PSI in Kumho tire

[SlamminRIde]

Hey this may be a bit of a newb question but I have a set of Kumho ecstra asx stock size on my mp5 atm and i havent done much since i've got it form the dealer. The tires say "max psi 51" and i checked all 4 and the are all within 30-35. i know the need some more air but should i really put in 50psi?

Thanks for your time.

 

[thecrash91]

usually no, around 30-35 is where you should be, look inside the door. max means thats how much before the tire blows up. having too much air can reduce gas milage and be hazardous in bad road conditions because the tire arcs out and you have less tread touching the road

 

[Fluffy Bunny]

If you like the feeling of riding in an old wooden wagon, then you can throw all that extra air in. Keep in mind, tire pressure will increase depending on driving conditions - get them hot enough pressure might go up from 5 to 10 lbs.

Follow tire pressure recommended by Mazda and you should be fine. (All this is with the understanding this is normal day-to-day driving)

 

[evilmonkeyMSP]

Higher tire pressure = rougher ride but better gas mileage....

 

[Flash5]

Higher tire pressure = rougher ride but better gas mileage....

my yokohamas have a max psi of 44 i think, i run about 37-38

 

[pureliquidhw]

I run 40psi in my Kumhos. No issues, ride isn't terribly rough.

 

[Ride92]

The size and type of your tire does not determine what tire pressure you should run. Many cars have differnt PSI needs for the front and the rear of the cars. On the P5 there is a sticker on the passenger side door jam that tells you what psi you should be running in both your front and rear tires. If my memory serves me right it is 32 psi in all four corners. Again remember that it doesn't matter what size tire you have because it's pressure on the tire, not the amount of air in the tire. Say you bump up to 17" rims and run a lower profile tire then your volume (the amount of air molicules) the tire can hold decreased but the pressure needs to remain the same. On the 16" rims you may put in therotically 1000 units of air to reach your 32PSI where as the 17" rims require only 800 units of air to reach that same 32psi, get it? Do not run your tires to high or too low. Follow the Psi recomendations on the car, it's there for a reason. Unless of coarse you really like replaceing your tires sooner then you have to or enjoy running around on tires that are readdy to blow at any moment. thanks

 

[Skywlkr]

+1, Nice Explanation

 

[SlamminRIde]

No, thank you Ride92!
(10)

 

[poison]

There's some misinformation in this thread. The recommendation on the car doorjam is nonsense: an all season tire will take a different pressure than a summer. The 33psi recommendation that is average for most cars, and the standard Jiffy Lube fill, is absolute crap. It's low for 99% of the cars/tires out there. It lowers gas mileage, and under very hard cornering (ie accident avoidance) the tire can roll off the rim and/or provide other very undesirable handling traits. It's impossible to provide an ideal psi for a car, it's tire dependant.

If your tire has a max pressure of 51psi, you need to take into account 4-5psi of added pressure from heat. That lowers the max PSI to 47. I would start with the PSI you are at, and every week add 3psi all around to get a feel for what it does, up to the max of 47, then back off to what feels best to you, which I would say off hand would be around 40psi.

You can dial in oversteer and understeer through tire pressure, too, but that's a whole different topic.

BTW, I did a 3 day defensive driving school for bodyguards, Tony Scotti's school; he developed the driving school for the Secret Service. They back everything they teach up with first hand experience, your driving on the tarmac. Cool stuff.

 

[bgibb68]

and don't forget....the tire pressure that is usually recommended is cold, aka if you test it, do it before you go driving around.

too low of pressure, you will wear out the outsides of the tire....
too high and you'll wear out the middle of the tire

 

[Ride92]

Right, I guess I forgot that every car manufacture and wheel and tire place that I've ever been too or every heard of must be wrong. The person was asking about a tire pressure, he should follow mazda's recommondations for tire pressure for that car. It's not a number that Mazda just pulls out of there ass. And Yes I do know that different driving conditions warrant different pressures. I assumed that the tire psi was being check cold as it should be. Under normal driving conditons the tires will heat up and slightly increase the tire preasure as a result. Now if your driving in the winter generally speaking a lower tire pressure is recommended to give the tire a larger foot print for traction. I said driving not racing, racing is a whole different story.

 

[Ride92]

in fact read this, it just about covers every senario that you ever encounter regarding tire psi and driving conditions. http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=1

 

[slavrenz]

There's some misinformation in this thread. The recommendation on the car doorjam is nonsense: an all season tire will take a different pressure than a summer. The 33psi recommendation that is average for most cars, and the standard Jiffy Lube fill, is absolute crap. It's low for 99% of the cars/tires out there. It lowers gas mileage, and under very hard cornering (ie accident avoidance) the tire can roll off the rim and/or provide other very undesirable handling traits. It's impossible to provide an ideal psi for a car, it's tire dependant.

If your tire has a max pressure of 51psi, you need to take into account 4-5psi of added pressure from heat. That lowers the max PSI to 47. I would start with the PSI you are at, and every week add 3psi all around to get a feel for what it does, up to the max of 47, then back off to what feels best to you, which I would say off hand would be around 40psi.

