jadatis

Mayby your tire-pressure advice is to high for the way you use the car. I kept my self busy with that and found out a lot about it and more about tires. Bridgestone had troubles in the past on the Ford- Explorer and mayby now is keeping extra high pressures. To get a more balanced answer I need to know the exact sises of the tires and the maximum load and type of tires of the Michelins and bridgestone. Read it from the sidewall like this " 235/50 ZR 19 92 W XL Then The 92 means loadindex 92 can look it up in a list to get the maximum load. W means speedcode up to 270km/??m/h and XL means extraload/reinforced. The last if you dont see it its a normal car tire called P-tire in America. From the car the GAWR's ( gross axle weight rating) and GVWR ( gross vehicle weight rating). and if you have it empty weight and the built ( motor in front fronwheeldrive for the estimation of the load division) and how you mostly load it ( persons and load). If I have all that , I can give you the lowest pressure at wich the tires are save, and with the most comfort and gripp. Lower gives even more comfort and gripp but at a sertain moment your tires blow and you have an accident with damage and mayby injuries.

Found this topic googling for "tire-pressure" because I have been busy with calculating that since 2007 of and on, with use of the formula that the European tyre-makers use and since 2005 also the American for P-tires and Extra load, and prooved to give save answers for the tires. Dont have a lexus,so wont introduce myself in a seperate topic. Live in Holland and made spreadsheets for it, and translated a few to English to go worldwide with it. https://skydrive.live.com/?cid=a526e0eee092e6dc#cid=A526E0EEE092E6DC&id=A526E0EEE092E6DC%21128 This link leads to my public map of skydrive, that belongs to my hotmailcom adress with the same username as here ( combine it yourselves to contact me, spamm machines cant this way) To use a spreadsheet , best open it with Excell or compatible programm ( open office calc for instance) , to use it fully , in the browser wont work for most of them , because it cant handle some things I use in them. To download , click on the line , but not on the name of it, then in the right barr at download. Then you can check it for virussus firs if you want. Now a direct answer. The 35 psi is , as it is called in the formulasheet, the reference-pressure, so the cold pressure at wich the maximum load of the tire may be bare, up to maximum speed of tire, or if lower ( sertainly here the case) 99m/h. This is not the maximum cold pressure of the tire, as they put it on modern tires of 44 to 50 psi. The extra is used for higher speed and alignment ( camber angle tires like this/-\ instead of this |-| on the axle). The calculation is meanth to give the same deflection as for referencepressure with maximum load on it. For Extra load tires ( reinforced, XL all the same) the Ref-pressure ( further Pr) is 41 psi in America. European tires mostly normal 36 psi, XL 42 psi. So tire pressure advice is all about load on the tire, and a bit about speed and alighnment ( alighnment seldomly needed). For the loads the American tire makers use the Gross Axle Weight Ratings ( GAWR) to be save for every situation. But in Europe before 2000 also a normal use for 3 persons and a little load was given, wich gave for frontwheeldrive cars ( motor always in front so front more weight) a higher advice-pressure then behind. After 2000 , to my opinion as overreaction to the Ford/Firestone-affaire, this is not given anymore, for normal use now the GAWR's are used in the formula, heavy use behind even maximum of tire sometimes or Pr. So what you have to do is calculate the pressure with one of my spreadsheets , to see if you can go lower savely . But for low aspect ratio tires ( the 30 in fi 225/30 R 18 91W XL) I have my doubts if the maximum load is calculated right , I think to high. That maximum load is also calculated , but with a much more complex formula. So if you have those tires, keep to the high side, wich is bad for gripp and comfort, but a blewing tire gives more damage. The sidewalls are the delicate parts in this, the tread can have more, though it can come loos by the to much deflection of the sidewalls. So before you go experimenting with lower pressure, first use my spreadsheets and information on my skydrive, you can navigate over it like in a forum. Greatings from Holland Peter