Tire pressure monitor recommendation?

[Wingeezer]

I have used the Hawkshead system for three seasons now and it has worked fine for me. I have had no problems with it, nice to be able to change batteries myself in the sensors,and although I have yet to encounter a tire problem (touch wood) it gives a somewhat improved feeling of confidence in knowing that by having the system, plus renewing tires every five years, plus doing a walk around at every stop en route, I am doing all I can to keep the odds in my favour.

Gives me something to do on long rides also to periodially check tire pressures and temps manually with the Hawkshead just to see how things are going back there!

I have however found that sometimes at the start of a trip, it can take a few miles at highway speeds before all teh sensors register - not sure why the delay. I can easily tell which ones have started registering as the others will still show higher temps and pressures from the previous day's driving until they kick in with the new lower figures - until the tires come up to operating temperature once again.

Brian.

[dznf0g]

I believe we should all be aware that unless the sensor is inside the tire, it cannot read temperature. I believe these systems use a formula to calculate pressure rise and ambient temp, and then calculate an internal temp by using the1 PSI= 10*F rise in temp.

If you use your noodle, all of them tell you the temp, if you can do a little math.

[Wingeezer]

Originally Posted by dznf0g

I believe we should all be aware that unless the sensor is inside the tire, it cannot read temperature. I believe these systems use a formula to calculate pressure rise and ambient temp, and then calculate an internal temp by using the1 PSI= 10*F rise in temp.

If you use your noodle, all of them tell you the temp, if you can do a little math.

Must admit I didn't realize that was how they worked. I figured they did measure temp just by means of heat transmitted via the metal valve stem that they say you must use with these units. I assumed that would be far less accurate than it would be if the unit was inside the tire, but at least you could use it as a relative indication of one tire versus the three others and suspect something might be amiss.

Not disputing at all what you say, but just wondering, do you know for a fact that they just use ambient temp + a calculated temp rise based on pressure increase? There is no indication that I recall seeing on the advertising material that suggest that and so it seems to me a bit misleading on the part of the manufacturer if such is the case.

Thanks for the info ---------- Brian.

[Bigventure]

I have this item for sale in the classified. Orange Electronic P409S Retrofit Tire Pressure Monitoring System I was going to use it on a trailer but sold the trailer instead.
It highly rated and new in the box. $120.

[dznf0g]

Originally Posted by Wingeezer

Must admit I didn't realize that was how they worked. I figured they did measure temp just by means of heat transmitted via the metal valve stem that they say you must use with these units. I assumed that would be far less accurate than it would be if the unit was inside the tire, but at least you could use it as a relative indication of one tire versus the three others and suspect something might be amiss.

Not disputing at all what you say, but just wondering, do you know for a fact that they just use ambient temp + a calculated temp rise based on pressure increase? There is no indication that I recall seeing on the advertising material that suggest that and so it seems to me a bit misleading on the part of the manufacturer if such is the case.

Thanks for the info ---------- Brian.

I don't know it FOR A FACT, but a sensor on the stem would be nowhere close to the temp in the tire with the cooling effect on the sensor itself, the stem, as well as the metal wheel. They might use some sort of other algorithm, but pressure rise with some sort of memory of starting point is the only way I could fathom any accuracy in the system, based on my auto industry experience only.

For example, most, if not all OEM auto TPMS sensors shut off after X amount of time not sensing rolling of the tire. They turn on when sensing rotation again. If these systems have that feature, the "starting point" pressure could easily be locked into memory of the head unit and a calculation applied. This new base number could only be accepted after, say, 8 hours of off time. I know mine has a clock and calendar in it for other reasons. My Doran does not readout temp, but I calculate it in my head using this formula. BTW, my estimated interior temps run roughly 35* over the readings of the infrared thermometer readings between the tread blocks.
I would be interested in knowing from you folks, what kind of readings you see on your TPMS units vs. outside temps (ambient).

