rominl

iTrader: (4)

lol doc is too funny

anyway, measure it in the garage first thing in the morning, that's good enough

i don't see why it's riskier to release pressure when warm as well

garyr

19PSI is absolutely correct with both statements. Search the net, there's more than ample info on the subject. Quality tires made 5 years ago are made totally different today, because how there made and what they use to make them, they don't wear the same as you would think.

I personally run 39 front and rear. Perfect tire wear and handling.

FYI: Most all, even among the best tire guages are at best 2 psi off. Guages costing about $300 are accurate. Because I have a stable of motorcycles as well, tire pressures are critical to me.

I researched and found this guage to be the best most accurate and cost effective on the market. Many vendors sell the same brand ans stick there name on it.
http://griotsgarage.com/product/tool...rrivals&page=2

350Dave

zzzzdoc:

The logic behind not releasing air from a warm tire (warm meaning heated up from driving) is that when the tire cools (you stop driving) you will be left with too little air pressure due to having let air out. ALL tires are engineered to deal with the higher operating pressures associated with weight and friction that tires encounter while being used. That is why they state the "cold" tire pressure (for reference). "Cold", in this sense could mean a car parked for several hours, even in Death Valley at 125 degrees. Tire temps can reach much higher than that, depending on many factors...

CEOEngr

My car came back from the dealer Thursday after service with 39 PSI cold i.e. 43 psi warm. The SA had no explanation as to why the Techs have it at 39 PSI when Mama Lexus says 33 PSI. BTW I normally keep it at 35 PSI.

Have we reached a consensus on this matter?

rominl

iTrader: (4)

the correct psi is stated in two places. the door jam, and the manual. i will follow those numbers

SoCalSC4

So, 19psi is saying the Lexus techs know something the Lexus Engineers
and the tire manufacturer don't?

With OE rubber, I'd run the pressures right at the OEM's recommended
pressure. Best combination of wear, low noise, and ride comfort.

For a long trip with a load of passengers and luggage, I'd raise the pressure
by about 2-3 psi to maximize the stability of the tire's load rating.

I think running any more than 37 psi on aftermarket wheels only make the
Lexus cars ride like rubbish, and it really does not increase the "pothole
protection" factor to go any higher than this. Internet propaganda with
no basis in reality...

zzzzdoc

Yeah, but you wouldn't release air until the pressure was the cold pressure. You would release it until the pressure was as high as you felt safe having the tire reach. Then when the tire cooled, the cold pressure would likely still be reasonable.

350Dave

Doc -

I know you to be very articulate, but I do not understand this post.

zzzzdoc

I agree, when reading it again. Let me explain my point with numbers. Say that my Lambo on the track reached 50psi. Tire temp 140-150F. Knowing the pressure is too high, I would lower the air pressure to 45 psi. That's still higher than the recommended cold pressure of 40psi, but safe to drive with the tires at track temperatures.

Once the tires cool, the pressure would go down to roughtly 38psi. A little low, but not dangerous.

Let's do it how I think you are suggesting (and sorry if I am putting words in your mouth that you don't intend.) Once the tire pressure hits 50psi, you lower it to the recommended cold pressure of 40psi. Now when the tire cools, it will go down to a pressure of about 33psi which is very low.

My method above, to me, seems quite safe and prudent. Taking out air from a hot tire made it safer. But using method two, while safe on the track, would necessitate adding pressure at the end of the day or it might be unsafe.

Just taking care of the problem with two different methods.

Hopefully that explains it better, Dave.

Nospinzone

Rominl, typically the car manufacturers recommend an air pressure that will give you the smoothest ride. However, you usually need at least a few more psi to give you the best handling characteristics, as well as better tire wear.

The tire manufacturers would like to have them recommend higher pressures, but since the car manufacturer is the customer ..................

350Dave

I am not experienced with racing tires, they might be different. I have been through some safety training courses, and was instructed (by Bridgestone and Michelin factory reps) to never bleed air from a warm or hot tire.

What you said about what you might do with your exotic sounds reasonable.

I think that rule of thumb is the tires can handle a few extra psi at operating temp, but many people might check tires while on a summer vacation in the middle of a full days drive, bled air down to 32, for example, and think (wrongly) that they would be at 32 the next morning.

Thanks fo' the clarification - - enjoy both vehicles!!!

350Dave

I agree that this is often, but not universally, the truth...

19psi

oh, they know, but for the general public who desires a soft ride first and foremost out of aluxury car, they ahve to specify as they do or people will complain that their lexus rides like a sports car. (not a bad thing to me)
some people would rather have a soft ride than have their tires last longer. personal preference. my pet peeve is unevenly worn tires due to low air pressure, so i always set it higher than spec.

whether your theory of internet propaganda regarding high air pressure in low profile tires is true or not, i don't know, as i have no real evidence other than my own experience and that of clsoe friends. having had at least a dozen cars over the past 10 years with supe rlow profile tires and aftermarket wheels, i have yet to bend a wheel on a pothole or any other road debris. i keep my air pressure at 38psi or higher. i recommend this to my friends and wife who also run low profiles on their cars and none of them have bent a wheel.
at work i see a lot of cars come in with an aftermarket set up running 30 psi and their wheels are lumpy as hell. what does it all mean? i'll leave that up to everyone to decide for themselves based on the evidence.

oh, land rover recommends 40 and 42 psi on their oe tires.

19psi

well.... i wouldnt go to 40 psi on factory 18's. i set them at 38 in customers cars and my own. never seen center wear on either mine or customer's cars that show up for scheduled services. their tires are always in good shape adn worn evenly.

i think you guys are thinking of high air pressure in an old school big sidewall tire. in that case, high air pressure will cause center wear. it's even visual, blow one up to about 42 psi and look at it. the center bulges out.
try that with a modern performance low profile. the carcass is much stiffer. the center doesn't bulge out at all.

i dont' care either way, they're your tires, i just try to share my first hand experience and knowledge. i'm factory certified to work on lexus, audi, jaguar and nissan. i've been through all the school and classes and done all the work. working on cars isnt just a job to me, it's what i do for fun too.

zzzzdoc

I agree wholeheartedly with that.

I also think that for the average joe-six-pack, overinflating the tires by about 2psi leaves the tires in the good range for driving/safety for longer. Half of the time they are a little high, but safe, and half of the time they are a little low before someone remembers to check the pressure and fill up the tires again. Not something a NASCAR team would do, but for the average bloke it's probably pretty good real-world advice.