Winter Tyre Pressures

[GrahamW42]

I've never had TPMS in a car before - so concerns over relatively small changes in tyre pressures is a new issue to me (and may perhaps be filed away as a "first world problem").

My S90D has been running with 42psi all round in my 245/35R21s when at ambient summer temp - ~20C.

As the weather has cooled, I often start the day (in my garage) at 38/9psi (~10C). I've only done short trips recently so, although I've only climbed back to ~40psi, I assume that 42 or more would be achieved during a longer/faster drive.

So I haven't put more air in.

The other day, when left outside in the cold for a while, the car got colder than normal and gave me an "advisory" on one tyre which had dropped to 36psi. It quickly climbed back to 38 after a short drive though.


So my questions are :

Is it OK to drive around on 37/8psi tyres in winter ?

Or is it the "done thing" to pressure back to 42psi when cold (say 5C) ?

Will this not result in "overpressures" during motorway driving ? (and how high is too high)

Do people here pressure-up their tyres in winter ... and then let air out in the summer ? I've never done so in decades of driving !

 

[MrBadger]

Its 42 psi when cold, less any comfort factor

To do it 'properly', you would pre-empt extreme pressures and change tyre pressures a few times a year with seasonal differences. Or just leave it and react to when the tpms screams. Shock - I've never put air in my other car fitted with TPMS and its never reported anything other than all green. I just leave it to servicing.

On our M3, we have seasonal tyres, I set winters to 42 when we put them on and probably wont adjust until they come off. When non winters go back on, I'll set again then just because its convenient, and see how it goes. I'll probably do that when mornings are largely above 7C and no cold snap forecast. I wouldn't want them any higher than 42 when cold, so may let some out as it warms then leave it. If they drop below 38/39 when cold, I'll probably top up as when ours got to 37/38, TPMS started screaming.

So I guess I'm saying, 38/39 to 42 when cold. I don't think you will have issues with over pressure with that. 4psi drift was more than 15C temperature difference. Easy to get too devoid from common sense for the sake of a few numbers.

Obviously, if one starts to drift more than the others, then that may indicate a problem.

imho.

 

[Adopado]

So my questions are :

Is it OK to drive around on 37/8psi tyres in winter ?

Or is it the "done thing" to pressure back to 42psi when cold (say 5C) ?

Will this not result in "overpressures" during motorway driving ? (and how high is too high)

Do people here pressure-up their tyres in winter ... and then let air out in the summer ? I've never done so in decades of driving !

The pressure should be set to 42psi when the tyres are at ambient temperature ("cold"). Obviously this means that you have to put a couple of pounds in the tyres as the temperatures drop in winter. Being at 37/38 will not break anything but your range will suffer a bit and the tyre will be generally operating outside of its optimum performance parameters. This has always been the case with tyres ... this advice has not changed ... it's just that we are humans who often can't be bothered doing stuff! It was easier to ignore tyre pressures in the past because you never knew what the tyre pressures were unless you were already motivated enough to check them manually on a regular basis .. which only a minority of drivers did.

Higher pressures on the motorway are a good thing. People rarely do it but we should actually add a couple of pounds if doing long motorway journeys. So, the natural increase in pressure is "no bad thing".

 

[mswlogo]

Are Tesla’s folks first cars or something?

OP should know this basic car owner stuff long before TPMS. No wonder government made TPMS a requirement. Pretty soon they will make auto inflation a requirement too.

<Shacking head>

 

[Adopado]

Are Tesla’s folks first cars or something?

Yes .... I know, I know ... you would think ... but let's not be unkind!

 

[pgkevet]

Are Tesla’s folks first cars or something?

OP should know this basic car owner stuff long before TPMS. No wonder government made TPMS a requirement. Pretty soon they will make auto inflation a requirement too.

<Shacking head>

That's 'cos it didn't used to matter. you had a spare and a foot pump anyway and only worried about the tyres when the canvas showed through. Then they brought in all these silly regs like an annual check and expecting cars to be serviced.
WE never worried about oil changes..it got through a pint every 200 miles anyway and an ocassional egg in the rad to stop up the leak..

