mowmow

Hi
I searched and couldn't find a definitive answer, what is the correct
tire pressure for the RX400h ? I looked at the sticker on the door it said 30PSI
but when I talked to the service dept manager, he told me 40PSI and I checked
all 4 of my tires, they are all at 40PSI, the max on the Michellin is only 44PSI
so can anyone tell me what is the correct amount to achieve optimum fuel efficiency ?

chinalfr

I quote this based on my experience with Prius as I'm still learning my driving style on the RX.

1. inflates tires to the max PSI ~ 44 PSI.
2. Light footed.
3. P&G. On local traffic, try speed up to 41 mph and then glide till the car slow down. Continue the same procedure.


So far, our first tank of gas averaged about 26 mpg.

joedaddy1

iTrader: (1)

we do 35~36 on our car..

mowmow

Joedaddy1:
when you refer to 35-36psi is this on cold morning prior to driving or after driving a while when the tire is already warm up and tire pressure already increase due to heat ?

chinalfr, ok thank you for your info, I'm doing about the same and getting on average 25-26 on mix driving. In some area where there more traffic, I get up to 36mpg for the entire traffic jam ( i.e from start to finish )

jfelbab

You should NOT inflate your tires to the maximum pressure listed on the sidewall. Heres why; When cold and you inflate the tire to the maximum PSI and start driving the tire will heat up due to friction. It is likely that the tire will reach a temperature 20-60 degrees warmer than when it was cold. The tire pressure inside the tire will increase one pound for every 10 degrees it heats up. So now you can be running 2-6 PSI over the maximum pressure. For the best ride and handling you should consult your owners manual or the tag in your glovebox or door.

salimshah

Do not inflate to Max pressure. There may be headroom above the posted max BUT the tire can explode when you are at Max pressure and it can be lethal. Even if the tire does not explode the steel cables and rubber may separate causing permanent failure.

I typically will over inflate the tire and measure in the morning and let out to get to the right pressure.

Now the question of what is the right pressure. There are tradeoffs. Manufacturer posts the pressure [on the door jamb and the owners manual] after a good bit of study and typically it is the best pressure to go with. I tend to go +2psi, which does not sacrifice the ride quality. +5 psi makes the roll better but I start loosing the ride comfort and braking. I have not played with lesser than suggested pressure.

Salim

mowmow

Thank you for all the input, I think I should just go with the factory suggested pressure to be safe

GQD_GS4

the max is 44 PSI. I ran 35 PSI and averaged 25-26 mpg. Now I run at 40 PSI, average 27-28 mpg, and havent looked back since.

jayvis

At 40 psi, you're not only compromising comfort and safety, you're also causing excess tire wear. You might be gaining a few more MPG but you won't like the bill when those Michelins wear out in 30,000 miles or less.

salimshah

I guess you mean un-even wear (more in the middle/crown) ... the edges would look like hardly used

Salim

GQD_GS4

i guess when the middle starts to wear a little more...say after 5000 miles, then i can go back down to 35 psi and let the edges start to wear. no harm done

jfelbab

From the Tire Rack...

http://www.tirerack.com/tires/tirete...jsp?techid=147

As can be seen from the article it is acceptable to over-inflate up to a point based on the temperature and driving conditions expected.

How and when to check pressure...
http://www.tirerack.com/tires/tirete...e.jsp?techid=8

salimshah

Talking about tire pressure, have you checked your spare lately?

Salim

Grumpa72

I would believe the tire manufacturer before I believed a service manager. In my experience, the recommended tire pressure is a compromise between ride, comfort, and drivability. As has been suggested by others, marginally increasing tire pressure may improve mileage but may decrease ride quality. Try increasing it in 1-2 psi increments, on the same road, similar temperatures and load to see if there is an improvement or decrease. I have four cars and I leave them all at 30-32 psi.

LEXveryG8

I'm currently on 33psi, the 30psi suggested on the door is really not that inflated. The tire looks flat. The dealer here just inflated mine everytime to 32~33psi.