Model 3 Tire Pressure

[gilscales]

But 45 is between 39 and 49!

TYPO! should be 39 to 40

 

[AlanSubie4Life]

Sorry about the typo on my post but it should read 39 to 40 psi, I have been running 42, at times before I adjust air it gets down to 40 psi and after measuring my tread I am still slightly lower (not by very much) in the center which suggests to me a slight over inflation condition, I have run a lot of my 17k plus miles loaded down with extra people and or luggage but most is with 1 or 2 people in t he car.

Maybe go to 45 and corner harder?

 

[EVnut]

Just from my limited experience, with the 19" stock Continental tire you would have to run approx. 39 to 49 psi. to get even tread wear across the tire, running at 45 psi. would wear out the center section early due to over inflation unless you carried the max load everywhere you went.

Oop! I see you've corrected this to 39-40, so I won't mention that 45 is in the middle there...

For about 300,000 miles of driving, I have inflated my tires to *at least* the max side-wall rating for my EVs (done totally for range). And of course I've worn out many sets of tires in that time. And not ONCE did the center wear faster than the edges. I do hear about this issue of running reasonably high pressure, but I've not yet experienced it.

 

[gilscales]

Oop! I see you've corrected this to 39-40, so I won't mention that 45 is in the middle there...

For about 300,000 miles of driving, I have inflated my tires to *at least* the max side-wall rating for my EVs (done totally for range). And of course I've worn out many sets of tires in that time. And not ONCE did the center wear faster than the edges. I do hear about this issue of running reasonably high pressure, but I've not yet experienced it.

On all my other cars I would just adjust tire pressures to get even wear across the tread, not sure how you are not wearing out the center faster with those high pressures?

 

[StealthP3D]

Oop! I see you've corrected this to 39-40, so I won't mention that 45 is in the middle there...

For about 300,000 miles of driving, I have inflated my tires to *at least* the max side-wall rating for my EVs (done totally for range). And of course I've worn out many sets of tires in that time. And not ONCE did the center wear faster than the edges. I do hear about this issue of running reasonably high pressure, but I've not yet experienced it.

That's more of a problem with cheap tires that don't have good structure. I wouldn't be surprised if oil companies PR departments don't slyly try to amplify this rather minor risk. Because they make a lot more money if everyone and their brother is so afraid of center treadwear that they are all running 4-6 PSI below the most efficient pressure. It takes a lot of oil to make tires and they last too long when properly inflated! Not to mention the way it makes cars drink more gas.

 

[GregD60]

Ok! Mysterious. I do wonder if something is wrong with @voip-ninja 's sensors then. Intriguing; it's nearly as interesting as vampire drain.

FWIW, I run 45PSI cold in my PS4S. I get 270Wh/mi driving efficiency on my daily 20-mi roundtrip commute (500 feet net elevation gain on the way home, about 800 ft cumulative), and the expected wall-to-wheel efficiency of 380Wh/mi, for that same 270Wh/mi driving efficiency (40Wh/mi charging losses, 70Wh/mi standby losses (which breaks down into 10 Wh/mi charging loss, 60Wh/mi from battery)). Sweet. When I went from 42 to 45PSI in my crappy 20" wheels, perhaps the efficiency improved a bit, but at most 10-15Wh/mi. One of these days I should do a careful controlled experiment I suppose.

If there's something wrong with voip-ninja's sensors, then all of as who live at altitude have the same defective sensors. StealthP3D is wrong about the sensors.

 

[GregD60]

That's more of a problem with cheap tires that don't have good structure. I wouldn't be surprised if oil companies PR departments don't slyly try to amplify this rather minor risk. Because they make a lot more money if everyone and their brother is so afraid of center treadwear that they are all running 4-6 PSI below the most efficient pressure. It takes a lot of oil to make tires and they last too long when properly inflated! Not to mention the way it makes cars drink more gas.

The bolded part is incorrect. Any tire will tend to wear out more in the center at higher inflation pressures, but there are a number of factors that can override this such as wheel width, tire design, driving style, and various other factors.

 

[StealthP3D]

The bolded part is incorrect. Any tire will tend to wear out more in the center at higher inflation pressures, but there are a number of factors that can override this such as wheel width, tire design, driving style, and various other factors.

