TPMS in autumn

[Jobbo]

I've avoided cars with proper TPMS sensors previously; they seemed like a bit of a faff and I thought they would constantly be warning of punctures which you don't have. I like the older style which use the ABS sensors to identify that a wheel is rotating at a different speed to the others.

Turns out I couldn't avoid them forever. Both my MX5 and our Cayenne have the sensors in the wheel which send the pressure reading to the car. However, this autumn both have given false warnings of punctures on the first cool morning. Even once my MX5 warmed up this morning and the pressures climbed back to normal (identical all round) the warning light stayed on. Grrr. I like the fact they tell me the pressures without having to get out of the driver's seat. I don't like the fact that they're so bloody oversensitive.

[John]

That's bizarre for both to trigger and something I've never experienced even in one car.

I've often wondered why they don't sense the pressure difference when one side of the car is in baking sunshine in the summer.

[Matty]

I'd just name this "TPMS" if it were me. Yet another over complication in cars that ends up being a money sink

*old man yells at clouds*

[mik]

Weirdly I was having a discussion on this exact topic with my mum yesterday, as the warning had gone off on her car (ABS sensor system as opposed to TPMS). Pressure varies with temperature etc etc. I'll stick some air in them next time I see her.

Evora has TPMS, which I much prefer. It's never given any false alarms, but it has given alarms for dull reasons outlined below - only read further if bored:

<clears throat>
"Series 1" Evora (like mine) came on Pirelli's with book pressures of 33F/36R (psi obvs).
When the Evora 400 was launched, they switched the OEM tyre to Michelin (Supersports) with significantly lower book pressures of 29F/32R

I got my car at 2yrs old > the 400 had already been released, and the previous owner of my car had (like many other series1 owners) switched over to the newer (and far more capable) Michelin. As there were no significant suspension changes on the 400, most folks logically reasoned that they should drop their pressures accordingly.

Problem is - the TPMS on series1 cars doesn't like that much > occasionally throwing pressure warnings.

I've played around and landed on 31.5F/34R as a middle ground that feels good. (My specialist has set them to series1 book pressures a couple of times as part of the std service and it feels noticeably harsher - like the car (particularly the front end) is skipping slightly across surface imperfections....

[GG.]

Range Rover and Porsche (991 - can't vouch for newer stuff) are both fine in this regard and don't trigger excessively. Only times I've ever had them bong was when there was an actual puncture.

The Smart on the other hand - what a pain in the arse. It just tells you "check tyre pressures" but has no readout so you have to do all four. Even once you've done that it then does not go away until you go into the menus and ask it to relearn the new values. Useless.

[mik]

The Smart on the other hand - what a pain in the arse. It just tells you "check tyre pressures" but has no readout so you have to do all four. Even once you've done that it then does not go away until you go into the menus and ask it to relearn the new values. Useless.

Sounds like an ABS sensor system. It is triggered when 1 wheel is rotating faster than expected (beyond a pre-set tolerance of course) indicating that the rolling radius is reduced due to low pressure. Unlike tank tracks.

It doesn't therefore know when you've reinflated the tyre(s), or what pressures you've put them to - you are really just telling it to reset the error and start monitoring again.

[Mito Man]

Range Rover and Porsche (991 - can't vouch for newer stuff) are both fine in this regard and don't trigger excessively. Only times I've ever had them bong was when there was an actual puncture.

The Smart on the other hand - what a pain in the arse. It just tells you "check tyre pressures" but has no readout so you have to do all four. Even once you've done that it then does not go away until you go into the menus and ask it to relearn the new values. Useless.

That’s the same as the old BMW system - it becomes doubly useless when you’re on run flats so visibly there’s no knowing which tyre has gone. I once stopped, had a brief look and they all appeared normal, then drove off on the motorway for a bit. Got home and noticed a strong whiff of Bridgestone as I got out the car. Went round touching the tyres and one was very hot to the touch!

[Jobbo]

I got my car at 2yrs old > the 400 had already been released, and the previous owner of my car had (like many other series1 owners) switched over to the newer (and far more capable) Michelin. As there were no significant suspension changes on the 400, most folks logically reasoned that they should drop their pressures accordingly.

Problem is - the TPMS on series1 cars doesn't like that much > occasionally throwing pressure warnings.

I think that's the reason for the MX5; my tyre sizes are larger than standard and I have lowered the pressures as recommended but the TPMS doesn't know this. So the normal operating pressure must be at the bottom end of the range of pressures which don't set it off, and the cooler air must have dropped it just below the threshold for both rears.

It's a useful thing to have, and to be able to see pressures pretty much live on the screen, but when the warnings go off and you have to live with them on the dash it's fucking irritating.

[Mito Man]

I think any tyre shop these days will have a tpms programmer. The programmer lets you change the base tyre pressure and values before you get a warning a - it’s called TPMS placard value on the Autel.
Might be worth popping down to one to get its values adjusted if it’s that bothersome.

