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Discussion Starter #1
Picked up my 2500 159 high on Fri night. It was cold out, upper 20's low 30's. Dealer warns me that its cold out and tpms will signal low pressure. I'm not new to it being cold out and tire pressure being lower. So, I drive off the lot with it signaling low pressure. Yesterday and today it was in the 60's. Still signals low pressure, so I check them. All are at or near 70 psi cold. Door jam sticker says front should be 65 and rear 80. All tires themselves say 80 cold. Which is it?
 

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I have being doing 80 psi . The light comes on in the cold winters and then I check with a gauge
and ignore the light in the extreme cold. My light is off now because it is warmer out.
 

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For me it was the spare tire tpms that ended up being the problem. I ended up with 75 lbs in each then a 50 mile drive and it went away. Mine happened the second day of ownership. It was brand new. Hope this helps.
 

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...cut.... Door jam sticker says front should be 65 and rear 80. All tires themselves say 80 cold. Which is it?
Tires are molded with the maximum pressure on sidewall, which is required for their maximum rated capacity. That's also on sidewall.

However, tires that are not loaded to their maximum rated capacity don't necessarily require operating at maximum pressure. That happens often with vans and trucks because the front axles are not rated to carry as much weight as the rear axle.

Since all four tires are usually the same, the front ones can often be operated at a pressure that is significantly below the tires' maximum. If we were to increase pressure beyond the door jam sticker, it can affect ride harshness, traction, and handling. I recommend not exceeding the specified pressure.

If anything, I can understand running a van that is always empty or very lightly loaded with tires that are inflated at lower pressure. But that can be dangerous.

The "80 PSI Cold" means the tire should be filled and or measured near ambient temperature. That's because when the tire gets hot during normal operation the pressure will increase significantly. And engineers don't want people letting air out of a hot tire because it's above 80 PSI. Or whatever the correct cold inflation pressure is.
 

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Discussion Starter #5
Well I guess if I never exceed the recomended pressure on the door jam, the tpms light will never go off. I'll have to check the spare, didn't think of that.
I understand the whole concept of cold tire pressure and over inflating affecting ride characteristics. What I don't understand is why Ram recommends 65 in the front and they don't set the tpms for those tires to alert at that pressure.
 

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Well I guess if I never exceed the recomended pressure on the door jam, the tpms light will never go off. I'll have to check the spare, didn't think of that.
I understand the whole concept of cold tire pressure and over inflating affecting ride characteristics. What I don't understand is why Ram recommends 65 in the front and they don't set the tpms for those tires to alert at that pressure.
Was your van recently built or was it older dealer stock? Mine was built 7-2014 and it still needed the TPMS recall performed. Prior to that, I would get the light on at times. Since having the recall performed I haven't seen the light at all. Even after airing up the tires, it took a while driving before the light will go off. I run mine @ 80 PSI all four corners. It does make the front ride a little harsh at times though.
 

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Discussion Starter #7
Built about three weeks ago. I'm thinking I may have to do the same and air up to 80 psi all around. Right now the fronts are 70 and the rears 80. Light still on after a few hundred miles driven.
 

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Built about three weeks ago. I'm thinking I may have to do the same and air up to 80 psi all around. Right now the fronts are 70 and the rears 80. Light still on after a few hundred miles driven.
Try it and see what you think. The ride feels good for me at 80psi.
I do not know if the spare has the sender? The light should go out after a couple of blocks or so.
 

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It sounds from comments above that PMs have direct TPMS. Does it display each tire's actual pressure, or just a warning if one falls below a predetermine pressure level? In other words, can driver check current PSI for each tire from dash?
 

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Just a warning that one or more tires have low air pressure.
 

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It sounds from comments above that PMs have direct TPMS. Does it display each tire's actual pressure, or just a warning if one falls below a predetermine pressure level? In other words, can driver check current PSI for each tire from dash?
I have a OBDII reader, but the software I use can't show me the individual tire pressures, even though the computer clearly knows them. It bugs me when this functionality isn't included by the OEM - it would cost exactly zero dollars to make true tire pressures available to the driver.

On Nisans and I think Infinitys, they do something brilliant. You get the light if the tire is low, but as you are filling it when it gets to the correct pressure, the horn honks. If you go over, the horn honks in a different pattern. Simple, elegant, cost free.
 

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Software isn't free but so cheap that it might as well be. Write it once use it forever. We are still in the dark ages when it comes to software for the driver as opposed to software for the car and techs.
 

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Yes the spare has a sender.

But does the spare have a receiver?


TPMS in my previous vehicle (2009 Jeep Wrangler) used a combination of pressure and info from the ABS sensor to determine if there was a problem or not, and that's why it needed to be driven to reset the system. There was no receiver for the spare, but the spare had the transmitter as required by law. My 2010 Xterra behaves the same.



John
 

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Really old thread.

The receiver is under van below the cab.
All tires have sensors.
They activate with rotational forces.
So only 4 will send data and the spare could be missing or flat doesn't matter.
Doesn't know which tire is low.
 
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