TYRE TEMPERATURES

Yes, I agree. I have a set of tyredogs and for temperature they're useless.

They're not particularly accurate with pressure either but I don't mind much about that because I set pressure with a decent gauge of my own.

However, they DO rapidly report CHANGES in pressure from what's been set, and that's what you really want. They've saved two tyres for me, so I reckon they've paid for themselves.

Cheers

They also report changes of temp, even if the absolute temp may be inaccurate. If one tyre is 10 degrees hotter than the test it has a problem!
Bob

Bob the problem is that the temp reading is not related to tyre temp because it is to far away - the temp they report is essentially ambient air temp.

Because of this they also read higher when in the sun.

Fortunately you can infer that everthing is ok from rise in pressure as tyre heat ups when driving , this is what I look for (about 4psi on road running).

Phil, you must have unusually responsive "pants seat" if you can readily detect a tyre going low whilst operating at reduced pressure on a rough and winding bush track. The tyre pressure has dropped from say 24psi to say 10psi and is now heating up wildly yet is still on the rim and supporting the vehicle. Before it becomes obvious by departing the rim the carcase is ruined. A tyre pressure monitor would have warned you in adequate time to save a $350 tyre.......about the cost of a TPMS.


The only two tyre punctures I have had in recent years have both been on the bitumen with no sense of performance change but the monitor sounded the alarm well before the pressure had dropped to a possibly hazardous value. Prior to having the monitor I was leaving a caravan park when a bystander alerted me to a dead flat rear tyre. Only rolling at maybe 15kph with no unusual sensation but it would not have been doing the tyre any good.


Now don't tell me that I am insensitive. I can detect low tyre pressure in the Camry on bitumen no problem, but a fully loaded Troopy on a rough track is another thing entirely. That tyre pressure monitor system on the Troopy is great insurance against a ruined tyre at the least and a dangerous situation at worst. Wouldn't leave home without it.

Phil,

Spot on

Grant

The other very real issue is that in the name of comfort, the car manufactures have isolated the driver from as much road feel as they possibley can.

My mums old 1200 civic you could drive over a match stick & tell if it had been struck or not, so many of the modern cars have so little road feel your only reference is looking out the front window.

Untill I checked the tyres on the hand brakes RAV one of the rear tyres had been running on 18 PSI when it should be well over 30.

I'd driven it like that, she'd been driving it like that.....felt no different...and the RAV is much less vague that lots of other madern cars.

But as far as tyre temperature......pressure is a far more important and reliable indicator.

cheers

Allan

After Parramattas recent failures and having their "tail" kicked it is quite sensitive.

Look at it this way. When you drop your tyre pressures to around 15 to 20 from 35 - 40 you immediately "feel" a difference. That is an example of what I am talking about. When a tyre is heavily deflated on dirt or even mildly deflated on bitumen it makes a difference to the "feel", responsiveness, balance and whatever other word you can conjure up. It says that something is not right somewhere inside of you if you are properly attuned to the car. It's simply a hunch if you can understand it that way. Dad showed me back around the 60's when I frist started driving our old Armstrong Sidley.

But if you can't then by all means get the electronic gadgets. It's a free world mate.

Thanks Grant

Phil

Phil

I know what your'e talking about Phil, but it doesn't happen in a laden Troopy with heavy duty springs, believe me.

I am very much in tune with my vehicle but not so arrogant that I won't avail myself of any assistance going - stability control, ABS, low coolant alarm and TPMS. Having functioning tyres in rhe middle of nowhere is too important to leave to the seat of my pants.
Bob

Allan
Fair enough mate. All's cool. Just my opinion. Not jumping on you at all. I hate this written word system sometimes as it is so easy to be misunderstood.

Bob
Arrogant you say. Please show me where I attacked you. I was stating my opinion.

Of course there are some electronics in our car as well and between you and I, I think about what would happen if one of the sensors went faulty in the middle of the Canning and stopped the car when nothing was really wrong with the car. How would we know if the tyre monitoring system was fauilty and did not report a low tyre. Oops. What if the ABS locked the brakes on etc

With that in mind I would still regularly check the oil and water levels and all those "first aid" vehicle checks and of course still be conscious of how the car was handling. Just as we do now.

Personally we go to such rough and corrugated remote places that if it was an external type any tyre monitoring system could be knocked off anyway. We did look at them but decided more fuel capability and other self reliant systems were more important.

