Whatever money you save on tires, you'll lose back spending more on gas because you'll be spinning your engine higher due to shorter gearing.The difference in diameter is more than an inch not 5mm, that's huge.

 

Man falkens get mad shoulder wear real quick. I had a set on my old jetta that only lasted like 4 months. Nice sticky tires, but man no tread life.

 

This maybe too late but here is the right size tires for you for $180.

 

I kind of skip over all the other posts, so please excuse me if I repeat or contradict anyone.

The short answer is "it depends." Tires from different manufacturers are probably going to be different physical sizes. Take for instance, the Falken RT-615 and the Dunlop Direzza Star Specs. There is an image online where they stacked the RT-615's and the Star Specs next to each other. The Star Specs stacked higher. See this thread:

http://sccaforums.com/forums/10/291603/ShowThread.aspx

I think the best thing to do is call a shop and ask. I am sure they've dealt a lot with various tires, and they could probably tell you what you need to know.

 

how much bigger can i go. my falken i wanna get are 225/45/17. how much bigger can i go without debeading?

like what would be safe safe width and what could i push to the max?

 

With 17x7" stockers... I'd say 225/45-17. 09 WRX MT comes w/ THAT tire size now. 235+ requires 7.5"+ width.

 

205 is too small unless you're running 6.5 inch rims and snow/rally tires. Woot for skinnies in the snow.