[BrightonSA]

I have always  inflated my Tyres according to the metal plate recommendation on the driver door.  It is 32 psi 

Yesterday I was checking my Tyres & discovered that the recommendation on the Tyre is 44 psi max! 

Comment please   

[Surferdude]

The tyre "Max pressure" is simply the maximum that tyre can safely be inflated to. It relates to a number of rim/vehicle fitments and also gives tyre fitters advice as to how high they should inflate it when fitting and seating the beads. Nothing to do with your car on which the placard makes a recommendation for the"optimum" pressure for that sized tyre on your model of vehicle.

You should also be aware that this "recommended pressure" is set by the vehicle manufacturer which takes into account a range of factors and the over-riding one is in essence, what's the lowest pressure you can run which will give you a smooth comfortable ride. However, the best handling and wear rates will generally occur at slightly higher pressure - 36psi seems to be the most generally accepted figure. The difference in ride and comfort will be hardly noticeable at first and after a few days you will adapt to it and not notice at all.

[BrightonSA]

The tyre "Max pressure" is simply the maximum that tyre can safely be inflated to. It relates to a number of rim/vehicle fitments and also gives tyre fitters advice as to how high they should inflate it when fitting and seating the beads. Nothing to do with your car on which the placard makes a recommendation for the"optimum" pressure for that sized tyre on your model of vehicle.

You should also be aware that this "recommended pressure" is set by the vehicle manufacturer which takes into account a range of factors and the over-riding one is in essence, what's the lowest pressure you can run which will give you a smooth comfortable ride. However, the best handling and wear rates will generally occur at slightly higher pressure - 36psi seems to be the most generally accepted figure. The difference in ride and comfort will be hardly noticeable at first and after a few days you will adapt to it and not notice at all.

So in a nut shell, I keep inflating my Tyres to 32 psi as recommended by the metal plate?

[rustynutz]

If you're happy with the ride and handling as it is...otherwise I'd be trying 36 or even 38psi, which is what I run.... 
Higher inflated tyres will give you slightly better fuel economy too....

[BrightonSA]

If you're happy with the ride and handling as it is...otherwise I'd be trying 36 or even 38psi, which is what I run.... 
Higher inflated tyres will give you slightly better fuel economy too....

So you pump in 38 psi & experience no problem?   

[rustynutz]

None whatsoever....

If you do a lot of higher speed driving you'll find upping the tyre pressure is actually recommended.

[Phil №❶]

We run 36 psi on both our diesels and no worries at all. 

[Doggie 1]

I run 36 all round, all good.

[Shambles]

Yep, 36 here too, though I do look younger


As for Max Pressure, that's probably the name of the guy who designed the tyres...

[Doggie 1]

I don't know him.
But I've met his wife, Min Pressure.

[Dazzler]

I don't know him.
But I've met his wife, Min Pressure.

and one of his kids "under pressure" 

[Lakes]

i think about 36 38psi front & about two pound less for rear in CRDi as there got more weight to support at front. i think that gives about best handling, yesturday i checked mt tyre pressure & was 32 34, i pumped them up to 40psi bit harder ride but could notice car rolls much easier. anyway from the start of this tank full ( almost 1,000k up now ) i have not re set the trip PC & the entire tank full has been used in Sydney traffic no motorway as i'm too cheap to pay the toll   i found if i used the motorways they just deduct $100 per month from credid card. so i never told them new CC # & have not used toll roads unless i have to & when i started this about two years back i had $80 in credit it still has not run out.
anyway  have just about had climate control on coldest setting for the tank full. and just drive it normal not slow not fast. its been sitting on 5.6 Lt / 100k for past week. then put 40psi drove 60km & it dropped to 5.5lt /100k to me that amount is nothing but it showed it might help.

[Doggie 1]

Thankfully, we don't have toll roads over here.

[Dazzler]

Thankfully, we don't have toll roads over here.

 

[Surferdude]

The tyre "Max pressure" is simply the maximum that tyre can safely be inflated to. It relates to a number of rim/vehicle fitments and also gives tyre fitters advice as to how high they should inflate it when fitting and seating the beads. Nothing to do with your car on which the placard makes a recommendation for the"optimum" pressure for that sized tyre on your model of vehicle.

