A little math...
#1
04-09-2007 | 12:59 PM
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From: Oklahoma
A little math...
Ok so I was driving back home from easter weekend and I got to thinking about something while I was driving. I guess I just want a second opinion on this or to be told I dont know what the heck Im talking about. Here it goes..
I went from 265/70/17 (stock) to 285/70/17. The tire calculator said my speedo changed by about 2.5 mph. If I'm going 70, Im really going 72.5.
So...[1-(70/72.5)]= .035 or 3.5% change from stock. Also, I looked at my odometer as I passed every mile marker and it was off by just small amount every time. But as I kept track of the mile markers and my odometer, it started to be off by alot after a while. SO, does this mean that odometer is off by 3.5% as well?
If this is the case, I should take 3.5% of my trip mileage and add that on to my total? For example.... I had traveled 301 miles on my last tank of gas. (.035x301) = 10.535. So 10.535 + 301 = 311.535. My mileage divided by the amount of gas used (311.5 miles/22.6 gal) = 13.78 MPG as compared to 13.3 MPG if I hadnt accounted for the percent that it was off.
Its not really important at all but I was just curious to get other peoples opinions on if I'm on the right track
I went from 265/70/17 (stock) to 285/70/17. The tire calculator said my speedo changed by about 2.5 mph. If I'm going 70, Im really going 72.5.
So...[1-(70/72.5)]= .035 or 3.5% change from stock. Also, I looked at my odometer as I passed every mile marker and it was off by just small amount every time. But as I kept track of the mile markers and my odometer, it started to be off by alot after a while. SO, does this mean that odometer is off by 3.5% as well?
If this is the case, I should take 3.5% of my trip mileage and add that on to my total? For example.... I had traveled 301 miles on my last tank of gas. (.035x301) = 10.535. So 10.535 + 301 = 311.535. My mileage divided by the amount of gas used (311.5 miles/22.6 gal) = 13.78 MPG as compared to 13.3 MPG if I hadnt accounted for the percent that it was off.
Its not really important at all but I was just curious to get other peoples opinions on if I'm on the right track
Last edited by ross2388; 04-09-2007 at 01:02 PM.
#5
04-09-2007 | 06:09 PM
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Joined: Apr 2007
Posts: 52
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From: AL
yeah, that sounds about right. i just got my 285 BFGs put on Friday and I love em. Odometer just a little off, a trip that normally takes a little over 52 miles came out to be just over 50 miles with the new tires compared to the 265s. Will all be taken care of when the TP tunes are installed! 
#7
04-10-2007 | 09:50 PM
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Joined: Feb 2007
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Originally Posted by ross2388
Ok so I was driving back home from easter weekend and I got to thinking about something while I was driving. I guess I just want a second opinion on this or to be told I dont know what the heck Im talking about. Here it goes..
I went from 265/70/17 (stock) to 285/70/17. The tire calculator said my speedo changed by about 2.5 mph. If I'm going 70, Im really going 72.5.
So...[1-(70/72.5)]= .035 or 3.5% change from stock. Also, I looked at my odometer as I passed every mile marker and it was off by just small amount every time. But as I kept track of the mile markers and my odometer, it started to be off by alot after a while. SO, does this mean that odometer is off by 3.5% as well?
If this is the case, I should take 3.5% of my trip mileage and add that on to my total? For example.... I had traveled 301 miles on my last tank of gas. (.035x301) = 10.535. So 10.535 + 301 = 311.535. My mileage divided by the amount of gas used (311.5 miles/22.6 gal) = 13.78 MPG as compared to 13.3 MPG if I hadnt accounted for the percent that it was off.
Its not really important at all but I was just curious to get other peoples opinions on if I'm on the right track
I went from 265/70/17 (stock) to 285/70/17. The tire calculator said my speedo changed by about 2.5 mph. If I'm going 70, Im really going 72.5.
So...[1-(70/72.5)]= .035 or 3.5% change from stock. Also, I looked at my odometer as I passed every mile marker and it was off by just small amount every time. But as I kept track of the mile markers and my odometer, it started to be off by alot after a while. SO, does this mean that odometer is off by 3.5% as well?
If this is the case, I should take 3.5% of my trip mileage and add that on to my total? For example.... I had traveled 301 miles on my last tank of gas. (.035x301) = 10.535. So 10.535 + 301 = 311.535. My mileage divided by the amount of gas used (311.5 miles/22.6 gal) = 13.78 MPG as compared to 13.3 MPG if I hadnt accounted for the percent that it was off.
Its not really important at all but I was just curious to get other peoples opinions on if I'm on the right track
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#8
04-10-2007 | 09:59 PM
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Joined: Apr 2007
Posts: 52
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From: AL
Originally Posted by jjcsnlynn
Where do I find the "Tire Calculator" ? I went from 235/16s to 255/16s. How much am I off, and what do I need to do to correct this?
This thread is helpful if you're wanting to find out the width and height of your tires.
https://www.f150online.com/forums/sh...d.php?t=281530
BF Goodrich's website also has a tire calculator which will tell you the effects on speedo, gear ratio, ground clearance, rpms, etc. You will need to know your old and new tires' diameter though. I think the calculator is under their tips section. Hope this helps.
#9
04-10-2007 | 10:01 PM
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From: Oklahoma
Originally Posted by jjcsnlynn
Where do I find the "Tire Calculator" ? I went from 235/16s to 255/16s. How much am I off, and what do I need to do to correct this?
http://www.discounttire.com/dtcs/infoTireMath.dos