Depending on the width of the tire. If you're going to be running 205's I think 50 series would be more correct. 60's will make your car look as if it's riding on bubbles.

 

BTW, my rims have a -42mm offset and rub the fender in the rear on hard bumps, though I have 225's in the back and has aftermarket suspension.

 

I run 205 50 15's in the back and 195 50 15's in the front. But my car is lowered. You can pull off 205 50 15's in a non'lowered car easy. Good Luck!

 

I was thinking 55... would that still be safe?

 

I run 205/50-15's all around, with a very low car. I can bottom the suspension, and not have any rubbing. The car sits about 1.5-2 inches max above the bump stops. Of course, my car is an 83 GS, which originally used 13" wheels/tires.
Running a 55 series tire will limit the width you can run, before getting too tall, which will throw the speedo off. It can also cause minor issues with the front spring perches, and lower front fender lip.
Have the tire shop determine which size was OEM, and use an "Inch up" crossover guide, to determine which sizes will keep you at the same overall diameter, and see what your tire choices are in those sizes.
If a 205/50 is the same diameter, then generally you would need about a 195/55 to keep the same overall diameter. Of these 2, the 205/50 will have more rubber on the ground.

 

Here they are.... 205/55-15 on Koenig GT-R wheels.

http://www.geocities.com/pjr300/rx7-wheels.html

Thanks everyone for all the feedback and words of advice!