largest size tires on stock 15 inch rims, 99 4runner?

[srash]

Hello,

I know the recommended manufacturers tire size is 225/75/15 on a 99 4runner, but what is the largest size tire i can put on a 15 inch rim without mods?

 

[PhdNPrerunners]

You can fit a 31x10.50x15 stock

 

[eric_simo99]

You can fit a 31x10.50x15 stock

does that go for all years of 3rd gens?

 

[kaiser]

No not all 3rd gens had 15's most had 16's, in which case you can fit a 265/75-16

 

[Dagobah]

forgive me for sounding stupid, but how does wheel size dictate how big of a tire will fit in a wheel well? I admit I know nothing about tire sizing...

also what do the numbers in, say 265/75-16 mean? How do know the size of the tires from this number?

 

[ChildrenOfBodom]

forgive me for sounding stupid, but how does wheel size dictate how big of a tire will fit in a wheel well? I admit I know nothing about tire sizing...

also what do the numbers in, say 265/75-16 mean? How do know the size of the tires from this number?

265 Is the width of the tire.

75, or the second number, is the percentage of the first number on how tall the tire's sidewall is.

16 is the size of the rim.

For example, a 265/75/16 sized tire fits a 16 inch rim and is approximately 32 inches in diameter. A 265/70/16 has a smaller sidewall, equating to about a 31" diameter.

This can also be applied to the first number.

A 265/75/16 is approximately 31.5-32 inches tall, 10.5 inches wide, while a 285/75/16 is 33 inches tall (note the larger first number, overall width is larger), width is 12.5 inches (the tire width is larger, and therefor the percentage 75, or the second number, now becomes larger as well) and they fit on that same 16 inch rim.

It also works for the 3rd number. A 265/75/16 is a 31.5-32" tire (depends on manufacturer). Note the middle number, 75.

Now, if you increase the size of the rim to 17", while still keeping the same width of the tire, you can compensate the middle number to have the same diameter of the overall tire but decreasing the size of the tire's sidewall to a smaller percentage.

So, essentially, since 265/75/16 is one inch larger than 265/70/16 (stock 4Runner tire size on a 16" rim model), 265/70/17 is equivalent to 265/75/16. The extra one inch of rim size was compensated be decreasing the size/percentage of sidewall, therefor leaving you with the same diameter tire.

Some more examples with common tire sizes for you to wrap your head around:

Stock 16" Rim tire size on 4Runner (approx 30in tire) = 265/70/16
Maximum tire size for stock 4Runner (approx 31.5 inch-32) = 265/75/16

That would be the same as:

Stock size tire on 4Runner with 17" rim (approx 30 inch) = 265/65/17
Maximum tire size for stock 4Runner with 17" rim (approx 31.5-32) = 265/70/17