Tyre pressures ?

[Peteski]

That is a good point about load, on all my BMWs there was one set of pressures for up to 3 occupants, another higher set for up to 5 occupants and luggage. I wonder why Tesla only list one set of pressures!?

I'm going to try mine at 38psi

Likewise. Mine have dropped to 41 psi at the moment and I think going lower will continue to be an improvement. I ran my MX with about 5 psi less than recommended for 4 years and nobody died!

Yes most manufacturers quote 2 sets of pressures while Tesla seem to have simplified it! If these pressures are safe for a fully loaded car, then you can assume they are unnecessarily high when lightly loaded.

 

[teaston]

Likewise. Mine have dropped to 41 psi at the moment and I think going lower will continue to be an improvement. I ran my MX with about 5 psi less than recommended for 4 years and nobody died!

Yes most manufacturers quote 2 sets of pressures while Tesla seem to have simplified it! If these pressures are safe for a fully loaded car, then you can assume they are unnecessarily high when lightly loaded.

I think you're probably right.

Did you get any abnormal tyre wear in your X? That would be my only worry about running lower pressures, could wear out the outer edges of the tyres faster.

 

[Peteski]

I think you're probably right.

Did you get any abnormal tyre wear in your X? That would be my only worry about running lower pressures, could wear out the outer edges of the tyres faster.

That's a good question. The answer in my case was no, wear was pretty even. BUT the factory tolerances on camber angle are quite wide (certainly for the MX) and wear was sensitive to what ride height you ran - basically you get more static camber with a lower ride height as the suspension follows its geometry curve. What I found on my car was that low ride height happened to work well with the lower tyre pressure. It was just luck of the draw. Another identical car at the opposite end of the camber tolerance range might have been different. There was a lot of variation in tyre wear reported by MX owners for this reason.

What I would do is just keep an eye on the tread wear across each tyre and see how it goes. If wear rate appears excessive on the outer edge then adjust pressure and/or static camber. I don't know how consistent factory geometry setup is on the MY, but it could definitely vary from car to car. At least it's less complicated without adjustable ride height.

 

[Tony Hoyle]

Say “show tyre pressures” while driving and it does

It just prints that on the screen (showing it has recognised it at least) and says 'command not implemented' which is a bit crap.

I ended up parking up and fiddling with the screens directly. If only they'd bring the damned cards back.

 

[pgkevet]

Would there be consequences after an accident investigation if tyre pressures were subnormal?

 

[Peteski]

Would there be consequences after an accident investigation if tyre pressures were subnormal?

It's a good point, but I'm not worried about running a few psi lower. I think you would have to be running severely under-inflated tyres for this to be a potential issue.

 

[MrT3]

The alert only tells you if a tyre is losing pressure on the move. So for example if they are all manually set to something stupid like 50 psi (like at delivery!) then you don't get any alert. Same applies if they are all set too low.

No, the system will tell you if a tyre drops below 20% of the cold set threshold, or 20% below the maximum temperature that has been achieved during a trip.

Whilst the system only gets an update from the wheels once they are moving, if a tyre went down overnight you should get a warning very quickly after you set off - the tyre doesn't need to deflate on the move.

 

[Overworked]

View attachment 790294
This is what I see ?

I went and checked mine when I entered the car this morning and what I see is different to you. I have the car image and beside each wheel I have a sign saying “ - - psi”. As I start moving the - - is replaced by the pressure, eg “45psi”

 

[Peteski]

No, the system will tell you if a tyre drops below 20% of the cold set threshold, or 20% below the maximum temperature that has been achieved during a trip.

Whilst the system only gets an update from the wheels once they are moving, if a tyre went down overnight you should get a warning very quickly after you set off - the tyre doesn't need to deflate on the move.

Fair enough, it's a bit more detailed than I made out. My point was that if pressures are set wrong to start with e.g. 50 psi cold, then you don't get an alert unless you get a puncture. Also if cold pressures move around with ambient conditions, you don't get an alert then either. So you could be quite a long way off on pressures without seeing any alert.