[purman]

I have tire minder the same system as hawkshead. When I had to move my sensors around on the tires as they where on the wrong tires from putting new tires on. It was cold out and the sensors hasn't been used. And they read the correct temp. It was 45 degrees out, and they all read within 2 degrees of this temp. I'm guessing the air in the tires where the same as the outside air as the trailer had been sitting for two weeks. When I stared driving they started to rise before the tire pressure did.

I have also noticed when traveling that the tires on the south side are hotter than the north, because of the direct sun light. I also confirmed this by touch. Either way I believe the temp is accurate in these two systems and is measured by a temp gave in the sensor not an estimate.

[dznf0g]

Originally Posted by purman

I have tire minder the same system as hawkshead. When I had to move my sensors around on the tires as they where on the wrong tires from putting new tires on. It was cold out and the sensors hasn't been used. And they read the correct temp. It was 45 degrees out, and they all read within 2 degrees of this temp. I'm guessing the air in the tires where the same as the outside air as the trailer had been sitting for two weeks. When I stared driving they started to rise before the tire pressure did.

I have also noticed when traveling that the tires on the south side are hotter than the north, because of the direct sun light. I also confirmed this by touch. Either way I believe the temp is accurate in these two systems and is measured by a temp gave in the sensor not an estimate.

Jason,

What you say is correct, but all those variables are predicated by pressure. In other words, yes, the initial reading on a cold tire is the ambient temp. Any rise in heat is directly proportional to a rise in internal pressure. It doesn't matter if it is sun load, a change in ambient, or rolling friction. one psi rise = 10*rise and visa versa. (pretty close, per my observations and per TireRack.com here: Tire Tech Information - Air Pressure, Temperature Fluctuations

Unless a TPMS has an actual sensor inside the tire/wheel assembly, it cannot read direct temp with any accuracy.

And actually, if we want to get picky, the air temp inside the tire is not exactly the same as the tire carcass temp (which is the real issue to be concerned with) at any given time. That's why race teams have temp PROBES which penetrate the tread to get as close to the areas of potentail failure as they can.

[73shark]

Originally Posted by Tom and Robin

Do yourself a favor and take a good, long look at the Hawkshead system. I read all the reviews on the Forum, asked a lot of questions, and settled on the Hawkshead.

It has several features I found attractive.

One: you can change the batteries in the sensor yourself using a standard watch battery. Most of the others required you to send the sensor back or replace at the tune of $35 or so for each sensor.

Two: the unit tells you the temperature the tire is running. I thought this was a great feature which could tell me if I had a sticking brake or bearing going bad.

Three: the standard monitor will handle up to 22 (I think that is the number, but it is a bunch) sensors. The others required different monitor models for more sensors, which increased the cost. My tow vehicle has pressure sensors, but thought that would be a good feature if we change tow vehicles and perhaps wished to monitor the tow vehicle tires. I ended up with five sensors and put one on my spare trailer tire. Now I know at a glance the pressure of all trailer tires and no longer have to check each one prior to starting out on the road. Turn on the monitor in the morning you plan to depart, and in about five minutes (while you are disconnecting your water and shore power) it is up and tells you all you need to know about tires prior to departure.

Four: the folks at Hawkshead were outstanding to work with. Could not have been nicer or more helpful.

Five: Cost. It was the most reasonable. I purchased direct from the manufacturer.

Have had the system for about four months now and could not be more pleased. It was very simple to install even for a non-tech guy. Easy to follow instructions.

By the way, this system has sensors which attach to the existing tire stem, no need to remove the tire. And there is an audible warning if you lose tire pressure or exceed the pressure and temperature limits you set when you install the monitors.

Hope that helps you with your decision.

FWIW from what I can ascertain, the Hawkshead system is made by Tire Traker which is the one in my link. This one is the latest design w/ the new monitor design. My only concern w/ the flow-thru sensors is the extra weight hanging on the valve stem.

As to the tire temp. discussion, couldn't one simply add air to the tire and see if the temp. reading increases? If it does, then it's calculating temp. from pressure. If it doesn't then it is doing it some other way.

