The right size tires
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From: anchorage, alaska
The right size tires
I just bought my 04 cobra and it has some little punk tires on it. What size do most of you all have. I want a good all terain/street tire, so if your answer is 35" swappers don't bother. I just want it to look a little better with out getting silly. What did all of yours come factory with?
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From: Central Texas
Originally Posted by utahtom
Many report the 285's correct the read of the speedo- Stranger things could happen!
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From: Central Texas
Help me out with tire sizes here. Is the 285 bigger in tire diameter or tread width than a 285? On a tire description of 265/75 R16, what do each set of numbers stand for? I know the R16 stands for Radial ply and 16" diameter rim, right?
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Let me clarify that. The first # is the width in mm, then the second # is measured by the percent of the width, which creates the height of the tire. So, if you bump up the first #, it will get wider but also increase the height of the tire also. That is why low pro tires will be like 315-35s, they just take a small fraction of the width.
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From: Second star to the right!
Indeed, 265 or 285 is the width in millimeters and 75 measurement of the sidewall which is the percentage of the width. Like was said before. 
So on a 285/75R16 the side wall heigth is 285 * 0.75 = 213.75 mm = 8.42 in.
16 + 8.42 + 8.42 = 32.84" tire. (8.42 gets added twice, 2 sidewalls in the overall diameter)
The general findings from people are that the speedos with the factory tires are 2 mph off the actual speed at highway speeds. This is what is has been for me on two different trucks. The 285's have corrected for that 2 mph. The question was asked how this affects fuel economy. On both of my trucks, when switching to 285's, I lost 0.9 mpg. Doing all of the math, 0.7 mpg is from correcting the speedometer. The other 0.2 I surmise is from the extra width and weight of the tire.
So on a 285/75R16 the side wall heigth is 285 * 0.75 = 213.75 mm = 8.42 in.
16 + 8.42 + 8.42 = 32.84" tire. (8.42 gets added twice, 2 sidewalls in the overall diameter)
The general findings from people are that the speedos with the factory tires are 2 mph off the actual speed at highway speeds. This is what is has been for me on two different trucks. The 285's have corrected for that 2 mph. The question was asked how this affects fuel economy. On both of my trucks, when switching to 285's, I lost 0.9 mpg. Doing all of the math, 0.7 mpg is from correcting the speedometer. The other 0.2 I surmise is from the extra width and weight of the tire.
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From: anchorage, alaska
(SNIP) I thought it would of help, seeing the truck has so much tq. I thought it would help the over gearing. My bad.
Last edited by IB Tim; Dec 12, 2004 at 09:13 AM. Reason: Language