Correct Tire Pressure
01-30-02, 09:43 PM
#1
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Correct Tire Pressure
Guys,
What is the correct tire pressure for the aftermarket tires? I have 235/45/17 and 255/40/17 Yokohama A520 tires and used to have 35 tire pressure until last night, I changed the pressure to 38 all around to correct my car from wandering on freeways and streets, is this safe?
Peter
What is the correct tire pressure for the aftermarket tires? I have 235/45/17 and 255/40/17 Yokohama A520 tires and used to have 35 tire pressure until last night, I changed the pressure to 38 all around to correct my car from wandering on freeways and streets, is this safe?
Peter
01-30-02, 10:15 PM
#2
Should be.
I believe Lexus reccomends 35 lbs of pressure on the stock 16" wheels setup. I'm sure someone will correct me if I'm wrong. With smaller tires you need to increase the lbs of pressure. I run ~37lbs on my 245/40/18 and ~38lbs on 275/35/18.
I believe Lexus reccomends 35 lbs of pressure on the stock 16" wheels setup. I'm sure someone will correct me if I'm wrong. With smaller tires you need to increase the lbs of pressure. I run ~37lbs on my 245/40/18 and ~38lbs on 275/35/18.
01-31-02, 04:19 AM
#3
Read the Max pressure on the side wall of the tire. Then, after a long drive where the tires are all nicely heated up, you can inflate your tires up to that point as a maximum. Its good to leave a little room for error there, because over inflated tires wear out unevenly, and are more prone to blowouts.
35-38 is a good range. You will handle better on 38, but you might wear the center of the tire down faster.
I run 35 on the street in my SC, 38 in my RX, then bump the SC to 42 and the RX to 44 when I race.
Its all about meeting your needs, and there is no correct tire pressure. A good default is the rec from lexus, but if your not running stock tires, use the tire manufactures rec.
Keith
35-38 is a good range. You will handle better on 38, but you might wear the center of the tire down faster.
I run 35 on the street in my SC, 38 in my RX, then bump the SC to 42 and the RX to 44 when I race.
Its all about meeting your needs, and there is no correct tire pressure. A good default is the rec from lexus, but if your not running stock tires, use the tire manufactures rec.
Keith
I will try the max pressure tonight and see how my car reacts.
01-31-02, 12:19 PM
#5
Lexus Champion
No, original is not 35psi. Look in your glove compartment. Original tire for SC400 is 225-55-16, tire pressure 32 psi.
You can run a few psi above the recommend press.
Don't know the answer for up grade tire.
You can run a few psi above the recommend press.
Don't know the answer for up grade tire.
Originally posted by hellasboy
Should be.
I believe Lexus reccomends 35 lbs of pressure on the stock 16" wheels setup. I'm sure someone will correct me if I'm wrong. With smaller tires you need to increase the lbs of pressure. I run ~37lbs on my 245/40/18 and ~38lbs on 275/35/18.
Should be.
I believe Lexus reccomends 35 lbs of pressure on the stock 16" wheels setup. I'm sure someone will correct me if I'm wrong. With smaller tires you need to increase the lbs of pressure. I run ~37lbs on my 245/40/18 and ~38lbs on 275/35/18.
01-31-02, 03:02 PM
#6
Intermediate
Originally posted by Keith13b
Read the Max pressure on the side wall of the tire. Then, after a long drive where the tires are all nicely heated up, you can inflate your tires up to that point as a maximum. Its good to leave a little room for error there, because over inflated tires wear out unevenly, and are more prone to blowouts.
Keith
Read the Max pressure on the side wall of the tire. Then, after a long drive where the tires are all nicely heated up, you can inflate your tires up to that point as a maximum. Its good to leave a little room for error there, because over inflated tires wear out unevenly, and are more prone to blowouts.
Keith
Although negligible, usually air from the pump is cooler than what's inside your tires already. When you mix air like that, you get different pressures. (WTF is this guy talking about?)
Air, like any other solid (yes, air is a solid), expands as ambient temperature rises (that's why turbo guys use intercoolers for better performance). Say you had a tire that was 15lb cold (tire A), and another tire that was 25lb cold (tire B). After you drove your vehicle until you're at operating temperature, tire A would go up to 20lb, whereas your tire B goes up to 35lb. So ... by Keith's theory, you add 15lbs of air to tire A, and nothing to tire B.
After you let it sit overnight, tire B goes back down to 25lb, and tire A goes go 20lb. You still have this 5lbs difference, which in turn is NOT the proper way to do it. By Keith's method, both tires would be at 35psi MAX at normal operating temperature, but improperly inflated when at ambient temperatures.
That's why the manufacturers rate the MAX psi at cold. The best time to add air is when your tires are relatively cold (or at ambient, meaning they haven't been driven). Just remember not to exceed the absolute maximum of the tire and you should be okay.
