I know that you need to keep the difference between front and rear tires height under 3/4". So if I maintain that relationship but drop to a 17" wheel, down from my Touring's 18", will the VDC still work?

There are more tire choices for 17s and I want to run as light as possible. And Racing Hart 18s or 19s, as light as they are, are just too darned expensive. That goes for most light weight wheels in 18" and 19" sizes.

For running around the track 17s are just more desirable, I hope I can run them and not lose the VDC for daily (wet) driving.

 

No the wheel diameter doesn't matter it is the overall tire diameter that makes a difference as the sensor is in the hub.

 

Ah cool, so it's in the hub, thanks!