Keep in mind I said "more of a problem". That's a relative thing. And tire construction is definitely a factor in how likely you are to get excessive center tread wear with higher pressures.

 

[AlanSubie4Life]

I happened to be at 4200 feet today. And at 800 feet where I live. Difference is 1.6psi between these elevations.

4200 foot reading:
TPMS: 44 all around
Gauge : 45 all around

Tires were relatively cold.

800 foot reading:
TPMS: 45 front, 46 rear
Gauge: 45 all around

Tires were somewhat warmer.

So for the gauge, the increased temp of the tire at low elevation was offset by increased pressure. Doesn’t matter, but that is what happened.

Meanwhile the TPMS are behaving the way one would expect if they were measuring absolute pressure. Since the gauge is measuring differential pressure, the TPMS will reflect the reduced pressure at elevation if the gauge pressure is the same.

So yes @StealthP3D appears to be wrong (though this is a relatively small change to draw a conclusion).

Would be nice to have a greater elevation change to check of course, but sounds like all the high elevation owners already know the true state of things. So no more checking needed.

If anyone has a chance to check at 12k feet (unlikely this time of year), that would make the situation very clear! Just need a gauge and a record of the TPMS readings and compare at two elevations. I think it actually does not matter what the temp of the tires is (will just cause gauge and TPMS to read lower/higher), or whether the gauge is exactly accurate, as long as the same gauge is used and pressures being measured are pretty close. Not 100% sure of that at this late hour, but I think that is true.

Actually, you won’t need any of that, because at 12k feet it should be super obvious your TPMS in your Tesla is reading 5PSI lower than your trusty gauge. As everyone has said.

 

[StealthP3D]

So yes @StealthP3D appears to be wrong (though this is a relatively small change to draw a conclusion).

I think you're right about that. I was basing my comments only on the fact that the valve stems have double barrels. Interestingly, Mitsubishi since 2008 have come equipped with TPMS that adjust for altitude (except for their i-MiEV subcompact EV):

https://www.schradersensors.com/sites/default/files/2017-07/Mitsubishi_tsb1231001_0.pdf

It would be nice if Tesla would get with the program. Of course, I pay very little attention to the TMPS readings since my gauge is more accurate. But I'm sure there are plenty of people that set their tire pressure based on what the TPMS says!

 

[gilscales]

I pay very little attention to the TMPS readings since my gauge is more accurate.

Same, the TMPS is just there to warn me about needing to check air pressure after 2 or 3 months or in case of a leak it is handy but my gauge is what I go by.

 

[AlanSubie4Life]

Same, the TMPS is just there to warn me about needing to check air pressure after 2 or 3 months or in case of a leak it is handy but my gauge is what I go by.

Yeah the TPMS is great for those of us at sea level. Unfortunately does not work for those at elevation (if they want properly inflated tires) until Tesla gives them an option to widen the warning limits. And it is kind of annoying having incorrect readings of the relevant variable. No one cares about absolute pressure minus 14.7PSI. They care about the pressure on the inside of the tire relative to the pressure on the outside.

 

[GregD60]

Yeah the TPMS is great for those of us at sea level. Unfortunately does not work for those at elevation (if they want properly inflated tires) until Tesla gives them an option to widen the warning limits. And it is kind of annoying having incorrect readings of the relevant variable. No one cares about absolute pressure minus 14.7PSI. They care about the pressure on the inside of the tire relative to the pressure on the outside.

Correct. The low tire pressure warning kicks on at 38 PSI in my car. If I inflate my tires to the 42 PSI it says on the door placard, the TPMS system shows 39 PSI. All it takes a particularly cold day, or just slightly underinflating one of the tires, to hit 38 PSI and trigger the warning. As a result, I inflate my tires to 45 PSI.

 

[StealthP3D]

Correct. The low tire pressure warning kicks on at 38 PSI in my car. If I inflate my tires to the 42 PSI it says on the door placard, the TPMS system shows 39 PSI. All it takes a particularly cold day, or just slightly underinflating one of the tires, to hit 38 PSI and trigger the warning. As a result, I inflate my tires to 45 PSI.

