Tyre Size Questions

[Triptych]

Hey guys, I recently picked up a set of Nismo LMGT3's but the tyre size on them has me confused. The rims are 17" and the fronts are 7" and the rears are 8" but I am confused about the tyre size that is on them. The rear tyres are 235x40 but the front tyres are 215x45. The bit that has me confused is that seeing as though they are 17" rims shouldn't it be either 40 or 45 all the way around. I need to replace the fronts so I was wondering should I try and find tyres that are 215x40 to match the rears therefor giving me the same height all the way around or am I looking at this wrong?

[KiwiRS4T]

The numbers 40 and 45 are the aspect ratio not the height in mm. if they both had the same aspect ratio number then the wider tyre would be higher ( have a larger rolling diameter) then the narrower tyre. Google "tyre aspect ratio" for a longer explanation with diagrams etc.

[Triptych]

Cheers for that buddy, So the 40 and 45 are the correct sizes. Sorry I don't know too much about tyres as you can prolly tell but I always thought the 40 and 45 etc was the height of the tyre itself which is why I was under the impression that I was running to different heights. So I would still hunt down some 215 x 45 to match the 235 x 40.