im running 205/50/16's all around except 1 tire its 205/55/16. its on my rear left tire. i got it for very cheap

 

as long as the car isn't all wheel drive you will be fine if you DID rotate it to the front theres a possibility of slight strain on the tranny, and it might even cause the car to pull slightly....but both of those are iffy....

 

 

Define "ok". It's certainly not recommended...