Hi luki343, welcome to NICO Club!
A few things. Look at the date of the post you reply to. This one was dated 05 May 2012. It's way old for a discussion topic. Try not to resurrect old stuff, maybe a year tops, or start your own thread. You could have introduced yourself in the same thread. Also, you posted the same question twice, in two different areas, at the same time. Try to post once and give someone a few days to respond before starting more conversations. So, I'll answer here and let the other post lay.
If you haven't upgraded your front rotors, then your rear might not need anything. So I assume you have done something to the front. Do you know how much bigger the pad contact area is in front and if it moved from the center? You probably want the same percentage of upgrade in the rear for bias.
There's a handful of OEM brake options. This wiki page has some pretty useful information.
https://en.wikibooks.org/wiki/Nissan_24 ... ion/Brakes
As far as your question for Altima size, I looked, but found lots of information based on trim and year. So, maybe you can pick a year and ask or look for yourself. Each year has a FSM and the FSM will have the rotor size for that year. Please see this link for Altima FSM by year and go to the BR chapter...
http://www.nicoclub.com/archives/nissan ... nuals.html
For Tida sizes, see the FSM for Versa...
http://www.nicoclub.com/archives/nissan ... nuals.html