(Tire) Pressure

When towing a tandem-axle trailer with a pickup, you have eight tires on the ground (or more, if you have a dual set-up.) Eight tires means double the probability of a tire problem, and all that weight means the consequences of a failure are much worse. You may not want a tire failure on your family car, but you REALLY don’t want a tire failure while towing an RV.

We have a basically new truck and a basically new trailer, but we have still had two “tire failure events”. The first time, we were driving along a winding road near the Oregon coast, and ONE trailer brake locked up. Almost immediately, we had a puff of smoke and a blown tire. It turned out that the brake/hub/axle was defective from the factory. Airstream got us a new one express shipped and installed within a day under warranty.

The second tire incident may have been related to the first. About 2,000 miles later, we were towing up another winding road in the Oregon Cascades. It was nighttime, and we were on the way to Detroit Lake State Park. About 10 miles before our destination, I felt a very slight tug from the trailer. It was fairly subtle, and lasted only a fraction of a second. After that, everything seemed normal. I was concerned that maybe a trailer brake had started to lock up again (although the entire hub/brake assembly had been replaced with a new one, so it seemed unlikely). The trailer towed normally for the rest of the ten miles into the campground. Laura jumped out when we arrived at our site and went back with a flashlight to make sure we went smoothly into the pitch black campsite. I backed into the spot easily, and Laura came to my window (which she normally does to say something like “looks good, back up maybe six more inches, we’re level left-to-right…”).

This time, she did NOT say that.

“Um, honey? We’re missing a wheel."

(OF COURSE that’s not what she meant.)

“We have a flat?”

“No, we are missing a wheel. From the trailer. The wheel, tire, everything. Gone.”

I then fine-tuned my entry in the “stupidest question in the world” contest…

“Are you sure?”

“…” (My question did not rate a response)

“Come look. I was looking to make sure the stabilizers would clear the curb, and it was really dark, and something was weird. I could see one silver part of one wheel, but then there was just black for the other one. I put my hand out and there was nothing there. Just that gnarly metal nub, like when they grind a tooth down to put a cap on it."

I grabbed a light and went back to look. Front trailer tire and wheel…check. Rear trailer tire and wheel… GONE. There was only the hub/brake assembly hovering in space with two of the studs broken off at the hub. Behind that, there was some bodywork damage to the rear underside of the trailer – apparently inflicted by the wheel/tire assembly as it departed the scene. THAT was the “slight tug” we had experienced ten miles before.

Not good.

I should take this opportunity to modify my alarmist statement above about “tire failure events” towing an Airstream. While it seems like a sudden and complete tire failure on a loaded 6,000 lb trailer being towed up a winding mountain road, with steep drop-offs on the sides, in the dark, would be a VERY BAD THING – the truth is we noticed nothing. The trailer towed as normal for ten more twisty, hilly miles, into the campground, and into the site, as if nothing had happened. Also, in the first incident – with a sudden blowout, the trailer towed as normal (although in that case I knew about the problem so I went very slowly and carefully to a safe pull-off).

I know this would not be true of every trailer, and it makes a good argument for a tandem-axle design versus a single axle design. If a single axle trailer had a wheel depart, I’m certain you would not continue calmly to your destination unaware.

In retrospect, the loss of the wheel was probably due to lug nuts either being too loose (wherein the vibrations would slowly cause the lug nuts to back off until the tire started to wobble – causing the lugs to shear and the wheel to break free) or by the lug nuts being over-tightened damaging the studs and causing them to break under load much later. The last time these lug nuts had been touched was when the shop replaced our hub/axle. That shop, I believe, either over- or under-tightened our lug nuts. I did not heed the warning (which I believe is posted on a sticker on many trailers) to “re-check lug nut tightness after 50 miles”. Do it. Really.

We went searching for our missing tire/wheel the next day. It was an exercise in futility.

We called a towing and roadside service company in the nearest town, and they sent a guy with some replacement studs. He took the hub off the trailer in our campsite, removed the broken studs, pressed in some new ones, and then we fitted our spare tire. $300 later, we were good to go again.

Once back home, we dropped the trailer at Airstream Adventures Northwest for repairs to the damage to the rear of the trailer, plus a replacement wheel/tire. They did a perfect job – the damage is completely gone. Total repair cost was about $2,000. (Ouch!)

Having two wheel/tire failures in a relatively short period of time gave rise to an unreasonable paranoia about our wheels and tires. I now check the lugs before each trip. I check the tire pressure before each drive.

We wanted a peace-of-mind solution for tires. We decided to get a remote tire pressure monitoring system. After a bit of research, we decided to go with the:

Hopkins 30100VA nVision Tire Pressure Monitoring System

This system sits on the dashboard and gives you a nice green light if all tires are at the proper inflation. If one of them gets a tiny bit low, it beeps and gives a yellow light. If pressure drops substantially, it beeps LOUDLY and lights a red light. It has a popup screen that shows air pressure in every tire you have.

The system requires you to put a special transmitter on each tire – where the valve cap would normally go. The main unit plugs into a 12V plug and sits on your dashboard. It monitors the tire pressure wirelessly.

There are some issues we’ve had with this unit. First, the user interface for setting it up is very clunky and unclear. It took quite a bit if futzing around to get all the sensors installed and working properly.

Second, it only comes with six sensors. You can buy extras in pairs. If you’re using a four-wheeled tow vehicle plus a four wheeled trailer, you need at least two extras. If you want to monitor the pressure in your two spares as well – you need two more.

Third, the sensors have to be replaced periodically – every couple of years maybe? We don’t know for sure yet. We’ve had one sensor fail in two years of use.

Fourth, in our configuration, the signal from the trailer sensors to the receiver on the dash was intermittent. The company sells a special “booster” add-on (which we mounted in the canopy in the back of the truck) to help when there is a long distance between the truck and the trailer. That’s an extra and hidden cost to the system.

We’ve had good service from the unit. Three times, we’ve had tires get a bit low and it has warned us before a problem developed. Twice, it was a screw or nail in the tire which could have later turned into a bigger problem. Overall, I’d recommend one of these systems, although the door is wide open for one that performs better and is easier to use than this one.

And finally – I need to point out that a system like this would not have caught or prevented either of our failures. One was a brake lockup with instant blowout. The second was a wheel that departed the rig – with tire pressure sensor intact, and tire fully inflated. Yep, the pressure was just fine – but the wheel and tire were in a ditch several miles back… 

(Posted by Kevin)