pontiac g5 need some info or pics

anyone got some g5's with 17's or 18's my neice was told 18's would not fit ...but it was a sterio shop that told her ...so i put one of my 20's with a 225/30/20 and they would fit but hard turning so then i put a old 18 with a 235/40/18 and would fit and about the same as the 20 little turning so if a 18 had a 215/35/18 would fit and should turn ...my question is does anyone know if the g5 and gto are the same base model the bodys are the same shape and size ...he 1st new car so she wants to trick it out

i have an ion on hydros with a 225/40/18 and i have no problems. i would like to switch to a 225/30/20 but its basicly the same sized tire. I don't think there is much difference in the cars. Maybe the off set is wrong?

I know that one of the years of this car has big issues with the electric power steering. May want to keep that in mind throwing heavier wheels at it.