Tire pressure with different size tires...

[joe603]

I have the stock 19" rims, but larger tires. What tire pressure should I be using? The data plate has 36psi...should I inflate more? What are you guys running in your Gs?

My sizes are:

245/35-19 front275/35-19 rear

[JeromeS13]

I'm running 35psi all around, with my 19" Volks/Advan Sports.

-Jerome

[szh]

Anything nearly 36psi is likely to be good.

Do check it often ... once every week or two, since it is normal for 1 to 2 psi drop in that time.

And, of course, tire pressures should be checked cold. In the garage in the morning if you have a garage. Before even the sun has had a chance to warm up the black tire (absorbs warmth).

Z

[joe603]

Sounds good! Guess I'll keep it at the stock pressure.

[impalaron]

My plate said 35psi but when I checked the tires it said to inflate to 51 psi I did and I am getting much better gas milage. I bought the car used and I belive these are after market low profile tires.I always infate what the tire spec are. I don't know if thats right but it works for me.Hope I didn't confuse you.

[JeromeS13]

No, no, no. I see this WAY too often. Your tire says "Max Tire Pressure 51psi". Notice, this is the MAXIMUM inflation pressure for this tire. This is NOT what you should have in your car. That is calculated based on the max load capacity of the tire.

You should always follow the vehicle's suggested air pressure, unless there's a drastic change in tire size/load rating. If you keep 51psi in your tires, you'll be regretting it in about 10k miles, because the center of your tire will be completely worn out.

So, please, for your tires' sake, let some air out...

-Jerome

[joe603]

You should always follow the vehicle's suggested air pressure, unless there's a drastic change in tire size/load rating.

So what do you consider drastic? My car seems to no be as snappy now...but i have more traction...

[deanfootlong]

lets not forget here that PSI (pounds per square inch) stays the same, no matter how big or small your tire.

just because you bought a bigger tire than stock, doesn't mean the PSI needs to be more. PSI is always static. it will just take more air to create the same amount of PSI.

Hopefully you're not thinking that since you got a bigger tire, the PSI needs to be more.

[joe603]

Actually I was thinking because I went from a 40 series tire (stock) to a 35 series tire, I would have a smaller sidewall. This would affect the distribution of pressure as it is a smaller tire (height-wise). Thus, the tire pressure to maintain an even contact patch on the tire to the ground could be different.

[impalaron]

Thanks.I will take your advice. But I do seem to get better milage with higher tire pressure.Whats up with that?

[szh]

My plate said 35psi but when I checked the tires it said to inflate to 51 psi

No! That is the maximum inflation pressure of the tire. When it gets hot, it is likely to get even higher and be dangerous.

Please reduce down to about 36psi to 38psi maximum (when measured completely cold - in the garage in the morning for example). This will increase about 40 or 42psi when driving (i.e., when the tire is hot) and is sufficient for the car.

Z

[szh]

Thanks.I will take your advice. But I do seem to get better milage with higher tire pressure.Whats up with that?

Pretty much that the tire is overinflated and less of it is touching the ground - this reduces friction a bit and improves mileage a bit. But, the pressure on the center of the tread is greatly increased.

So, (a) this is dangerous and (b) the tires will wear much, much faster in the center. You may end up going through tires and the cost of tire replacement will more than outweigh the gas savings you may be getting ...

Z

[impalaron]

Ok Ok Ok I will let the air free. All kidding aside thanks for looking out for a member

[szh]

Ok Ok Ok I will let the air free. All kidding aside thanks for looking out for a member

You are welcome. We want to retain our members, not lose them!

Thanks for doing this!

Z

[gwoods]

Good advise from everyone...

I'd run anywhere between 32 psi and 38 psi.

I drive my car hard and frequently triple digits so I keep my tires are 38 psi.

The wifes Sequoia I keep at 32 psi cause I want her to have the softest ride possible, the gov kicks in at 95 mph and she never corners hard.

The harder you drive the more pressure I'd keep in the tires up to 38 psi.

Jeff

[Q45tech]

The Tire industry set standards for 44 psi max tires unfortunately there are none for 51 psi tires YET!

The 35 psi COLD 35/44 or ~~ 80% of max load hot worked for years because tires only see max load in panic braking or 0.9 G handling and only for a few seconds at a time. Heat up but time to cool off before next heat up.The same 80% of 51 would be 40.56 psi.

Tires are tested in lab at 35 psi, 41 psi, 44 psi, and 51 psi.

Only by measuring tread temperature will you learn the ideal psi for your instant driving conditions.

http://www.millikenresearch.com/TTC_SAE_paper.pdf

" Running them all under the same load, the air pressure in all of the tires went up about 1 psi during every 5 minutes of use for the first 20 minutes of operation. Then the air pressures stabilized, typically gaining no more than 1 psi of additional pressure during the next 20 minutes. This means that even a short drive to inflate your tires will result in tires that will probably be under-inflated by a few psi the following morning.

Add all of these together, and you can understand why the conditions in which you set your vehicle's tire pressures are almost as important as the fact that you do set it.

It's important to remember that your vehicle's recommended tire pressure is its cold tire inflation pressure. It should be checked in the morning before you drive more than a few miles, or before rising ambient temperatures or the sun's radiant heat affects it.

And by the way, if you live in the North and park in an attached or heated garage you will lose pressure when you leave its warmth and venture into the real world outside during winter. Add 1 psi cold pressure tire pressure to compensate for each 10° Fahrenheit temperature difference between the temperature in the garage and outside................Tirerack

"A roadwheel test inflation of 80 percent of the pressure at maximum tire load will serve to both increase belt edge temperatures over current FMVSS 119 levels and to help minimize tread centerline temperatures.

A direct translation of operating conditions from the flat surface to the curved surface based upon tread centerline temperature yields an average roadwheel highway equivalent speed of 68 km/h (42 mph) for highway severe service conditions of 120 km/h (75 mph) at 100 percent maximum load, 80 percent maximum inflation, and 38 °C (100 °F) ambient temperature."

Without one of these pretty dificult to know anything for sure:http://www.mts.com/stellent/gr...6.pdf

[Q45tech]

It appears that manufactuers are trying to get 75% [of T&RA maximum] of 51 or 38.25 psi as a new standard for 51 psi tires and 58% [29.6 psi] as the extreme lower limit.http://www.unece.org/trans/doc...e.pdf

Personally I don't see how a thinner wear sidewall depending more on inflation psi for support should use a weaker 75% vs the 15 year standard of 80% but vehicle manufacturers will do things to make the ride smooth as long as the number of deaths are reasonable.

I would trust a lower psi on a Michelin than I would on lesser tires especially Asian low cost copies.