Author Topic: Tire pressure !  (Read 68 times)

Offline tmsnyder

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  • Posts: 495
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  • Year: 1990
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  • Engine: 454
Tire pressure !
« on: February 25, 2019, 10:57 PM »
One of the main causes of tire blow-outs is an under inflated tire.  They build up heat faster than they dissipate it then fail by delaminating.  That's my understanding of it anyway.


So I check air pressure pretty regularly, even during a trip.  (And I feel the tire temperatures when filling up with gas)


Pulling off the valve stem caps and checking each tire with my pressure gauge was getting a little tiresome so I bought two sets of these:


https://www.amazon.com/gp/product/B07BFBN76B/ref=oh_aui_search_asin_title?ie=UTF8&psc=1


They replace the cap with a pressure indicator.   I inflate my tires to 90 psi, so I bought the 100 psi variant of these caps.  The top/sides of the indicator shows green when the tire is at 100% pressure rating, yellow when it's low, and red when it's really low.  I don't have the instructions in front of me, but it was something like yellow is 75% pressure, and red is 70%.  Something like that. 


At 90 psi, they are all green with a tiny bit of yellow showing.   I have one tire that has always had a slow leak, these didn't change the leak for better or worse.  And the rest of the tires don't leak at all, even with these installed. 


I really like them, now I can just walk around the rv and look closely at the indicators to see if they are properly inflated.  They are not the easiest things to see b/c they are small and you need to look at them from the side, but they are a heck of a lot easier to use than unscrewing the cap, gauging it, then screwing the cap back on. 


Something to consider to make travels safer and easier.

Online Sasquatch

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Re: Tire pressure !
« Reply #1 on: February 25, 2019, 11:15 PM »
You are only seeing half the equation.  The other half is temperature.  You fill your tires to 90 psi COLD.  Cold means 65 degrees F according to the tire industry.  Your tire will gain about 1.5 psi for every 10 degrees above 65 psi.  Seeing 140-150 degrees on a warm day is not uncommon.  (195 degrees is the max for most tires)


90 psi cold
150 degrees
Your tire should be at 112 psi  That is 22 psi over your cold inflation pressure, and exactly where it should be.


If your tire is hot (like at a mid day fuel stop), and your tire is at 90 psi where your little monitors show green so all is good, you are actually 22 psi under inflated for the temperature.  So even when your monitors show green, you are under inflated.


That said, you would not be critical, but you would be low.  Some warning is better than none.


This is the system I have in my coach, and one that I hold a patent on and worked 15 years on to develop.  I have done more tire pressure/temperature comparisons than I care to remember.  (Dont get me started on nitrogen in tires...)





It measures absolute pressure and temperature inside the tire.  It then calculates what the pressure should be at any given temperature (based on your programmed cold inflation pressure) and then gives you a deviation number where it tells you +/- psi from where it should be.


My suggestion to you is to get an understanding on what pressure your tire should be at any given temperature, then when you check it with a gauge, you will know where it should be.

Offline Rickf1985

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Re: Tire pressure !
« Reply #2 on: February 26, 2019, 10:07 AM »
I have tried for years to find someone who can tell me what the recommended tire temperatures should be. That is what I set my initial pressure by since the door panel tells me 65 lbs. which is waaaay to low and when the tire shop put them at that they were at the 150 degree mark just on the ten mile ride home at 40 MPH!! I have been running them at 80 and the temps stay around 120. The problem with Sampson is they do not provide a weight/pressure chart.

Offline ClydesdaleKevin

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Re: Tire pressure !
« Reply #3 on: February 26, 2019, 10:15 AM »
What a brilliant idea, tmsnyder !

Not a bad price either on Amazon!

How long have you been using them?  I would be concerned with a leak from the cap if they failed.  So far, I've been checking my pressures with a gauge before every trip, and then using a tire bat when fueling up to "listen" to the tire pressures before getting back on the road.  These look like a much better idea that the old tire bat.

Kev
Kev and Patti, the furry kids, our 98 Cherokee lifted beastie tow vehicle, and our 1995 Itasca Suncruiser Diesel Pusher.

Offline BrandonMc

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Re: Tire pressure !
« Reply #4 on: February 26, 2019, 08:27 PM »
I have tried for years to find someone who can tell me what the recommended tire temperatures should be. That is what I set my initial pressure by since the door panel tells me 65 lbs. which is waaaay to low and when the tire shop put them at that they were at the 150 degree mark just on the ten mile ride home at 40 MPH!! I have been running them at 80 and the temps stay around 120. The problem with Sampson is they do not provide a weight/pressure chart.


I've been looking for an old thread you posted about tire psi trying to figure out what to run my tires.  I run the Bridgestone Duravis 500 HD. Probably going to shoot for 75psi and see how that does after running 60psi from what the door calls for on the old 7.50x16



Offline Rickf1985

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Re: Tire pressure !
« Reply #5 on: February 26, 2019, 08:48 PM »
Well, It calls for 65 front and 80 rear on my Dodge one ton dually with the 215-85/16's so take it from there. My Winnebago has the 19.5's on it so you can't really compare tires pressures to mine.

Offline tmsnyder

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  • Posts: 495
  • Member since: 2016
  • I own: a Motor Home
  • Year: 1990
  • Make: Holiday Rambler
  • Model: 30' Aluma-Lite XL
  • Chassis: Chevy P-30
  • Engine: 454
Re: Tire pressure !
« Reply #6 on: February 26, 2019, 09:53 PM »
I've had 8 of them on the rv since Sept 2018.  They didn't cause any leaks.   They are made of brass and some tough plastic.  The seal seems very positive when screwing them on, you can tell it presses the schraeder valve tip just as the seal is making contact b/c there's a little hiss as it's screwed on and makes contact, then seals up the hiss quickly.  Just put them on a little bit past contact.   We just got back from a 3000+ mile trip and pressures stayed good the whole way.


Like I said though, they are a little tough to read.  Have to look at their tips from the side of the cap.  Sometimes this means hanging my head upside down looking at the indicator, depends on how it ends up when the rv is put in park. Still much easier then checking with a gauge.  Takes one of my check list items and makes a 1 minute job out of what used to take me 10 minutes.

They come in various pressure settings for whatever pressure you need, should be one close.

Offline Rickf1985

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  • Posts: 5087
  • Member since: 2013
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  • Year: 1989
  • Make: Winnebago
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  • Engine: 454
Re: Tire pressure !
« Reply #7 on: February 27, 2019, 11:13 AM »
As far as a manual system you can't beat these for dependability. You see them on over the road trucks a trailers all the time. Or you used to, now they mostly use auto inflating and management systems on the big trucks.

 

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