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AFChap 03-12-2009 10:47 PM

TPMS General Questions
 
Without stirring controversy once again on which tire pressure monitoring system (TPMS) is better and/or which system each list member likes/dislikes, I would like to ask a few questions of experienced users of whatever TPMS each happens to have used/like/etc... I know some TPMS systems have temp sensors and some do not, and I know there are discussions of how accurate the temp sensors in these things are. I don't need to get into those technicalities at this point. I don't want to start another prolonged discussion of which is system is better or not. My questions should apply to ANY TPMS system. What I am curious about is the following:

1 - Do you find you must adjust tire pressures by adding or releasing air when the seasons change from cold to hot, and then back from hot to cold, or do you just set the min/max parameters of the sensors to handle the seasonal pressure changes due to ambient temp changes?

2 - What is a "reasonable" max psi reading before being concerned? (some/most TPMS systems have a max PSI at which they will alarm) I know the psi will rise as the tire temp rises while driving, especially on a hot summer day, but how high is bordering on too high?

3 - What is a "reasonable" max temp before being concerned? I have always checked my tires with an infrared thermometer whenever I stop, paying more attention to temp differences between tires in similar posotions that the actual temps, but don't recall ever seeing a tire temp beyond 135 F or so. Of course, anytime one tire is significantly warmer than another, I would want to know why, but if you are speaking of just one tire in particular, how hot is too hot? ...or is that a question that just can't be answered ... maybe I just need to ask "at what temp will my 22.5" tires begin to melt??" :D

DAN L 03-13-2009 03:55 AM

afchap:
i use the tst truck wireless tire pressure and temperature monitoring system. this system is performing well for me. it cost about $300. i have set the low pressure alarm for 85 psi, the high pressure alarm for 151 psi, and the high temperature alarm for 158 deg. my new normal tp is 90-92 psi. prior to adding the tst system, my normal tp was 100-105 psi.
1 i have not experienced any seasonal problems so far. from info on this forum and tire manufactures, cold (not hot) max tire pressure should not be more than 10% above max pressure shown on the sidewall of the tire. tire pressures will always increase with tire temperature and altitude. this is normal. "never let air out of a hot tire".

2 from info from tire manufactures and others on this forum you can expect normal tire temperatures at the bead to be about 60 degrees warmer that ambient temperature. the inboard rears will be somewhat hotter than the others. (20-30 degrees).
tire temperatures at the bead above 190 deg are not good, 200 degrees is dangerous.
brakes above 400 degrees indicate a problem.
use the search function of this forum to find more info on tires and brakes.

RV Wizard 03-13-2009 04:16 AM

In my opinion the old fashion way is sufficient. Manually check the pressure each day you travel, know the weight you are carrying and pressurize according the the manufacturer's pressure chart for your model tire. When the tires get to a 5 year age consider replacement if you have been prudent in this maintenance. If not replace sooner.

DAN L 03-13-2009 04:49 AM

tires...
 
Quote:

Originally Posted by RV Wizard (Post 480049)
In my opinion the old fashion way is sufficient. Manually check the pressure each day you travel, know the weight you are carrying and pressurize according the the manufacturer's pressure chart for your model tire. When the tires get to a 5 year age consider replacement if you have been prudent in this maintenance. If not replace sooner.

michelin says 10 years now...
obviously, you do not have a workhorse chassis with brake overheat issues...

Gary RVRoamer 03-13-2009 09:40 AM

Quote:

michelin says 10 years now...
But they also say to have the tires professionally inspected every year and especially if 5 years or more in age.

http://www.michelinrvtires.com/asset...r-RV-Tires.pdf

historyljc 03-13-2009 09:50 AM

I've been using the Pressure Pro system for over two years. When the weather got cold I added 5 pounds to bring the pressure back up to where I keep them. There can be a little fluctuation in the cold pressure depending on the temperature and which side is facing the sun. Once I get rolling everything evens out. I normally pick up 12-15 psi after the tires have warmed up. Can't help on the temperatures as my system doesn't monitor that or have high pressure alarm. Mine will alarm if the pressure drops 12% below whatever the sensor is set. The sensor sets automatically to the pressure that you air the tire to. I use the dash mounted monitor to check the pressure in the morning before we leave and generally several times during day as we roll down the highway.

