Fit the PSI.
Fit the Wheels.

Start from the cold pressure on your tire sidewall or the placard, then pick a system rated above the highest number your tires ever reach. If your cold pressure sits around 100 PSI or below — most travel trailers, camper vans and passenger-class tires — the RV01's 116 PSI ceiling is the right path, with 4/6/8 wheel kits and a trailer-layout display. If your cold pressure runs higher, or you tow a heavy travel trailer or 5th wheel, go to the 200–217 PSI path and the S04, which carries headroom above 116. The S08 is also 217 PSI rated if you specifically need 8 or 12 wheel positions.

Answer the pressure question before the vehicle question. If your 5th wheel tires are rated near or above 100 PSI cold — common on Load Range G/H/J — take the 200–217 PSI path and the S04. If the trailer runs around 100 PSI cold or below and you want a display that mirrors the trailer layout, the RV01 covers the dually plus trailer in its 6-wheel and 8-wheel kits. Either way, add up the truck's wheels and the trailer's before choosing: a dually is already 6 positions.

One question separates them: how much headroom you need above your cold pressure. The S04 runs to 217 PSI and is fixed at 6 wheels — it is the pick for heavy travel trailers, 5th wheels and any tire whose cold rating sits near or above 100 PSI. The RV01 stops at 116 PSI but offers 4, 6 and 8 wheel kits and a display laid out like a trailer, which suits light and mid-weight trailers plus camper vans. Same sensor standards, different ceilings — the pressure number decides.

External sensors (RV TPMS & Solar model) screw onto your valve stems — easy to install, and swappable between vehicles. Internal sensors (AN-15) mount inside the rim for 100% anti-theft protection and slightly more accurate temperature readings. Internal sensors require a tire shop to install.

For rigs over 30 feet, we recommend adding a Signal Repeater — RV chassis and metal attenuate RF signals, and the repeater amplifies the 433.92MHz signal to keep rear sensors connected on long motorhomes, 5th wheels and towing setups. Why do the 550S and 860 list 5 m and 10 m when the other models show 40 m? Because that's the sensor's base range before the included Booster or Repeater extends it — the 4-to-12-wheel systems (RV, Solar, S08, AN-15) list their 40 m open-air range, while 550S kits at 14 wheels and up ship with the Signal Booster and 860 kits at 22+ wheels include the Repeater. So it's not less range on the heavy-duty systems — it's the relay that carries the signal the full length of the rig.

Most sensors deliver up to 12 months of continuous operation under normal driving conditions — and the 550S and 860 sensors run up to 2 years on a user-replaceable CR1632 cell. The display unit will proactively alert you when any sensor battery runs low, so you're never caught off guard.

Check two numbers first: cold pressure, then total wheel positions. For a trailer with 8 tire positions running around 100 PSI cold or below, the RV01 8-wheel kit covers it — that is a trailer kit, not a truck-plus-trailer mix. Above that, the 550S scales 6 → 36 wheels, the D550 covers 6 → 40 with independent per-axle thresholds, and the 860 goes to 110 wheels across multiple trailers on a 5" touchscreen. All three run the Infineon chip, and the larger configurations ship with a signal booster.

Yes — the RV01 is available in a 4, 6 or 8 sensor kit. The 8-sensor version is meant for trailers with eight tire positions running around 100 PSI cold or below, and it keeps the same trailer-layout display. It is not a substitute for a high-pressure truck-plus-trailer setup: if your cold pressure sits near or above 100 PSI, or you are mixing drive tires and trailer tires above that number, move to the 200–217 PSI path instead. Count the positions on the trailer first, then match the kit to that number.

Yes — the Grundig 860 stores multiple trailer profiles. Pair each trailer's sensors once, then switch profiles on the 5" touchscreen whenever you swap trailers: no re-pairing, no re-learning, and no false alarms from a trailer parked at home. The 550S keeps a single configuration, which is why it suits dedicated semi and fleet trucks rather than multi-trailer switching.

