I have been looking at the difference in tire valve stems on my H3 and actually others. The four wheels on the ground happen to have what looks to be a steel type of stem where as the spare has a rubber type stem.
Could anyone shed a little light as to why this may be?

 

My guess would be the TPMS. I believe the spare is not monitored at least not on the newer models. So if you do have a flat you have a light reminding you to get your tire replaced or repaired.

 

You may have something here. My on star report came in saying check tire pressure and could not complete. Well I checked the pressures all 4 tires were fine. I open the fiberglass spare cover and BAM no TPI just a plain rubber valve stem. This is on my 09 H3X. I traded in an 06 H3 Adventure that had all 5 tires with TPI's. Do the new ones come only with 4 TPI's or did I get screwed? I want all 5.

 

can anyone tell me the widest tire that can be fit on the stock 16" wheel?

 

The 2009 H3's only have 4 TPM's. The spare is not included. The system is too sensitive anyway.