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Thursday, February 9, 2012

Tire Pressure Monitoring Systems (TPMS) Reports [No Cover Page Needed!]

Kind of puts some fear into you!
We all wonder about safety. I only have 4 tires on my RV, so when I'm on the highway driving at a "high" rate of speed, fully loaded, I wonder if the tires are going to blow, or burst, or decide they'd like to take off into the sunset on their own.

I've been wanting to explore Tire Pressure Monitoring Systems (TPMS) because I believe they are a good idea. Most cars today come standard with some way to monitor pressure....as usual I wanted a bit more. In my mind, tire pressure is important to prevent problems, but recognizing a problem before something catastrophic happens is critical. Monitoring temperature can really save your nether regions. If one tire temperature rises dramatically in relation to another one on the RV, than it's likely there is a problem and you should stop and investigate.

Only a few systems available today can monitor both pressure and temperature.

Typical Internal Sensor
There are internally installed sensors (usually a metal band holding the sensor to the outside diameter of the wheel, within the tire) or ones that replace your valve cap and hang out on the valve stem. I like the internal ones, but if something goes awry you are going to have to dismount your tire to get to the sensor. Hardly ideal when you're miles from anywhere! The external valve stem types can have replaceable batteries and many of them lock on so they don't vanish at a convenient truck stop dark corner. Being a tinkerer I prefer the ability to work on my own stuff, so I'd opt for the external, lockable, replaceable battery type.
Typical Internal Sensor

These systems are wireless, they use a radio signal to get info to the base unit that you can either power by batteries (not ideal!) a 12V socket or hard wired into your system. Then you have to find/have a place to mount them. They vary in size from tiny to 7" plus wide behemoths and are various shapes.

Typical LCD TPMS Display
They display the tires pressures and temperatures. You can have up MANY sensors running on MANY tires simultaneously. That's great if you're towing or have a rig that's more a millipede on wheels than motorhome.

I spoke with the president of a well know manufacturer. He agreed that tire safety was a serious issue for heavily loaded vehicles such as RVs. I did get the feeling his core business wasn't RVs. We both agree that temperature is a much better indicator of something about to fail. He believes that most folks in older vehicles are riding on outdated tires that have the potential to be very bad for you indeed! I'll admit my tires are more than three years old (more likely six!) I'm a prime candidate for a catastrophic failure.

Since no one offered to send me a test unit and I only received a response from a single manufacturer, I will not be able to review the systems individually.

Rest assured, I WILL be buying one of these systems as soon as I can get real comparison data. I have some likely candidates and will report back when I settle on one. I know, that's a butt weasel, fence post sitting thing to say, but I will ONLY recommend things I personally rely on for my own safety and well being. Okay, maybe entertainment and joy is included there too....

Be Seeing You....Down The Road,

Rich "The Wanderman"
http://www.thewanderman.com

16 comments:

  1. Temperature is a good gauge of the state of your tire, however, the PSI is the first warning signs that something is wrong, which is what makes these TPMS so wonderful.

    If you know your starting pressure, what the normal behavior range for your pressure is going to be, you can catch a problem before the tires start to get hot (Excessive Heat = Tire Failure).

    ReplyDelete
    Replies
    1. Big Matt,
      I agree, if your pressure is decreasing (or increasing) than there is a problem! Boyle's Law is pretty clear that it would be both affected.

      Rich "The Wanderman"

      Delete
    2. Actually, it is not unexpected to see a 5 PSI increase in your tires after warming to normal operating temperatures, however, anything more would be signs of an underinflated tire, which would also be accompanied by a measurable rise in temperature as well.

      Delete
    3. Big Matt,
      Absolutely! Under-inflation can be a real problem. It does horrible things to tires.

      Simply, seeing a normal warm-up increase in pressure and temperature each time and noting any anomalies would be a good indicator of tire health.

      Rich "The Wanderman"

      Delete
  2. Five pounds is not the norm using our system. All four corners of our coach as been weighed wich I recommend that every RVer do. Our tire pressure is based on the manufactures chart, don't forget to add the 5 pounds that is a footnote. Additionally, I add another 5# to the front tires because at 45,000 to 50,000 miles the outside edges start to cup. My dealer suggested the extra 5#. He installs 400 plus truck and RV tires a week. Our pressure increases 10 to 15 pounds after traveling about 100 miles and will stay there.

    ReplyDelete
    Replies
    1. Anon,
      A bit confusing, but I get what you are saying. Each and every trailer or motorhome will behave differently. You should ALWAYS tailor the monitoring to your own experience and/or the manufacturers specifics.

      YMMV (Your Mileage May Vary!)

      Rich "The Wanderman"

      Delete
    2. In the case of a Pickup camper, the majority of us run our tires at 80PSI, which is the pressure required for maximum load capacity when hauling our RVs as all of the weight is carried by the truck's tires.

      At 80PSI on 6 10 Ply E rated 235/85/16s on warm asphalt (Common summer time running conditions that most RVs are in) we do see around a 5PSI increase in the tire pressure after extended driving at freeway or highway speeds.

      An F, G, or H rated 19.5 and 22.5" rim tire will have a different heating ratio as they're bearing a great deal more weight with a monster coach than with a Joe-Average Truck Camper, Class C, or Moderate 5th wheel.

      Me, I perform the good ole chalk test on my tires.

      Rub a band of Chalk on each tread and roll a little ways and watch the wear pattern (need flat dry asphalt for this) of the chalk as it comes of the tire.

      This will tell you if you need to add or release air to maximize your tread's contact patch based upon your current load.

      Delete
    3. Matt,
      Monster Coach.....I see a class a with giant monster truck tires...

      I want one. Don't you what I'd DO with it, but....

      Rich "The Wanderman"

      Delete
    4. I classify most of the giant workhorse/bus chassis style motorhome as "Monster Coaches" as they're roughly the size of a mobile home going down the road these days, especially given the price tags they have :p.

      Delete
    5. Big Matt,
      I couldn't agree more. Obviously they didn't get the "down-sizing" memo!

      Rich "The Wanderman"

      Delete
  3. Can these systems handle up to 6 tires at one time? It seems logical to monitor the inside tires as well as the outside one on dualies. (Thanks)

    ReplyDelete
    Replies
    1. drdoolittle,
      Most of them will handle 22 or more tires with the addition of extra sensors, either purchased when you buy the main system or later on.

      Rich "The Wanderman"

      Delete
  4. Hi Wanderman

    You say that "my tires are more than three years old (more likely six!)". I believe that all tyres have to have a manufactured date on them. In New Zealand the markings (usually on the outside but sometimes on the inside side of the tyre)are :(1) tyres manufactured before 2000 : DOT...[last three digits]408 = week 40 in year 8 of the decade. (2) Tyres manufactured since 2000 : DOT ....[last four digits] 5107 = week 51 in year 2007. Go check your tyres !

    Regards

    Graeme Ward
    New Zealand

    ReplyDelete
    Replies
    1. Anon,
      We have essentially the same markings here in the US...I'd go look, but my tires are covered in SNOW! After the thaw, I'll check.

      Thanks!

      Rich "The Wanderman"

      Delete
  5. Wondering what more you have found out about TMS.

    ReplyDelete
    Replies
    1. Dondi,
      Next weeks article is about the TPMS system I found and installed. It is working GREAT and is less expensive than the alternatives.

      Stay Tuned!

      Rich "The Wanderman"

      Delete

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