Ram’s Trailer Tire Pressure Monitoring System

Greetings RV enthusiasts!

This post is about Ram’s “Trailer Tire Pressure Monitoring System” or “Trailer TPMS.

When I special – ordered my 2022 Ram 3500, I purchased this particular option to save real estate on my dashboard.  Unfortunately, after the truck arrived I was soon met with a disturbing problem:  The supplied sensors didn’t fit my wheels!

In this post,  I will describe the after-market solution that solved this problem, and then describe my successful Trailer TPMS system setup. First up, however, is a photograph of the Ram-supplied sensors that don’t fit:  There’s not even one exposed thread available for the capture nut!

From Stellantis to Dealer

My first attempt at solving this problem was to contact Ram Customer Care, where I discovered that the technical resources I once enjoyed under Fiat Chrysler have been dismantled:  Anything that cannot be addressed by a non-technical support agent is re-directed to the local dealer’s service department.  However, even that road was a dead end, as my dealer dutifully stayed on script, citing the trailer length recommendation found in the owner’s manual to explain my problem:

“The TTPMS may have difficulty transmitting through steel-walled tires or on trailers longer than 30 ft. It is recommended to use standard tires and trailers less than 30 ft. long to avoid dropouts or difficulty when pairing.”

I discovered that this recommendation is used to disclaim Ram’s obligation to support any trailer over30 feet in length – and apparently not even trailers with steel-belted tire as well.  Since my fifth wheel is listed at 35 feet (pin to bumper), no support within the Ram ecosystem was available to me.   I discovered that there are no alternate stems available for thicker wheels, for example, and that dealers have been given no additional guidance regarding this problem.

Problems are meant to be solved!

Closer reading of the above statement in the owner’s manual reveals that the problem is not about wheel thickness it is about radio wave propagation.  I turned to the after-market to solve the sensor fitment problem and decided to take my chances on the radio wave propagation issue.  After all, at approximately 18 feet, the distance from my bumper to my fifth wheel’s axles is not that much different from a 30 foot conventional trailer.

It turns our that a custom-machined valve stem from Nichols Manufacturing and Welding Services in Phoenix, AZ was the answer.  The Nichols stem fits the Ram sensor perfectly and provides a superior solution. Here is the instruction sheet that arrives with the Nichols stem:

Note the advantages of the Nichols stem, shown in the next photograph (below). At the top of the photograph is the sensor and stem combination as supplied by Ram.  In the middle of the photograph is the valve stem supplied on my trailer’s wheels, for comparison purposes.  At the bottom of the photograph is a Ram sensor built with a Nichols stem, which the combination I used.  You can see that the grommet supplied by Ram certainly fits the 5/8” opening for heavy duty wheels, for example, but does not extend very far into the wheel itself.  This produces an inferior seal that is more likely to leak.   Compare this with the grommet supplied by Nichols and the one supplied on my trailer’s wheels.

In addition to the grommet, the keeper nut supplied by Ram introduces problems of its own, due to its “recessed threads” design which makes it impossible to capture the stem (See photograph below):

Installation with the Nichols stems

Building the sensors themselves with Nichols stems was trivial, using their instructions.  Installing the completed sensors into heavy-duty trailer wheels is another matter, but one easily performed by a competent tire shop.    Not just any shop will do—you must find one that can perform a custom installation.   One shop that I tried, for example, refused to follow Nichol’s instructions stating that they didn’t even have Loctite on hand.  The shop I chose is part of a well-known regional brand in the Northwest, and the technician who worked on my tires was very experienced.

Getting your trailer tires into the shop for this installation could be challenging, although good shop will have all the right equipment to dismount a tire from your trailer.  Consider, however, that you need to be able to change a trailer tire on the road anyway, so this is a good time to exercise that capability.  I ended up taking my tires in, two at a time.  Here are some photographs of the install:

Here is the completed install:  The Nichols stems are the same length as those supplied with my wheels.

Notice the seal produced by the Nichols stem.  This one is not going to leak!

I used Loctite on the sensor-end of the stem  to ensure that the assembly won’t work loose over time.  Red Locktite overkill and ensures I’ll have to replace both the stem and the sensor at the same time if either of them fails. Blue Loctite would have been sufficient.

Now for the fun part

With sensors installed in all four of my trailer tires, I began the pairing process, following the on-screen instructions as shown below.

The pairing process itself is rather finicky, even when following directions to the letter.  All four tires must be paired in sequence, and allmust be successful or you have to start over. On some of my pairing attempts, the system pre-populated the target tire pressure with some ridiculous number that made no sense, as shown below.   The pairing process always failed when this occurred; clearing this problem required a hard reset by disconnecting the truck’s batteries.

Success!

After several attempts and a greater understanding of the finicky pairing process, I achieved success.  Below is a photograph of my U-connect screen patting me on the back for good work.  But now the question remained:  would the sensors populate the instrument panel with useful numbers?

The photograph of my instrument panel (below) shows my trailer tire pressures after an hour of highway driving.  Having filled to 110 psi (cold) you can see the result:  My trailer tires are runing about 16 psi above the cold inflation pressure, which includes the effects of rolling resistance,  hot pavement and a rising ambient temperature.

Conclusions and Observations

My trailer length is probably near the edge of reliability for this system, but it works.  I observe that the numbers on the screen change about as frequently as the truck’s own TPMS system, which tells me that radio wave propagation and dropouts aren’t a problem.  The convenience of avoiding another display on my dashboard, for an after-market TPMS system, is quite gratifying!

My overall assessment is that this is not a well-thought-out system but a rush to market.  It puzzles me that Ram would supply a solution for trucks capable of puling large, heavy trailers, and then withdraw support for trailers longer than 30 feet and/or using steel-belted tires. Fortunately, the system works on my 35’ fifth wheel, but it took an after-market product and some heroics to be successful.  In the future, I hope that Ram will provide a repeater or some other way to accommodate the longer distances associated with the trailers for which we buy model 3500 trucks. After all, the after-market has solved this problem with complete systems that work reliably.

Here are some additional observations:

1. The trailer does not have to be connected to the truck for the pairing process to work – the two just have to be close. In fact, the truck doesn’t know or care where the tires are – they don’t even have to be on the trailer.
2. It can take up to three minutes per tire for the system to pair. The correct procedure is to deflate by 5 psi, and then wait for the horn chirp as stated by the on-screen guided instructions. Do not keep letting air out ‘slowly’ as more than one internet source has advised.

For reference, here is the Nichols company website.  You’ll find them to be a good honest small business that produce a good product.

Here is a post on tire inflation that you might find useful as well.

happy RVing,

-Doug