[Richtrash]

I stopped using the air pumps at petrol stations when they started charging for the air, it used to be 20p but now 50p seems to be more usual, for that you get to use the compressor for 5 mins, make sure you take all the valve caps off before putting your money in and starting the compressor or you will likely have to put another 50p in.

 

[EVMeister]

I've never used a petrol station for air in my life. The little portable electric compressors work great for topping up.

 

[DBMandrake]

Ahem:

Halfords Essentials Metal Barrel Foot Pump and Gauge | Halfords UK

Shop the latest Halfords Essentials Metal Barrel Foot Pump and Gauge at Halfords UK

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Who wants to pay 50p a time to drive to a smelly garage (especially in an EV that won't be fuelling up there) to top up your tyres when you can do it for free in a few minutes with a foot pump without leaving your house ?

Another reason to do it yourself at home is that tyre pressures should always be checked with cold tyres when the car hasn't been driven for at least a few hours.

If you have more than a mile or so to drive to a garage to check your tyres you're not checking the cold pressure, which means you will under inflate the tyres unless you compensate for this by pumping them up to a higher pressure, however estimating how much higher you need to go on a warm tyre is difficult as it depends on both the temperature of the tyre and the size of the tyre, (volume of air within) so best to just check when the tyres are cold - eg before leaving home to get consistent results.

These kind of foot pumps don't have particularly accurate gauges so if you care about accurate tyre pressures (and you should) my advice is to have a small but accurate tyre pressure gauge which you keep in your glovebox, and always use that same pressure gauge as your reference to check the pressure - regardless of whether you top it up with a foot pump or at a garage.

Some garage pumps are notoriously inaccurate, so I would always over inflate about 2psi then use your pressure gauge to bleed and measure to get it spot on - and do the same with the foot pump - over inflate then bleed back and measure using the gauge.

Another advantage of having a small, quick to use pressure gauge in the car is that there's no reason to get the foot pump out or drive to the garage if the gauge confirms the pressures are OK. This can be done very quickly before setting off on a long trip for example.

Pressures should be checked at least once a month, and if all is well you'll lose less than 1psi a month. If you're losing more than about 2psi a month you probably have either a leaky valve or an undiscovered nail/screw in the tyre which is sealing the hole but not perfectly!

Those with tyre pressure monitoring systems are not off the hook either - those systems will only warn you if pressures are getting dangerously low (many psi low) before safety is affected or tyre damage is caused, they won't warn you if you're only a couple of psi down which would be reducing efficiency and causing extra wear to the shoulder of the tyre. So waiting until the tyre pressure warning comes on before doing anything is not the way to go....

 

[toscal353]

When I was a lad I had a part time job in a petrol station. We used to put the fuel in for customers, add oil for them if they asked us to check it, top up washer bottles, check their tyres if we were not busy, all part of the service! Some times you were given 6d for your trouble! Three gallons of petrol for a quid.
Eeeee, when I were a lad, thems was the days....
Back to reality - buy a pump that runs of the 12v and carry it with you and use it at home.
Still need to visit the local garage for a pint of milk though!

 

[Hitstirrer]

Seasonal variations alone should mean you need to adjust tyre pressures at least once a quarter.

That's a popular misconception. But it isn't tyre manufacturers opinion. They do not mention any need to vary pressures winter and summer. But do say that specific winter tyres need different pressures to summer tyres.

This is just one on-line report on this subject.

" Vehicle manufacturers do not list a separate setting in colder weather for summer tyres but in some cases, for winter tyres they do list a slightly different tyre pressure but this is usually only 2 – 6 PSI difference from the standard pressure.
So basically unless you have winter tyres (M + S means Mud and Snow) and your vehicle manufacturer states a change in pressure, you should have no need to adjust your tyre pressure from the standard pressure."

Which is why I only now adjust pressures if the car dash light shows an actual problem. Experience has shown that that happens well before there is any visual indication of low pressure from tyre kicking. I do still use a handheld checker monthly. But that is just part of my deeply engrained and routine monthly checks of all levels. As I said, it's over a year since any intervention was required.

 

[proddick]

We bought a portable, rechargeable tyre pump to keep in glove box of Model 3 because (unlike Zoe) it doesn't have a factory one. The idea is that it should be sufficient to top up a slow puncture.

I actually used it on Zoe recently (less faf than 12V one) and it did a great job of adding 5psi to each tyre. The torch and battery pack facility is a bonus.

