Basically, i know that it is the "50" or the "55" that makes the difference, but i am curious if my speedo, which was calibrated from the factory to read a "55" size tire, is clicking on miles quicker than it would with my "50" series tires...I know the difference will be minimal, but will it be 500 miles? 1000 miles? Just a thought.

If anyone has any idea how to figure this out, please enlighten me. Thank you.

 

the 195/55/15 will have an extra 14 mm's added to the overall diameter of wheel/tire. So less turning.

 

Let me take a stab at this:

Using the tire calculator: http://pw1.netcom.com/~sgalaba/tiresize.htm
It says that if i was travelling at 60mph with the stock tires, I would have to go 60.97mph with my current set-up (205/50/15) to truely go 60mph.

Additionally, 81.3mph with the "50's" = 80mph stock

Lets figure this out in two higway scenarios:

32,000 miles/60mph = 533.33 hours (what is clocked)
32,000 miles/60.97 = 524.85 (what is reality)
8.48 hours (difference) x 60mph = 508 miles

32,000 miles/80mph = 400 hours (what is clocked)
32,000 miles/81.3 = 393.6 <U></U> (what is reality)
6.4 hours (difference) x 80mph = 512 miles

So you see, the difference between the two tires is roughly 500 miles that is overstated on my odometer in the current situation. Not that much difference, but interesting notheless....