Why is it so hard to check your tyre pressures.

[eltawater]

On my old seat Leon, I've seen a difference of between 3-4 psi driving one mile down the road.

Recommended pressures on the front were 32psi and the difference in handling was certainly noticeable as the pressure dropped below 29psi on the front thanks to the heavy diesel lump, which is why I always test after the car has been parked up overnight.

[Super Slo Mo]

LeoSayer said:

227bhp said:

Doing a Google search brought this thread up so I thought i'd ask here;
How exactly do cars monitor their own tyre pressures?

Most don't...they just use the ABS sensors to detect a wheel/tyre that is rotating less than it should be for the actual vehicle speed...because that it a symptom of a deflated tyres.

The wheel with the soft tyre would be rotating faster than the rest

[Vipers]

oyster said:

RobM77 said:

If you're driving the car to a garage just before you check the pressures it makes the whole operation pointless. The act of driving your car will create heat in the tyres and therefore heat the air in them, raising the pressure. This means a) the cold pressures given in the handbook won't apply and b) the heating will be uneven depending on the number of left and right bends, acceleration and braking. Ergo what you'll end up doing is having all of the pressures too low and they'll all be different - utterly pointless.

Get yourself a tyre pressure gauge and a pump and do it yourself when the car is sat cold and out of the sun; then you can enjoy the handling, economy and safety that was designed into your car in the first place. It'll take five minutes and it'll be done properly.

I'm all ears as to how much difference that makes to the pressure?

I'll bet it's a fraction of the difference between doing it in winter versus summer (which in itself probably makes little difference).

If you want to calculate increase in pressure due to increase temperature, use Charles law, using absolute values.

So add 1 bar to the tyre gauge reading in the calc and deduct it at the end, and if using Celcius take the ambient temperature and add 273.16, in Fahrenheit add 459.67

So final pressure = Initial pressure x final temperature, divided by initial temperature Minus 1 bar

[Harji]

This is a good monitoring method via a phone app from Maplin

http://www.maplin.co.uk/p/fobo-bluetooth-tyre-pres...

[robinessex]

OK. EVERY time I jump into the car, I do a visual type gawp. Spotted a semi flat tyre on more than a few times. If a tyre looks a bit suspect, quick press of the sidewall gives me an idea if all is well. A digital pressure gauge is in the centre consol box if required. And a mini electric air compressor, in a nice little zip bag sits in the a cubby hole in the boot. And I am constantly amazed by the number of cars I see with obviously under inflated tyres. And I won’t bother with some replies I’ve had from some cars drivers (especially women) when I’ve pointed it out to them. Some think the MOT is when you pump them up !!!!! And they look flat because they have 5 kids in the back/lots of shopping in the boot !!!

[Wills2]

Mine tells me the pressure and temp of each tyre which I quite like, with foot pumps and even compressor inflators being so cheap these days I'm amazed people still use the garage forecourt.

[Vipers]

robinessex said:

OK. EVERY time I jump into the car, I do a visual type gawp. Spotted a semi flat tyre on more than a few times. If a tyre looks a bit suspect, quick press of the sidewall gives me an idea if all is well. A digital pressure gauge is in the centre consol box if required. And a mini electric air compressor, in a nice little zip bag sits in the a cubby hole in the boot. And I am constantly amazed by the number of cars I see with obviously under inflated tyres. And I won’t bother with some replies I’ve had from some cars drivers (especially women) when I’ve pointed it out to them. Some think the MOT is when you pump them up !!!!! And they look flat because they have 5 kids in the back/lots of shopping in the boot !!!

Same here. Quick visual, digi gauge in co sulk and pump in boot.

I once flagged down a woman motorist in a ground floor car park, told her her rear wheel wasn't turning it was locked.

She asked if it was dangerous, told her why and to park up and phone for a mechanic.

She said thank you, and drove out dragging the wheel with her. Women😄

[eltawater]

Purity14 said:

eltawater said:

On my old seat Leon, I've seen a difference of between 3-4 psi driving one mile down the road.

One Mile, 3-4 psi?

Driving down the road, or wheelspinning down the road?
Had your bearings failed, or did you have sticky calipers?

Because otherwise, I don't believe you.

You are perfectly entitled to disbelieve me and perform your own testing. AFAIK there were no issues with sticky calipers or bearings on the old Leon, I eventually had the rear pads replaced after 60k miles from the factory delivery.

This was four miles in the daily driver this morning, half of which was 30mph, half of which was NSL dual carriageway with three roundabouts.

Naturally this was not under laboratory conditions nor was it performed with a recently calibrated pressure gauge, but I wouldn't expect those from a normal car owner either.

[Vipers]

34 to 37 psi assuming 20 Celcius at the start, will need an increase of temperature to 40 Celcius, can that be right, how hot do tyres get in a mile?

[DonkeyApple]

If you are driving clockwise round the M25 what must the left and right hand tyre pressures be set to to prevent everyone dying?

[saaby93]

eltawater said:

What phone is that? and pressure guage

If you look on ebay some electric pumps have screw on pipes, saves messing about trying to make the stupid clip on things work and release half the air while doing it (same at garages).
Surely theres a better clipping way?

A Footpump is much quicker than a compressor and is less likely to blow the puny accessory fuse

[MGJohn]

RenesisEvo said:

Raize said:

Can't be bothered. Didn't check them in 2 months, went to check them, they were still correct from last time after about 1500 miles.

Can I offer a precautionary tale for those who don't regularly check tyre pressures?