 

[mswlogo]

That's 'cos it didn't used to matter. you had a spare and a foot pump anyway and only worried about the tyres when the canvas showed through. Then they brought in all these silly regs like an annual check and expecting cars to be serviced.
WE never worried about oil changes..it got through a pint every 200 miles anyway and an ocassional egg in the rad to stop up the leak..

Yeah maybe it didn’t matter on a Ford Model T. Air or no air.

I’ve checked my tires every couple couple months for the last 3 decades.

If you want maximum tread wear and efficiency you always keep your tires at proper pressure. Always. This is nothing new.

 

[MrBadger]

Actually most people can see or feel when their tyres needed topping up. I can easily detect less than 2psi drop on a car that I have owned for a bit. 42psi is a new game to me though.

 

[zayn]

This is probably 70% of this forum full of such questions. Shocking

Are Tesla’s folks first cars or something?

OP should know this basic car owner stuff long before TPMS. No wonder government made TPMS a requirement. Pretty soon they will make auto inflation a requirement too.

<Shacking head>

 

[GrahamW42]

OP here. No, not my first car <g>.

In the past I've always put the "right" pressure in and then kept a careful eye on the tyres. I'm one of "those guys" who actually casts an eye over the car, especially tyres, pretty much every time I drive. When one tyre looks (even SLIGHTLY) odd I've re-inflated it.

I would have gone on this way and, given the relatively narrow range of temps in UK built up areas, that would probably have been fine.

However, with TPMS, I now know with certainty each single psi of variance. So should I let my tyres vary from 42psi in the summer to 38psi on the coldest winter mornings ?. Is that a significant problem ? One worth making a special trip to a petrol station half a dozen times of year to put right ?

Given the even larger variances I see whilst driving (e.g. long motorway journeys) I thought that being ~4psi down for the first few miles of my local journeys for 2-3 months of the year wouldn't be the end of he world.

In the spirit of compromise I've put an extra couple of psi in my tyres today. I'll probably reverse this in Mar/Apr. Twice a year is no biggie.

 

[mswlogo]

OP here. No, not my first car <g>.

In the past I've always put the "right" pressure in and then kept a careful eye on the tyres. I'm one of "those guys" who actually casts an eye over the car, especially tyres, pretty much every time I drive. When one tyre looks (even SLIGHTLY) odd I've re-inflated it.

I would have gone on this way and, given the relatively narrow range of temps in UK built up areas, that would probably have been fine.

However, with TPMS, I now know with certainty each single psi of variance. So should I let my tyres vary from 42psi in the summer to 38psi on the coldest winter mornings ?. Is that a significant problem ? One worth making a special trip to a petrol station half a dozen times of year to put right ?

Given the even larger variances I see whilst driving (e.g. long motorway journeys) I thought that being ~4psi down for the first few miles of my local journeys for 2-3 months of the year wouldn't be the end of he world.

In the spirit of compromise I've put an extra couple of psi in my tyres today. I'll probably reverse this in Mar/Apr. Twice a year is no biggie.

If you waited until it looked low, it was too late.

I probably adjust every 2 months on average. Big difference between 100F and -10F. Just two pressures doesn’t cover it. I keep a compressor always ready to go in the garage so that it’s quick and easy to tweak them.

 

[GrahamW42]

If you waited until it looked low, it was too late.

Actually, in "the olden days", I reckon I could spot a small psi diff in my high sidewalled tyres. My new low-profile 21in wheel/tyre combo is a different thing though. I really need TPMS now.

I probably adjust every 2 months on average. Big difference between 100F and -10F. Just two pressures doesn’t cover it.

Well in a UK town, during daytime driving, the extremes are more like 40F and 80F (and both would be quite rare events, occurring on only couple of days each). I reckon two pressures, one for the winter months (40-60F) and one for the summer (60-80F), would be enough.

I keep a compressor always ready to go in the garage so that it’s quick and easy to tweak them.

An interesting difference in experience. Until recently I lived in a large UK city for several decades. In all that time, like most people, I had no garage. Additionally, like a lot of people, I didn't even have off-street parking. I parked on the street ... almost never closer than 20 yards, often over 100 yards. So adjusting tyre pressures "at leisure" was never an option.