Do you get my point now? We. me also, as drivers are at risk of all being passengers and forgetting the real basics of being in control.

Phil

Bantam

When do we all get remote terminal (not controls) for the back seat.

My wife used to rally a mini back inthe days of the Redex etc. She also finds a lack of feel in the car. It's still there but we are as you say so isolated. We wouldn't buy a 200 or any new 4WD for quids. We enjoy the touch of the road, track or whatever as well as the environment.

This car will see us out.

Phil

Phil

You asked what has happened to all the good drivers, implying that anyone who has had a puncture, or uses tyre monitors isn't a good driver like you. Frankly, if I had to come up with a word to describe your position it would be arrogant.

I have used various tyre montoring systems over the years, since they became available. The Smartire was effective but damaged by tyre changes. The screw on ones I presently have have been very effective, and have resisted damage in all terrains including many kilometers of off track in the western deserts (ie across the desert with no tracks).

I find the temperature warning as important as the pressure. If one tyre heats up faster than the others it clearly has a problem. The pressure may not change until the blowout occurs. If all the tyres heat up to excessive levels I need to reduce speed for the pressure I am running (or ditch some load).

Bob

Total rubbish. It the introduction. I made my point later on.

Absolute rubbish.

By all means you are welcome to use anything that you want. This was my opinion of how they are taking the skills of our forefathers away from us.

Two examples; How many ways could Tom Kruz unbog his mail truck. We wouldn't know half of them. And what about "Toots" Holzheimer's. Mate we aren't drivers nearly as good as they were.

Just being able to drive one of these modern machines over a sand dune or up into the high country doesnt make us gooddrivers. It doesn't hold a candle to the skills that they had back then. Now tame that down a bit to the last 40-50 years and you will maybe understand what I have already said. That we are losing the skills we once had by relying on all the modern electronics etc. Not that I use the plural "we" meaning you, myself and everyone reading this dribble.

IS THAT CLEAR ENOUGH FOR YOU.

Phil

"50 years of driving without any tyre monitors, and not one damaged tyre over hundreds of thousands of miles on both bitumen and dirt. At least 1/4 of it towing everything from 1 ton toy backyard trailers to 80 ton tank transporters."

Sorry Phil I thought you were talking about yourself there, and what a marvellous driver you were.

I must have misread it.

Bob

Just the truth. As I stated earlier, the last flat tyre was back at Oran Park, 40+ years ago. We have never blown a tyre. No shredding the tread off one. Sure tyres have deflated some but have always been detected and pumped up or replaced before any damage done. But never destroyed one or had a blowout.

A real pity that you cannot say that you look after your tyres. Maybe don't put price at the top of the heap in the future.

Just the truth Bob.

Phil

I made stiff foam pads to push over the rubber valve stems on my trailer to stop the sensors bashing against the rim.

Mfewster you have too much common sense.
We tend to go overboard with automated control and alarm systems these days.
Use the 6 PSI rule and feel the tyre temperature with your hand.

What's the 6 PSI rule for us idiots [ there may be others, other than me] !!!!!

I agree that tyre temperature is pretty well meaningless and inaccurate.

No matter how you measure it.

If under inflated and or over loaded a tyre will fail regardless of temperature.

Yes there are issues with running tyres heavily loaded in high temperature situations.
For example truckies that run recaps and run heavily loaded, will reduce speed under hot conditions...even if they are half smart.
AND hot road temperatures are known to increase tyre faiures.

BUT & this is a big BUT, the problem with tyre temperature is,

what part of the tyre are you measuring.....

Rubber is a fairly good insulator and the whole wheel and tyre device is fairly complex.
So, are we measuing the temperature of, the tread, the sidewall, inside or out side or in the core, the rim, the air temperature inside the tyre or in the valve stem.

Is this influenced by the road temperature, the air temperature the sun shinning on the tyre, heat transfered from the brakes, road speed air flow over the tyre, water on the road.

and on an on.

AND the temperature of whatever will be an inaccurate indicator any way. A perameter than lags cause considerably and tracks poorly.

The fundamental thing we have to understand is that the load on the tyre is supported by the air volume within.
AND if run close to recomended pressures the tyre is a more or less self equalising system.

The only two reliable indicators for tyres are air pressure and hub centre height.......every other thing we can measure about tyres is unreliable at best.

