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  1. Join Date
    Aug 2004
    Posts
    22,710
    #81
    Not as much less contact as you might think.

    Tests have shown that underinflation causes poorer braking distances. Empirical data from racing suggests that higher inflation rates provide more stable handlng in emergency situations.

    A lot of people will warn you that inflating past sticker is "unsafe", but without any real world technical testing to accurately describe how much more dangerous and why.

    Here's an article on emergency vehicle handling and tire pressures:

    Maximum Tire pressure (a police perspective)
    (the original article is no longer on officer.com... basically, they recommend 44 psi for high performance and emergency driving, based on testing at police high performance training centers... note that autocrossers usually use a high-30s to 40 psi inflation rate)

    And here's one of the few actual technical tests with regards to tire inflation and braking distances:

    FEA chapter III. tire pressure survey and test results

    You'll note that 35 psi of inflation gave better braking than 30 psi or similar braking, even in the wet, when higher inflation pressures supposedly increase the chance of hydroplaning. Note that in this case, 35 psi was the maximum sidewall pressure for the tire, and at the time, the door placard pressures of the vehicles being used were in the 28-30 psi range (nowadays, most door placards are in the 32 range).

    Hm. I think it's something that we can test at the next PCOTY, given that's the one time we have a track available for testing, to show the differences in safety in handling and braking with different inflation pressures from 25 to 45 psi.

    Different "authorities" will go on and on about the dangers, but nobody provides concrete data against higher inflation pressures, but rely merely on hearsay and theory based on older tire designs which were prone to crowning and extra wear at high inflation pressures.

    Which is strange, because, on the other hand, there's a ton of testing showing the dangers of underinflation. I hate that these people, whom others trust to "know" the answers simply parrot answers handed down from time immemorial without bothering to ever test their assumptions.

    On modern tires, I've run for years overinflating by 5 psi and have rarely seen a tire crown and wear down the center patch first. That's your indication that a tire is over-inflated and will cause poor braking and handling. Which is why I say YMMV... your mileage may vary... you find the pressure that doesn't cause abnormal wear and that one will give you the best handling and performance, because that's the one that gives you the most consistent contact patch.

    Ang pagbalik ng comeback...

  2. Join Date
    Jan 2010
    Posts
    282
    #82
    Quote Originally Posted by niky View Post
    Not as much less contact as you might think.

    Tests have shown that underinflation causes poorer braking distances. Empirical data from racing suggests that higher inflation rates provide more stable handlng in emergency situations.

    A lot of people will warn you that inflating past sticker is "unsafe", but without any real world technical testing to accurately describe how much more dangerous and why.

    Here's an article on emergency vehicle handling and tire pressures:

    Maximum Tire pressure (a police perspective)
    (the original article is no longer on officer.com... basically, they recommend 44 psi for high performance and emergency driving, based on testing at police high performance training centers... note that autocrossers usually use a high-30s to 40 psi inflation rate)

    And here's one of the few actual technical tests with regards to tire inflation and braking distances:

    FEA chapter III. tire pressure survey and test results

    You'll note that 35 psi of inflation gave better braking than 30 psi or similar braking, even in the wet, when higher inflation pressures supposedly increase the chance of hydroplaning. Note that in this case, 35 psi was the maximum sidewall pressure for the tire, and at the time, the door placard pressures of the vehicles being used were in the 28-30 psi range (nowadays, most door placards are in the 32 range).

    Hm. I think it's something that we can test at the next PCOTY, given that's the one time we have a track available for testing, to show the differences in safety in handling and braking with different inflation pressures from 25 to 45 psi.

    Different "authorities" will go on and on about the dangers, but nobody provides concrete data against higher inflation pressures, but rely merely on hearsay and theory based on older tire designs which were prone to crowning and extra wear at high inflation pressures.

    Which is strange, because, on the other hand, there's a ton of testing showing the dangers of underinflation. I hate that these people, whom others trust to "know" the answers simply parrot answers handed down from time immemorial without bothering to ever test their assumptions.