AFChap 03-13-2009 01:30 PM

DAN L - Good info. Curious why you made the following change? Were you just keeping a plus-up margin for safety's sake?
Quote:

my new normal tp is 90-92 psi. prior to adding the tst system, my normal tp was 100-105 psi
I have run my tire pressures according to my last weight results and the mfg chart, and tend to add 5 psi (still staying within max recommended for the tire). Didn't figure that would differ with a monitoring system...

Expecting tire temps to be around 60 degrees above ambient temp (at the bead ...that's not where I normally measure my tire temp) provides at least a guideline to go by ...and a warning against traveling far in very hot weather. I recall blowing lots of rear tires on heavily loaded wheat trucks on those hot summer days when I was younger!! ...I've been curious since what load rating those tires were, and how overloaded we were running with 330 bushel of wheat on board.

JIM -- From your comment that you normally see your tires pick up 12-15 psi after they have warmed up, guessing your tire pressures are close to 100psi, I presume that means they are picking up at least 12-15 percent (probably a bit more) of their cold pressure. And your Pressure Pro alarms at -12% of cold pressure. Does it alarm at a set % above the set pressure, or can you adjust the max pressure alarm point? (if there is one...)

historyljc 03-13-2009 03:48 PM

Paul,
I'm running 105 in the fronts and 120 in the rears. I have the "Fat Boy" singles on the rear and they take a little more pressure. Axle weight I could run 5 pounds less all the around, but I haven't been able to get individual wheels yet so I have the max in the rear just in case. The 06 Phaetons tend to be heavier on the passenger side rear than the driver side.

My system is too old to have the high pressure alarm. Mine will only alarm is the pressure drops. They automatically re-set if you have the sensor off the valve stem for more than 90 seconds. They will reset the base to whatever you have in the tire at that time. A 12% or more drop from that and the alarm goes off. In my case it would be at around 92-93 psi on the front and 105-106 on the rear.

The alarm did go off when I had flat. However, since the tire simply exploded the pressure when from 113 psi running pressure to 0 instantly. It took a few minutes for me to get enough hearing back to hear it.

DAN L 03-13-2009 05:32 PM

monitor system
 
Quote:

Originally Posted by AFChap (Post 480252)
DAN L - Good info. Curious why you made the following change? Were you just keeping a plus-up margin for safety's sake?



I have run my tire pressures according to my last weight results and the mfg chart, and tend to add 5 psi (still staying within max recommended for the tire). Didn't figure that would differ with a monitoring system...

Expecting tire temps to be around 60 degrees above ambient temp (at the bead ...that's not where I normally measure my tire temp) provides at least a guideline to go by ...and a warning against traveling far in very hot weather. I recall blowing lots of rear tires on heavily loaded wheat trucks on those hot summer days when I was younger!! ...I've been curious since what load rating those tires were, and how overloaded we were running with 330 bushel of wheat on board.

JIM -- From your comment that you normally see your tires pick up 12-15 psi after they have warmed up, guessing your tire pressures are close to 100psi, I presume that means they are picking up at least 12-15 percent (probably a bit more) of their cold pressure. And your Pressure Pro alarms at -12% of cold pressure. Does it alarm at a set % above the set pressure, or can you adjust the max pressure alarm point? (if there is one...)

