What tyre pressure? Quick one I hope!
Discussion
Needed pressure is all about weight on tyre, and maximum speed used.
Goal is that not any part of tyre reaches a temperature at wich it hardens, and beginning crackes. Once cracked, the tire is lost, and mechanical forces crack it further, until mayby only after 3 years that far, that it blows.
I once got hold of the official european formula and system, to calculate pressure for load and speed, and went running with it.
Now call myself " pigheaded Dutch selfdeclared tyrepressure- specialist"
So if you provide the data I will calculate for you.
Need from tyres next, and can be read from sidewall.
1. Maximum load or loadindex.
2 kind of tyre to determine the reference-pressure. Do you see XL/ extraload/ reinforced then reference pressure is 290kPa/42 psi , otherwise its a standard load normal cartyre, with Pr 250kPa/ 36 psi.
3. Speedcode, not verry important , because mostly Q or higher, for wich maxload is given for Pr and 160kmph/99mph.
From car , best seperate wheelweights, 2nd best axleweights, in lack of that Max permissable axle weights,.
Also max speed you use, and wont go over for even a minute.
Collect this, and I will calculate, and show how I come to it.
Determining the weights is the hardest part in it all, and your responcibility.
Goal is that not any part of tyre reaches a temperature at wich it hardens, and beginning crackes. Once cracked, the tire is lost, and mechanical forces crack it further, until mayby only after 3 years that far, that it blows.
I once got hold of the official european formula and system, to calculate pressure for load and speed, and went running with it.
Now call myself " pigheaded Dutch selfdeclared tyrepressure- specialist"
So if you provide the data I will calculate for you.
Need from tyres next, and can be read from sidewall.
1. Maximum load or loadindex.
2 kind of tyre to determine the reference-pressure. Do you see XL/ extraload/ reinforced then reference pressure is 290kPa/42 psi , otherwise its a standard load normal cartyre, with Pr 250kPa/ 36 psi.
3. Speedcode, not verry important , because mostly Q or higher, for wich maxload is given for Pr and 160kmph/99mph.
From car , best seperate wheelweights, 2nd best axleweights, in lack of that Max permissable axle weights,.
Also max speed you use, and wont go over for even a minute.
Collect this, and I will calculate, and show how I come to it.
Determining the weights is the hardest part in it all, and your responcibility.
Edited by Jadatis on Monday 25th May 23:07
Jadatis said:
Needed pressure is all about weight on tyre, and maximum speed used.
Goal is that not any part of tyre reaches a temperature at wich it hardens, and beginning crackes. Once cracked, the tire is lost, and mechanical forces crack it further, until mayby only after 3 years that far, that it blows.
I once got hold of the official european formula and system, to calculate pressure for load and speed, and went running with it.
Now call myself " pigheaded Dutch selfdeclared tyrepressure- specialist"
Sovif yoy provide the data I will calculate for you.
Need from tyres next, and can be read from sidewall.
1. Maximum load or loadindex.
2 kind of tyre to determine the reference-pressure. Do you see XL/ extraload/ reinforced then reference pressure is 290kPa/42 psi , otherwise its a standard load normal cartyre, with Pr 250kPa/ 36 psi.
3. Speedcode, not verry important , because mostly Q or higher, for wich maxloadvis given for Pr and 160kmph/99mph.
From car , best seperate wheelweights, 1nd best axleweights, in lack of that Max permissable axle weights,.
Also max speed you use, and wont go over for even a minute.
Collect this, and I will calculate, and show how I come to it.
Determining the weights is the hardest part in it all, and your responcibility.
Now that is what you call an answer...Goal is that not any part of tyre reaches a temperature at wich it hardens, and beginning crackes. Once cracked, the tire is lost, and mechanical forces crack it further, until mayby only after 3 years that far, that it blows.
I once got hold of the official european formula and system, to calculate pressure for load and speed, and went running with it.
Now call myself " pigheaded Dutch selfdeclared tyrepressure- specialist"
Sovif yoy provide the data I will calculate for you.
Need from tyres next, and can be read from sidewall.
1. Maximum load or loadindex.
2 kind of tyre to determine the reference-pressure. Do you see XL/ extraload/ reinforced then reference pressure is 290kPa/42 psi , otherwise its a standard load normal cartyre, with Pr 250kPa/ 36 psi.
3. Speedcode, not verry important , because mostly Q or higher, for wich maxloadvis given for Pr and 160kmph/99mph.
From car , best seperate wheelweights, 1nd best axleweights, in lack of that Max permissable axle weights,.
Also max speed you use, and wont go over for even a minute.
Collect this, and I will calculate, and show how I come to it.
Determining the weights is the hardest part in it all, and your responcibility.
