Tire size

I've got a 2005 Rendezvous and need to replace the back tires only. The owner (my mom) hasn't been getting them rotated. They're 225 60 R17. I have a pair of the exact same tire (used) that I can have to replace them but, the size is 225 65 R17. If I put these on the back, would it be a big difference?

Those tires will be slightly narrower and taller
, no good if you have awd. Under extreme height difference the abs could be affected also. Other than that should be ok.

Tires will be the same width.

Tire size is figured out in the following manner.

The stock size you mention is 225/60/17

225 is the width in millimeters
60 is a percentage of the width to determine the sidewall height
17 is, obviously, the rim diameter

To figure out the size you can do the following

225/25.4 = 8.86" wide (25.4 millimeters in an inch)
8.86 x .60 = 5.316 (because as noted percentage of width)
5.316 x 2 = 10.632 (because 2 sidewalls)
10.632 + 17 = 27.632" tall

So if you do the same formula the 225/65/17 are going to be 28.52" tall.

If you have Excel you can input the following formula

=SUM((((A1/25.4)*(B1*0.01)*2)+C1))

Place the tire size in A1, B1, and C1, and paste the fomula in D1

So 225 would be in A1, 60 in B1, 17 in C1 and the formula will automatically do the math for you.

Like Max said, a difference in circumference could affect ABS/all wheel drive performance.....