Vastar Portable Air Compressor, 100PSI / 2000mAh Lithium Battery Mobile Air Pump Tyre Inflator, Air Pressure Detection and Automatic Stop Inflation, Suitable for Bicycle Tire Swimming Ring : Amazon.co.uk: Automotive

Vastar Portable Air Compressor, 100PSI / 2000mAh Lithium Battery Mobile Air Pump Tyre Inflator, Air Pressure Detection and Automatic Stop Inflation, Suitable for Bicycle Tire Swimming Ring : Amazon.co.uk: Automotive

www.amazon.co.uk

 

[CoWplagued]

Those with tyre pressure monitoring systems are not off the hook either - those systems will only warn you if pressures are getting dangerously low (many psi low) before safety is affected or tyre damage is caused, they won't warn you if you're only a couple of psi down which would be reducing efficiency and causing extra wear to the shoulder of the tyre. So waiting until the tyre pressure warning comes on before doing anything is not the way to go....

Not the case with Tesla. While it's worth checking the calibration of your TPMS with a known good guage, I found mine to be spot on. And they update fairly quickly too. So you have a good indication of the tyre pressure there for you to view when ever you want. It also alarms well within safety, I'd possibly argue that for safety you should run them lower than the alarm state, say 39 psi, but you can't (unless you're running track mode). While temperature should be set when cold there's no issue with balancing them when they're a bit warm, as you can then check the final pressure in the morning before you set of with a swipe of your finger. Also, unless you're driving like a nutter, the temp will not change much with a gentle drive to a near by petrol station, again you can see the pressure changes in near real time. But I'd always use at least one trusted guage at some point so you know what the real pressure is, garage air guages are notoriously inaccurate, and you could have dodgy TPMS sensors.

 

[CoWplagued]

That's a popular misconception. But it isn't tyre manufacturers opinion. They do not mention any need to vary pressures winter and summer.

This seems like a bit of a contradiction. If the started cold pressure does not change, then you would absolutely need to add air in winter. In summer a "cold" tyre could be 20 degrees c, in winter it could be -5. That could result in a pressure difference of over 5 PSI, so too keep the same cold pressure, you would need to add or remove air.

 

[Hitstirrer]

This seems like a bit of a contradiction. If the started cold pressure does not change, then you would absolutely need to add air in winter. In summer a "cold" tyre could be 20 degrees c, in winter it could be -5. That could result in a pressure difference of over 5 PSI, so too keep the same cold pressure, you would need to add or remove air.

You misunderstand. They say the pressure doesn't need to change winter or summer. Which might mean adding or removing air over large ambient temperature changes to get to that same pressure.

 

[donald]

You misunderstand. They say the pressure doesn't need to change winter or summer. Which might mean adding or removing air over large ambient temperature changes to get to that same pressure.

I think you are contradicting yourself now.

In reply, you said...

"

RunningStrong said:
Seasonal variations alone should mean you need to adjust tyre pressures at least once a quarter.

HS... That's a popular misconception. "

So is it a misconception, or is it not?

RS didn't say why an adjustment was necessary just that it was. Which I agree with, technically, however in practice I just let my car run a lower pressure in colder weather because it lets the tyre warm up a bit quicker.

The bigger issue for tyre pressures these days is the unnecessary proliferation of alloy rims, which tend to leak due to porosity, in a way that steel wheels simply don't.

 

[Bob Bobbins]

I bought the Von Haus portable compressor best bit of kit I've bought in ages, bought it for other family cars , as previously owned a range of generally crap compressors over the years. But this is a solid bit of kit. It's digital, it's small and really portable, and the battery seems to last 'forever' I've done about 10 different tyres with it, including 4 from completely flat on a project car - the reviews of it all say the same thing too - have a look for yourselves. https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.co.uk/ulk/itm/282864240430 it's on amazon too

 

[Hitstirrer]

So is it a misconception, or is it not?

The misconception is that you need to change the pressure over the seasons.

ie - move it from one setting to another.

Not that you need to add/subtract air to maintain the same pressure as temperature changes. That's physics Jim.

 

[donald]

The misconception is that you need to change the pressure over the seasons.

ie - move it from one setting to another.

Not that you need to add/subtract air to maintain the same pressure as temperature changes. That's physics Jim.

RS said 'adjust' not 'change'. You sought to correct him on that.

 

[DBMandrake]

The misconception is that you need to change the pressure over the seasons.

ie - move it from one setting to another.

Who says it's a misconception ?

The car is supported partially by the air pressure inside the tyre and partially by the physical strength of the tyre carcass and sidewall. (Since a tyre is not just a thin elastic balloon with no strength of its own)

Rubber gets softer and more flexible in hot weather, therefore contributes less strength towards supporting the cars weight, so the sidewall will flex and sag more. To restore the previous optimal tyre and contact patch shape the "cold" tyre pressure would need to increase a bit in hot weather so that more of the support was provided by the air pressure than when the rubber was cold.