[dznf0g]

Originally Posted by 73shark

FWIW from what I can ascertain, the Hawkshead system is made by Tire Traker which is the one in my link. This one is the latest design w/ the new monitor design. My only concern w/ the flow-thru sensors is the extra weight hanging on the valve stem.

As to the tire temp. discussion, couldn't one simply add air to the tire and see if the temp. reading increases? If it does, then it's calculating temp. from pressure. If it doesn't then it is doing it some other way.

Maybe....depending on the "turn on/turn off" logic, if a particular system has it. It would be an interesting experiment. I'd bet you would have to have the pass through fill though. I think most of these sensors shut off when removed. That may set a new baseline at ambient vs. new pressure setting in tire when reinstalling the sensor.

[Ag&Au]

Originally Posted by dznf0g

I believe we should all be aware that unless the sensor is inside the tire, it cannot read temperature. I believe these systems use a formula to calculate pressure rise and ambient temp, and then calculate an internal temp by using the1 PSI= 10*F rise in temp.

If you use your noodle, all of them tell you the temp, if you can do a little math.

I do not believe that your calculation theory is correct for Hawks Head or tire minder at least. If someone really wanted to know for sure they could verify with the manufacturer.

This is what I was told by Hawks head. The temperature sensor reads the temperature of the air in the valve stem. I will readily admit that especially while in motion, this is probably somewhat less the the temp in the center of the tire.

Regarding metal valve stems:
I had this discussion about them when I first got the TPMS. I asked Discount tire to install metal stems on my wheels. The manager asked why, and when I told him, he said that the stems on my tires were already metal covered by rubber and should work fine. I called HawksHead and asked him about this. He said yes this is correct, and told me he includes the metal stems with the units because they are inexpensive, and so many RVers were adamant about wanting them, and he was tired of trying to convince them they were not necessary. As I think about it now, it seems that rubber covered is better because it insulates the valve stem.

Personally, I am not interested that much in absolutes as I am in changes as I drive. I am not saying that is correct. I am only saying that is how I feel about it.

Ken

[Moflash]

Bought my system at the Tire Rack.com.Inexpensive and works as it should.Gives pressure and individual tire temps with alarm.Comes with metal valve stems and the sensors are inside the tires.They go into sleep mode when trailer is not moving and wake at 20mph.I monitor 4 tires continuously.I would not travel without it.Dill is the mfg.Price $239 complete

[Ag&Au]

Originally Posted by Moflash

the sensors are inside the tires.

Excuse this probably dumb question. Do the tires have to be removed from the rims to install and/or service the sensor?


Ken

[dznf0g]

Originally Posted by Moflash

Bought my system at the Tire Rack.com.Inexpensive and works as it should.Gives pressure and individual tire temps with alarm.Comes with metal valve stems and the sensors are inside the tires.They go into sleep mode when trailer is not moving and wake at 20mph.I monitor 4 tires continuously.I would not travel without it.Dill is the mfg.Price $239 complete

These are the most accurate for temps, but are still a ways from the hot part of the tire.

These are just like OEM sensors, except with a temp feature that FMVSS does not require of automakers.

[dznf0g]

Originally Posted by w7ts

I do not believe that your calculation theory is correct for Hawks Head or tire minder at least. If someone really wanted to know for sure they could verify with the manufacturer.

This is what I was told by Hawks head. The temperature sensor reads the temperature of the air in the valve stem. I will readily admit that especially while in motion, this is probably somewhat less the the temp in the center of the tire.

Regarding metal valve stems:
I had this discussion about them when I first got the TPMS. I asked Discount tire to install metal stems on my wheels. The manager asked why, and when I told him, he said that the stems on my tires were already metal covered by rubber and should work fine. I called HawksHead and asked him about this. He said yes this is correct, and told me he includes the metal stems with the units because they are inexpensive, and so many RVers were adamant about wanting them, and he was tired of trying to convince them they were not necessary. As I think about it now, it seems that rubber covered is better because it insulates the valve stem.

