He guys,

I just bought myself a set of 6ul's for a decent price due to discontiued colors. (Here in europe they cost way higher than in the us).The only downside is that they are in 8 and 9 inches width and a offset off 36.
I've been searching for tyres and the option are little
I can only choose between the toyo R888 or the nankang AR-1

Now about the size's at first i was planning to run the nankangs with 245/40r15 on the 9's at back and 225/45r15 on te 8's at front.
I've read about under steering but will this also occur with the same offset, wheel diameter etc.

Does someone has anyone tried this and experience the understeer or something else?

 

Do yourself a favor and run 225's on 9 inch wheels on all 4 corners. This topic has been thoroughly documented in these forums. Try searching around a bit more

 

You do not want to stagger wheels on a miata. square. 205 on 8, 225 on 9, 245 on 10.

 

This came clear to me after i purchased the wheels
I first thought it wouldn't be an issue but after searching i become clear.
I was just still hoping that with a 245 rear 225 front setup the understeer wouldn't crazy, and hoped that somebody had experienced it.

Anyhow there is no turning back now sadly.
I think i am going to run 225/45 on all fours and hope the best off it.

 

That would be your best bet, you might be able to loosen the rear sway bar, tighten the front or adjust the same direction with springs to make the best of it. The turn in on the fronts will lack a bit of feel everything else equal on this setup

 

Road or race?

 

Most off the time road and maybe an trackday once or twice a year..

 

unless you are hard core full race I agree with Slammed. Run the same size tyre, on road it wont be an issue. Track day, you might notice but if your not going for 10ths it should be fine.

Internet advice is usually to the nth degree of whats right (or wrong) there are many more degrees of gray that will still work okay.

 

225's all around. Obviously 225's on 15x9's all around is the best choice, but 225's with an 8 and a 9 will be way closer to ideal than a 225 and a 245. Basically a wider wheel will increase the cornering stiffness, which increases the response. Increasing response in the rear with respect to the front (ie: wider wheel in rear with same tire) will make it a bit more oversteer on turn in, but unless you are experienced behind the wheel on track, you probably wouldn't even notice.

 

Alright thanks guys! The 245 225 option is a no go. Coming winter i am planning to rebuild the complete rear suspension and the wheels will be spraypainted and some 225 tyres will be ordered.
Cant wait to install them