[GG.]

I got my car at 2yrs old > the 400 had already been released, and the previous owner of my car had (like many other series1 owners) switched over to the newer (and far more capable) Michelin. As there were no significant suspension changes on the 400, most folks logically reasoned that they should drop their pressures accordingly.

Problem is - the TPMS on series1 cars doesn't like that much > occasionally throwing pressure warnings.

I think that's the reason for the MX5; my tyre sizes are larger than standard and I have lowered the pressures as recommended but the TPMS doesn't know this. So the normal operating pressure must be at the bottom end of the range of pressures which don't set it off, and the cooler air must have dropped it just below the threshold for both rears.

It's a useful thing to have, and to be able to see pressures pretty much live on the screen, but when the warnings go off and you have to live with them on the dash it's fucking irritating.

On the Porsche - are they set to the lower comfort pressures? That might be a quick way to get it to disappear whilst you check at your next scheduled fill up.

[Jobbo]

Good question - I've no idea but I'll check. I just pumped it up but decided not to bother in the MX5 because it was dark, I was heading for work and they weren't far out and obviously all the same so no punctures.

[IanF]

Can’t say I’ve ever had an issue with a car owned, but rentals are a different story altogether. Typically, if a car has a slow puncture , their preferred method was to pump that tyre over 40psi and leave the rest lower than recommended (but high enough not to give warning).. it is one of the things I check when collecting a car now after having a GLE with a slow puncture that needed topping up daily - thankfully they’d left the MB elec pump in the boot which worked a treat but still

[mik]

I think any tyre shop these days will have a tpms programmer. The programmer lets you change the base tyre pressure and values before you get a warning a - it’s called TPMS placard value on the Autel.

Interesting. I’d always assumed the TPMS sensors were dumb, and the car gave the warning based on their readings.

[Jobbo]

I think any tyre shop these days will have a tpms programmer. The programmer lets you change the base tyre pressure and values before you get a warning a - it’s called TPMS placard value on the Autel.

Interesting. I’d always assumed the TPMS sensors were dumb, and the car gave the warning based on their readings.

And me. Since it's pretty much impossible to get to the TPMS sensor itself once it's in the tyre (short of demounting the tyre) it must be the car whose settings are changed and not the sensor, surely?

[GG.]

I think any tyre shop these days will have a tpms programmer. The programmer lets you change the base tyre pressure and values before you get a warning a - it’s called TPMS placard value on the Autel.

Interesting. I’d always assumed the TPMS sensors were dumb, and the car gave the warning based on their readings.

And me. Since it's pretty much impossible to get to the TPMS sensor itself once it's in the tyre (short of demounting the tyre) it must be the car whose settings are changed and not the sensor, surely?

Yes agree - it won't be the sensor but re-setting when the warning value goes off on the ECU it feeds into - just as we've been discussing re Comfort v Handling pressures and resetting values on the dashboard.

[DeskJockey]

Range Rover and Porsche (991 - can't vouch for newer stuff) are both fine in this regard and don't trigger excessively. Only times I've ever had them bong was when there was an actual puncture.

The Smart on the other hand - what a pain in the arse. It just tells you "check tyre pressures" but has no readout so you have to do all four. Even once you've done that it then does not go away until you go into the menus and ask it to relearn the new values. Useless.

That’s the same as the old BMW system - it becomes doubly useless when you’re on run flats so visibly there’s no knowing which tyre has gone. I once stopped, had a brief look and they all appeared normal, then drove off on the motorway for a bit. Got home and noticed a strong whiff of Bridgestone as I got out the car. Went round touching the tyres and one was very hot to the touch!

Zoe is the same. I suppose it is better than no warning, but it is an odd decision.

In a similar vein the blown bulb warning on the Galaxy just shows which end of the car (except for brake bulbs which get a separate specific message on the display), but if you use a modded version of the software it can show you side/bulb. Why not just enable that from the start? Not like it is a feature anyone would pay extra for.

[mik]

Interesting. I’d always assumed the TPMS sensors were dumb, and the car gave the warning based on their readings.

And me. Since it's pretty much impossible to get to the TPMS sensor itself once it's in the tyre (short of demounting the tyre) it must be the car whose settings are changed and not the sensor, surely?

Yes agree - it won't be the sensor but re-setting when the warning value goes off on the ECU it feeds into - just as we've been discussing re Comfort v Handling pressures and resetting values on the dashboard.

Looks like we might all be correct.

It is the car/ECU that triggers a low-pressure alarm, but you can use the Autel to adjust the target pressure in the ECU - which presumably shifts the alarm value accordingly.

[Mito Man]

Yep I had to do that on the F150 but fortunately the Ford specific tuner supported that function. I think Autel just splits the functions to force garages to buy 2 separate devices...

[Jobbo]

Driving home tonight the low tyre pressure warning in the MX5 was off. I had not pumped them up at all.