 

[init6]

You will get an alert if they are set too high:

As an added safety feature, your vehicle has been equipped with a TPMS that displays a tire pressure telltale (Tire Pressure Warning) on the touchscreen when one or more of your tires is significantly under- or over-inflated

 

[Peteski]

You will get an alert if they are set too high:

Well I never got an alert when our MY was delivered with 50 psi all round.

 

[M1tch]

If the car was told that’s correct, that’s what it will think is correct. It needs to be told what normal is and it then looks for presence of the abnormal.

 

[Adopado]

I generally find the recommended pressures ok. With modern low profile tyres we also have the pothole protection issue to keep in mind. Lower tyre pressure will result in more compression of the tyre against the rim in the event of whacking a sharp edged pothole. It’s quite easy to take out a tyre and a rim if you’re unlucky.

 

[Peteski]

If the car was told that’s correct, that’s what it will think is correct. It needs to be told what normal is and it then looks for presence of the abnormal.

All I was commenting on originally is that you can't rely on the alert system to warn you that your cold pressures have dropped low.

IME it doesn't notice if your pressures gradually drop over time. So let's say I start out at 42 psi cold and then a month or so later they have all dropped to 38 psi, I will get no warning. Where do you tell it what "normal" is supposed to be? Or does the software already have that value from the car spec?

 

[teaston]

Well, there is a problem setting the tyres to 38psi, if they dip below 38 this is where the car alerts kick in! There doesn’t seem to be any way to reset the pressure monitor to accept the current set pressures as normal, like there is on BMWs, unless I’m missing something?

The ride does seem much better at these pressures though! I have a feeling it’s not just stiff suspension causing the hard ride, but actually also the high recommended tyre pressures!

 

[mnobleuk]

I went and checked mine when I entered the car this morning and what I see is different to you. I have the car image and beside each wheel I have a sign saying “ - - psi”. As I start moving the - - is replaced by the pressure, eg “45psi”

I was able to see the pressure when I was driving - initially it did come up as the "--" - I wonder does it initiate when you go into drive and then takes a moment to get the first reading.

 

[KennethS]

I was able to see the pressure when I was driving - initially it did come up as the "--" - I wonder does it initiate when you go into drive and then takes a moment to get the first reading.

My understanding is the TPMS sensors go to sleep after a period of time when the wheels stop rotating, to preserve the batteries. When the wheels begin to rotate they awaken and send the data signal.

 

[Peteski]

Well, there is a problem setting the tyres to 38psi, if they dip below 38 this is where the car alerts kick in! There doesn’t seem to be any way to reset the pressure monitor to accept the current set pressures as normal, like there is on BMWs, unless I’m missing something?

The ride does seem much better at these pressures though! I have a feeling it’s not just stiff suspension causing the hard ride, but actually also the high recommended tyre pressures!
View attachment 790915

Maybe just set them at 39 psi on a cold morning then and call it a day. At least you'll get a warning when they need topping up.

 

[Peteski]

I generally find the recommended pressures ok. With modern low profile tyres we also have the pothole protection issue to keep in mind. Lower tyre pressure will result in more compression of the tyre against the rim in the event of whacking a sharp edged pothole. It’s quite easy to take out a tyre and a rim if you’re unlucky.

I don't worry too much about that on the base wheels. Not within the limits of a few psi anyway.

Interestingly, Tesla appear to recommend the same tyre pressure on the Model Y regardless of wheel size i.e. 42 psi whether you are running 19" x45, 20" x40 or 21" x35 profile rubber. So they are clearly not optimised considering that the 19" has a lot more tyre air volume than 21".

 

[teaston]

Maybe just set them at 39 psi on a cold morning then and call it a day. At least you'll get a warning when they need topping up.

I've set them to 40psi cold now. I'll reduce them when the summer weather starts.