TIRE PRESSURE QUESTION

[KDP224]

I got a tire pressure warning that one of my tires was low on my 2018 Ram. Based on that I thought I would check all four tires using the dash readout and went about topping up all my tires to the required psi which if memory serves me is 39 psi or 269 kPa. I did this on a cool morning before I left for work. I got two tires to 38 psi as no matter what I did I was either over or under the required 39 psi and the other two were at 40 psi. I want the tire pressure to match up but does anyone have any suggestions on how to do this correctly and when I should do this

The other issue I have is that when I start driving for a few minutes the PSI readout starts to vary so that where I had 38 all of the sudden I might be at 35 and my 40 psi tires are at 42. Is the trucks computer accurate for this or am I making a big deal out of nothing

Any feedback would be appreciated

 

[jbrown5030]

That dang tire pressure readout is going to drive those of us with OCD insane. No matter what I do, one of them is always a pound high or a pound low. This time of year with cold mornings and warm afternoons is particularly hard to handle.

I'm not sure if the TPMS works the same on the Ram, but this time of year my wife's Honda always complains if one tire is some percentage different than the other three, and it's always the first really cold morning.

 

[ram1500rsm]

I don’t pay too much attention to the system, i check my tires pressure the old fashion way.

 

[69GWC]

My dash read out has one tire off no matter what I do..lol
Checked mine and just did 45psi in all four and checked them with two different gauges but the dash was still off no matter if I drove it around the block or to town.
So I dont even look at that crap anymore since it is not accurate anyway.

 

[TRCM]

Best way to get them all the same, is use a GOOD tire pressure gage when filling them up. and by good, I mean none of those stick gages....dust or dirt can throw them off.

Anyway, part of the problem is, the TPMS sensors need to be rotating to read correctly. The owners manual says they "....may need to be driven for up to 20 minutes above 15 mph
(24 km/h) in order for the TPMS to receive this information".

Driving it around the block, or even to town, may not be enough to reset it.

So, fill them up using a good quality pressure gage, then go drive it some to update the TPMS system.


On mine, I do this, and once out on the highway, all 4 equalize within 30 min or so. Worst case, 1 may be a pound low, and I can fix that easily if I chose to by either adding air, or dropping the other 3 to match.

 

[swexlin]

I'll beg to differ- the TPMS in both my Ram and Viper is pretty accurate (usually within 1 lb of the gauge). I look at the pressures all the time and actually drive with them up in the Viper - it alerted me to a slow leak due to a nail once.

That being said, the low pressure warning in my Ram won't go off until it hits 30 psi in my Ram - and 3 did this morning! I almost never run 39 PSI, usually 36-38 except when it's very hot in the summer. Funny thing is, I can run all day at 31 and it never goes off, but at 30, bingo, and then it won't reset until to take it up to 39.

 

[crash68]

I modified a tire inflater with a digital gauge that hooks up to two tires at the same time. There is many times I look at the TPM and the pressures will be off by 1 or 2 side to side. I usually run about 3 psi less if not planning on towing anything heavy.

 

[69GWC]

Best way to get them all the same, is use a GOOD tire pressure gage when filling them up. and by good, I mean none of those stick gages....dust or dirt can throw them off.

Anyway, part of the problem is, the TPMS sensors need to be rotating to read correctly. The owners manual says they "....may need to be driven for up to 20 minutes above 15 mph
(24 km/h) in order for the TPMS to receive this information".

Driving it around the block, or even to town, may not be enough to reset it.

So, fill them up using a good quality pressure gage, then go drive it some to update the TPMS system.


On mine, I do this, and once out on the highway, all 4 equalize within 30 min or so. Worst case, 1 may be a pound low, and I can fix that easily if I chose to by either adding air, or dropping the other 3 to match.

Well to town I mean like 25 miles there and 25 miles back.
I have 3 good gauges and all read the same.
My wifes Mustang is the same way its real hard to get them all to read the same.
I mean I can get them to read the same on the dash but buy my 3 different gauges the tires will really have different air pressure in them.

I just use the tpms for a alert to let me know if A tire is low that I did not notice before I got in.

 

[Fitz-0518]

I trust my quality pressure gauge. I don't believe that the tire pressure sensors in our trucks, along with the program design is as accurate. Static fill, will drive you nuts. It is as stated, an active system. After driving and the tires warming up, I found that the display read out difference is not more than 1 PSI in our 2018 2500 SLT.

 

[swexlin]

I trust my quality pressure gauge. I don't believe that the tire pressure sensors in our trucks, along with the program design is as accurate. Static fill, will drive you nuts. It is as stated, an active system. After driving and the tires warming up, I found that the display read out difference is not more than 1 PSI in our 2018 2500 SLT.

Agreed. It takes about 0.25 miles of driving for the pressures to update in both of my vehicles.