You should also be aware that this "recommended pressure" is set by the vehicle manufacturer which takes into account a range of factors and the over-riding one is in essence, what's the lowest pressure you can run which will give you a smooth comfortable ride. However, the best handling and wear rates will generally occur at slightly higher pressure - 36psi seems to be the most generally accepted figure. The difference in ride and comfort will be hardly noticeable at first and after a few days you will adapt to it and not notice at all.

So in a nut shell, I keep inflating my Tyres to 32 psi as recommended by the metal plate?

If you have a diesel, I'd be running 38 psi in the front and 36 psi in the rear.

If you have a diesel, I'd be running 38 psi in the front and 36 psi in the rear.

That's what I was running on the 16" rims initially but now just do 40psi all round. It's too firm on dirt roads but on the smooth...

[BrightonSA]

Ok, as I have posted in another thread before, I plan to drive from Mt Isa QLD to Adelaide.  The speed is 110km/hr - no limit in NT.   What pressure should I pump my Tyres?   

[Surferdude]

Ok, as I have posted in another thread before, I plan to drive from Mt Isa QLD to Adelaide.  The speed is 110km/hr - no limit in NT.   What pressure should I pump my Tyres?   

How many people? And luggage?
If you have two or more people and luggage for the whole trip, go 40 psi. Make sure you set the pressure in cold tyres and don't bleed any air out if you check them hot and they are reading higher because the pressure rises with heat and that's part of the design.

[eye30]

I understand that a vehicle involved in a serious accident the investigator will check the tyre pressure to the rating for the vehicle as under/over inflated tyres can contribute to an accident.

Does anyone know what % +/- is allowed?

[plasticphyte]

I don't know him.
But I've met his wife, Min Pressure.

and one of his kids "under pressure" 

I've met the uncle - no pressure. Pretty lazy guy actually. I did feel pretty flat after meeting him, and his kids, had to tread carefully or they would tire me out.

Back on topic, I've always preferred about 36psi. Thanks for reminding me to go out and top my tyres up!

[BrightonSA]

Ok, as I have posted in another thread before, I plan to drive from Mt Isa QLD to Adelaide.  The speed is 110km/hr - no limit in NT.   What pressure should I pump my Tyres?   

How many people? And luggage?
If you have two or more people and luggage for the whole trip, go 40 psi. Make sure you set the pressure in cold tyres and don't bleed any air out if you check them hot and they are reading higher because the pressure rises with heat and that's part of the design.

Just me & some luggage but only light items, nothing heavy. 
It's 40 degree C here everyday.  How can I get cool air? 

[Lakes]

I understand that a vehicle involved in a serious accident the investigator will check the tyre pressure to the rating for the vehicle as under/over inflated tyres can contribute to an accident.

Does anyone know what % +/- is allowed?
Lester i'm not sure, but i can't ever remember having an insurance assesor checking tyre pressure. also in an accident a rim could get broken and fail loosing air. but not contributing to accident.
also in Australia with high temps, the road could be 60c 70c? with air temps as high as 50c in some outback area's so wise to run Tyre pressure 40psi set cold as this will keep tyre runing cooler, if tyre run too hot they wear a lot faster.
this is just my personal experience anyway.

[Lakes]

Thankfully, we don't have toll roads over here.

well Dave & Dazz they the toll roads are great to have! you don't have to use them, but user pays & you have a choice, without them you have traffic jams & no choice. if i'm in a hurry i use them, i took interste friends from airport got them clear of sydney & into the country for a weekend. they were surprised how good the toll ways are as last time they were here was none and lot of traffic.
but they still get jammed up in peak hour but the money rolls in .so they will build more.
]but Queensland started this & Victoria not NSW

[Surferdude]

I understand that a vehicle involved in a serious accident the investigator will check the tyre pressure to the rating for the vehicle as under/over inflated tyres can contribute to an accident.

Does anyone know what % +/- is allowed?
Lester i'm not sure, but i can't ever remember having an insurance assesor checking tyre pressure. also in an accident a rim could get broken and fail loosing air. but not contributing to accident.
also in Australia with high temps, the road could be 60c 70c? with air temps as high as 50c in some outback area's so wise to run Tyre pressure 40psi set cold as this will keep tyre runing cooler, if tyre run too hot they wear a lot faster.
this is just my personal experience anyway.