They work on any trailer with standard valve stems — horse, boat, utility, cargo, equipment and travel trailers included. External sensors screw on in minutes and can be moved between trailers; the AN-15 uses internal sensors if you want anti-theft protection. If you tow more than one trailer, the Grundig 860 stores a separate profile for each, so you can switch on the touchscreen without re-pairing.

Both are 200 PSI systems that scale from 6 wheels up; the difference is display and ceiling. The 550S is the heavy hauler — solar + USB-C charging, a backlit LCD, and 6 → 8 → 14 → 22 → 36-wheel coverage, with the Signal Booster pre-packaged on 14-wheel-and-up kits. The 860 is the flagship — a 5.0" HD touchscreen, coverage from 6 to 110 wheels, and multi-trailer memory that stores each rig as its own profile so you can switch trailers in one tap with no re-pairing (an optional GPS edition adds compass, speed and altitude). Choose the 550S for one dedicated semi or fleet truck, and the 860 if you tow several trailers or want the touchscreen and the largest scale.

One sensor per tire. A dually truck by itself is 6 wheels (4 rear + 2 front), and you add a sensor for every tire on the trailer you pull — a single-axle trailer adds 2, a tandem-axle adds 4, and so on. Our systems come in fixed or switchable wheel counts so you can match your rig: the RV TPMS covers 4/6/8, the Solar 6-Wheel is fixed at 6, the S08 does 8/10/12, the 550S scales 6/8/14/22/36, and the 860 goes from 6 up to 110. Add up every tire you want to watch on the truck and the trailer, then pick the system whose wheel count covers the total.

Yes. The external-sensor kits are a DIY install you can finish in under 10 minutes with no tools — the sensors simply screw onto your valve stems and the display is ready to go. The AN-15's internal sensors are the one exception: they mount inside the rim, so a tire shop has to fit them. In the box you get the sensors and the display monitor, plus everything you need to start rolling; 550S kits at 14 wheels and up include the Signal Booster, and 860 kits at 22+ wheels include the Repeater.

External sensors screw onto the outside of the valve stem, so they're visible and easy to move between vehicles — that's their convenience. If tamper-resistance matters to you, the AN-15 is the anti-theft pick: its sensors mount inside the rim, invisible from the outside, so there's nothing on the wheel to remove. The trade-off is installation — internal sensors need a tire shop, while external sensors stay a do-it-yourself swap.

No — a single display covers both. The Solar 6-Wheel, for example, watches all 6 wheels of your dually plus your trailer at the same time, and the larger systems scale from there: the 550S reaches 36 wheels and the 860 covers up to 110, with each trailer stored as its own profile. Add up every tire you want to watch on the truck and the trailer together, then pick a system whose wheel count covers the total.

Most Grundig displays charge by Solar + USB-C, so there's no need to plug in — that covers the Solar 6-Wheel, the AN-15 and the 550S. The S08 runs on a built-in 650mAh rechargeable battery, and the 860 uses a 1250mAh battery that can be powered from a DC 9–36V source, which suits 12V and 24V vehicle systems. Whichever you choose, the display is a self-contained cab unit — the sensors talk to it wirelessly, so there's no wiring run out to the trailer.

Yes — every Grundig sensor is rated IP67, so it's sealed against dust and protected against water. Rain, car washes, wet roads and splashing through water crossings are all fine, and IP67 means a sensor can even handle temporary immersion without damage. That rating applies to the sensors on the wheels; treat the display like any dash electronics and keep it out of standing water.

Alerts appear in real time on the display, so you'll see a problem without having to watch the gauge. The 550S runs 7 real-time alarms covering pressure, temperature, fast and slow leaks, and sensor faults. The AN-15 flags 5 alert types and refreshes every 0.3 seconds, so it reacts almost instantly to a change. Our sensors also watch temperature, which catches a failing tire earlier than pressure alone.

Yes — both the Grundig 550S and the 860 let you set the pressure alert value for each axle independently, so the steer axle, the drive axles and the trailer axles don't have to share one number. That's useful on multi-axle trailers, dually trucks and semi tractors, where the correct cold pressure on one axle is often not right for another. Everything else about the alerts works the same way: pressure, temperature, fast and slow leaks, and sensor faults flag on the display in real time.