tire pressure

What is the best tire inflation pressure for 2007 RX350 with Michelin 18 inch tires?

Although the door stickers say 30PSI, dealer says to put in at least 35PSI. Only have 800 miles on car.

Reply to
oklaman
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When I worked for an automaker, I had the privilege of driving well over 100 new cars, keeping around 60 of them for at least 6,000 miles.

I've found that tread life will be extended by inflating tires about 5 PSI over the automaker's recommended tire pressure, with the tradeoff being a slightly harsher ride.

Reply to
Ray O

You also get much better mileage. My 2005 RX330 give me 28 mpg (US) with about 3 pounds over recommendation

Reply to
sapper

Lets face it guys an gals - time to think! Lexus dealers say to use dino oil because it has improved so much! So in the hundred or so years that we have been pumping it out of the earth, it has improved a lot. Right. And it is better than that dratted new stuff that was invented to do a better job of lubing and cleaning engines at high temps. Lexus says their engines run at higher than normal temps so there is less emission of bad stuff to the atmosphere. So we now have the question of tire pressure - expect to find that they have improved the quality of air so much recently that it is now ok to run tires at a lower pressure

- say 30 psi. And that higher pressure that some people use is just not required anymore, esp with these higher milage thin little bling bling

18 or 19" tires!

Ah so - improved oil and improved air!

mcbrue airily under the bridge in the trailer down by the river

06 LS430
Reply to
mcbrue

LOL its the tires that are improving. The new compounds in the rubber, as claimed by the manufacturer of the tire, will not wear as easily on lower pressures compared to the older tires. Hence, they can say that its OK to run them at 30psi. Understand that the tire pressure listed in your door jamb or owners manual or fuel door is the MINIMUM COLD AIR PRESSURE that the tire should be at 32 DEGREES FAHRENHEIT. When you drive, the air expands with temperature and you get a higher pressure when it counts, on the road. For every 10 degrees fahrenheit that the temperature is above freezing, you should add 1psi to the vehicle specification. If its 70 degrees out, you should add between 4-5 psi over the specs when your tires are cold, this means driving within 1 mile to get to the air pump or pumping it yourself at home if you have a compressor.

Reply to
NYLexSC

You are just plain wrong. Oil HAS improved greatly. No, not in crude form, bubbling out of Jed Clampett's "shootin' at some food" backwoods....but as refined and as sold for today's engines. The science of lubrication has moved forward. They now have additives that work better than years ago. I do agree that synthetic is probably better, but regular dino oil changes works fine for many many miles. Consumer Reports studied this a few years ago and concluded that following the manufacturer's recommedations (meaning NOT more frequent as most dealers and Jiffy Lube claims), in most cases, would have you squishin' bugs for many many trouble free miles.

As to tire air...I have found that the manufacturer's recommedations seem to work best for ride, economy and tire wear. Why reinvent the wheel? (So to speak!)

Reply to
D.D. Pallmer

Actually, you are incorrect when you say that the minimum cold air pressure applies (only) to 32 degrees F. It is the (minimum) pressure that your tires should be set to when they are at the temperature of the surrounding air. This is also known as the "ambiemt temperature".

Tires will heat up approximately the same amount above a wide range of ambient temperatures when driving -- and raise the pressure by the same amount -- irrespective of the starting temperature.

If your owners manual or tire pressure sticker says 33 lb/sq in, then set it to that (or slightly higher if you wish to improve tire and gas mileage) but set it the same for all outside temperatures.

Reply to
jss1941

Correct, it is the AMBIENT temperature (also known as 'cold pressure').

When I sold tires 22-23 yrs ago, we had a 'rule of thumb' with regard to tire pressure: if you drive more than 5 miles at any speed, the tire pressure will increase approx. 5 psi. On my 05 ES330, I always keep the tires at 35 psi 'cold.' If I've driven more than 5 miles when I stop in to check my tire pressure, then when I put the air pressure gauge (ALWAYS buy one and keep it in your car, service station gauges (usually built-in to the air nozzle housing are notoriously inaccurate) on the tire, the air pressure 'hot' should be about 40 psi (less the '5 psi rule' = 35 psi 'cold) therefore, I don't need air. Of course, if the gauge reads less than 40, then I add air 'til it equals 40.