:)that is correct. with the monitor system, i don't have to run the extra 10#
for a safety "cushion".:)

TST Systems 03-08-2011 09:08 AM

Quote:

Originally Posted by AFChap (Post 480001)
Without stirring controversy once again on which tire pressure monitoring system (TPMS) is better and/or which system each list member likes/dislikes, I would like to ask a few questions of experienced users of whatever TPMS each happens to have used/like/etc... I know some TPMS systems have temp sensors and some do not, and I know there are discussions of how accurate the temp sensors in these things are. I don't need to get into those technicalities at this point. I don't want to start another prolonged discussion of which is system is better or not. My questions should apply to ANY TPMS system. What I am curious about is the following:

1 - Do you find you must adjust tire pressures by adding or releasing air when the seasons change from cold to hot, and then back from hot to cold, or do you just set the min/max parameters of the sensors to handle the seasonal pressure changes due to ambient temp changes?

2 - What is a "reasonable" max psi reading before being concerned? (some/most TPMS systems have a max PSI at which they will alarm) I know the psi will rise as the tire temp rises while driving, especially on a hot summer day, but how high is bordering on too high?

3 - What is a "reasonable" max temp before being concerned? I have always checked my tires with an infrared thermometer whenever I stop, paying more attention to temp differences between tires in similar posotions that the actual temps, but don't recall ever seeing a tire temp beyond 135 F or so. Of course, anytime one tire is significantly warmer than another, I would want to know why, but if you are speaking of just one tire in particular, how hot is too hot? ...or is that a question that just can't be answered ... maybe I just need to ask "at what temp will my 22.5" tires begin to melt??" :D

Good Morning Sir,

Your questions are very good and I appreciate the opportunity to address them in this forum.

Typically, your tires should run approximately 20% above the ambient temperature under normal conditions.

Tires will typically fail between 180 - 200 degrees Fahrenheit. We at TST suggest setting your temperature alarm at approximatley 158 degrees Fahrenheit as this temperature setting is comfortably above a normal operating temperature, yet safely below a danger threshold.

You will also find tire temperature variences on the side of your RV that is facing the sun (if traveling North to South, etc.). This is normal.

In terms of setting alarm parameters, we suggest setting your low PSI alerts at 10% below your normal operating PSI and 15% - 20% above your normal operating PSI.

You will find that your PSI are sensitive to altitude changes, temperature changes, etc. This is normal due to airs reaction to said variances.

I have found (through personal RV experience) that Nitrogen is far less reactive to temperature changes, hence eliminating the need to add and remove air from your tires due to seasonal climate changes.

Please bear in mind that there are many differing opinions regarding the use of Nitrogen, and I DO NOT profess to be an expert regarding its use. I also do not seek to stir controversy on this subject. I am merely sharing based upon my own experience.

In terms of tire safety, I am a proponant of changing tires every 5 years.

Many RVers do not realize that tires often deteriorate from the inside out. With air in your tires, you will have condensation within your tires which will cause them to dry rot from the inside out.

The dangerous irony here is that the tires often look like brand new from the outside, meanwhile, you have a ticking time bomb that you may be completely unaware of.

As the CEO of Truck System Technologies, I cannot help but suggest our system based upon its performance, customer reviews, and technological innovations.

Thank you for your post and I hope all who read this find this information useful and helpful in remaining safe on the open roads!

Travel in Safety!

Dan Covington
President
Truck System Technologies, Inc

GaryKD 03-08-2011 09:21 AM

Hi AFChap,
I have used Pressure Pro for the last 6 years. It has save me two times. Both times were on the towed vehicle. My system measures PSI only. For me this is okay. For anyone considering a TPMS system, the most important factor is how does the system and you interface with each other? Can you see the monitor when driving. Will the alarms be confusing or readily understood, while driving? What are the setup process steps? What must you do to install the system in your coach? For me it is how the system and the driver interact with one another that makes the difference.

AFChap 03-08-2011 06:07 PM

Old thread revived... good info from Dan Covington on tire temps, and tire replacement due to age.

