Tire pressure management systems.

[geric]

I installed the eez tire TPMS and put 95lbs in all 6 tires. Next morning checked tire pressure and it was all over the place from 92lbs to 99lbs. Took a short trip to San Diego and they were still constantly changing. My question is, is this normal? This is our first rv and still learning. We have a Winnebago vista 35f. Thank you

[creativepart]

It's not unusual for the PSI reading on the TPMS to be different from your manual tire pressure gauge. So, setting all the tires at 95 with a manual gauge can easily display up to 3 psi plus or minus on the TPMS.

When driving the PSI of each tire will naturally climb with friction from the road and based upon the location of the weight of your coach. For instance if you have a full tank of fresh water on the right side of your coach it is normal for the tires on that side to heat up more as you drive and display a higher pressure.

When my tire are cold I set my fronts to 85 and rears to 95 with a manual gauge. But my EEZ TPMS shows about 83 on the fronts and between 93 and 96 on the rears.

So, if you see a bit of difference between the manual gauge and the TPMS that's normal. But if you see really wild differences then check again with the manual gauge or even try a second different manual gauge.

You want to set the tire pressure when the tires are "cold" not in temperature per se but as in not driven on at all - not even just a mile or so.

Also keep in mind that the pressure readings in the afternoon when it's warmer outside will always be different than in the morning when it's colder outside.

[Morich]

When first learning what the tire do, we had to reset the alarms a number of times as we found tire pressure goes up and down way more than expected. It will vary a bunch just as the sun moves around or you drive in a different direction! I know that a manual gauge is difficult to get a true reading due to letting some leak and the way we hold the gauge, so I go the the steadier long term reading as more reliable than manual!
But I no longer obsess over what the exact pressure I set as it is never the same for even a few miles. I no longer set for a spec of 82 as that soon becomes to harsh for ride and I have settled on 72 as a start and wind up with it often being 90!

[JoeC]

Originally Posted by Morich

When first learning what the tire do, we had to reset the alarms a number of times as we found tire pressure goes up and down way more than expected. It will vary a bunch just as the sun moves around or you drive in a different direction! I know that a manual gauge is difficult to get a true reading due to letting some leak and the way we hold the gauge, so I go the the steadier long term reading as more reliable than manual!
But I no longer obsess over what the exact pressure I set as it is never the same for even a few miles. I no longer set for a spec of 82 as that soon becomes to harsh for ride and I have settled on 72 as a start and wind up with it often being 90!

You are correct about tire pressure constantly changing, but, when you set tire pressure, it should always be done on cold (not driven on) tires. This is your base pressure to which all other pressures are measured. There is a known calculated percentage increase in pressure under various driving conditions.

[Morich]

Originally Posted by JoeC

You are correct about tire pressure constantly changing, but, when you set tire pressure, it should always be done on cold (not driven on) tires. This is your base pressure to which all other pressures are measured. There is a known calculated percentage increase in pressure under various driving conditions.

Works fine, sounds simple! But then it also has little to do with real world if we know that the same tire in Texas summertime is going to be totally different than one in Minnesota in the winter!
Setting tire pressure is an "estimate" of what should work best and like all estimates, it can be very wrong!
When we trek from here to Tennessee we have low pressure alarms when we set overnight in a campground, so we adjust the alarms and turn them off overnight to avoid them waking us at 4-5 AM!

[HollywoodGT]

LOL I have to find where my I believe inner stems are first before adding the TPMS. Plus the fact that the tire has only one valve stem showing in the back with the duallies. AlsoI have been told that is normal to have one stem points outward and the other points inwards. Why they did that and not just make both the same makes no sense to me. The other issue is using the valve stem caps. People have said that it can damage th stem if not supported from the force of the wheel spinning.

[creativepart]

Originally Posted by Morich

When we trek from here to Tennessee we have low pressure alarms when we set overnight in a campground, so we adjust the alarms and turn them off overnight to avoid them waking us at 4-5 AM!

Richard, I struggled with this between Texas and New Mexico. I did a lot of asking for solutions on IRV2 and was told that every morning, before driving away from the campground that I needed to add air to my tires for the cold (not driven and temperature) of the place I was at present.

So, if in Texas my cold pressure was 85 psi at 60 degrees and then I drive to West Texas and when I wake the tires are at 78 psi at 38 degrees that I should add 7 psi to get the cold (undriven) psi up to 85 psi. And, to do this every time so that the undriven psi always started at the recommended psi.

So, rather than haul out the air compressor every morning before we drove from Texas to New Mexico to Arizona I just stopped using the lowest tire pressure recommended for my actual weight.

After a 4-corner weigh the Michelin chart said I could run 75 front and 85 rears. But after daily alarms I gave up on that and now run 85 front and 95 rears. That way, even on very cold mornings at altitude I am no longer seeing pressures below that recommended psi and not getting TPMS alarms.

As expected the ride isn't as good. But I do see more even tire wear as well.

[geric]

Thanks everyone for the valuable input.

[Army Guy]

Originally Posted by Goodspike

Not if you want to know the pressure before you start off on your trip. They don't run 24/7 to increase battery life, they only send signals when they are moving.

But again the other reason was not being certain of my valve stems. They are at least half metal and are upgraded units compared to the factory, but they are just something the tire shop installed, not something I researched. I'd rather not cause a flat trying to monitor whether I have a flat!

I have Pressure Pros and have been using them on all my different rigs for the last 12 years. These don't need to be moving to read. Just power up the system and wait a few minutes for the signal to send. These are the kind that you cannot replace battery but have to replace sensor. Sensors batteries seem to last around 5-7 years and are $35 bucks each. Much cheaper than a blowout & those damages.

[Morich]

Originally Posted by creativepart

Richard, I struggled with this between Texas and New Mexico. I did a lot of asking for solutions on IRV2 and was told that every morning, before driving away from the campground that I needed to add air to my tires for the cold (not driven and temperature) of the place I was at present.

So, if in Texas my cold pressure was 85 psi at 60 degrees and then I drive to West Texas and when I wake the tires are at 78 psi at 38 degrees that I should add 7 psi to get the cold (undriven) psi up to 85 psi. And, to do this every time so that the undriven psi always started at the recommended psi.

So, rather than haul out the air compressor every morning before we drove from Texas to New Mexico to Arizona I just stopped using the lowest tire pressure recommended for my actual weight.

After a 4-corner weigh the Michelin chart said I could run 75 front and 85 rears. But after daily alarms I gave up on that and now run 85 front and 95 rears. That way, even on very cold mornings at altitude I am no longer seeing pressures below that recommended psi and not getting TPMS alarms.

As expected the ride isn't as good. But I do see more even tire wear as well.

We found that we could just set the alarms a bit different to allow for the overnight swings and when we start in the mornings, the tires warm so fast that they come to near the right temp in the first 5-10 miles so I am okay with just letting them wear a bit sooner, if that is what happens, rather than have the constant nightmare of trying to outguess what the weather it going to do for the next day and constantly checking the pressure.
I'm sure I've driven a million miles with tires that had the wrong air pressure and never knew it until somebody invented a gizmo to let me see it fulltime!
A thousand more miles out of the tires or a thousand hours of worry? I go going for the lower stress!
I can buy more tires but I'm running real short on time for worry!