Cap sensors are usually smaller and simpler to retrofit. Flow-through sensors can make pressure adjustments easier without removing the sensor, but their extra size makes valve-stem strength and clearance more important.
Cap sensors favour simplicity
A cap sensor replaces the valve cap and is removed when you need direct access to the valve. That makes the hardware compact and easy to understand.
The trade-off is an extra remove-and-reinstall step whenever you adjust pressure.
Flow-through sensors favour adjustment access
A flow-through sensor is designed so air can be added without removing the sensor. That can be useful for owners who check and adjust pressures frequently.
The sensor is typically larger, so stem compatibility and wheel clearance deserve closer attention.
Sensor count comes before sensor style
Count the tires you actually want the system to monitor. Tandem-axle trailers normally need a sensor for each road tire if you want complete trailer coverage.
Decide separately whether monitoring a spare is useful for your setup.
Temperature data is useful context, not diagnosis
Many RV TPMS systems show both pressure and temperature. Changes can provide warning that something deserves attention, but the display does not tell you the mechanical cause.
Stop safely and inspect rather than treating an alarm as a remote diagnosis.
Quick answers.
Are flow-through TPMS sensors better than cap sensors?
Not universally. Flow-through sensors make pressure adjustment easier, while cap sensors are often smaller and simpler. Fit and valve compatibility matter more than the convenience feature alone.
How many RV TPMS sensors do I need?
Use one sensor for each tire you want monitored. Count the trailer road tires first, then decide separately whether to monitor the spare.
Do RV TPMS sensors measure temperature too?
Many systems report sensor temperature along with pressure. Treat that reading as additional warning information and inspect the tire and wheel if the system alerts.
Use your saved trailer context.
Trailerstead can narrow the sensor style only after your trailer tire count, valve hardware and towing setup are known.