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Old 03-23-2014, 04:38 PM   #1
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TST Tire monitoring perameters

I purchased a TST 507 tire monitoring system. I have talked with some RV owners as to where to set the high pressure and the low pressure. Some have indicated to use 20% above and below where the tire is being run. Others say to run at 15-20% above the max tire pressure recommended by the tire manufacturer. Is there a safe rule of thumb for this? Also the literature from TST says to keep the temp set at 158*F because all tires fail at 180-200*F. Is this true for all brands or just the Michelins they refer to?
Thanks for the help.
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Old 03-23-2014, 05:33 PM   #2
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For my FRONT tires I run my alarms at 10% below my desired tire pressure based on wheel weights and 20% above the max tire pressure. So as an example based on wheel weights, my front tires cold tire pressure is 112 PSI and the max it 120 PSI so my limits are 101-144.

Low tire pressure is more problematic to safety and tire life than minor over pressure. From experience I have found that on hot days running 20% above my target PSI on the front tires causes a few nuisance high pressure alerts right at the upper cut off.

On my drive and tag axle wheels I run 10% below to 20% above my target PSI.

Why the difference? Well, in MY case my front axle tires are supporting nearly 55% more weight per tire than any of my drive or tag axle tires so they generate more heat thus higher internal pressure once we get up to cruising mode.

On average my drive tires each carry 3995# and each tag tire carries 3380#. These weights are well below the lowest value in the inflation table which is 75 PSI. I have also observed that they always run a tad cooler so I have found that 20% above target weight doesn't generate nuisance alarms. Well maybe it did once but, again, right at the upper limit. Thus my limits for the Drive & Tag are the same 68-90 PSI.

Now, if I wasn't at such extremes of target PSI vs the manufacturer minimum and maximum, I would probably find that about 25% above target PSI works well instead of using 20% of max. But...I would start with 20% and then see if you start getting nuisance alarms right at the upper limit. After that, I would add 1-2 PSI at at time to the upper limit until you get rid of nuisance alarms. If you needed to go more than 25% of the target PSI I would be asking some questions on why that is.

YMMV but it works for me.
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Old 03-23-2014, 06:04 PM   #3
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I also have a 507. When I installed, I followed TST's recommendation as I recall, and set 10lbs under and 20lbs over target PSI. I've lately had to boost my pressure due to weight gain, and I now get nuisance alarms on all wheels after a while. I usually pick up 14-18lbs after a while of running. An increase in the trigger is warranted.
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Old 03-23-2014, 07:12 PM   #4
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My coach came with the Valor system, with sensors mounted inside the tires. They recommend a high trigger at 185#, so this would seem to preclude false alarms. But yes, this does seem too high in my mind. It also has a built-in algorithm which allows a 2#gain in pressure with each 10 degrees of temp gain, so false alarms are not as prevalent.
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Old 03-24-2014, 12:42 PM   #5
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Ok Sky Boss. What brand and tire size are you running? We have a 2007 DSDP model 4023 and we are running TOYO 305/70R 22.5s load range J. Your configuring is right in line with my thinking esp for the front tires. I really felt 20% above Max allowed would be the way to go. The Max for the Drive tires is 85 #s but I guess I could also go with the chart recommended pressure and increase that by 20%. The low pressure then should be only 10% below the chart wt. that I choose-Correct?
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Old 03-24-2014, 01:33 PM   #6
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Quote:
Originally Posted by THERAPY GUY View Post
Ok Sky Boss. What brand and tire size are you running? We have a 2007 DSDP model 4023 and we are running TOYO 305/70R 22.5s load range J. Your configuring is right in line with my thinking esp for the front tires. I really felt 20% above Max allowed would be the way to go. The Max for the Drive tires is 85 #s but I guess I could also go with the chart recommended pressure and increase that by 20%. The low pressure then should be only 10% below the chart wt. that I choose-Correct?
Mine are Michelin of the same size load range L. Did you mean that according to the charts you should run 85 PSI for your drive axle? I would think the max PSI for your Toyos should be 120. Since you don't have a tag I would think your weight per tire will be closer front vs back.

