Tire Questions - All Terrains and Larger Sizes

[campy82]

^ very helpful info, thanks! I'd like to increase contact patch and keep or slightly inc oem tire height so that's why I was looking at bumping up 70... Maybe 245/70 or 255/70?

[jdstrickland]

Originally Posted by campy82

^ very helpful info, thanks! I'd like to increase contact patch and keep or slightly inc oem tire height so that's why I was looking at bumping up 70... Maybe 245/70 or 255/70?

I just (yesterday, 04/16) installed a set of 245/65x17, Bridgestone H/L Alenza Plus, with the 80,000 mile warranty. Factory fitment on my 3.0 is the the 235/65x17, so my tires are 10mm wider than stock. This is not much, but the weight rating goes up almost 200 pounds per tire, and my tiny brain thinks this is a stronger casing that won't go ape-shit in a blow out. Even flat,the stronger casing should be more stable than the one with the lower rating, and the abrupt change in steering dynamics should not be quite so abrupt if the casing is stronger. There's not much of a pricing difference between the factory tires and the larger ones that I bought.

You will certainly increase the contact patch with the 265.

It might help to understand what the numbers mean. In a 245/65x17, 245 is the tread width, 65 is the aspect ratio (percentage of the width that is the sidewall height), and 17 is the size of the rim.

245 is not exactly tread width, but close enough. 245 is a wider tread than 225 and narrower than a 265. The number is in millimeters.

Multiply 245 by 0.65 (65%) to arrive at the height of the sidewall.

Since there are two sidewalls between the ground and the opposite side of the tire, adding the (sidewall x 2) / 25.4 (convert the millimeters to inches) + the rim size will give you the overall diameter of the tire.In our example, 245 x .65 = 159.25 x 2 = 318.5 / 25.4 = 12.5 + 17 = 29.5 Knowing the overall diameter, you can then multiply by Pi, 3.14159, to get the circumference, and divide that into a mile to arrive at how many times the tire goes around.

You can work the formula and switch the numbers to 265 instead of 245.

If you were to buy new rims and wanted to end up with the same overall diameter of the tire, then you would go from the 245/65x17 to a 245/60x18 or 245/55x19. Knowing the formula, you could build a spread sheet that calculated all of the variations that get you to a similar overall diameter, but increase the width and rim diameter. You might not want a 265 on a rim that's 7 inches wide, and you surely would not want a rim that was 19 inches around and only 7 inches wide.

Therefore, if you bought a set of 19x9s to support the 265 or 275, then you would drop the aspect ratio to somewhere around 50, maybe 45. You would have a wide tire with a narrow sidewall, but still be at about 29 to 30 inches in overall diameter.