tire help needed ASAP 4 2003 350z

[kaya16]

I need 4 tires b/c tire wear is so bad 2003 350z so i found almost new 245/45/18 potenza's for back for $50 each. Well can't find replacements for 225/45/18 anywhere. A Guy got in almost new perrelli's no wear on them and give them to me for $70 piece but they are a size smaller then the 225/45/18 i have on now. He says won't make a much of a difference but I am not to sure b/c I don't know much about cars. I am all about saving $$$ b/c lost job. These tires are all in great mint shape and retail for big$$$. I need to know asap b/c i have a leak in front tire now. Please help!!! Or should I just get the backs and go online and order 2 new tires for front. If so can you recomend a solid but cheap pair I should look for. I really think I will be buying the used potenza's for the back for $50 need help for front

[evildky]

so your concern is that his 225/45/18's are smaller than your tires of the same size? it should be close enought o work, manufacturers will differ a bit but should still be close enough

[C-Kwik]

Tire diameter ratio between front and rear must be maintained. So if you are using the same size rear tire, then the front tire diameter can not be changed much. Too much change can activate the VDC or traction control on its own.

[xjmxstac]

... give them to me for $70 piece but they are a size smaller then the 225/45/18 i have on now...

You must define "a size smaller"....