The morning after our first day of driving the Model S, the car gave us a low tire pressure warning for the right front (35 psi).
We found an air pump at a local gas station (yes, driving to a gas station was something we didn’t think we’d need to do). It was a fancy air pump that required one to input the desired final pressure of approximately 45 psi using bar units (which is 3.1 bar, converted with the iPhone app Units Plus Converter).
All Model S have tire pressure sensors, but the older models like ours in the States from 2012 and 2013 do not specifically identify which tire is low or what the pressure is in each tire. The newer models like the one we rented from 2015 let you know which tire is low and have a car status view that gives the tire pressure for each tire.
The very next morning the Model S gave us the low tire pressure warning again for the same tire. We pumped air at Interlaken and verified by the handheld pressure gauge that the pressure was indeed low (38 psi). We called the nearest Tesla Service Center that was on our route for that day (in Bern). We didn’t know if this was a problem with the sensor or a slow leak (we looked for an object in tire but did not see one). They said of course we could come in without an appointment that very same day.
We had planned to tour the Lauterbrunnen valley and the Trummelbachfalle waterfalls before heading to Bern. Since we had been able to drive without a problem the previous day after filling with air, we decided to maintain our planned itinerary (about 60 miles to the service station). Driving along a narrow country back road afforded us the opportunity for some nice photos.
The previous day’s heavy rains filled the waterfalls with raging water giving us a spectacular view of waterfalls throughout the valley.
Later that afternoon we arrived at the Bern Tesla Store and Service Center where they immediately attended to us even though they were clearly very busy with new deliveries and service. Within a few minutes they identified the source of our leak, a screw on the inside edge of the tread!

They called EuropCar rental agency and arranged to charge their account for the service work.
While the tire was being replaced we chatted with the employees about our trip and explored the Tesla store.
The early warning given by Tesla’s automatic tire sensor saved us from the chance of getting stuck on the road with a flat. 20 minutes later, the tire was replaced and we were on our way to our first supercharger in Switzerland.