AND tyre inflation is specified as "cold inflation pressure" for a very good reason.....temperature is an unreliable variable.

Recommended "minimum cold inflation pressures" can be obtained from the load V pressure tables either in the standards manual.( and they are very consistent from tyre to tyre and brand to brand in the same size and profile & type of tyre) or from the manufacturers data.
Look at some of these tables and you will see how damn accurate and fine the data given is.

This information has been arrived at by extensive laboratory and practical testing over many decades.

The hub centre heiight can be measured with a common ruler with the vehicle at a known load and the correct load for pressure in the tyres.

As for the 2 psi, 4 psi, 6psi rule......its is as unreliable as any of the other hokus pokus.
On a lightly loaded tyre in cool weather it does not work at all...I don't mean inaccurate...does not work at all.

The firts thinge we all need to know about our tyres is the load V pressure data and how heavily we are loaded.

I can see benifit for monitoring tyre pressure, but I can see none at all for measuring temperature.

cheers

Hi Bantam, I generally agree, but not quite. You wont damage a tyre by running at low pressure (until you get so low that it may roll off the rim). The providing (and it's a big providing) is travel speed. Temperature can be an indicater of tyre stress but it is dependent on pressure. The flexing of the tyre as it revolves creates heat. The lower the pressure, the more flex and so the greater heat build up. The heat generated is way higher than that generated by running on high speeds on very hot days with hard tyres. ie the required pressure is directly related to the speed of travel. Too low a pressure and higher speeds leads to very high tyre temp and tyre destruction. Low speeds with lower pressures are better under many conditions. Temperature is just a by product of the pressure/speed combination.

Hi Hunter Gatherer
This is the rule that is promoted by a number of tyre manufacturers.
Drop into a Coopers dealer and he will hand you a booklet on the subject.
Start with the recommended pressure - drive for about 1 hour. Check the tyre pressures, if they have gone up by LESS than 4psi for a sedan or 6 PSI for a 4WD, then your starting pressure was TOO HIGH, drop 2 psi now, and remember to use a 2psi lower start pressure tomorrow. Test again the next day.
I use this rule, plus I feel the tyre’s temperature with my hands – if the tyre gets too hot you need to increase its pressure or lower your speed.
Once you have done this a few times you will get to know what your standard pressures are for your particular use. I now rarely test the PSI rise but feel the tyres tempuratures by hand a couple times a day on a long trip.

Yess I am well aware that tyres get hot when run too fast when overloaded or or under pressure.

But temperature is simply not a reliable indicator of anything.
By the time the tyre is hot and is detected as hot ...the damage is likley already done.

This is particularly true of steel belted radials....when run overloaded or under pressure...the belts squirm within the tyre structure and more or less cut the tyre appart and the whole of the tread delaminates so we get tread bubbles or other faults.

Rubber being such a good insulator...the heat does not readily transfer to anywhere it could be accurately measured.

Heat is not the cause, it is the result.....additional heat may make matters worse, but it is not the root cause, tyre flexure is.


I know only too well that it is necessary to run tyres under their recommended highway pressure off road...fine and beaut.

But the 2, 4 or 6 PSI rule is most unreliable......its may seem to work on a tyre that is being run an a particular part of its load range.

But there are so many variables that come into play that it is highly unreliable.

On the tyres on my vehicle that are toward the bottom their load range, the phenomenum behind the idea does not exhibit well, in cold weather it does not show at all.

If I was to run by the 4psi rule, my tyres would be flatter than they already look and many PSI under the recommended minumum cold inflation pressure.
People already comment that my tyres look under inflated when they are in fact inflated to specification after weighing the vehicle.

Believe me I have tried it.....it does not work on my vehicle that proves there is at least 1 exception and thus the "rule" is unreliable.

I know the Copper recomend and publicise this 4 psi rule.....tell me how many other tyre manufacturers ( companies that own factories and have their own R&D facilities) recomend the 4psi rule.

It is my opinion that the 2, 4, 6 psi ( opinion varies) has beeen propogated to placate people uncertain about running their tyres off road, under inflated and looking for some sort of assurance.

The truth is running tyres underinflated IS an uncertain matter and there IS NO clear and relaible way of ensuring that the aired down pressure is " correct" and you are not damaging your tyres.