If it where me I would try the 20% upper limit for the rear and adjust up!to 25% as needed to avoid nuisance alarms. Of course that is based on your target PSI according to Toyo's charts.
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Old 03-25-2014, 06:36 AM   #7
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Thanks Sky Boss, The drive axle Max, tire limit posted by the manufacturer-Newmar- is 85#s The front is 120. At this moment my rear axle wt., according to DOT scales, is 18,500# so that's 4625#/tire. Front is 12420, or 6210/tire. These numbers will go up. I weighed before being loaded to travel and without the dollie and car hitched, but with a full tank of fuel. But with this present wt. the TOYO chart put my rear air at 75psi/tire. If I get to 4900#s/tire the advised psi is up to 80#/tire. So I think I agree with you that the alarm would be best at 20% over the max recommended 85psi. That would be 102# and the low at 10% below the actual wt. per the chart after the final weigh in. Your Thoughts? Also,no one to date has responded to the tire failure question due to heat. TST said tires fail at 180*-200*. Is that ALL tires or was the reference to Michelins because they use that brand in their literature? Once again thanks to you and others that advise. I'm still learning.
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Old 03-25-2014, 10:54 AM   #8
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I think the heat point issue is one of "vast majority". Of tire failures directly attributable to heat, the vast majority occur in that range. I seem to recall reading somewhere that the 157 number is used because there's never been a documented heat failure below that point. Something like that.
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Old 03-25-2014, 02:10 PM   #9
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Quote:
Originally Posted by THERAPY GUY View Post
Thanks Sky Boss, The drive axle Max, tire limit posted by the manufacturer-Newmar- is 85#s The front is 120. At this moment my rear axle wt., according to DOT scales, is 18,500# so that's 4625#/tire. Front is 12420, or 6210/tire. These numbers will go up. I weighed before being loaded to travel and without the dollie and car hitched, but with a full tank of fuel. But with this present wt. the TOYO chart put my rear air at 75psi/tire. If I get to 4900#s/tire the advised psi is up to 80#/tire. So I think I agree with you that the alarm would be best at 20% over the max recommended 85psi. That would be 102# and the low at 10% below the actual wt. per the chart after the final weigh in. Your Thoughts? ...
OK...keep in mind that the tire pressure plate behind your driver seat is based on max weight for each axle. I like your thinking and may even adapt it to my rear and tag limits instead of the 20% above "target" PSI. That would make:

Steer Heaviest wheel 7340, Target 112, Low 101, high 144
Drive heaviest wheel 8053, Target 75, Low 68, High 102
Tag Heaviest wheel 3407, Target 75, Low 68, High 102
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Old 04-02-2014, 11:27 AM   #10
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Quote:
Originally Posted by THERAPY GUY View Post
Thanks Sky Boss, The drive axle Max, tire limit posted by the manufacturer-Newmar- is 85#s The front is 120. At this moment my rear axle wt., according to DOT scales, is 18,500# so that's 4625#/tire. Front is 12420, or 6210/tire. These numbers will go up. I weighed before being loaded to travel and without the dollie and car hitched, but with a full tank of fuel. But with this present wt. the TOYO chart put my rear air at 75psi/tire. If I get to 4900#s/tire the advised psi is up to 80#/tire. So I think I agree with you that the alarm would be best at 20% over the max recommended 85psi. That would be 102# and the low at 10% below the actual wt. per the chart after the final weigh in. Your Thoughts? Also,no one to date has responded to the tire failure question due to heat. TST said tires fail at 180*-200*. Is that ALL tires or was the reference to Michelins because they use that brand in their literature? Once again thanks to you and others that advise. I'm still learning.

Yes sir most tires typically between 180 and 200 degrees. You are correct
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