I check mine religously. No idea if the tyre pressure gauge I use is accurate or calibrated, but it doesn't appear far wrong. I noticed that one tyre was losing 4-5psi over the space of a week or so, the rest maybe 1psi a month. If nothing else, it was a chore having to re-inflate it to the right pressure every time I went for a long drive. So when I got the car serviced I had them check the tyre was seated correctly.

Turns out there was a huge nail through the rear tyre, the end of which had been scoring away the inside of the tyre sidewall. I hate to think what might have happened if I'd left it, and the tyre failed at speed. So check your pressures, you never know what that slow leak might be!

Also, for anyone thinking it's hard to check tyre pressures - go speak to an Alpina owner for a different perspective.

said:

... and the tyre failed at speed...

Wise words.

There are far too many never check nuffink types or those who are convinced their German/Japanese car is so reliable they save time by not doing those routine safety checks ALL manufacturers recommend car users do.

Sadly some users live to regret not doing whilst a very few others do not live long enough to regret not so doing. Not to mention the impact on their car finances.

OK so they get away with it most of the time but one day, S0D'sods Law will ensure that nail damaged tyre will let go or worse just when you really need it when that emergency scenario arrives.

Two of my cars are fitted with good quality low profile tyres which always LOOK fully inflated. Appearances can be dangerously deceptive. Over the years, some tyres having lost up to half the recommended pressure in less than a month. Still look fully inflated.

Never actually bought one but, over the years, I have found several of those pencil tyre pressure gauges tucked away in used cars I have bought. I have at least five. One day I checked the readings of all five of these gauges and ALL still read and measure accurately many years on.

One Christmas, one of my sons bought me one of those 12v Ring-Automotive Compressors as a present. With so many cars in the family it got a lot of use and eventually expired. The connecting rod drive on the still operating strongly electric motor disengaged from the little pump due to wear and would fly off so no drive to pump. It was a more substantial job than the one linked in an earlier post. So I got the exact same one as in that link to replace it and two years on, still gives reliable use.

Most local Petrol Stations charge 50p for Air. Even when I remove all five valve caps and clear access to the spare wheel in the boot ( remember them ?... spare wheels .. how quaint ... >) before inserting my 50pence coin there is never enough time to do all five even working quickly. The local Sainsburys has a free Air Line and it gets much use and as previously mention on this thread, is often out of use from careless of heavy handed users. Usually I'm first or second in the quueue. By the way, it's good to see so many car users of the fairer sex checking their tyres...

[MGJohn]

DonkeyApple said:

If you are driving clockwise round the M25 what must the left and right hand tyre pressures be set to to prevent everyone dying?

Please Sir! I know.

Not as much as when taking your favourite roundabout a tad too fast ... we all do it sometimes. Well, some of us do..

Rascal DA ..

[JuniorD]

I have a pen type pressure gauge and a halfords compressor with digital pressure gauage.

At around normal inflation ~30psi or so, the Halfords gauge reads 2 psi more than the pen gauge.

Which is the corect(est) measurement?

[lostkiwi]

Mains powered compressor in the shed.
Large 12v compressor (over 110 litres per minute) by the toolbox if required and cigarette lighter one in the car coupled with my own gauge. Job sorted.

[Rakoosh]

The OP has a very valid point though - which seems to have got lost. Yes a lot of us will have compressors/pumps and a gauge...

But conversely lots of people don't and only check their tyre pressures either when prompted or in my parents case any time they are about to embark on an epic road trip (read anything outside of the M25...).

I appreciate the 20p/50p charged will never pay for the compressor but so many petrol stations have one in various states of disrepair...

I remember getting the low pressure signal on my mini (and as I had never had any issues with the tyres and they are run flats - I don;t carry a compressor with me) . Tried two fore courts and no joy. This was a Sunday and I found a random garage open and asked there but got told the compressor did not work - more likely the sales person (as thats why they were open sunday) probably had no clue where it even was or what I was asking for...

[Motorrad]

227bhp said:

Why is that, presumably because they run at a lower TP?
Thanks for the reply btw.

No each set of sensors needed to be synced to the car (different wheels so therefore different sensors). I suppose to make it less likely your car would pick up that the 'tire' pressures of the Ford next to you are wrong. I can just imagine the intermittent fault driving me mad.

Re the ABS sensors, I had a Golf that used that system and it was fecking useless.

[SlipStream77]

In theory we should all be using a spirit level to ensure the car is level checking tyre pressures.

Also, I'm assuming that manufacturer's stated pressures are at sea level?

[Vipers]

SlipStream77 said:

Also, I'm assuming that manufacturer's stated pressures are at sea level?

Interesting, your probably right, then again even at 3000 FT above level it's only 1.52 psi less than at sea level. Can't believe it makes any difference, what's the highest drivable road in the world I wonder.

On the subject of tyres I wonder how many check the spare wheel.

[Sheepshanks]

Purity14 said:

JuniorD said:

I have a pen type pressure gauge and a halfords compressor with digital pressure gauage.

At around normal inflation ~30psi or so, the Halfords gauge reads 2 psi more than the pen gauge.

Which is the corect(est) measurement?

Halfway in between.

This bugs me too - the digital one on the Ring 12V compressor reads several PSI higher then the Halfords digital premium or whatever it's called gauge.

A really old dial type gauge that my dad gave me reads in the middle.

I've used Michelin tyres for years and they're well known for holding pressure and mine never budged. I changed for the last set and they're all over the place.