 

[hotrod45]

I have a couple good stick gauges. When I say good, I mean good, too. They are both professional tools. I check the onboard info and use it as a guide, but if I want to know what the pressure is, I check the tires with a gauge. I use a gauge when I'm adjusting pressure, too. The tires on the Ram trucks that I've had seem to be much more sensitive to temperature changes than any I've ever seen. I've had tires at 39 drop to 31 overnight because of a sudden change in ambient temperature. The onboard info shows one tire one pound lower in pressure almost all the time, but it is an error in the sensor. Lately, I have taken to running 40 psi up front and 39 rear. Driving is still cleaning the tread surface all the way to the shoulder up front and likewise in the rear. I have a little bit of weight in the rear, plus the cap, so 39 works out just right. Tires are definitely worth keeping a close check on, considering what they cost these days.

 

[TRCM]

Well to town I mean like 25 miles there and 25 miles back.
I have 3 good gauges and all read the same.
My wifes Mustang is the same way its real hard to get them all to read the same.
I mean I can get them to read the same on the dash but buy my 3 different gauges the tires will really have different air pressure in them.

I just use the tpms for a alert to let me know if A tire is low that I did not notice before I got in.

Me too.... I use a good gauge to fill them, then whatever the dash reads, it reads.....but usually, they are all the same.

 

[TRCM]

I have a couple good stick gauges. When I say good, I mean good, too. They are both professional tools. I check the onboard info and use it as a guide, but if I want to know what the pressure is, I check the tires with a gauge. I use a gauge when I'm adjusting pressure, too. The tires on the Ram trucks that I've had seem to be much more sensitive to temperature changes than any I've ever seen. I've had tires at 39 drop to 31 overnight because of a sudden change in ambient temperature. The onboard info shows one tire one pound lower in pressure almost all the time, but it is an error in the sensor. Lately, I have taken to running 40 psi up front and 39 rear. Driving is still cleaning the tread surface all the way to the shoulder up front and likewise in the rear. I have a little bit of weight in the rear, plus the cap, so 39 works out just right. Tires are definitely worth keeping a close check on, considering what they cost these days.

be careful.....the front will almost always 'clean' to the edge of the tire due to camber changes as you steer....that's why the chalk or 'clean' method is supposed to be used when driving straight...no turning.

 

[Ramit355]

I always fill mine @ 36 on cold tires that has sat over night. I use a round gauge that is expensive like 12 bucks or so. After all are filled to 36 lbs I leave it. The dash will have them with in a lb or so usually. At times they will inflate some and all be the same for a bit and then off a lbs or so.....depending on the "lean " of the pavement, upgrade, down grade,from steering and heavier in the back of truck, wet or dry pavement,etc it will vary as you drive. When it rains they change quite a bit as you drive. Old schools guys we all thought when you put the lbs in like at 36 they just stayed that way not knowing they vary while you drive and the ambient air around them changes as well never staying on the exact pressures you fill them with. My two cents! LOL.

 

[KDP224]

ok... it seems that there are many comments on filling the tires with air and then driving a certain amount. Is that then best way for me to see if my tires are properly inflated and not worry too much about what it says in the morning when the truck has sat still overnight. Second question is should I fill to the rated 39 psi for winter or keen them a tad lower?
thanks

 

[swexlin]

Yep fill to 39 for winter, or whatever your driving needs require. In summer, I never fill mine higher than 35, as on a hot day with normal driving, it will rapidly climb to 41.

My truck actually goes in tomorrow for PA state inspection and tire rotation (and for them to try to fix this oil leak for the third time) so I'll have them use their air hose to fill them! Tires are close to needing replacement anyway (pretty close to the wear bars, I hope they pass inspection). I hope to get another 5000 miles out of them (I have 33000 on them now).

 

[TRCM]

ok... it seems that there are many comments on filling the tires with air and then driving a certain amount. Is that then best way for me to see if my tires are properly inflated and not worry too much about what it says in the morning when the truck has sat still overnight. Second question is should I fill to the rated 39 psi for winter or keen them a tad lower?
thanks

If you read my 1st post, the owners manual actually says you may have to drive ~ 20 min above 15 mph for them to completely reset

 

[swexlin]

As I mentioned above the TPMS on my Ram, Viper (and my 2013 Dart and 2007 Charger when I owned them) never have taken more than about 0.25 miles of driving to reset. By the time I back out of my driveway, I bring the monitor up, and in about the 1 minute it takes me to my first intersection at the end my street, I watch them reset.

Never understood where the owner's manual got that 20 minutes stuff. My commute is 20 minutes!

 

[hotrod45]

I had one weird event when the sensors didn't get reset after driving 24 miles one day and maybe 12 miles the second day. On the third day, they seemed to be squared away again. Every other time, it seemed like they were reading correctly after just a mile or two.

 

[LouM]

I have two sets of tires, summer and winter both have tpms sensors in them.
When I use my good gauge on them in the shop cold and no sun shinning on them the readout will be within a pound.
That said the pressure will change considerably as the tire warms up, as it always has which is why we where always told to check and set cold.
You can reduce the heat build up and temperature changing pressure if you purge all the air out of your tires and use nitrogen.
It's not worth it to me, but it can be done and used. The reason it is more stable is the moisture content. Which is also why you have to purge the tires good when using N2 for the most "benefits". Your pressure will still increase with temperature but much less.