ajay60610

Have a 2009 RX-350AWD [130,000 miles]...wondering about what air pressure i should be filling my Michelin Defender tires...16inch....door frame state 32 lbs but i'm thinking that's too low...have been putting in 34 lbs...suggestions please...thanks

DennisMik

I run my fronts at 35 psi and my rears at 33 psi. The tire wear is even all the way across.

If you change the air pressure, remember to reset the TPMS tire monitoring system to the new pressures. Also, be advised that the spare tire is part of the TPMS system, meaning check/adjust the air pressure on the spare before resetting the TPMS.

ajay60610

okay...thanks for helping

ukrkoz

If you were to carefully read tire pressure instructions, it is, actually, relevant to vehicle load. There should be span between "normal" pressure and "max load pressure" Hence, definitive pressure rather depends on how much load your vehicle routinely carries. If you were, normally, driving alone, 32 is good tire pressure. I don't think you will notice any difference of 2lbs but, any unnecessarily added pressure results in more bumpy ride and more impact on suspension components. Also, you have lesser tire footprint on the road=less braking force and grip on it.
So why? But, should you routinely drive with 5 adults and luggage inside, that's max load and pressure needs to be set accordingly.
MPG chasers go radical, over pumping tires for better mpg.
I had my tire pressure changed whichever way I wanted to on my Totas with TPMS and NEVER had to reset anything. TPMS is dumb, it only sends sygnal when pressure drops below threshold. I does not really care about higher pressure, and I varied anywhere from 32 to 40 psi.

DennisMik

ukrkoz is correct in what he says and everyone that drives a car should be aware of it and know that. Most people drive their cars with the same load probably 98% of the time. Vacations are probably the most common reason that people dramatically increase the load. As for the manufacturer's recommended inflation pressure, those have traditionally been on the side of a soft ride, which will wear the edges of the tires. A couple more pounds of inflation pressure probably won't be noticed, but is better for tire wear.

The only problem is that there doesn't seem to be any definitive information availavble on how much to increase air pressure for a given load. I for one would like to see something in that area.

ToledoRX

I don't recommend over-inflating the tire pressure. When driving at 70 mph or higher, I've noticed that the tire pressure actually goes up by 2-3 psi, especially prolonged drives on hot asphalts like during the summer.

I would be carefully about over-inflating a cold tire, especially from an unknown or non-OEM brand. There are specifications that tire manufacturers and automakers publish that if you exceed may lead to a blowout at high speeds.

tomr51

as stated by Dennismik, manufacturers set the pressure on eh low side to get a "softer" , quieter ride. An extra few lbs will give more even tire wear, and slightly better ecomony. Tires lose pressure resulting in most cars running at too low a pressure which results in the edges being worn out on the tires. Checking at regular intervals and keeping a few lbs over manufacture specs is the way to go.

Broc

There's a bit more to this than meets the eye initially ... AWD and especially 4x4 systems like even rolling diameter among all the tires/wheels. So lets say you use 34 psi for daily driving and it's mostly you and your wife sometimes. Then the vehicle is front biased (engine and passengers). So the front foot print is say 6" long.

If the rear is also at 34 psi, it may be only a 4" foot print, and a higher rolling diameter. This is handled by the viscous clutch in the center diff. But it's much better to match rolling diameters. So inflate your fronts to what you want and tape measure top of rim flange to the ground. Now go set the rears so the top of rim to ground is same height.

If you load up the back with kids and stuff for an outing, up the rears to match fronts by rolling diameter. You'll get better mileage (less loss though center diff heat) and you'll have better handling