jadatis
Member
- Joined
- October 15, 2009
- Messages
- 30
- Reaction score
- 2
- Year, Model & Trim Level
- 1999 Seat Alhambra TDI
I live in Holland, so excuse me for mis-spellings and the use of wrong technical terms.
Since 2007 I have been busy with calculating and re-calculating tire-pressure , with use of the formula of the ETRTO ( European Tire and Rimm Technical Organisation). This is the formula European car-manufacturers use to determine the advice-pressures wich can be found on a Plackard on the car somewhere. Learned myself Excell to make spreadsheets for tire-pressure.
Found out a way to calculate back the loads they filled in for normal-use-advice-pressure, wich nowadays is seldomly given, they only give advice for what I call Heavy use and/or Vacation use with tow-bar load.
Because I want the normal use to be re-introduced I made a spreadsheet to determine the axle loads yourselves, but have not translated that yet because there is a lot of Dutch text in it. Can do it when more say that it is usefull.
In my search for information about tires and tire-pressure, I came by the Ford Explorer roll-over accidents, mostly courced bij tire-blewouts.
Also discovered that the TRA ( Tire and Rimm Association) uses a diferent formula then the ETRTO . TRA comes to lower pressures with the same load.
I concluded that the formula is so made that the tire gets the same temperature with a relatively low load on it, then with the maximum load on it.
Lower pressure at the same load, leads to higher temperatures of the tire.
Last spreadsheet is for re-calculating tire-pressure ( English Tyre) when non-standard tires are put on the car. Translated it to Englisch, and placed it on my public map of Skydrive from Hotmail.
http://cid-a526e0eee092e6dc.skydrive.live.com/browse.aspx/.Public/Recalculating tyre-pressure
In this map always take the newest spreadsheet, and there are examples placed.
needed from car
1 maximum Axle loads front and rear ( on metalish plate under motorhood or one of the door styles)
2 maximum speed of car ( in manual or estimated)
3 The advice pressures on the plackard somewhere on the car or manual , that are meant for the specific car. ( can do without if normal advice does not interest you)
4 If more then 2 degrees , the camber-angle ( When tires are placed on the axle so/-\) mostly not above 2 so not needed.
from tires example 195/65 R15 91T
1 maximum load in KG ,LBS or the Load index ( in example loadindex 91 stands for max. 615kg )
2 reference pressure or kind of tire. When there is on the tire-side-wall "At 240 kPa" or "at35 psi"then that always is the reference pressure, but for normal car tires in america that is almost always 35 psi. reinforced XL 280 kPa . so not the maximum pressure of tire.
3 Letter that stands for the maximum speed of tire ( in example T stands for up to 190km/h)
search for these data and fill in the spreadsheet, and see what the diferences are. Then draw your own conclusions.
Mind that in some cases the ETRTO formula comes to lower pressure ( mostly at front) . That is because with the TRA formula they have to stop at 26 psi, and the ETRTO goes down to 21 psi. To my opinion this lower pressure then is still a good one , though it looks a bit scarry .
If you have questions or find bugs in the spreadsheet , tell it here or in a Personal message.
Since 2007 I have been busy with calculating and re-calculating tire-pressure , with use of the formula of the ETRTO ( European Tire and Rimm Technical Organisation). This is the formula European car-manufacturers use to determine the advice-pressures wich can be found on a Plackard on the car somewhere. Learned myself Excell to make spreadsheets for tire-pressure.
Found out a way to calculate back the loads they filled in for normal-use-advice-pressure, wich nowadays is seldomly given, they only give advice for what I call Heavy use and/or Vacation use with tow-bar load.
Because I want the normal use to be re-introduced I made a spreadsheet to determine the axle loads yourselves, but have not translated that yet because there is a lot of Dutch text in it. Can do it when more say that it is usefull.
In my search for information about tires and tire-pressure, I came by the Ford Explorer roll-over accidents, mostly courced bij tire-blewouts.
Also discovered that the TRA ( Tire and Rimm Association) uses a diferent formula then the ETRTO . TRA comes to lower pressures with the same load.
I concluded that the formula is so made that the tire gets the same temperature with a relatively low load on it, then with the maximum load on it.
Lower pressure at the same load, leads to higher temperatures of the tire.
Last spreadsheet is for re-calculating tire-pressure ( English Tyre) when non-standard tires are put on the car. Translated it to Englisch, and placed it on my public map of Skydrive from Hotmail.
http://cid-a526e0eee092e6dc.skydrive.live.com/browse.aspx/.Public/Recalculating tyre-pressure
In this map always take the newest spreadsheet, and there are examples placed.
needed from car
1 maximum Axle loads front and rear ( on metalish plate under motorhood or one of the door styles)
2 maximum speed of car ( in manual or estimated)
3 The advice pressures on the plackard somewhere on the car or manual , that are meant for the specific car. ( can do without if normal advice does not interest you)
4 If more then 2 degrees , the camber-angle ( When tires are placed on the axle so/-\) mostly not above 2 so not needed.
from tires example 195/65 R15 91T
1 maximum load in KG ,LBS or the Load index ( in example loadindex 91 stands for max. 615kg )
2 reference pressure or kind of tire. When there is on the tire-side-wall "At 240 kPa" or "at35 psi"then that always is the reference pressure, but for normal car tires in america that is almost always 35 psi. reinforced XL 280 kPa . so not the maximum pressure of tire.
3 Letter that stands for the maximum speed of tire ( in example T stands for up to 190km/h)
search for these data and fill in the spreadsheet, and see what the diferences are. Then draw your own conclusions.
Mind that in some cases the ETRTO formula comes to lower pressure ( mostly at front) . That is because with the TRA formula they have to stop at 26 psi, and the ETRTO goes down to 21 psi. To my opinion this lower pressure then is still a good one , though it looks a bit scarry .
If you have questions or find bugs in the spreadsheet , tell it here or in a Personal message.
