Tires 265 Vs. 285's - Page 2

firemansdiesel · 10-16-2008, 06:19 PM

Bigger the tire, the more your RPM's drop and give better mileage on the freeway. On city driving you will lose 1-2mpg depending how big of a tire you go with.

**Johnasara** · 10-16-2008, 06:47 PM

I agree it gets worse in town because of greater rotating mass. But on the Highway you actually travel further per rotation.

**Tow Master** · 10-16-2008, 11:54 PM

Quote:

Originally Posted by tdpete

Strange, why would the smaller tire give less milage, would think it the opposite.. larger tire, more distance per turn of the hub...

I plan on correcting my speedo with my Juice Programmer.. can't I do that?http://i60.photobucket.com/albums/h3...ies/Really.gif

You know I always wonder the same thing! I agree with firemansdiesel though. The different RPM's cause it to kill the mileage.

**n0useforaname** · 10-17-2008, 05:46 AM

If you're anything like me, you'll contemplate for days on which size to buy...but in reality you want the 285's....I say get the 285's. I"m going to.

**bowhunternkbay** · 10-17-2008, 06:40 AM

The larger the tire size, the less revolutions per mile. Since the speedo is calibrated with the stock tire size, you need to recalibrate the speedo. When I purchased the 285's on my truck now,they were 4" larger in diameter than the stock tires(245's).When my speedo said I was goin sixty,I was actually going over 65 mph!! So, recalibrate the speedo.

tdpete · 10-17-2008, 05:57 PM

How do you like the Goodyear Silent Armor.. and are they E Rated?.. I am not finding a lot of E Rated 285's.. Most seem to be 265's in that size.

**Hook'em_Horns!** · 10-17-2008, 06:39 PM

Sent ya some sources.

MacRebel · 10-18-2008, 09:25 PM

The bigger the tire, the more rolling mass. The increase in torque to establish and maintain speed is what lowers fuel economy. Just like everything else, there's a happy medium between too small and too large. : )

LNXGUY · 10-19-2008, 11:36 AM

As long as the overall wheel/tire diameter doesn't change from stock, you won't have to re-calibrate anything, regardless how wide the tire is....

You could run a 245/75-16 and a 305/75-16 and as long as the diameter is the same, you are good to go.

Rolling resistance is also higher with a wider tire, so you'll lose fuel economy, not gain it.... Simple physics.

**Duramaximos** · 10-19-2008, 12:04 PM

Quote:

Originally Posted by LNXGUY

As long as the overall wheel/tire diameter doesn't change from stock, you won't have to re-calibrate anything, regardless how wide the tire is....

You could run a 245/75-16 and a 305/75-16 and as long as the diameter is the same, you are good to go.

Rolling resistance is also higher with a wider tire, so you'll lose fuel economy, not gain it.... Simple physics.

EXCEPT - those 305/75 - 16's are 3.5" larger diameter than the stock size you quoted.

You would need to buy a much lower profile 305 to get the same diameter as a 245/75.
I think a 305/60 would be close, but good luck finding an E rated tire in that size.

On the subject of fuel economy -
There is the issue of rotational mass. A wider tire WILL have much more rotational mass, and no matter how you slice it, more mass requires more power, regardless of the speed you are traveling - city or highway.

Also, the further away from the centre you move the mass,(ie 16" vs. 18" vs. 20" rim size) the more force is required to move the mass. So...a 265/75R16 will require much less force than the same rubber at 305/75R20. Although the rubber is the same size the latter is further away from centre so more force is required to turn it.

Unfortunately, tire size is one subject where you can't have your cake and eat it too.

Buy them because you like them, but don't expect better, or the same mileage because it won't happen.