I just got an OSW and had some issues with them both running at the same time. I've fixed most of them but now whenever the headset is too close to the wheel, the HMD and lighthouses basically disconnect. On SteamVR they grey out.
@Leagle, what is the model of your wheel? This is a pretty hardware specific question. Does the wheel have any reflective surfaces, have any sort of IR emitters, or emit any sort of EM/RF? Since this issue is spatalized and local to a specific region of your tracked volume, namely near the wheel, I would place my initial bets on EM/refectivity.
@Leagle, the cable (and part of the HMD) are shielded for normal usage but due to the bandwidth requirements of the Pro and the overall specifications of DisplayPort EMI interference there is definitely the potential for a strong EMI source to cause the types of interference you described. You could always add ferite cores to assist with EMI but overall it seems like this OSW can be picky about grounding and may just leak alot.
You may want to look into your USB controller and ensure that you're HMD is plugged into a controller that's preferably controlled by the CPU (Intel) rather than an OEM controller (such as Asmedia).