Yet Another Tire pressure Question

[jbikesv]

I understand I should check tire pressure every day, first thing. However, if the overnight ambient temperature is 25, but I know I will drive into 65 within , say, 3 hours...... will this likely  increase my tire pressure more than the 20% increase the factory recommends for a high pressure alarm on my TPSM system I will be adding?

[manholt]

No!

[wayne77590]

For every 10˚ of temperature change you will loose or gain 2%, so let's say your tires are set for 100 psi. At 40˚ temperature drop you would loos 8% equaling 92 PSI. If your minimum pressure is 92 or above for your load rating you will be okay, so set a fudge factor when setting tire pressure to anticipate gain or loss of pressure. 

Since you will be increasing temperature by 40˚ from 100 psi your tire pressure would be 108 degrees.  If that pressure is within the manufacturer's recommended maximum pressure you will be okay.  That is where the fudge factor comes in.  If you have tires rated at 110 psi and you minimum pressure for your load is 92 psi setting to 100 psi would mean that you would very seldom ever have to increase or decrease your tire pressure.

FYI, for every 1000 feet of elevation gain or loss you will have a pressure differential of .47 psi.  Typically when you change elevation by 1000 feet you would loose or gain some temperature so there is a slight compensation between the two.

[wolfe10]

Remember, the tire pressure rating (really the minimum PSI for the maximum load) is ONLY with the tires at ambient temperature before driving.  The tire manufacturers know that driving, exposure to sun, etc will raise the temperature. Not a problem.

[wayne77590]

....and they should be checked first thing in the morning before the sun gets to them.  It is amazing what a few minutes of sun can raise the tire temperature.

Also, consider a Tire Pressure Monitoring System (TPMS).  My early years I checked every morning before a departure. Not difficult but time consuming a few extra minutes.  Then thought prevailed and I wondered what was happening going down the road.  TPMS gives a great piece of mind.  Turn it on when you are getting ready to go and within about 5 minutes all your tires are reading pressure and temperature.  I think that those of us who have them are glad we took the step and made the investment.

[manholt]

Wayne.  That is very good advise!  Takes most of the math out of the equation..

Carl

[wolfe10]

Yes, the 2% change with every 10 degrees F is a pretty good approximation.

Anyone who wants more accurate info (can't imagine why), the Ideal Gas Law from your high school physics applies: PV=nRT.

[BillAdams]

I check my tire pressure from time to time (not every day) and that works very well for me.  I travel in and out of various temperature ranges frequently.  I do "thump" my tires every day and I usually "thump" my tires any time I stop along the way.  Do I do it every time?  No, but I try to!  I like the idea of TPMS but in the last 17 years can't remember a single time where they would have told me anything of any value in advance of a problem.  If I was going to add any accessory to my tires it would be a cross-fire system on the dual just to keep the temp/pressure difference on the inside/outside tires the same.  I am not convinced that even this is of any proven value but I think I might be able to mentally justified this expense.

[wildebill308]

I was checking my tire pressure at a campsite this summer and this "gentleman" was walking his dog by and asked "what are you doing?" I said checking my air pressure. He said "I have the dealer do that in the spring when the coach is in for maintenance." The moral is some obsess over pressure changes down to the tenth of a pound and some not so much.

Bill

[jbikesv]

My desire for TPSM coming from a trip I made when, in the rain, I noticed bits of the rear tire on my 5th wheel flopping in the rain. I hadn't felt or heard a thing and had no idea how many miles I had gone prior to seeing the flopping tire. Something I would not have seen if it were on the right side as my mirror couldn't be trained to see the back tires properly. I've heard similar stores of the inside rear on duel's. So... an alarm for tires I can't see on my new motor coach gives me piece of mind.  Thanks to all proving great advice.... this is a good community. 

J

[akadeadeye]

46 minutes ago, WILDEBILL308 said:

I was checking my tire pressure at a campsite this summer and this "gentleman" was walking his dog by and asked "what are you doing?" I said checking my air pressure. He said "I have the dealer do that in the spring when the coach is in for maintenance." The moral is some obsess over pressure changes down to the tenth of a pound and some not so much.

Bill

That "Gentleman" is asking for a problem.  Things happen.  I check mine before every trip.  Pretty boring at times. 90, 90, 100,100, etc. except one morning before a trip and it was 90, 35, 100, 100.  A valve stem had come loose from the rim.  Glad I checked.  If I had followed the "Gentleman's" routine, I would likely have had a blow out along the way.

 

Don

[manholt]

When I originally got into coaches, there was only one way to check tires, baseball bat and thump.  Every time we stopped and before leaving in the mornings, rain, shine or snow, I would thump.  I have TPMS and have had them on the last 5 coaches, but I still carry a bat and thump!

Carl

[hermanmullins]

57 minutes ago, manholt said:

 but I still carry a bat and thump!

Carl

Congratulations Carl, I didn't know you were dating now.

Herman 

[wayne77590]

There is about 8 inches of rubber touching the road on each tire. That is not a lot of "safety" if one of them is to go flat.  I have a realization that pulling out of an area I can pick up any debris that could puncture a tire. Whether it is a slow leak or a quick one a TPMS will alert me very quickly if the air pressure drops below my setting for "to low."

One time in the toad and at night I ran over a rubber bungee with those "S" hooks on the end and the hook penetrated the tire.  It was a pretty quick loss of air pressure.  I sure hope that never happens in the MH and I know that the TPMS will give me quick warning.  It also gives me a great peace of mind.

Driving any distance with a rear dual at a low pressure will most likely cause the other dual to be overloaded and that is just extra $$ for two new tires.

[jbikesv]

Next Question about TPSM: my 2017 Jeep has that as OEM I wanted to add External sensors ( so I can take them off when not towing) but am wondering if they external will harm or interfere with the OEM ones on the jeep?

[jleamont]

jbikesv, the only way to tell would be to try it and see what happens. I have the same dilemma with our 2014 Jeep, I was going to explore it in the spring and see what happens.

I always check my TPMS every morning before starting the coach to leave. I scroll through all tires on the toad and coach, if any are lower than they were the day before I am out looking at them with my bottle of soapy water.

Having a shop check them with annual maintenance only is crazy. That is the person in the videos with the blow outs that we all have seen. I'd be shocked if the mechanic actually checks them.... oh the stories of stuff I have seen in a shop with mechanics paid by the job .

[wolfe10]

Many of us have the external TPMS on our toad in addition to the standard one provided by the vehicle manufacturer.  NO PROBLEM.

[deenad]

Brett, that's what I'm going to be doing if I get to traveling more. Bought a TPMS for the DSDP and still have it, the Magna has a SmarTire system and I just had all new tires and sensors installed. Just bought a '14 CR-V to tow. Since Cindy died in August I need all the help I can get!