Hubcentric rings?

[araine901]

Do I need hubcentric rings for these wheels. They were on the car when I bought it. I think they are e38 16" wheels. I am getting a thumping vibration from the rear wheels more often when cold, and goes away. I have had the wheels balanced twice (two different shops) its Better but not gone.
Any suggestions.

Also just installed a EAT chip yesterday. That thing is awesome. I only wish it came with instructions or had instructions on the website. I used the ones on Turner Motorsport. Same process

Thanks,

Aaron