 

[pgkevet]

An interesting difference in experience. Until recently I lived in a large UK city for several decades. In all that time, like most people, I had no garage. Additionally, like a lot of people, I didn't even have off-street parking. I parked on the street ... almost never closer than 20 yards, often over 100 yards. So adjusting tyre pressures "at leisure" was never an option.

And repeating myself - foot pump

(I now own 2 compressors 'cos of farm stuff and cleaning stuff but still get the footpump out soemtimes 'cos it's quicker than uncoiling the hose and clean it after)

 

[Adopado]

I parked on the street ... almost never closer than 20 yards, often over 100 yards. So adjusting tyre pressures "at leisure" was never an option.

But there's an opportunity every time you visited a petrol station ... especially before a long trip perhaps? Most common reason for tyre failure on the motorway is incorrectly inflated tyres, I read.

 

[GrahamW42]

But there's an opportunity every time you visited a petrol station ... especially before a long trip perhaps? Most common reason for tyre failure on the motorway is incorrectly inflated tyres, I read.

Er, I don't visit petrol stations !

When I used to, in my pre-Tesla days, I would indeed avail myself of "free air" regularly.

Nowadays I have to make a special out-of-my-way trip to a smelly petrol forecourt for air - and PAY for the privilege !

As pgkevet said, a foot pump is a good idea. Oh, a bit of Googling comes up with loads of units powered from the car's 12V outlet. I feel a letter to Santa coming on !

 

[Jason71]

Are Tesla’s folks first cars or something?

Clearly it's not his first ever car. If it was his first car he probably would have read the manual

"Warning: Under-inflation is the most common cause of tire failures and can cause a tire to overheat, resulting in severe tire cracking, tread separation, or blowout, which causes unexpected loss of vehicle control and increased risk of injury. Under-inflation also reduces the vehicle's range and tire tread life."
"Warning: Check tire pressures using an accurate pressure gauge when tires are cold. It takes only about one mile (1.6 km) of driving to warm up the tires sufficiently to affect tire pressures. Parking the vehicle in direct sunlight or in hot weather can also affect tire pressures. If you must check warm tires, expect increased pressures. Do not let air out of warm tires in an attempt to match recommended cold tire pressures. A hot tire at or below the recommended cold tire inflation pressure is dangerously under-inflated."

So basically 42 is the minimum. Who knows what 42 set at 0 degrees C will rise to on a warm sunny day. I guess we will find out in a month or 3 but whatever it is it is apparently better than having it too low

 

[Jason71]

Er, I don't visit petrol stations !

When I used to, in my pre-Tesla days, I would indeed avail myself of "free air" regularly.

Nowadays I have to make a special out-of-my-way trip to a smelly petrol forecourt for air - and PAY for the privilege !

As pgkevet said, a foot pump is a good idea. Oh, a bit of Googling comes up with loads of units powered from the car's 12V outlet. I feel a letter to Santa coming on !

I imagine I will be topping up more often than I have before so I bought a cordless inflator. saves all the faffing about with cables and the accessory socket (except when charging it) . And before anyone old says, yes I know a foot pump is a cordless inflator! but I went with this one:
RTC6000
many others are available

 

[Chronic]

My tire pressure has been at 36, is that too low? how do i increase it? first car

 

[jimbo_hippo]

I don't get the impression from my experience or other posts that tyre pressures is part of pre-delivery inspection, hence most Model 3's this time of year in the UK (November at time of writing) will be delivered at around 37/38PSI because it's not 2 degrees C in California right now! When corrected to 42PSI (SR+) cold, they should sit there or thereabouts (when cold obviously) until spring unless there's some serious changes in temperature.

 

[Chronic]

Ag

I don't get the impression from my experience or other posts that tyre pressures is part of pre-delivery inspection, hence most Model 3's this time of year in the UK (November at time of writing) will be delivered at around 37/38PSI because it's not 2 degrees C in California right now! When corrected to 42PSI (SR+) cold, they should sit there or thereabouts (when cold obviously) until spring unless there's some serious changes in temperature.

Agree 100%