I want to know how the wheel adapter works.

I googled it but it doesn't tell me what's good or what's bad.

I am trying to put 20 inches on my gs, is it any customed wheel bigger than 19inches requires to have a spacer? and adapter?

Thanks in advance

 

no, if you get the right offset, you do not need spacers or adapters. it's only for wheels that are not spec correctly.

unless what you mean is hub rings, which you should have to avoid vibrtaions.

adapters are like spacers, but usually they are thicker and actually bolt on to the hubs directly and then have their own studs for the wheels to bolt on to. spacers on the other hand are just that, spacers in between the wheels and the hubs

 

Hub rings are used when your wheel bore diameter does not match your hub bore diameter.

Spacers are used when your wheel offset needs to be corrected to either clear your brakes, avoid top mounts or for an aggressive stance.

Spacers 15mm or thicker usually just bolt onto the hub and have their own studs embedded. Easy fitment.

Anything less than 15mm are slip on spacers, however.. you will need to replace the OEM studs with the ones supplied with the spacers. Not an easy job.