Perhaps not a big issue with summer rubber compounds but I definitely notice with an All Season tyre which has relatively soft rubber that a higher pressure by about 2-3psi is required in summer to avoid the tyre feeling "mushy" compared to the pressure you can run in winter.

As it happens if you were to just maintain the same quantity of air in the tyre year round the two effects compliment each other quite well - when the ambient temperature is very low the pressure will be low and the rubber stiff, then at higher temperatures the pressure will go up but the rubber will be softer. So if you had no leakage at all you could just leave the tyres alone year round and the pressure will change with the seasons.

The problem is tyres and wheels do have leakage and you can't measure the quantity of air in the tyre, you can only measure its pressure. So optimal tyre pressure will change with temperaure, and this ideally should be taken into account when setting the "cold" tyre pressure. Between say -5C and 20C you're talking about a difference of perhaps 4psi or so between optimal pressures, depending on the kind of rubber in the tyre and how much its stiffness changes with temperature.

 

[Hitstirrer]

Who says it's a misconception ?

I did. But you seem to be misunderstanding the misconception I am referring to. Some people seem to think that you need to change the pressure inside a tyre from summer to winter. You don't. You just need to add or subtract air so that the pressure remains constant summer and winter.

 

[donald]

I did. But you seem to be misunderstanding the misconception I am referring to. Some people seem to think that you need to change the pressure inside a tyre from summer to winter. You don't. You just need to add or subtract air so that the pressure remains constant summer and winter.

Are you talking about gauge or absolute pressure?

 

[Hitstirrer]

Are you talking about gauge or absolute pressure?

Absolute pressure is zero-referenced against a perfect vacuum, using an absolute scale, so it is equal to gauge pressure plus atmospheric pressure. Not something an average driver is concerned about when pushing a hand reader on a valve stem.

Gauge pressure is zero-referenced against ambient airpressure, so it is equal to absolute pressure minus atmospheric pressure. Such academic differences are outside normal usage when referring to a simple thing like pumping up tyres.

The view of tyre manufacturers is that the gauge pressure of a tyre ( measured by the device that we all recognise on home and commercial inflaters) should show the same level, as recommended by the car manual, summer and winter. A variation is that the recommended level can be changed by factors like loading and long-distance high-speed intentions.

Maintaining that same level year-round may involve adding some air in winter and removing some in summer. But that does not mean that you are changing the gauge pressure reading. On the contrary, you are simply adjusting the air content in a tyre so that the same gauge pressure is maintained summer and winter.

Preferably as measured by the same physical gauge, that has been correctly calibrated, throughout the year.

 

[donald]

Maintaining that same level year-round may involve adding some air in winter and removing some in summer. But that does not mean that you are changing the gauge pressure reading. On the contrary, you are simply adjusting the air content in a tyre so that the same gauge pressure is maintained summer and winter.

'Adjust' like RS said ... whom you sought to correct?

You got it wrong today. Sorry to point out. Never mind, tomorrow is another day.


"

RunningStrong said:
Seasonal variations alone should mean you need to adjust tyre pressures at least once a quarter.

HS... That's a popular misconception. "

 

[Hitstirrer]

This was the quote - " Seasonal variations alone should mean you need to adjust tyre pressures at least once a quarter "

I read that to mean adjusting the actual pressures. ie- increasing or lowering gauge pressure in tyres seasonally. Changing the readings themselves upwards and downwards.

I did not read it mean to maintain the same pressures by slight adjustment. Re-reading the quote I can see how it can be interpreted either way.

My reply was because I have been aware of many people thinking that they should lower or increase the pressure readings seasonally. This is based on them having read about people, quite correctly, checking winter summer pressures and adding or subtracting air to keep a constant pressure. And then them misunderstanding what was actually being done.

However, if the OP meant it as you have interpreted it then I agree. My reply was in error.

 

[DBMandrake]

I did. But you seem to be misunderstanding the misconception I am referring to. Some people seem to think that you need to change the pressure inside a tyre from summer to winter. You don't. You just need to add or subtract air so that the pressure remains constant summer and winter.

And I'm saying the opposite is true. You want the quantity of air to stay the same so that the pressure is higher in summer. For the reasons I explained with the change in strength and flexibility of rubber in summer/winter. A hotter, weaker sidewall needs a bit more support in the summer with a bit of extra pressure.

This of course is what happens naturally if you have no leakage and you don't bother to regularly check the pressures.