To answer your original question, always check with what's printed on your tire. The numbers in your glovebox are for those tire sizes which specifically came with your car. Different sizes require different air pressures.
Oh yeah ... your car's wandering is not necessarily tire pressure. It could be a bunch of other things, like loose suspension components, tires too wide, your tire's tread not cooperating with the road surface, etc., etc.
Last edited by moshlub; 01-31-02 at 03:06 PM.
01-31-02, 03:12 PM
#7
The numbers in your glovebox are for those tire sizes which specifically came with your car. Different sizes require different air pressures.
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01-31-02, 03:36 PM
#8
Intermediate
Most tire manufacturers recommend relatively the same pressure for the same sizes -- usually the only thing that changes is the max. So your answer would be yes. But always consult what's printed on your tire.
01-31-02, 05:25 PM
#9
The recommended tire pressure with stock 225/55 16" tires is 32 PSI all around. With lower profile tires, higher pressure is required in order to carry the same load, due to less volume of air contained in the tire.
By the way, air is a fluid, not a solid. Like all fluids, it expands and contracts with changes in temperature. The only exception to this rule is water, which expands as it solidfies into ice, due the the hydrogen bonds.
DJL
By the way, air is a fluid, not a solid. Like all fluids, it expands and contracts with changes in temperature. The only exception to this rule is water, which expands as it solidfies into ice, due the the hydrogen bonds.
DJL
02-01-02, 01:09 PM
#10
Normally I never flame, but this response will be the closest thing you'll ever see me get to a flame. It's just ignorance and arrogance somehow seem to go hand in hand, and it quite frankly annoys the **** out of me.
Exactly, WTF is this guy talking about ?
The VOLUME of air added to a tire to increase it from 32 psi to 35 psi is minimal. The temperature of of compressed gas is negligably less than ambient - I agree with you there, but it is just soooo minimal that I can't even believe you'd bring it up. So now the net loss of TOTAL temperature of air in tire is extreemely minor compared to the total VOLUME of air already compressed in the tire. REMEMBER>>>>>>>>>the air in the tire is also compressed, soooooooooo the net temp loss is again minimally cancelled out. BUt if everything is tested after all the air in the tire is the same, then they will be balanced out WHEN WARM.
Air, like any other solid (yes, air is a solid),
Who the hell taught you 3rd grade science man. Air is a LIQUID not a solid. In present state its a gas; but it holds the characteristics of highly spaced apart liquid molocules. Look in your kids science book. A solid.....now I think I've heard it all.
....expands as ambient temperature rises (that's why turbo guys use intercoolers for better performance). Say you had a tire that was 15lb cold (tire A), and another tire that was 25lb cold (tire B). After you drove your vehicle until you're at operating temperature, tire A would go up to 20lb, whereas your tire B goes up to 35lb. So ... by Keith's theory, you add 15lbs of air to tire A, and nothing to tire B.
You sooooooo lost me by attempting to use incorect physics here, and I see no correlation on how what you said relates to anything in my last post. If the two tires started off with different densities cold, then the rate of expansion is proportional to the initial density. Both tires would not gain equal amounts of pressure . i.e you stated 5 lbs. The greater density tire air would increase more than the lower density air. So your results would be more like Tire A would now have 16.875 lbs air at operating temp and Tire B would have 31.25 lbs air to be exact.
After you let it sit overnight, tire B goes back down to 25lb, and tire A goes go 20lb. You still have this 5lbs difference, which in turn is NOT the proper way to do it.
You ignorance of physics is making you look like an idiot. If you let the tires cool down, they will proportionaly go back you their original pressures, not what ever 5 lbs difference your talking about. Your logic makes no sence to me or relevance for that matter. Where in the hell do you get that 5 lb difference?????????????????????????????
By Keith's method, both tires would be at 35psi MAX at normal operating temperature, but improperly inflated when at ambient temperatures.
First off, they wouldn't be improperly inflated at ambient, they would just be at a proportinatly lower pressure of equal values. And by the way, you want to be at your optimum temperature AFTER the tires are warmed up, not prior. So you are aware of how the tires will handle at a specified PSI.
To put it simply, if your tires handle best at 38 psi, then fill them to 38 psi WARM, because if you fill them to 38 COLD, then they will be at a higher pressure after they are heated up, and now you just lost your optimum handling temp.
When inflated warm, they will cool down to a lower (but proportional) psi when cold, but you must have all tires at the same optimum pressure. Your tire pressure will change over the course of the year, so thats why you always inflate the tires before every race.
I think this guy is confusing MAX and optimal pressures. Your optimal pressure is not the max. I hope I didn't get too offensive, but just make sure you know what you are talking about before you start saying someone else is wrong.
Keith
I'm gone for the weekend, and won't be able to respond (defend) my post until monday. Enjoy.
Originally posted by moshlub
Although negligible, usually air from the pump is cooler than what's inside your tires already. When you mix air like that, you get different pressures. (WTF is this guy talking about?)