I've been running my Sottozero 2's at 47 PSI and really liking them. Excellent cornering, braking and range. I can't figure out why people want to go so soft (low PSI), I find the ride firm but smooth. There's a little bobbing at higher speeds on wavy roads but less air pressure just makes it worse. Maybe the low air pressure people are on lower profile tires that might naturally feel firmer with less air. But low pressure increases the risk of rim damage that low profile tires are already susceptible to.

 

[AlanSubie4Life]

Correct. The low tire pressure warning kicks on at 38 PSI in my car. If I inflate my tires to the 42 PSI it says on the door placard, the TPMS system shows 39 PSI. All it takes a particularly cold day, or just slightly underinflating one of the tires, to hit 38 PSI and trigger the warning. As a result, I inflate my tires to 45 PSI.

I do 45PSI as well, but not due to TPMS since I am at sea level. I figure the higher pressure better protects the useless 20” wheels, gives better efficiency, and I have had bad experience in the past creating excessive wear on the shoulders of performance tires because I was not vigilant about inflation, with my driving style. Also the shoulders on the PS4S seem pretty soft (prone to chunking during autocross), so I figure the more weight I can take off of them the better. I ran 44-45 or so during a wet autocross and they definitely still took a beating, but at least they did not overheat at all, with all the evaporative cooling. Still serviceable for quite a while, just need to make sure I wear the center more to even things out.

 

[StealthP3D]

I just took the tread depth gauge to both our Model 3's In 32nds of an inch from outside, middle, inside:

Hers: Long Range w/Michelin MXM4 235/45/19 8,800 miles, not rotated yet, PSI maintained between 44 and 48, mostly 45-46 PSI

LF 8 8 8 8
RF 8 8 8 8
LR 6 6 6 6.5
RR 6 6 6 6.5

His: P3D- w/Pirelli Sottozero 2 235/45/18 3,000 miles PSI maintained between 42 and 48, mostly 46-47 PSI

LF 9 9 8.5
RF 9 9 9
LR 8.5 8.5 8.5
RR 8 8 8 8

All tires wearing very evenly across the tread even though we run both cars with well above the PSI recommendation of the door sticker. Interestingly, the right rear tire on my P3D is wearing faster than the left rear. Probably due to the road crown and hard launches or making left turns from a stop across a lane of traffic. The Pirelli's came with 10/32".

My wife is a very conservative driver. I'm mostly conservative when I'm driving her car and she is with me. When I'm driving her car alone (which doesn't happen much since I got my P3D) I thrash it

 

[voip-ninja]

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Checked three of my cars with TPMS. I guess I see what you are saying about the separate gap on the outside of the valve stem, but one of my cars with TPMS just has a regular looking rubber valve stem (the Chevy Spark EV). Only the metal stems have the outer gap; I suspect it is a feature of how those metal stems are assembled. It seems like that other gap could get filled with junk too, submerged in water, etc. I really can’t see it as a path to the inside pressure, separated only by a differential sensing element that would allow water/moisture ingress into the sensing cavity - and an easy leak path if the extremely fragile MEMS membrane were damaged. But who knows?

Seems easier to just make a MEMS membrane, make it hermetically sealed behind the membrane, and then just calibrate it at the factory to read absolute pressure accurately.

Someone who has worked in a tire shop could probably set the record straight easily.

 

[AlanSubie4Life]

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Story checks out! If I were you, I would just go to 44psi or so. Not much else you can do.

 

[StealthP3D]

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So you're running 42-43 PSI. Why do you run it so low? Do you have tires I'm not familiar with? In my experience, manufacturers recommended PSI is generally around 5-10 too low for performance, tread life and range. Tesla's original recommendation was 44 or 45 PSI (I forget). I would run at least that much.

 

[voip-ninja]

So you're running 42-43 PSI. Why do you run it so low? Do you have tires I'm not familiar with? In my experience, manufacturers recommended PSI is generally around 5-10 too low for performance, tread life and range. Tesla's original recommendation was 44 or 45 PSI (I forget). I would run at least that much.

Because it runs hard as a rock on shitty roads with higher PSI