Agree about the pressure John.
Also, it is possible in certain impacts for a tyre to pop the bead off a rim and allow the loss of just some air. The air rushing out acts like the jet from a tyre fitting machine and forces the bead back onto the rim, maybe leaving 10 or 15 psi in it. So any investigation would need to be able to reclude that possibility - which it can't, even if there's no rim damage.

[eye30]

This is interesting and from :
 http://www.maic.qld.gov.au/forms-publications-stats/pdfs/tyre-pressure-report-final.pdf

Report Prepared for:

Heads of Compulsory Third Party Insurance in Australia and New
Zealand

A quick skim details under pressure but not over pressure from that quoted for the tyre.

Page 5:

2.2 Definition of under-inflated tyres
Under the Australian Design Rules vehicle manufacturers must fit a Tyre and
Rim Placard in a prominent place. The placard must list, as a minimum, the
recommended tyre inflation pressures for a "normal" vehicle load.
There is no universal definition of what constitutes an "under-inflated tyre".
The US Federal Motor Vehicle Safety Standard 138 requires a warning if tyres
are under-inflated by more than 25%. Based on this FMVSS requirement, we
regard a severely under-inflated tyres as 50 kilopascals (kPa) or more below
the recommended pressure. For reference, 1 psi = 6.9kPa so this equates to
7.2psi.


10.0 CONCLUSIONS
As indicated at the outset of this report, maintaining correct inflation pressure
in tyres helps to keep vehicle handling and braking at its best, as well as
improving fuel efficiency and tyre life. In addition it can prevent such events as
tread separations and tyre blowouts which may cause loss of control of a
vehicle and severe crashes such as rollovers.



Now lets find a similar report looking at over inflated tyre pressure...

[Phil №❶]

It was previously mentioned that max tyre pressure is 44 psi, so running at 40 would not cause an insurance problem. Insurers concentrate on evidence of driving under pressure as this does directly relate to the cars handling ability and whether a tyre blow out caused any accident.

The recommended tyre pressure on your sticker, is the motor vehicle's preferred pressure, designed as a compromise between comfortable ride and handling. Certainly, don't go below it.

[rustynutz]

This, from the RACQ Tyre Fact Sheet.....

So what’s the correct pressure?

All vehicles built since 1973 will be fitted with a tyre placard that lists the specifications of the original tyres fitted to the vehicle and the correct inflation pressures. It will be located in an easily accessible spot such as the glove box lid, fuel filler flap or the driver’s door or opening. The information will be contained in the owner’s handbook as well. Diagram 1 shows an example of a tyre placard.

The pressures shown for normal use are the minimum suitable for average suburban driving with minimum loads. For increased load carrying or sustained high speed driving (around 100km/h for more than 1 hour) tyre pressures should be increased as advised on the placard or, if not shown, as recommended by a reputable tyre dealer.

Remember, the pressures shown on the placard are the minimum allowable cold pressures and you should not allow your car’s tyres to drop below them. In fact it’s acceptable, if not wise, to keep them inflated to the high load / speed pressure listed on the tyre placard or suggested by a tyre dealer.
Tyre pressures should be checked cold as it is normal for pressures to increase as the tyre heats up from driving. Don’t bleed air from hot tyres to obtain the recommended cold pressure. It’s not a bad idea to have your own tyre gauge for doing your regular (at least once a fortnight) pressure checks – and don’t forget the spare. If you notice any significant pressure drop, especially on just one tyre, have the cause checked out – you might have a leak – possibly from a puncture or defective valve.

Remember to replace the valve dust caps after checking tyre pressures. It’s important they are fitted to all your tyre valves as they help seal air into the tyre and exclude dirt, which may cause the valve to stick or leak.

Tyre pressures are measured in Kilopascals (kPa) or in pounds per square Inch (PSI).

Conversion: 7kPa = 1 PSI

[Phil №❶]

Thanks Wiki-Rusty 

[rustynutz]

 
You're welcome....

[BrightonSA]

Your are all whizkids.  So much knowledge to absorb.  My little brain is exploding!