I'll try and get all of that to you tomorrow. I had assumed there was a formula to calculate this stuff rather than trial and error.
You daubt the tyres to be streched.
I once asked a tyremaker how it works and made calculator for it .
For 8.5 inch rimm , smallest tyre within standards 215mm, ideal 240mm, widest 260mm.
The other way around .
225 section width.
Smallest rimm 7.35inch, measure rimm is ideal 7.97inch ( 8 inch) , widest rimm 8.86 inch.
So your combination is within standards, so pressure advice given also can be calculated the normal way.
You have to round yourselfes.
I once asked a tyremaker how it works and made calculator for it .
For 8.5 inch rimm , smallest tyre within standards 215mm, ideal 240mm, widest 260mm.
The other way around .
225 section width.
Smallest rimm 7.35inch, measure rimm is ideal 7.97inch ( 8 inch) , widest rimm 8.86 inch.
So your combination is within standards, so pressure advice given also can be calculated the normal way.
You have to round yourselfes.
Googled your sise 225/40R18 , and only found XL 92 W or Y . Means maxload 630kg AT 42PSI upto 160kmph/99mph. Official system says W upto 190kmph and Y 220kmph, and for higher speed the 42psi reference-pressure has to be highened up before putting it in the official formula.
My system is upto 160kmph also for W and Y, and lowering the loadindex by 1 step, for every 10kmph/ 6.5mph?, befire putting it in my determined formula, that comes to higher pressure.
But check this on siddwall. And now only weights and speed needed
My system is upto 160kmph also for W and Y, and lowering the loadindex by 1 step, for every 10kmph/ 6.5mph?, befire putting it in my determined formula, that comes to higher pressure.
But check this on siddwall. And now only weights and speed needed
Righty,
I can't tell you the weight over each axle (will be able to soon when the car is setup on coilovers, not for racing hah).
The door card says 33F and 29R, the tyre says max. pres 50psi, max. load 630kg. The tyres are falken Ziex ZE914 ecorun, extra load. The plate under the bonnet lists 1 weight of 1085 kg which I find hard to believe.
I can't tell you the weight over each axle (will be able to soon when the car is setup on coilovers, not for racing hah).
The door card says 33F and 29R, the tyre says max. pres 50psi, max. load 630kg. The tyres are falken Ziex ZE914 ecorun, extra load. The plate under the bonnet lists 1 weight of 1085 kg which I find hard to believe.
VIN plate of my audi A3, no diesel says.
MPVW 1650 KG
Axle 1 is front MPAW 875 KG
Axle 2 is rear 925 kg.
But its an old one from 1999.
A Diesel is a bit heaviër.
The 1050kg you give, is probably the empty weight.
But in your country ( Britain??) , also such a VIN plate, must be on the car, I think.
For normal use ,I could estimate thevaxleweights, if you give empty weight, and the way you load it( persons and front or rear seats, and loading and place) .
MPVW 1650 KG
Axle 1 is front MPAW 875 KG
Axle 2 is rear 925 kg.
But its an old one from 1999.
A Diesel is a bit heaviër.
The 1050kg you give, is probably the empty weight.
But in your country ( Britain??) , also such a VIN plate, must be on the car, I think.
For normal use ,I could estimate thevaxleweights, if you give empty weight, and the way you load it( persons and front or rear seats, and loading and place) .
Then gives Fr 40 psi and rear 36 psi.
Then you can drive with axles max allowed loaded 99mph constant, wuthiut overheating any tyre.
Even 10 % first added for little overloading, and unequall weight R/L.
That front has higher max axleload is because of the Diesel motor , wuch is heaviër then my benzine- motor( or what you call it)
If you now give empty weight, and way you load it, it will give lower pressures, and then that once fully loaded, you can keep lower speed. For 130kmph max is 81mph, 36F and 32R is enaugh fully loaded with all the reserves.
Then you can drive with axles max allowed loaded 99mph constant, wuthiut overheating any tyre.
Even 10 % first added for little overloading, and unequall weight R/L.
That front has higher max axleload is because of the Diesel motor , wuch is heaviër then my benzine- motor( or what you call it)
If you now give empty weight, and way you load it, it will give lower pressures, and then that once fully loaded, you can keep lower speed. For 130kmph max is 81mph, 36F and 32R is enaugh fully loaded with all the reserves.
Jadatis said:
Then gives Fr 40 psi and rear 36 psi.
Then you can drive with axles max allowed loaded 99mph constant, wuthiut overheating any tyre.
Even 10 % first added for little overloading, and unequall weight R/L.