Almost without exception the major tyre manufacturers ( companies that own factories and have equipment to test tyres) will not even discuss running tyres under inflated, let alone present any guidance or data.

Running tyres underinflated or overloaded regardless of speed WILL reduce the life of the tyre.....the faster you go, the speed of damage ramps up dramaticaly.


Running tyres underinflated is a risk we take....it will remain a risk regardless of where any false assurance comes from.


BUT it is a risk that we manage for a considerable benifit.....If we do not push our luck the tyre will probably wear out or fail otherwise long before the damage we cause every time we run under inflated makes any difference.

As far as highway pressures...there is one and only one reilable source for the correct pressure....load V pressure tables for that tyre.

There is a second reliable and accurate method that IS recommended in the standards manual and by tyre manufacturers.

inflate the tyre correctly from the load V pressure tables.....measure the hub centre height.

Then changing cold inflation pressure to maintain the correct hub centre height, this will pretty accurately maintain air pressure for load.

consider this 4psi rule.

If you look at the load V pressure tables for flotation type tyres in the standards manual
you will see that the steps in pressure are about 4PSI..and those 4psi steps on a 31x10.5R15 tyre increase around about 50Kg per tyre per 4psi.

so ya recon ya 4psi rule is that accurate...I do not think so.

To anybody that recons their 4psi rule works...I chalenge you to go out and work it then compare to the load v prerssure tables for that tyre.

It may be close on some tyres under some loads under some conditions.....but I betya there will be casses where it is way out.

cheers

Hi Bantam.
I will take a manufacturers recommendations over yours.
I am driving a 4WD not a 20 wheel road train.

Does this manufacturer publish a load v pressure table for that tyre...bet they do...somewhere

Even if you cant get it from the manufacturer there will genearlly be a load v pressure table for it in the Standards manual.

Did I say "Standards Manual"...a manual that represents " Technical specifications bassed on engineering principles and approved practices"

Secondly...this manufacturer you are talking about.....do they own factories and have research facilities that test tyres....or are they just a marketing company that has someone else make their tyres for them.

Do Goodyear, Bridgstone, Dunlop, Perilli, Michilin, Maxxis/Chingshin, Yokahama, Toyo, Sumitomo or any of the other manufacturers ( that own factories and reserach facilities), make a wide variety of tyres and have been doing it for a long time, discuss this 2,4,6 psi rule

Do any of the standards documents published in any country...especially the Tyre and Rim Association of Australia - Standards Manual discuss this 2,4,6 psi rule.

OH and BTW...is it a 2 psi rule a 4 psi rule or a 6 psi rule.....if its different for different tyres then where does the demarkation lie.
which tyre do you use what pressure difference for.
is it bassed on air volume, tyre size or construction.
Where is this documented.

It does not matter if it is childs bicycle or a oversized mine haul truck with 12 foot tall tyres the principles of load V pressure remains the same and works the same.....the results are the same....the consequences are the same
the only difference is the size of the numbers.

BTW most truck tyres are run with more safety margin than many passenger vehicle tyres especially tyres on trailers and caravans.

Most trucks unless it is a front tyre, if a tyre fails there is a mate right next door to bear the load and if it is a heavy truck there are at least another 3 tyres holding up that corner of the vehicle.

Load V pressure tables are accurate....surprisingly so.....and reliable......no fiddling or experementation.....weigh the vehicle.....consult the table.. inflate the tyres........if you want to account for change of loading buy a ruler, and work off hub centre height....this is detailed in the standards manual...is approved practice.....and is surprisingly accurate and requires no fiddle or experementation

seriously think about it

cheers

Bantam
If I were running a trucking company I would probably go to that trouble.
But I have a 4WD with varying loads and it’s impartial for me to go weighing or measuring the vehicle when loads or road conditions change. My tyres on the caravan and 4WD are both light truck construction and are well within their load limits.
I am quite capable of judging the temperature of an overheated tire by hand. That in conjunction with the 6 PSI rule suits me ideally.

Most trucking companies don't go to that trouble. they simply inflate the tyres to the maximum load the vehicle is registered for or the manufacturer recommended pressure
.
And because of the way trucks are designed, specified and regulated it is pretty consistent.....typically arround 90psi ish for duals and arround 120 ish for singles.

Trucks by the way have a very narrow choice of tyres and they are very rarely running tyres substantially different to those they came out of the factory with....so the whole thing is very much simpler


To use load v pressure tables, in conjunction with hub centre height.

