+18 with a 9.5 inch rim will be seriously pushing it on a 34, would like good with some guard work and camber.
I have 17x9" rims on my 33 and with +28 the sit quite well, with a 9.5 inch rim that makes it the equivalent of +40ish to sit the same... So anything under Probley a +25/30 will be pushing it.
(better yet borrow ur mates rims, test fit, profit lol)