What Tire Pressure And To What Effect?

[Jetlagged]

Only have had Lexus about 6 weeks. Had some minor things taken care of at dealer about 2 weeks ago. Just checked TP at cold pressure, and all were 35.5 PSI, spare was 36. Only about an ambient temperature spread of about 10 degrees between that time. Which should only make for maybe a 2 psi pressure increase at most. So I assume they set it that high. Is this standard? Door decal says 30 psi, manual up to 32 psi if I'm hitting the autobon. Unlikely. I dropped it down to 34 psi for compromise for now. Checked it with two different quality gauges, one digital and one dial. Both read the same. I'll be traveling to Iowa in a few months, with a loaded car. Would like to get it right. Has factory bridgestones. What pressure is everyone running. Did a quick search here reading titles, seems mostly about TPMS and aftermarket. I want the quite comfortable ES ride, with good fuel economy and minimal wear. So what's the best pressure?

[SW03ES]

I run mine at 30. You'll notice a HUGE difference in the ride between 34 and 30, its like driving two different cars. Drawback is higher pressure means better economy, and longer tire wear, but like you I bought the Lexus for the rode...so I run 30.

[jadatis]

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

[SW03ES]

All of thats well and good...

...but the manufacturer of the vehicle recommends a pressure of 30PSi. So thats what I run. I've put over 200,000 miles on Lexus ES sedans, and over 200,000 miles on Lexus LS sedans and I can tell you with authority that the cars ride the best under the factory recommended PSI and increasing PSI rapidly diminishes ride comfort.

[pj8708]

Unless I missed something in reading your missive, there is a tremendous difference in ride and comort based on the specific tire, not just brrand, Within any tire manufactuers offerings there are dozens of selections that may work on say a 2010 ES350 , but on my personal car I have found only one that gives me the comfort, and specificaly the smooth ride that I demand.. The tire is Michelin Primacy. I use 32 psi.

Paul

[Gapwedge]

All of thats well and good...

...but the manufacturer of the vehicle recommends a pressure of 30PSi. So thats what I run. I've put over 200,000 miles on Lexus ES sedans, and over 200,000 miles on Lexus LS sedans and I can tell you with authority that the cars ride the best under the factory recommended PSI and increasing PSI rapidly diminishes ride comfort.

What tires do you run @ 30 psi? Getting some Michelin Primacy's installed Monday. Just curious. Thanks.

[LexBob2]

When in doubt go with the mfgrs recommendation. It's the best starting point. You can go up or down a couple of pounds later to suit your prefrences.

[Gapwedge]

When in doubt go with the mfgrs recommendation. It's the best starting point. You can go up or down a couple of pounds later to suit your prefrences.

LexBob,

That is my intension. However, being new here I was curious the rubber SW03ES was riding on.

[pbxcomm]

There's some very informative info here..

So, most of the gauges out there are 2 to 3 PSI off and usually on the low end.. For instance, my "Digital" Gauge reads 30 PSI and the Schrader Master Gauge reads 33 PSI. The only gauge I would trust is the "PCL". The TPMS are surprisingly accurate within .5 PSI of the Master gauge. That's said my GS 350 sweet spot is a bit over 32 PSI (32.3) according to the TPMS, the PSI recommendation is 33 PSI. This is cold tires that have sat overnight.