You don't have to go weighing the vehicle over and over...you weigh it once.

And making a striaght forward hub centre measurement is well and truly simpler and easier than the whole rigmarole of this 2,4,6 or whatever PIS rule...there is no need to drive the vehicle, there is no need to repeatedly measure tyre pressure.
The tyres can be correctly inflated for an unknown load, by use of hub centre height before the vehicle even rolls a wheel.

If you think you are capable of judging tyre temperature by hand you ARE dreaming.
What IS a normal tyre temperature, what is the maximum permissable tyre temperature, how hot does a tyre have to be before you burn you hand.

I have seen competitive vehicles with brake disks glowing orange and the rims so hot you would burn yourself if you touched them...How hot is the tyre?

Besides as we have already established tyre temperature is pretty much an irrelivency and a very unreliable indicator.

Cold inflation pressure in the tyre is a very very reiable that is why the tyre and car manufacturers specify it and why there endless tables for it in the standards manuals, that is why most load engineering in tyres revolves around cold inflation pressure.........and hub centre height will track air pressure pretty damn accurately.

I think people are over thinking this whole thing.

Tyre inflation COLD from load V pressure tables is very simple, straight forward and relaible...if you have this right.....very little else will matter.

cheers

Bantam this is getting to be a bit of a novel.
I think most people will have got sick of it by now – thanks for your information.

UM....you are lowering air pressures on a hot tyre.....sorry mate this is specificaly and universlally not recommended.

The pressures specified by the tyre manufactures and the standards manuals are" minumim cold inflation pressures"

What makes you think they are getting too high?

It is a normal thing for air pressure in tyres to increase when run loaded......if the pressures increase considerably the tyres where not pumped up enough to start with.

As for measuring 1psi over at all times...serrioulsy you think they are that accurate....I doubt it...especially after 6 years.

cheers

My tyre monitors are constantly telling me the pressures so I know that they are increasing. I am only talking around a 2 psi drop needed on the rear.
Towing I like to keep them at a mazimum of 42 psi....the recommended pressure for my tyres is 38 cold as advised by two tyre dealers, due to side wall strength. I get great kilometres from my tyres so this process works for me. I will not go into the complexities with modern vehicles and ABS sensors with significanlty different tyre pressures from front to rear.....suffice to say that they need to be close. I could increase the front to compensate, but happy with the 4 psi difference from cold to hot.
Doubt away.....my tyre dogs are that accurate. I check with a quality gauge when I adjust the pressures on the ground and they are always 1 psi over....seriously.
Brett....

OH do tell about these complexities.

Above all the most important thing is to have the tyre correctly inflated for the load carried.

What possible effect could different tyre pressures have on ABS.....when you consider if all the tyres are corretly inflated all wheels should have the same hub centre height and the same rolling diameter.

As for tyre dealers......Oh please....what do the load V pressure tables from the manufacturer say.

cheers

As I said....works for me.

Agreed about the correct pressure for the load....I am anal about pressures hence why I monitor them continously. You have your own method that works for you too....i just prefer to know sooner if there is an issue, as it saves a packet.

Higher pressures will give slightly higher rolling diameter and ABS Sensors DO pick up on this. Seen it happen to two different brands. Sends their systems into a frienzy. Match the pressures the faults go away. Simple as that.

As to tyre dealers....your opinion is yours....everyone has one. I suppose tyre dealers in the bush who have a stack of the same brand of tyres out the back that have fallen to pieces on roads in their area...what would they know about brands and pressures. Someone from the city always knows more as we often see on Exploroz.

Brett....

There you go you have disproved your own argument.

What matters to the ABS system is the rolling diameter.

If the rear tyres are more heavily loaded than the front they will require more pressure to maintain the same rolling diameter.

If you are concerned about upsetting your ABS....I'd be out measuring my hub center height...that will ensure the same rolling diameter.

As for the recomendations of tyre shops......truth to tell in over 30 years of driving I have never come away from a tyre shop with the tyres correcty inflated....most of these guys can not even read a tyre plackard when inflating factory standard tyres.

You can however rely on what it printed on the tyre plackard, the tyre manufacturers published load v pressure tables and those published in the standards manuals.
This is not a matter of opinion, this is a matter of specifiication.
Contrary to what most tyre fitters believe.

cheers