That front has higher max axleload is because of the Diesel motor , wuch is heaviër then my benzine- motor( or what you call it)
If you now give empty weight, and way you load it, it will give lower pressures, and then that once fully loaded, you can keep lower speed. For 130kmph max is 81mph, 36F and 32R is enaugh fully loaded with all the reserves.
When you say fully loaded? The car 70% of the time is just me in it, maybe a passenger 30% and rarely anyone in the back. Speed wise, the car isn't really capable of much over 90mph and mostly driven around 70-80mph tops on the motorway.Then you can drive with axles max allowed loaded 99mph constant, wuthiut overheating any tyre.
Even 10 % first added for little overloading, and unequall weight R/L.
That front has higher max axleload is because of the Diesel motor , wuch is heaviër then my benzine- motor( or what you call it)
If you now give empty weight, and way you load it, it will give lower pressures, and then that once fully loaded, you can keep lower speed. For 130kmph max is 81mph, 36F and 32R is enaugh fully loaded with all the reserves.
I just want to understand what tyre pressures should be is all, I don't like vague!I searched on Dutch " marktplaats" site for Audi A3 tdi, and from picture , I took the licenceplate number.
With that I searched on RDW site for weights.
1335kg empty weight and MPVW 1920 kg, make it 1350kg.
So in the nabourhood of your specifications.
Once read empty front 200kg more heavy then rear, would mean Fr 775kg and Rr 575 kg. Mayby with Diesel even 300 kg difference.
Yust to point out estimating is dangerous.
But we go on 2 persons in front seats of each 75 kg ( correct me if wrong) . Person sitting in car has gravetypoint about at his/ hers/ its belly button, and so a bit more to front axle then rear , so again estimated( ooh dangerous) 80 kg to front and 70 kg to back.
Gives front 775+80= 855kg and rear 575+70=645 kg.
Filled that in my calculator for 160 kmph/99mph. This gives max reserve with still acceptable comfort and gripp.
Gave Fr 31 psi Rr 23 psi.
Bumping of frontwheels you notice in steeringwheel, rear to hard pumped is lesser noticed in comfort.
And on highway comfort is better, so draw your own conclusions.
I can imagine you think 23 psi scary.
In the former milenium advice was given for 3 persons and a little load, and even as low as 21 psi was normal.
If you mail me at my hotmail.com adres with same username as here ( jadatis) I can send you the filled in spreadsheet, and the official formula from page 14 of standards manual 2007 of ETRTO, and more . Cripted my mailadres to prevent spamm, combine yourselves. And ofcource this also counts for others here who are interested.
Also in England I think they write that 50% uses to low pressure, but reference they use is what the carmaker advices, and that is pretty high nowadays. Only for safety , you now see, mayby only 10 to 20% to low.
The higher advices after about 2000 are for responcebility reasons, carmaker can be hold responcible to if accidents happen related to pressure. I think the Ford/ Firestone affaire in America has had a large inpact on that, search for it.
The lower pressures will give more fuell-consumption.
With that I searched on RDW site for weights.
1335kg empty weight and MPVW 1920 kg, make it 1350kg.
So in the nabourhood of your specifications.
Once read empty front 200kg more heavy then rear, would mean Fr 775kg and Rr 575 kg. Mayby with Diesel even 300 kg difference.
Yust to point out estimating is dangerous.
But we go on 2 persons in front seats of each 75 kg ( correct me if wrong) . Person sitting in car has gravetypoint about at his/ hers/ its belly button, and so a bit more to front axle then rear , so again estimated( ooh dangerous) 80 kg to front and 70 kg to back.
Gives front 775+80= 855kg and rear 575+70=645 kg.
Filled that in my calculator for 160 kmph/99mph. This gives max reserve with still acceptable comfort and gripp.
Gave Fr 31 psi Rr 23 psi.
Bumping of frontwheels you notice in steeringwheel, rear to hard pumped is lesser noticed in comfort.
And on highway comfort is better, so draw your own conclusions.
I can imagine you think 23 psi scary.
In the former milenium advice was given for 3 persons and a little load, and even as low as 21 psi was normal.
If you mail me at my hotmail.com adres with same username as here ( jadatis) I can send you the filled in spreadsheet, and the official formula from page 14 of standards manual 2007 of ETRTO, and more . Cripted my mailadres to prevent spamm, combine yourselves. And ofcource this also counts for others here who are interested.
Also in England I think they write that 50% uses to low pressure, but reference they use is what the carmaker advices, and that is pretty high nowadays. Only for safety , you now see, mayby only 10 to 20% to low.
The higher advices after about 2000 are for responcebility reasons, carmaker can be hold responcible to if accidents happen related to pressure. I think the Ford/ Firestone affaire in America has had a large inpact on that, search for it.
The lower pressures will give more fuell-consumption.
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