock so he calculated the 6% into the fuel logs for 6% addition to the miles driven. The tires I had on for a while are 10% bigger then the stock/ones I have on now. Was I suppose to add in that 10% :confused:
http://ecomodder.com/forum/attachmen...1&d=1249782310

Yes. :P You screwed up.

What you actually have to do is calculate the difference in rolling circumference, not diameter. You add in the % difference of the circumference, since you've gone that much further.

So can you tell me what I need to do to my fuel logs for when I had those tires on? add or subtract from them and by how much?

If your tires were 10% bigger circ, you add 10% to the miles driven.

So that chart is correct? I DO use 10% in this situation?
If so then for ex. if I drove 300 miles I should take 10% from 300 and add it to the 300, that being 330 and put 330 in the place of the 300 right?

:thumbup:

are you 100% sure before I go and modify 9 of my fuel logs 4ever?

Do I have to support my statements with logic?

No, besides I cant argue with writing down a less-good FE than it was :D

It'll show better mileage... more distance on the same fuel.

Also, your speedometer and odometer are off, but you probably knew that.

OMG**********sigh**** from this change I realize that I should have kept those over sized tires! I got great gas mileage with them ;( and the whole time I thought they were making me get worst mileage >;(

It should only equate to a couple 1/10's anyway. Not enough to cry about.

So where are your air dam, wheel skirts, and belly pan? I bet no one would car jack you if you had all those on there. :P

Nothing to cry about? Lol I was beating my goals and I didn't even know it... AND the LRR tires I bought that I THOUGHT was giving me +1 mpg compared to the old tires actually get -1mpg..... :(

Don't get me wrong, I'm happy my 90 day went from 30.59 to 33 but erg... that just means I'm not going to be able to get those reading again unless I do something crazy like the airdam, wheel skirts, and belly pan your talking about :p

Less post - more build thread. MOAR NAO!!!

RandomFact314 -

Beg, borrow, or rent a GPS to do an odometer correction. I borrowed my wife's :

http://ecomodder.com/forum/showthrea...ires-2642.html

CarloSW2

I have a gps but I already have gotten rid of those tires

Still a good idea to check and make sure, since the margin of error for some OEM's is up to 5% @ 60 MPH, or 3 MPH correction.

RandomFact314 -

Hrmmmmm, I apologize for not reading more closely. Even with the tires you have on now, I think you should do an odometer correction test to see if your odo is accurate.

If I were you I would :

1 - Do the GPS odometer correction test on your current setup. Let's say for the point of example that your odometer is incorrect by -1% in your disfavor.

2 - Instead of +10%, make it +9% to be "conservative" in your estimate (because you can't prove it with test data). My wife's GPS shows greater than 2.5%, but I only give myself a 2% credit. I do this to insure that my claimed benefits are well within the range of error.

3 - +9% + -1% = +8% Correction.

4 - Go over your fuel logs and add the data in. I put tons of info my "details" section of my fuel log :

But that's just me. YYMV. (Your "You" May Vary)

CarloSW2