TPMS Pressure Threshold for TST 507

[ccgraves100]

Hi -

Recently purchased a TST 507 for my Solitude 377MBS. I was worried about the Westlake tires since they were approaching 4 years old. I filled the tire pressure to 110lbs, the max cold psi rating. My question is what pressure should you set the "high pressure alarm" setting? The manual says to set the high pressure alarm 20-25% above the max cold psi rating. For my load range G tires, they have a 110 psi rating so I set the alarm to 135 psi.

I was on the 2nd day of a 1200 mile NJ to Florida trip and about half way thru the day, the pressure on one of the tires exceeded 135 psi. The rest of the tires were just below that mark (around 132 psi). So I let a little air out of that particular tire and also raised the alarm threshold to 140 psi. At the end of that same day, the tire pressure on two of the tires was near that 140 psi threshold (the 2 other tires were in the 135/136 psi range). My travel speed averaged around 70 mph. The outside temperature was around 70 degrees F. None of the tires came anywhere near the high temperature alarm setting, which I left at the default of 158 degrees F. (I think the readings were in the 80-90 degree F range for all 4 tires.)

I have since replaced all 4 Westlake tires with Hercules due to some dry rot cracks, but my question is what should be the high pressure alarm limit? Should I keep it at 135 psi? Raise it to 140 psi? And if all the tires are hovering in that range, what is the recommended action? Pull over and let things cool down? Slow down? Let air out of the tires? My thinking was that I should be more concerned about an outlier (only 1 tire significantly greater than the others) than all 4 hovering in the same range even if it is in the range of 140 psi?

I appreciate that these may be dumb, obvious questions. While having more data from the TPMS was great, it also drove the wife crazy (and hence me) whenever it alarmed. So in preparation for my 1200 mile drive home next week, trying to figure out how to interpret the TPMS alarms before my wife chucks the whole unit out the window.

Thanks!
-Charlie

[Steven@147]

Hi -

Recently purchased a TST 507 for my Solitude 377MBS. I was worried about the Westlake tires since they were approaching 4 years old. I filled the tire pressure to 110lbs, the max cold psi rating. My question is what pressure should you set the "high pressure alarm" setting? The manual says to set the high pressure alarm 20-25% above the max cold psi rating. For my load range G tires, they have a 110 psi rating so I set the alarm to 135 psi.

I was on the 2nd day of a 1200 mile NJ to Florida trip and about half way thru the day, the pressure on one of the tires exceeded 135 psi. The rest of the tires were just below that mark (around 132 psi). So I let a little air out of that particular tire and also raised the alarm threshold to 140 psi. At the end of that same day, the tire pressure on two of the tires was near that 140 psi threshold (the 2 other tires were in the 135/136 psi range). My travel speed averaged around 70 mph. The outside temperature was around 70 degrees F. None of the tires came anywhere near the high temperature alarm setting, which I left at the default of 158 degrees F. (I think the readings were in the 80-90 degree F range for all 4 tires.)

I have since replaced all 4 Westlake tires with Hercules due to some dry rot cracks, but my question is what should be the high pressure alarm limit? Should I keep it at 135 psi? Raise it to 140 psi? And if all the tires are hovering in that range, what is the recommended action? Pull over and let things cool down? Slow down? Let air out of the tires? My thinking was that I should be more concerned about an outlier (only 1 tire significantly greater than the others) than all 4 hovering in the same range even if it is in the range of 140 psi?

I appreciate that these may be dumb, obvious questions. While having more data from the TPMS was great, it also drove the wife crazy (and hence me) whenever it alarmed. So in preparation for my 1200 mile drive home next week, trying to figure out how to interpret the TPMS alarms before my wife chucks the whole unit out the window.

Thanks!
-Charlie

Charlie, I wouldn't worry about it. Don't let air out of the tires hot! Raise the high TST psi alarm threshold. For the pressure you're running in the tires, I would set the high PSI alarm at 140 psi. You're are thinking about it correctly, you are looking for an outlier. One tire way off from the others. The tires are manufactured to handle the increased pressures due to heat. Just run them at the max cold pressure (110 psi) or adjust the pressures if you know how much weight is on each tire from the tire manufacturer inflation table.

