Thanks, You are right. I did not really think about that prior to your post. They sent some metal valve stems with the units. Next time tire change comes up I will replace.

 

I checked into them thinking a little advance warning of low pressue might help, but any sudden deflation at highway speed probably would be too late. Seems you have to get solid metal stems to replace stock rubber which are not recommended for the application. Harley dealer didn't have them, but Mfg. of monitoring system sells them for Harleys. Laying down on the ground with a full-dresser to check the rear tire pressue is a pain, which is why I was considering them. So far I've held off due to price, but it's still in the back of my mind.