I've never had a 15 x 7 SBP rallye wheel in my hands, so I don't know. OP has those wheels and hopes to keep them. If I remember right, the wheels are hub centric instead of lug centric. The only 14" SBP Rallye wheel I have is buried under 30 years of parts hoard in my shed, so I ain't digging it out to see if a 1/2" stud will fit...lol. The 15" SBP Rallyes are an aftermarket wheel, so who knows what size holes they have.