TPMS & Unknown Variables

[pigfacedalarm]

We all know there is no formal TPMS sensor in the FL5, it’s an indirect TPMS. The owners manual states you need to calibrate it each time you adjust air pressure, change tires, or rotate tires. This part confuses me, was wondering if anyone has details on how this works?

For example, I inflate my tires to 35/33 per owners manual. I recalibrate the TPMS, drive the 30 cumulative miles over 30mph or whatever it is. TPMS is calibrated, life is good.

A week later, temperatures are chilly, so I check air pressure. Each tire lost a pound or two of air. I put a pound or two of air into each. My TPMS light didn’t come on obviously since it was such a minor change. Would I need to recalibrate the TPMS yet again? Pet owners manual, I would, because I adjusted the pressure. But I set the pressure back to what it was when the system was calibrated, so the indirect TPMS should not read any different than the original calibration.

Does anyone know what the actual process is on this? Am I right? I assume the owners manual meant to calibrate if you’re making major adjustments, not tiny incremental 1-2psi adjustments.

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[TypeRD]

I think your assumption is correct. The TPMS measures tire pressures based on rotational speed. So if you’re simply maintaining the same pressures, to account for the drop in environmental temps for fall/winter, then the system doesn’t see a difference.

 

[dkhm3]

So many good 3rd party TPMS systems to choose from. Get one of those.

 

[HorizonsEdge]

So many good 3rd party TPMS systems to choose from. Get one of those.

The basic Type R system works without additional hardware. Simple is good. Swapping wheels is easier. All you need is a pressure gauge and some common sense.

 

[pigfacedalarm]

So many good 3rd party TPMS systems to choose from. Get one of those.

I’m happy with it. Just want to know how it works when it comes to small, incremental adjustments. The owners manual can be wrong when it states to recalibrate after adjustments. They could have omitted “major” or “more than 4psi” before “adjustments”.

 

[Higgs Boson]

I set my tire pressure to 32 cold......and then I don't do a damn thing and everything is perfectly fine.

Follow me for more tips on how to not worry about things that don't matter.

 

[AZCWTypeR]

It just counts wheel revs with the ABS sensors. If all tires lose the same psi, it probably won't notice. It will notice one or two tires being lower than the others.

 

[zumbooruk]

In my experience, the indirect TMPS will not alert till one tire is nearly flat, esp. with low profile tires, since their circumference (and therefore tire revs) does not change much when they lose air.

I installed a TPMS with external sensors, an added benefit is that I can also monitor tire temps.

 

[dkhm3]

I’m happy with it. Just want to know how it works when it comes to small, incremental adjustments. The owners manual can be wrong when it states to recalibrate after adjustments. They could have omitted “major” or “more than 4psi” before “adjustments”.

it does not work with incremental changes. I’ve had mine drop incrementally on one tire and it was -7 psi from the recommended psi. No alerts, nothing. My aftermarket TPMS alarms went off immediately when I started the car in the morning. YMMV, there could be an issue with my passive TPMS.

nearly 80% of my miles on this car is on a canyon drive. It is not a daily driver. A slow leak from a nail is a risk not worth taking when I am driving on narrow roads with possible opposing traffic. It is reassuring to see real time psi and temps on my tires.

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