ISF001

While Lexus suggests 36psi for the front and rear for my 225/40 and 255/35 tires, I would like to hear what others suggest for optimal performance at speeds up to 100 mph.

And, at speeds above 100, are you adding 9 psi?

chris6878

I've never put much thought into it. Does this go for nitrogen filled tires?

Supraman16

iTrader: (5)

It all depends on the tire. Some tires have really soft sidewalls and do best with 35 to 40 psi in the ISF to stiffen up the sidewall a bit. But this takes away straightline traction and too much makes the car feel "floaty". I can usually feel a difference between 1 to 2psi and I suggest if you are running the stock tires go with the Lexus recommended pressures, if not, still start off at 36psi but you may need to add or subtract some PSI depending on the feel...Darshana

ISF001

Thanks. I will try 36 psi.

I' m curious if many folks are using nitrogen as it escapes 30-40 percent slower than compressed air.

RCB

iTrader: (18)

Don't forget the important part about nitrogen. It's pressure doesn't fluctuate with ambient temperature changes the way oxygens does.

Defratos

^ to add to this as well, I usually only inflate my tires when they're cold and measure them when cold.

Once the tires get hot I measure again and see how much pressure has risen as that is the psi that most people will be actually running at.

So for instance if you do 36psi when cold then expect to see close to 39~40 psi when they are hot.

I never fill my tires up when they are warm as it doesn't give me a clear unbiased reading.

lobuxracer

iTrader: (2)

Yes it does. Just like any other gas does. There's nothing special about nitrogen in tires except it costs you more money.

To answer the OP's question - use the pressure on the sticker. If you're going to a track day, start at 32 psi and adjust, but for everyday all around performance under 100 mph, the sticker pressure works best.

RCB

iTrader: (18)

I should first disclose that I don't use or plan on using nitrogen in my tires.
I guess I should have been more specific. The most important benefits of nitrogen are that it is less effected by ambient temp. changes and the fact that it doesn't escape from a rubber tire as easy as oxygen. That is nice piece of mind in an area of the country with major temp changes. Here in Boston we see can see 10-20 degree F. in one day, sometimes greater changes. When I worked in a dealership on those days we would get 10-20 cars pulling in with TPMS lights on.
I have a garage with a compressor at home and don't drive any of my cars every day. If I lived in an appt. and didn't want to go get air at 6am on the way to work when it's 30F outside I might consider nitrogen.

lobuxracer

iTrader: (2)

Actually none of that is really true. The big difference between nitrogen and whole air is the water content, not the oxygen content. Standard air only contains 20% oxygen. 78% is already nitrogen, but with water vapor, the impact of temperature changes is greater because n in PV=nrT is greater with the same V. Dry air and nitrogen are indistinguishable in service. Oxygen's permeability isn't the problem, its the water vapor which is present in both of our compressors in our garages. But for street duty, it's worth a lot more to check frequently instead of wasting a lot of money on a nitrogen fill.

RCB

iTrader: (18)

This is good learning. I was under the asumsion that nitrogen
permeability was due to larger molecules.
Not that I would do this but would using a high quality air drying system with an air compressor lower the water content enough to have positive results?

streetx

iTrader: (4)

I get my nitrogen free

lobuxracer

iTrader: (2)

It's too hard to do economically. There are dryers and they work to an extent, but to get truly dry gas, you need to liquify air and boil off the gas(es) you want. I used to work in a gas analysis lab so it used to be easy. Now it's really hard, so I don't get wrapped around the axle with it. But there are coalescent filters and chemical dryers capable of removing quite a bit of water from an air stream, they're just not cheap to buy or maintain.

RCB

iTrader: (18)

Lobuxracer, thanks for the info. I learned something new today.

ming15237

iTrader: (3)

Another thing to consider here is you would have too pull a vacuum on the tire before installing the Nitrogen for it to have any discernible effect... simply NOT going to happen. These Nirtogen filling machines are a bunch of boloney! And too boot the state of Pennsylvania bought over $1,000,000.00 worth (yes you read that right 1 MILLION DOLLARS) of machines free of charge for tire service dealers to help with "green energy". And we wonder why out country is broke! Lets build windmills where there is no wind! oops we already did that too! arrgggg!