Vibration issue

[Gregvip1]

Hi Guys
My 3.0d has just has the lower arm replaced on the drivers side. i have also gone up a size to the facelift 20inch alloys. Since all this i have had a vibration between 45-60. we have a balancer machine at work but i dont believe it is designed for 20inch alloys so i went ahead anyway and rebalanced them but to no avail. still i get the vibration. do u guys have any idea what it could be down to. also since having the lower arm done at bmw the steering wheel is very slightly off centered but the car still drives in a straight line without pulling to the side.
thanks guys this issue is really peeing me off