Personally, I am not interested that much in absolutes as I am in changes as I drive. I am not saying that is correct. I am only saying that is how I feel about it.

Ken

Well....I disagree, but that's the way it is. I think stem temp is WAAAAAY too far away from what matters to be of any value...without some sort of mathematical correction.

I am truly plagued with a need for absolutes....right or wrong, that's the way I'm built. That's why politics drives me bonkers!!!!

I am sure each brand does it differently anyway, so until then, I'll use my mental pressure to temp math. Now, if I could find any credible source to tell me how hot is too hot for tires, it would definitively let me determine what pressures to run in the tires.

[dznf0g]

Originally Posted by w7ts

Excuse this probably dumb question. Do the tires have to be removed from the rims to install and/or service the sensor?


Ken

Yes, a dismount and remount/balance is required.

[Ag&Au]

Originally Posted by dznf0g

Well....I disagree, but that's the way it is. I think stem temp is WAAAAAY too far away from what matters to be of any value...without some sort of mathematical correction.

I am truly plagued with a need for absolutes....right or wrong, that's the way I'm built. That's why politics drives me bonkers!!!!

I am sure each brand does it differently anyway, so until then, I'll use my mental pressure to temp math. Now, if I could find any credible source to tell me how hot is too hot for tires, it would definitively let me determine what pressures to run in the tires.

If you think about it you can't disagree, you can only feel differently. That sounds much better. I was simply talking about how I feel about it, not what I think is right or wrong. I'm going to keep that secret.

For me, the purpose of the TPMS is to make me feel better(more relaxed). If I start analyzing it too closely I will start to worry about whether it is doing it the best way possible. Then it won't be serving its purpose. I prefer to just assume it is doing its best, and feel good that is there.

Ken

[dznf0g]

Originally Posted by w7ts

If you think about it you can't disagree, you can only feel differently. That sounds much better. I was simply talking about how I feel about it, not what I think is right or wrong. I'm going to keep that secret.

For me, the purpose of the TPMS is to make me feel better(more relaxed). If I start analyzing it too closely I will start to worry about whether it is doing it the best way possible. Then it won't be serving its purpose. I prefer to just assume it is doing its best, and feel good that is there.

Ken

True, and well said. But, after living the ramifications of the Ford/Firestone issue (which resulted in TPMS being required on all light duty vehicles) I am particularly sensitive to this issue. There was MUCH that was never made public about that whole thing that is SCARY!!!! Simply feeling comfortable as a panacea is not good enough for me. I NEED to know more. "Trust but verify"

[73shark]

Originally Posted by dznf0g

Yes, a dismount and remount/balance is required.

Not necessarily. The dealer is going to replace the OEM TPMS units on my wife's Tahoe and all they do is break the bead next to sensor and R&R and reseat the tire.

I asked one of the vendors how they measured the temp.

[Taylormade]

Originally Posted by Bigventure

I have this item for sale in the classified. Orange Electronic P409S Retrofit Tire Pressure Monitoring System I was going to use it on a trailer but sold the trailer instead.
It highly rated and new in the box. $120.

It's highly rated, but not for trailers... or crew cab even trucks for that matter. People are complaining that it won't read the rear right tire on an extended cab pickup. Do you have some sort of repeater for it to make it work? Otherwise, there's no way that'll work for the trailer with the brains sitting in the truck.

Furthermore, the highest alarm setting is at 60psi. If you fill your trailer tires to 65psi as recommended, you'll have to turn off the alarm every time you start your vehicle, and keep a close eye on the monitor as there'll be no usable alarms.

[dznf0g]

Originally Posted by 73shark

Not necessarily. The dealer is going to replace the OEM TPMS units on my wife's Tahoe and all they do is break the bead next to sensor and R&R and reseat the tire.

I asked one of the vendors how they measured the temp.

Ah, that's true, didn't think of that shortcut.

What did the vendor say?