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2003 Lexus ES 300, 3439 pounds weight, 61 to 39 front rear weight ratio. Factory wheel/tire size is 215 60 R16. The door sticker says 29 psi both front and back. My new wheel/tire size is 225 45 R18. What should my front and rear psi be?

Thanks very much. Tire pressure is confusing for me.

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After running 2 calculations mentally pertaining to the width and contact patch. I would recommend between 26 to 28 PSI. Try this range and let the one which feels normal remain. If I had to bet, I would lock it on 27 PSI. But you be the judge of your comfort. And do monitor the sidewall.

*I will await results from other senior members, until then delay my initial recommendation.

Conventional way would require you to add 33 to 36 PSI on this new setup. In my experience it gives more of a center patch lock, high speed cornering would cause moderate slip.

  • You're suggesting to run a lower than stock air pressure in the tires? You realize this will cause the outside tread to wear out faster than the inside? With a lower profile tire, the last thing you want to do is run a lower tire pressure. If you were going with a larger tire, then you'd think about lowering the tire pressure. This is very poor advice. – Pᴀᴜʟsᴛᴇʀ2 Aug 6 '18 at 22:49
  • Please run the calculation. Overall circumference is lacking by half inch, sidewall height is lacking an inch, and the width has been increased by half an inch. So the contact patch can do with adequate air. Super inflation to 33 or 34 PSI will cause tire noise and add extra weight. Gone are the days when we used regular air (N2 was 68 to 75%), in this new era we use N2 at 96 to 99%. And these new tires are either run flat or descent radials which have stronger reinforced and well supported sidewalls. Only on race tracks at high speeds is it necessary to compensate for the temperature gain. – Numair Aidroos Aug 7 '18 at 6:51
  • Brother, I know you know very well about the industry. So please share your thoughts. – Numair Aidroos Aug 7 '18 at 6:52
  • Please read Bob Cross's answer on the Question I closed this after. – Pᴀᴜʟsᴛᴇʀ2 Aug 7 '18 at 14:43
  • I just read through. He agrees with the contact patch theory. But does point out at higher speed low PSI will damage the wheel when met with a pothole. – Numair Aidroos Aug 8 '18 at 5:45

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