Tyre pressure warning threshold/variance

[Moonlighter]

2024 CX5 Akera 18” wheels and factory Toyo tyres.

Winter here in Aus right now, so cooler temps than usual. Todays max about 23C and overnight min 17C. Yeah we do it tough here in winter LOL. But it did get down to 5C early one morning a couple of weeks ago.

Went for a short drive this morning, the first time the car has been driven today, got about 4km and the low tyre pressure warning sounded and light came on. Was only about 500m away from my destination so thought I would check the tyres as soon as I got there. But after about 30 seconds the light went off and no more alarms. Tyres looked OK when we arrived.

Drove home again later and no warnings. But checked the tyres a bit later and found:

FR - 36.5psi
FL - 35.0 psi
RR - 36.5 psi
RL - 38.5 psi. (This tyre had a puncture repair done a few weeks ago and I suspect they pumped it up to around 40psi)

So a 3.5psi max variation between the lowest and highest pressures. Maybe when the tyres were warming up after the overnight cool temps it triggered an alarm momentarily due to variation in pressures between the tyres??

Does anyone know the point at which the low pressure alarm activates? Is it based on the variation between highest and lowest pressures across all tyres?

Of course I have now inflated them all and set back to 38psi which is where I normally run them.

 

[sm1ke]

I have a 2018 CX-9 with a similar TPMS system. On my previous set of summer tires, I had slow leaks in two tires. Normally they're inflated to 37-38 psi. In my case, from what I recall, the low tire pressure warning would trigger around 29-30 psi. I'm not sure if it's any different with the newer CX-5s.

Additionally, in my experience, I'd get the low tire warning almost immediately after I started driving, maybe 50-100 ft (15-30 m).

 

[HyFlyer]

I would think that your 2024 has the in-wheel transmitters so the car brain is receiving individual actual pressures (and temperatures as well). It would trigger a pressure warning either low or high. I don't believe it's comparing between individual tires.

The Internet says 25% +/- is "usually" the threshold so if the recommended PSI is 36, then the TPMS would light up at +/- 9psi (27 / 45)

 

[Moonlighter]

I have a 2018 CX-9 with a similar TPMS system. On my previous set of summer tires, I had slow leaks in two tires. Normally they're inflated to 37-38 psi. In my case, from what I recall, the low tire pressure warning would trigger around 29-30 psi. I'm not sure if it's any different with the newer CX-5s.

Additionally, in my experience, I'd get the low tire warning almost immediately after I started driving, maybe 50-100 ft (15-30 m).

Yes, when I had the nail in the RL tyre the warning buzzer and light came in within 50m of leaving home. And stayed on.

This may have just been an odd one-off incident. Weird that it came on, then turned itself off.

I was just curious to know if the system like ours with the internal wheel pressure sensors worked on a set psi for low pressure or a differential between the tyres. As per data from my earlier post, none of the tyres had less than 35psi when checked after this incident.

I usually keep a pretty close eye on tyre pressures but had been a bit slack lately. Will check them again in 2 weeks to see if the front left that was lowest has changed.

The Leader of the Opposition Forces is the main driver of the CX5 but maintenance duties fall to yours truly.

 

[sm1ke]

It may be a good idea to check the spare, just in case