So I have some 20mm spacers I recently put on when I installed my Swift springs on my xS. The spacers are a 2 piece design, where the center section can be removed. I am curious if I can run them without the center section. I have had a sligh vibration since installing them and I am trying to think what could be causing it.

 

The center piece is what makes them hubcentric, which is what you want. Make sure the inside of the wheel were it mates to the hub is clean and not full of scale or rust. I live in FL and mine had some rust buildup inside. Clean that area the best you could,I usually use coarse sandpaper or a wire brush, then coat it with a light coat of grease. Then make sure to start tightening the lug nuts on a cross pattern by hand then slowly tighten to specs. Also make sure that the wheel studs from the spacers are not too long and touching the back of the wheel, keeping it from sitting flush on the hub.

 

I've had this same problem, mine were 15mm ichiba spacers, but the idea still applies.

What can be causing this vibration is that the center part of the spacer isnt seated completely into the OEM rim, its just a few mm short of whre it needs to be. I imagine this is to make sure that it fits any wheel and wouldn't be too long.

The fix, I made a spacer from come solid copper wire and put it behind the center part of the spacer to push it out. Now the wheel will ride on the spacer like it should.

Here is the DIY from g35driver that explains it really well:

DIY: Wheel spacer vibration fix - G35Driver

 

Is it really necessary to keep the center part on? If that is the part vibrating, other than the link, what other tricks can I do to to stop the vibration?

 

Yes it is.

You can buy one piece spacers.