Tires - Proper Inflation
 

I am starting a separate thread on this because while it was commented on it may get lost buried in another thread (that has little to do with tires).

The side panel of my car states tries should be inflated to 33 - when I picked up my car two weeks ago I had the dealer exchange my Bridgestone for the Michelins. Checking the inflation a few days ago I saw that the dealer filled them all exactly to 38 - I didn't think much of this until I read in another thread that dealers always put more air than what is recommneded. Also, I read that at 33/34 you get a better ride. So that brings up a little confusion:

1) Is 33 the proper inflation for Michelin tires or do they require more?

2) Another responder in the other thread stated dealers always inflate more than what is recommended - why do they do this and is there a reason for it?

3) I am wondering if riding in tires at 38 would give you better gas mileage and maybe they do it because it's a hybrid.

4) How much air is in all of your tires?

Thanks

My '12's door label recommendation is 30.I go 30-31.I like a smooth ride.
38 would give you a few tenths better MPG,rough ride.
Just go with what Lexus recommends on the door label.


Tire Rack

Disadvantages of Overinflation

An overinflated tire is stiff and unyielding and the size of its footprint in contact with the road is reduced. If a vehicle's tires are overinflated by 6 psi, they could be damaged more easily when running over potholes or debris in the road. Higher inflated tires cannot isolate road irregularities well, causing them to ride harsher. However, higher inflation pressures usually provide an improvement in steering response and cornering stability up to a point.

I don't know about specifically Michelin tires, but higher inflation leads to better mileage (less resistance) and when I got my oil changed recently, they set the tires to be inflated higher than normal because the low temps with winter will cause the pressure to drop.

1)...33 is correct & Michelins Don't require more.

2)...In Japan they inflate the tires higher for the appox. 2 week trip to the US, so they don't get flat spots on the ship, that is what I read.... So I just think some dealers never ck. the preasure before they sell the cars.

3)...It would ride harder. From 33 to 38, I think if there is any better mpg it would be so extremely small it would be hard to see it.

4) ...Mine came with 33 lbs. it rides GREAT & I am getting 40.5 MPG so far.

I've also heard that the tires are over inflated for shipment.

On the other hand, I've taken my car in for service with the tires set at my preferred 32-33 psi and the dealership has changed the inflation to 35+.

I always forget to tell them I want 32-33, so I have to reset them when I get home.

It's been my experience that the dealer always sets the tire pressure on all models at 35. I have also found that the TPMS display doesn't agree with the readings on either of my pressure gauges. I consider the TPMS as the most accurate, so when adding air, I add/subtract the reading on my gauge to agree with the TPMS.

I suppose it can happen that the tech's gauge reads different than your TPMS display and so even if his gauge reads 32-33, it would disagree with yours.

33 and 38.5 after 500 miles...

Higher tire pressure also requires a higher speed for hydroplaning. At 38#, you risk hydroplaning at 55 and at 33# it is at 51 mph; there about..... I doubt that is what the reason is though. My car delivered the same at 38#, even after I watched them do the prep and check tire pressures. I asked them the last time I was there and the service manager told me that the car gets better gas mileage. He put it in my record that I want inflation to be at 33#

For the best mix of handling, fuel economy and tire longevity, in general, use what the manufacturer of the vehicle recommends.

They are not always right, and you get some air pressure to "tune" the way the car rides and handles. There is such a minimal increase in fuel economy, generally, .5 or less MPG, even for a severely overinflated tire, and tread life is generally the #1 sacrifice, that it doesn't make it worth it in the long run.

When cars are shipped, the tires are generally set to a quite high pressure. I see it all the time that the dealership forgets to set the air pressure to the manufacturer recommended. It doesn't make any sense why a service manager or technician, especially one that worked for that brand, would set air pressures to something not directly stated by the owners manual / door placard, or the owner.

Unless a tire has a different load index than the factory recommended, there is no reason to change this pressure (again, unless you want to tune the way the car feels when cornering). I purposely changed mine from 33 to 36 front, left them at 33 in the rear. This gives (on my IS300 and slightly larger than OE tires) a little better turn in feel, while keeping the rear firmly planted. When experimenting with higher pressures in the rear, I found that it made the car oversteer more, which is undesirable to me.

Most tire gauges are inaccurate by a small amount. Unless you shell out some real cash on a high end gauge, your pressures will just be "close" but so long as they are the same per axle and close, it is not that huge of a deal... Always go for overinflated vs. underinflated, and it does make sense to bump up air pressure a little right before winter. In general, for every 10 degree F drop in temp, expect a 1 psi decrease in air pressure. Set the air when its 85 degrees outside like it is supposed to be, and three days later, when it is 30 degrees at night, there may be a 5 psi pressure swing. (Gotta love Missouri weather!) This is a general rule, but seems to hold true.

Well, I can tell you that dealers DO NOT ALWAYS over inflate - our car was delivered with all 4 tires set at 33.

Mine came with 33 PSI. It's 20 degrees colder here now and the PSI dropped to 30 so I topped it up back to 33. If it was not for the new display showing the PSI, I would never had known. I have a digital PSI gauge and it is within 1 PSI of what the car is displaying. I can trust what the car is telling me.

As for adding PSI. There are numerous threads on PriusChat.com on this subject. It will improve your MPG but "we" probably care more about ride comfort that the folks on PriusChat.com :)

Well, mine came with 42 at LF and 38 on all the others. I had just sold my GS350 and got the ES300h and thought the ES rode ok. If it wasn't for the tire pressure read out on the display, I wouldn't have noticed the tire pressures were set so high. I've since set them to 35 and will drive it hoping that the ES will be smoother and won't drift to one side. It kinda makes you start thinking that if the tire pressures weren't set right, what else in the pre-delivery inspection did they miss..

Which dealership?

"For the best mix of handling, fuel economy and tire longevity, in general, use what the manufacturer of the vehicle recommends. "


The ES 300 comes with one of two types of tires, Michelin or Bridgestone. The he Michelin's have a lower maximum tire pressure rating In the Bridgestone's, So the recommended pressure may be good for one brand , but not both.

manufacturer tire pressure
 

I had learned that as long as you have the correct tire size the pressure in the tires should be what the car manufacturer recommends on the sticker they put in the door jams