difference between 245/75 r15 and 245/70 r16

i'm looking at buying a set of 245/70r16 already on rims to replace the stock 245/75r15 tires. my question is what is the difference between the two sizes other than the rim size? and would i have to modify the vehicle at all the make the new tires fit? any reply is greatly appreciated

 

[toypaseo]

They are almost identical in diameter, width, and circumference...

 

[CDW6212R]

No difference, both are 29.5" tires.

I'm running 255/65/16's, which are 29.0" tires, the same as the stock 235/75/15 tires that my truck came with. I have used that same 245/70/16 tire also, my snow tires are that 29.5" diameter also.

The speedometer is the most accurate with 30.0" tires, which is the common 16" size(99-01's(255/70/16)). Ford made all the 1991-2001 Explorer speedometers to be accurate with the 30" size, 29's will display slightly faster than the actual speed.

 

[Jason94sport]

245/75r16 I ran on my last 1st gen. I should have put them on my 2nd gen but the deal I got was stock size.