Tweetz77

Hey,

I was curious as to the criteria that would throw a TPMS light. Basically at what pressure would the tpms kick on in a completely stock truck.

Mine came on today, checked pressures, and all are at 28 psi. The door recommends 35. I just find it odd that all 4 tires are the same at 28, and wasn't sure exactly how the TPMS worked on my truck.

I'm gonna air the tires up in the morning. Thanks for your input.

Z7What

Good question, i believe factory is set to 32-33#, just not sure at what pressure the light comes on.


Wayne

Ricktwuhk

20%.

You should NOT be using TPMS to decide when to add air to your tires. Check them at least monthly.

Tweetz77

Yessir, I know. I was just curious if it would only come on if one Tire was different from the other three thanks for the info.

morehousej

the TPMS sensors are set at a predetermined setting for your truck, they should send a fault notice if one or more of the tire pressures drops out of the "safe" range, typically 4-5 psi
for all your tires to have dropped evenly could be caused by outside air temp, did the temp drop a fair ammount since the tires were installed/last pressure check?

Tweetz77

So I might catch he'll for saying this, but the tires have nitrogen in them. Same tires since I bought the truck in November of '13, always just kinda kicked 'em and made sure the air was in them.

Light came on last night and figured I'd check, 28 PSI, all four tires. Door jam says 35. I was just making sure that the TPMS would work in a way that if any one Tire dropped below a minimum value it would kick on. Instead of just one Tire being different from the rest.

I'll be sure to check periodically from here on out.

mlheck

iTrader: (1)

In the early days of TPMS they used the ABS wheel sensors to detect one wheel spinning faster due to a smaller diameter due to low air pressure. The newer systems like we have use sensors in the wheel to measure the actual air pressure.

Nitrogen in the tires does NOT mean that they won't lose pressure it will just happen at a slower rate.

Tweetz77

This is a 2013, I don't think it uses the ABS sensor.

dannytexas

And just to answer your specific question.. The sensor will alarm if a single tire goes out of the preset range from Ford...which as you state on yours is 35.

Each wheel has its own sensor and will communicate to the truck independently.
Yours just sounds like all 4 tires naturally bled the nitro at a nice equal rate and when it finally hit 28 (20% below the 35 psi) they likely all 4 sent communication to activate the dummy light in the dash.

I know many aftermarket tuners allow one to change what the TPMS value is if you're running a different tire than OEM that requires more or less air.

lutter5-0

Preset from Ford is a relative term, lol. When I got my 2011, it was set in ForScan to 40PSI, I didn't change it. I like 40psi in the tires, and my light comes on right under 30psi. I'm more than happy with the light working like that, rather have a alert, then an "oh by the way, your tire is flat light on".

My fusion I run 35 PSI in, and the ForScan was set to 32 I think. All the tires dropped below 20psi when it got sooo cold, and hadn't been adjusted since peak summer temps. I had no light on the dash then. So I changed it to 40 PSI as well. We will see when they throw the light, may try leaking some out when it warms up more.