We are currently running the TireTracker system, and it is working well for us. It does measure both PSI & tire air temp similar to the TST system. The alarm points are not user adjustable ...they are preset at 15% under and 20% over the set PSI for each tire. Temp warnings occur at 167 (intermittent) and 185 (constant), which are very close to what Dan recommends.

If you are are interested in reading more about my tire and TPMS experiences since my original post, you can find some comments on my web site at Tire Date Codes/Tire Care

Cruzer 03-09-2011 12:58 PM

I use the SmarTire system on my coach. The SmarTire is the best there is but it was also the most expensive. Unfortunately Bendix bought them out and their new systems are not designed for RVs. What I like about the SmarTire is that it uses internal sensors so that you don't have to mess with external "valve cap" type sensors. They do need to be installed into the rims so there is some up-front cost for that as well. They utilize temperature compensation algorithms to allow for proper inflation pressure at the corresponding temperature.

As tires warm up the air pressure within them will rise. Tires are rated to carry a certain presure in them for the weight they are designed to carry but that is rated as "cold inflation pressure", which is probably right around 60 degrees. My 120 PSI cold steer tire may read up to 135 PSI when driving on a hot day but this is the correct pressure. The dash display gives me the ability to display tire pressures as well as temperatures. It also can display a pressure differential, such as -2 PSI or +3 PSI. This differential is calculated based upon the actual temperature so if my tire was correctly inflated coldat 120 PSI then it will the differential will read -0 at 135 PSI with a hit tire. This basically lets me check my tires pressure at any temperature. Conversely, when it's 10 degrees outside my 120 PSI tire may only show 110 PSI but that too will be normal.

The temperature displays can also alert you to a dragging brake or bad wheel bearing issue and it's interesting to see the temperature rise on a hot day after driving a while. You will also find out which tires are more heavily loaded by viewing these temperature readings. If one corner of your coach is heavier than the opposite side the temperature of that tire will be higher because it's working harder.

Anyway, it's all immaterial now that SmarTire is no longer sold. At least they still have the wheel sensors available to keep my system running. I'm hoping that by the time I need a new coach someone will have a similar system on the market with internal sensors and temperature compensation logic.

To me, not having any TPMS is a bad idea. Checking them manually each morning before a trip is fine but if you pick up a slow leak from a nail you probably won't feel it until it's too late and by then you might be in for the ride of your life. Having a warning system will let you pull over and address it before it's critical.

wa8yxm 03-10-2011 12:49 PM

All the systems are good and have advantages and disadvantages. All of them.

The Pressure Pro system uses "Screw on" sensors that replace the valve stem cap.. The ones I have tend to leak a bit, major pita but they are also old and in need of replacement,, I'm hoping when I get new sensors they have addressed this issue.

TST also uses screw on sensors

Smart Tire uses 'internal" sensors, less likely to leak but you need professional help to install and they won't fit all towed cars.

Some systems alarm on temp as well as pressure, Some on hot/high as well as low pressure.

However no matter what you get do not do as one person did..
First my story:

Got the Pressure Pro and put it on, Headed north, abut 150-200 miles and about 1/4-1/3 the way the alarm went off, Left front on the towed was low.. Broke out the huffer puffer (air compressor) and aired it back up.. Did so again several times over the weekend and on Monday headed to the tire store where I found I'd been screwed,, So they removed the screw from the tire, properly patched it (Boot type) and re-inflated it to the proper pressure.. Total damage, A little bit of gasoline driving the 3 miles to the tire store and back.

The other guy: He got his (Same system) and tossed it in the basement intending to install at his next stop.. Hooked up, and not fifteen miles from the campground people are honking and pointing and when he pulled over and did the walk around.. The left front tire on HIS towed was gone, I mean gone, the Rim was totaled as was the brake rotor and the fender and over 2,000 in secondary damage.

Humm. six miles (about a dollar at today's prices) v/s over 2,000 in SECONDARY damage, and that did not include the tire.


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