Tire Pressure

[mikeandd]

Hey gang, I just bought a 91 LS400 with '98 wheels and 225-60-16 tires. What air presure should I run? Would it be the same as a '93 and up, what ever that is. Thanks for the help.

Mike

[sprk408]

Normal 30psi, Max 32psi.

[Lexusing]

Hey Pal,

The tire pressure for my 96 LS400 is locate in the glove box...check yours. Good luck.

[mikeandd]

Thanks for the repies. Since I don't have the original 15" wheels and tires on my '91 what's posted in the glove box may not be correct. The 16" wheels and 225/60/16 tires may require a different pressure. I will go with 30 unless someone tells me different. Thanks for your help.

Mike

[wrd]

I keep 33/34#'s in my 97. The Michelin MXV4+'s have 78,000 miles on them and still look good.

[thewzdoc]

Look on the side of the tire, it will tell you the max PSI. If you want good mileage then max the psi. If you want a softer ride then take a few #’s out.

[Lexusing]

<_< Thewzdoc....not sure if I agree with you there.....the pressue listed on the tire is recommend for the tire by the tire manufacture....car owner should go with what is recommend by the auto maker not the tire manufacture. Please correct me if I am wrong....

[VBdenny]

I run 34 PSI in all tires. Most manufacturers the optimum tire pressure, but it is a matter of preferrence as they aren't always right. For example, Ford recommended a tire pressure for Explorers and it was to low which caused the tires to heat up and blow. They they flipped over and people got kilt. Higher pressures give a harsher ride, but it's safer, the tires last longer, and you get better milage. Most new tires all can take 35 PSI or more.

[SRK]

Lexusing is correct. The max pressure listed on the sidewall is that which is used to achieve the maximum load rating of the tire, which is far above the loading the tire sees one the car. The correct pressure is that listed by the car manufacturer, and in this case 32 PSI should be fine.

I installed a 215/70-15 on my '92, one of the optional sizes Lexus suggests to replace the stock 205/75-15. I run them at 32-33 and the car rides and handles very well. Lexus advises 36 in the rear tires for continuous high speed duty, and 30 in the fronts, 30 all round for city driving, at least that's what the tag claims in the glovebox.

[id1]

I have a 95 LS400 and the owners manual recommends FRONT/REAR tire pressue of 29psi for 4 adults and 32psi for full load (900 lb). The tire size is P225 / 60R16 97V: I have the same tires and I tried 29/30psi which provide comfortable cushy ride. I tried 32psi without full load and the ride becomes harsh.

I drive around suburban CT and the roads are generally devoid of pot holes.

[thewzdoc]

<_< Thewzdoc....not sure if I agree with you there.....the pressue listed on the tire is recommend for the tire by the tire manufacture....car owner should go with what is recommend by the auto maker not the tire manufacture. Please correct me if I am wrong....

If you want max gas mileage go with the max PSI on the tires if you want the engineered comfort level for the LS400 then use the indicated PSI in the owner’s manual.

I've always used the MAX PSI on the tire, you can feel the road through the car a bit but the higher mileage is worth it.

[basher_boy]

The tire pressure in the glovebox is the pressure that is required for the original equipment tire on that car. This pressure is the preassure which results in even wear of the tire at that load rating. There are almost always two pressures, one at "normal" load, and the other at high speed/max load. As both the speed and the weight on the tires goes up the tires heat up more and the structure of the tire becomes softer, requiring a higher pressure.

The main reason that people increase the tire size is to increase the contact patch and have more grip. This would neccesitate a lowereing of the tire pressure. If the car had 500 lbs per tire and the tire pressure is 32 psi, that the contact patch would be about 15 square inches. If you want a larger contact patch (i.e. more grip) than you must decrease the tire pressure. At 30 psi the car will have a 16.6 square inches on the road.

Now every tire and every car has an optimum preassure and contact patch etc. for a specific condition. When I used to auto cross with grossly wide tires I used an inferred themometer to measure the temperature of the tire across the tire to find the pressure that gave even heating of the tire. This preassure was very closs to where the car handled the best. Bassically this was the preassure that wore the tire evenly at the average load that was applied at that run. Ususally this was quite a bit higer than the "street" preassure. This is not to say that the pressure is wrong on the car (that is the pressure that allows even wear of the tire at the load indicated.

Now as an aside: If your car is oversteering, you have too much preassure in your front tires realative to your rear and just the oppisite if you are having understeer.

This does not answer the original question, but should help pepople understant that there is no one right tire pressure. It is dependent, on weight, speed, tire size, lateral acceleration, etc.

[basher_boy]

there is however a minimum safe tire preassure (ala ford explorer), and a safe maximum preassure (on the sidewall).

[thewzdoc]

there is however a minimum safe tire preassure (ala ford explorer), and a safe maximum preassure (on the sidewall).

Right and the sidewall MAX PSI is referring to the cold pressure. If you inflate the tire to 35 PSI cold it may be 40 or 41 PSI when hot. The tire manufacturers engineer the tires with this in mind.