Although negligible, usually air from the pump is cooler than what's inside your tires already. When you mix air like that, you get different pressures. (WTF is this guy talking about?)
The VOLUME of air added to a tire to increase it from 32 psi to 35 psi is minimal. The temperature of of compressed gas is negligably less than ambient - I agree with you there, but it is just soooo minimal that I can't even believe you'd bring it up. So now the net loss of TOTAL temperature of air in tire is extreemely minor compared to the total VOLUME of air already compressed in the tire. REMEMBER>>>>>>>>>the air in the tire is also compressed, soooooooooo the net temp loss is again minimally cancelled out. BUt if everything is tested after all the air in the tire is the same, then they will be balanced out WHEN WARM.
Air, like any other solid (yes, air is a solid),
Who the hell taught you 3rd grade science man. Air is a LIQUID not a solid. In present state its a gas; but it holds the characteristics of highly spaced apart liquid molocules. Look in your kids science book. A solid.....now I think I've heard it all.
....expands as ambient temperature rises (that's why turbo guys use intercoolers for better performance). Say you had a tire that was 15lb cold (tire A), and another tire that was 25lb cold (tire B). After you drove your vehicle until you're at operating temperature, tire A would go up to 20lb, whereas your tire B goes up to 35lb. So ... by Keith's theory, you add 15lbs of air to tire A, and nothing to tire B.
After you let it sit overnight, tire B goes back down to 25lb, and tire A goes go 20lb. You still have this 5lbs difference, which in turn is NOT the proper way to do it.
By Keith's method, both tires would be at 35psi MAX at normal operating temperature, but improperly inflated when at ambient temperatures.
To put it simply, if your tires handle best at 38 psi, then fill them to 38 psi WARM, because if you fill them to 38 COLD, then they will be at a higher pressure after they are heated up, and now you just lost your optimum handling temp.
When inflated warm, they will cool down to a lower (but proportional) psi when cold, but you must have all tires at the same optimum pressure. Your tire pressure will change over the course of the year, so thats why you always inflate the tires before every race.
I think this guy is confusing MAX and optimal pressures. Your optimal pressure is not the max. I hope I didn't get too offensive, but just make sure you know what you are talking about before you start saying someone else is wrong.
Keith
I'm gone for the weekend, and won't be able to respond (defend) my post until monday. Enjoy.
Last edited by Keith13b; 02-01-02 at 01:14 PM.
02-06-02, 06:54 AM
#11
Pole Position
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This thread got me to thinking. Yesterday, while applying some tire finish (Zaino of course) to the new Bridgestone Pole Position S-03's, I noticed that the tire has embossed on th MAX TIRE PRESSURE = 65 pounds!
So this morning I called TireRack and the Bridgestone's 265-35YR-18 and 245-40YR-18 should be inflated for the SC400 at a maximum of 51 pounds but probably less. Tire pressure test should be done when tire is COLD. Inflation to your car's reccomended pounds should be performed when tire is as COOL as possible, preferably in the morning.
You should check you air pressures once a week (I do not) as you can loose 1 pound per week.
So guys, what have we learned here about the thinner wider tires???
1) the wider and thinner tires do require more pressure. Reason being is the sidewalls are thinner and according to TireRack the higher pressure provides a firm sidewall in the event that the tire hits a big rutt or pothole.
2) we have to modify the standard tire pressue on the door or engine compartment so that if the car is at a dealer or shop, they do not lower the tire pressure to "factory" 16" specs.
for more information on tire pressure:
http://www.tirerack.com/tires/tirete...l/pressure.htm
So this morning I called TireRack and the Bridgestone's 265-35YR-18 and 245-40YR-18 should be inflated for the SC400 at a maximum of 51 pounds but probably less. Tire pressure test should be done when tire is COLD. Inflation to your car's reccomended pounds should be performed when tire is as COOL as possible, preferably in the morning.
You should check you air pressures once a week (I do not) as you can loose 1 pound per week.
So guys, what have we learned here about the thinner wider tires???
1) the wider and thinner tires do require more pressure. Reason being is the sidewalls are thinner and according to TireRack the higher pressure provides a firm sidewall in the event that the tire hits a big rutt or pothole.
2) we have to modify the standard tire pressue on the door or engine compartment so that if the car is at a dealer or shop, they do not lower the tire pressure to "factory" 16" specs.
for more information on tire pressure:
http://www.tirerack.com/tires/tirete...l/pressure.htm
Last edited by Red93sc400; 02-06-02 at 06:54 PM.
02-06-02, 02:59 PM
#12
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Nice work there!
I have mine setup at 38PSI front and 35PSI rear on 235/45/17 and 255/40/17, I should increase the pressure to 38 in the rear section as well...
Peter~
I have mine setup at 38PSI front and 35PSI rear on 235/45/17 and 255/40/17, I should increase the pressure to 38 in the rear section as well...
Peter~