I have the TST-507 as well. I start out running our tire pressures at 105 psi cold. We were running Westlake "G" tires but changed to Sailun "G" rated.
But I also know about how much weight is on every tire and our overall weight (Escapee's Smart Weight) . At 70-75* ambient temp the pressure in our tires will increase from 105 psi cold into the 125-126 psi range. We also run 65-70 miles per hour. Up into the 80* temps here in Texas the tires will gain even more pressure up into the 127-130 psi. Especially the tires in direct sunlight. I always check every morning that we are towing that the tires are 105 psi cold. If they are higher I'll let some cold air out to maintain 105 psi.
I don't let any pressure out of the tires when hot. We always start out at 105 psi in the tires. If we expect 80* + temps and sunny hot on our travel day I can expect the tires to run at increased pressure around 130 psi - I raise the TST high pressure alarm threshold.

Sometimes too much data is alarming! Thats a pun LoL's

[jleonard]

[QUOTEAt the end of that same day, the tire pressure on two of the tires was near that 140 psi threshold (the 2 other tires were in the 135/136 psi range][/QUOTE]

A 4-degree difference is nothing to get excited about. Maybe within the accuracy range of the monitors?
Could be those tires were on the sunny side? Maybe a little heavier loaded? Maybe the crown of the road putting more load on them?

[ccgraves100]

Thanks Steve. Really appreciate your input. I think one lesson was to make sure all tires were starting from the same cold air pressure. With my analog stick gauge, I noticed variation in the measurement and it was tough to determine how close to the target I was. With the TST-507, I can finesse it much better.

And yes, too much data certainly can be alarming!

Thanks again!

[ccgraves100]

Thanks. I need to look up the accuracy range of the monitor. That's a good point. I also need to get my trailer weighed. I don't think I'm heavier loaded, but I'm sure everyone thinks that. And yes, I did notice the difference for the side that's facing the sun.

[jleonard]

Thanks. I need to look up the accuracy range of the monitor. That's a good point. I also need to get my trailer weighed. I don't think I'm heavier loaded, but I'm sure everyone thinks that. And yes, I did notice the difference for the side that's facing the sun.

As far as loading goes, I know that my trailer is 500 lbs heavier from the factory on the street side. Then add stuff in the fridge and storage cabinets as they are all on that heavy side and I'm probably close to 1000 lbs heavier there.

[ccgraves100]

Hi all -

Just a follow-up post regarding my TPMS pressure alarm threshold question. The reason I was so concerned about the TPMS readings (mainly the max pressure alarm threshold) was because I was running on the factory provided Westlake tires which had about 4 years from their manufacture date, plus I was starting to see severe dry rot cracks on one of the tires and I was preparing for a 1200 mile trip to Florida. (I should have checked the tires well in advance of the departure date, but alas didn't before it was too late...) I made it to Florida with no problems (I swapped the spare with the heavily dry rotted tire and crossed my fingers) aside from the tire pressure readings of the G-rated Westlake tires hitting between 135 and 140 psi. This prompted my question of the typical high pressure alarm threshold for G-rated tires. The TPMS monitor manual had suggested +20-25% from the cold inflation pressure, which was 132-137 psi.

Anyway, when I got to Florida, I promptly bought 4 new tires (Hercules H-901 ST) for the 1200 mile return trip. What was interesting to me was that for similar loading and driving conditions, the new tires never ran a pressure higher than 120 psi (with a cold inflation of 110 psi).

I am curious about the difference in the pressure reading between the Westlake and the Hercules tires. Is it related to the design of the tire? Or does the age/wear of the tire factor in? Anybody have any insights on the difference? This is my first experience with a TPMS.

Thanks,
Charlie

[Steven@147]

Charlie, I don't have any insight for you, I would think your new tires would run about the same pressures as your old tires given the same ambient temps, loading and over all weight in towing conditions, and not towing in the rain and similar road pavement temperatures..

When I changed from Westlake "G" to Sailun "G" tires they run around the same pressures with given similar towing conditions. Towing in the rain will cool the tires off and also whether towing in full sun or on a cloudy day.