They are safe. For example, if you buy 15mm spacers, they are supplied with lugs that are 15mm longer, to allow for proper engagement of the lug nut so that you have enough threads to properly secure them in place. You are safe to do 5 to 25mm spacers. I would be cautious about anything longer than that. In that case, you should make sure the wheels you have/want to buy have the proper offset instead (always more desirable). Using 15mm for the front and 20mm in the rear is a very common configuration among 370Z owners. If you go with lowering and/or more negative camber, you could get away with 20 and 25 mm respectively and still have the tire positioned nicely in relation to the wheel wells. Good luck with your decision. The wider stance does look really good.
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2012 GT-R Black Edition Jet Black
2010 370Z 40th Anniversary // SOLD
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