You can dial in oversteer and understeer through tire pressure, too, but that's a whole different topic.

BTW, I did a 3 day defensive driving school for bodyguards, Tony Scotti's school; he developed the driving school for the Secret Service. They back everything they teach up with first hand experience, your driving on the tarmac. Cool stuff.

I also disagree with you on this to some extent (although you do make valid points). Generally, saying that the tire psi recommendations on every single car manufactured in the last 20 years is crap is not going to make you look credible.

Believe me, I'm not trying to be an ass, but you just need to objectively back up your opinions with data rather than just saying other people are wrong.

 

[poison]

How can a manufacturer say xx psi is what the CAR needs, when there are 120 different tires you can choose that will work on that car, all with different tire pressure requirements? The PSI on the car is for the tires the car is spec'd with from the factory, and a generally safe pressure that'll keep the morons generally safe in generally most conditions with generally most tires (READ: this limits liability to the auto manufacturer). Generally, these tires are 1) not the best, 2) the ultimate compromise tire to fit as many markets/conditions as possible (sunny california? snowy Colorado? Got ya covered with ONE sweetahemshitty tire!), and 3) if you believe the psi on your door, then you probably believe the 'your car's suspension was developed around the Bridgestone Supermaxx All Season blahblah tire it comes with from the factory, using something else is not optional, and may even be dangerous' line you'll get from your friendly authorized Mazda dealer.

Again, there is NO WAY an auto maker can tell you, in one blurb on your door, what pressure to put. The tires spec on the sidewall is a much better guide, along with a judicious butt-dyno.

Keep in mind you don't have to be a racer to care; one near-death experience on the freeway at 75 mph, with a low 33 psi in your Falken 912's that pop a bead off the rim, will make you a believer.

The tires are the only thing connecting 3000lbs of car, and all the complex systems therein, to the road. That's some rubber, air, and a bit of steel wire. They are the easiest things about a car to do right: add the correct psi, and upgrade when they're toast.

 

[thecrash91]

because no matter what size the tire is, its what pressure is needed to keep it correctly off the ground. if you have too much air in the tire, the tire will bow, and too little the tire will arc. causing uneven tread. that specific psi will keep it just right. no matter what size of the tire. psi doesnt measure volume, it measures pressure. its pounds per square inch. does the tire company know how much your car weighs? no, they dont. and for the people who say well what about the people in colorado or in cali, well with the weather, the air will be more dense in cold climates, therefore if you live in colorado you set it to however psi while you are IN COLORADO same goes for the people in cali. whats 34 psi in colorado is NOT 34 psi in california. so, when weather changes, check the pressure. too little pressure can also cause more friction which can make the tire explode. maximum is just how much pressure before the tire explodes from pressure. thats usually all that is printed on the side of the tire.

 

[poison]

because no matter what size the tire is, its what pressure is needed to keep it correctly off the ground. if you have too much air in the tire, the tire will bow, and too little the tire will arc. causing uneven tread. that specific psi will keep it just right. no matter what size of the tire.

But different tires have different construction. A crappy all season will have soft, thin sidewalls and far lower speed rating; a max performance summer tire will have ultra-stiff sidewalls, beefy as hell construction, and higher speed rating. Both tires do not call for the same pressure.

 

[bgibb68]

But different tires have different construction. A crappy all season will have soft, thin sidewalls and far lower speed rating; a max performance summer tire will have ultra-stiff sidewalls, beefy as hell construction, and higher speed rating. Both tires do not call for the same pressure.

well than....get a new set of max performance and fill to the max psi on the sidewall and tell us how long they last

 

[pureliquidhw]

Another thing to keep in mind is that Auto manufacturers don't care about performance or longevity. they care about comfort and quiet. the lower PSi recommendation is a balance of ride comfort and road holding. Higher PSI will increase tire responsiveness but it will also make for a harsher ride.

Do what works best for you between 35 and 45 PSI.

 

[poison]

well than....get a new set of max performance and fill to the max psi on the sidewall and tell us how long they last

That's not what I said to do. I said everyone, regardless of tire or car, should start with the manufacturers recommendation, and weekly add 2-3 PSI all around to get a feel for the change, all the way up to the max PSI (which is 4-5lbs less than the max stated on the sidewall due to heat expansion). THEN back off to the pressure which feels the best to you, which in my experience is about halfway in between the manufacturers recommendation and the tires max PSI.

I generally run around 38-44, depending on tire. Right now I have Falken 912's, and 40 psi.

If you think 33 psi will wear better for me and the way I drive, you're wrong. 33 psi allows way to much sidewall flex, and the shoulders wear poorly. The higher pressure allows less deflection, and keeps the contact patch on the ground under higher loads. I've only experienced poor wear when using Lower pressures.

And BTW, the 912's came on my car. I live in sunny SoCal; I have no business driving AS tires. I'm going to wear these out, as I'm poor, then put some 452's or StarSpecs on there.