For my 2012 SV everywhere that I've checked the tires on the 19" wheels should be the same size......
but on mine the rears are 245/45/19".

Am I missing something? I have larger tires on the rear of my '84 Benz coupe but they're wider not taller and it's RWD.

 

Someone put the wrong size tires on.

 

Are the tires the original RSA's?

 

No, the car had 85,000 Kms on it when I got it 2 weeks ago. But they are the crappy Goodyears that are quite recent, they still have nipples.
Being on the front they lower the front end about 1/2" to give it a SPORTY look but must screw up the speedo readings.
I'll go for a run with my TomTom to check how much up or down the speed actually is.

This is the picture that clued me in, thought it was just the camera angle.

 

I would take it back to the dealer and see if they will change them to the correct size. More than likely the business that changed the tires didn't have four of the same size and put on the larger size hoping no one would notice, or the previous owner permitted the different size.

 

The rear wheels seem be just there for the ride cause the front wheels seem to control the speed and any programing like MPG average etc.
The speed was almost the same as read on the GPS.
I'll just keep it the way it is until it time to replace the Crapyear RSA's.

 

If you got the car from a nissan dealer, i would be right back on the front door, that is nothing more than shoddy crap to do that, If it was gotten from any one else i would still be talking to them. Why settle for this if you dont have to.

 

Won't hurt to try.

 

Take it back to the dealer. When I first bought my car I noticed I had four different brand tires on it (lol). They replaced them no questions asked. But they did manage to put the wrong size on again, so they replaced those as well. But then they managed to 3 of the same tire and 1 different brand, so now I finally have 4 of the same times and I got to keep two brand new ones as spares. Just my two cents. Definitely would be worth trying if you recently bought the car.

 

All the work of pulling and steering the car are done by the front wheels. The rear wheels just go along for the ride and participate in the braking action. I would just leave them alone as they will not harm the car if the remaining tread life is low. If tread life is high it would be problematic for tire rotation.
PS my BMW 535i has different tires for the front and back by design

 

I agree!

 

I agree that the back wheels dont do much, but that will also keep him from rotating his tires. If he moves those tires to the front, the speedometer and odometer will be off by 3.7%. Its up to the OP if he wants to live with that 3.7% difference.