Been using that 'rule of thumb' for 20+ yrs and all the tires on all my cars have always worn evenly (less of course shock/strut/alignment wear).

Reply to
Mike Piacente

I've just bought a 2004 RX330 and the tyres seem fairly worn at 38000 K's. Took it to a tyre dealer today, he checked them and said the previous owner probably ran them at 30 psi as the sticker says, which gives soft ride but terrible wear. Told me to run at 36-38 and will be much better - haven't noticed much change in ride yet...

Reply to
Bear

I wouldn't run them higher than 36 psi.

The ruled USED TO BE: if the tire was a 'P metric' tire (size on sidewall started with letter 'P,' e.g., P20550R15) then maximum 'cold' psi should be

  1. IF it was a 'metric' tire (no 'P' at beginning of tire size, e.g.,

20550R15), then max 'cold' psi should be 36.

Yes, 30 psi will give you a much softer ride and you will feel the bumps and road roughness much less, BUT 1) the tires will wear ALOT faster, you'll probably get 20,000 to 30,000 miles out of them (this depends of course on whether they're 'high performance' or 'regular passenger/truck' tires -- performance tires are made out of a softer rubber compound so they're 'stickier' and grip corners better even if they're inflated to 35 or 36 psi and they wear out much faster than normal equally inflated passenger car tires). Passenger tires inflated to 30 psi will only get about 30,000 miles; 2) the braking is longer -- you'll notice you'll have to apply the brakes earlier than you would if the tires were at 35/36 psi; 3) a tire inflated at 30 psi has much more 'rolling resistance' than a tire at 35/36 psi. 'Rolling resistance' is essentially another term for 'friction' or 'drag:' the higher the rolling resistance, the harder the powertrain has to work to move the car forward or backward; therefore, you use more gasoline. If you want to conduct an experiment (this worked great at the tire store to show customers why they should keep their tires properly (35/36 psi -- by the way, tires made specifically for trucks usually have psis of 40-60+), take two tires which are mounted on rims (some call them 'wheels'), inflate one to 30 psi and inflate the other to 35/36 psi. Now, try and roll them using just one finger. You will see that the 30 psi tire requires more effort than the 36 psi); 4) cornering is 'mushier' in a 30 psi tire -- you will have to turn the steering wheel harder, it feels kinda like you're 'fighting' the wheel, not to mention the rolling resistance in taking a corner is much higher than a 35/36 psi tire. A tire at 30 psi has much more sidewall flex especially in cornering and that's why it feels 'mushier'.

A tire at 35/36 psi does 'ride harder' -- you'll feel the bumps and road roughness alot more BUT:

1) you should get at least 40,000 - 60,000+ miles out of them (again, it will depend on whether they're high performance or passenger car/truck tires). Routinely, I've always gotten AT LEAST 50,000-65,000 miles out of my tires because I kept them at 35-36 psi); 2) braking is ALOT better/faster; 3) lower rolling resistance and therefore better gas mileage; and 4) much quicker cornering (you can take corners faster and almost with just one finger on the wheel) because the sidewalls are much more stiffer at 36 psi than 30 psi and therefore less flex.

Sorry if this is rather 'long winded.'

"Bear" wrote in message news:4515e546$0$26426$ snipped-for-privacy@per-qv1-newsreader-01.iinet.net.au...

Reply to
Mike Piacente

thanks for all replies.

i did go ahead and inflate to 35psi (cold) and haven't noticed a big change in ride.

Although the door stickers say 30PSI, dealer says to put in at least 35PSI. Only have 800 miles on car.

Reply to
oklaman

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