    On modern tires, I've run for years overinflating by 5 psi and have rarely seen a tire crown and wear down the center patch first. That's your indication that a tire is over-inflated and will cause poor braking and handling. Which is why I say YMMV... your mileage may vary... you find the pressure that doesn't cause abnormal wear and that one will give you the best handling and performance, because that's the one that gives you the most consistent contact patch.


    nothing personal and just for the sake of discussion, unless you are the author of this theory, you are just another parrot like the rest of us. peace brader

  3. Join Date
    Aug 2004
    Posts
    22,710
    #83
    Quote Originally Posted by barako ba ma View Post
    nothing personal and just for the sake of discussion, unless you are the author of this theory, you are just another parrot like the rest of us. peace brader
    There is a difference between parroting without analyzing and understanding and sharing knowledge gained from personal experience, study and research. Just because I cite research evidence that agrees with me doesn't mean I have opinions or thoughts of my own.

  4. Join Date
    Nov 2009
    Posts
    1,745
    #84
    I would say "yes" from the topic "Increased fuel economy from over-inflated tires".
    But for me, +4PSI sa standard concrete road is fine. Pero pag gamit na sya sa off road, I will still reduce my tire pressure to 31PSI (32 = Standard PSI), because I will not compromise comfort & car stress versus fuel economy, and besides hindi ganun karamdam ang fuel economy pag over inflated ka, except siguro kung over-over inflated ka at long run! Finally, mas ramdam mo ang car vibration pag 4PSI & up ka na versus -1 tire pressure sa standard tire pressure pag off road.

  5. Join Date
    Oct 2002
    Posts
    29,320
    #85
    Quote Originally Posted by barako ba ma View Post
    nothing personal and just for the sake of discussion, unless you are the author of this theory, you are just another parrot like the rest of us. peace brader
    Posters like this would be better if they simply keep to themselves. Posted messages like this add nothing to the actual discussion thread.

    Peace.

  6. Join Date
    Aug 2004
    Posts
    22,710
    #86
    Quote Originally Posted by Noel Salisipan View Post
    I would say "yes" from the topic "Increased fuel economy from over-inflated tires".
    But for me, +4PSI sa standard concrete road is fine. Pero pag gamit na sya sa off road, I will still reduce my tire pressure to 31PSI (32 = Standard PSI), because I will not compromise comfort & car stress versus fuel economy, and besides hindi ganun karamdam ang fuel economy pag over inflated ka, except siguro kung over-over inflated ka at long run! Finally, mas ramdam mo ang car vibration pag 4PSI & up ka na versus -1 tire pressure sa standard tire pressure pag off road.
    Yup. Heck, off-roaders even run less pressure for bad trails.

    The reasons are two-fold... One, if you hit a sharp rock at higher pressures, the chances of bruising the tire are higher. Two, you will have less chance of sinking.

    Both these reasons have to do with why "over" inflated tires give you more grip. Pressure per square inch on the tread of the tire. Underinflation gives you a bigger contact patch, so the weight is spread out over a greater area, and no area of the tire pushes down into the ground with as much force is with a fully-inflated tire (sort of like the difference between lying flat in the water and floating upright... if you lie flat, you won't sink as deep).

    On tarmac, you want the opposite... for tires to grip. So you inflate higher, and the difference is like trying to hold down a stack of papers in the wind by laying your hand flat on them or pressing down on them with your fingertips. You can more effectively hold them down with the same amount of force with just your fingertips. (This is also why we sprinters run on our toes, it gives us more grip and allows us to "dig in" for better traction)

    But like you said... it's uncomfortable, so it's really not for everybody.

    Ang pagbalik ng comeback...

  7. Join Date
    Jun 2011
    Posts
    4,509
    #87
    Quote Originally Posted by niky View Post
    If the van is for cargo carrying, I'd say stay within the maximum number.

    This is because an ultra-stiff tire does not cushion the suspension from shock as well as a tire inflated within the suggested pressure zone. If you hit a pothole with a full load, this increase the chances of the rubber 'bruising', leaving an uneven lump in the tread. You can experiment if you want, but this experimentation is at your own risk and at the risk of the safety of your driver. note that unlike more modern car tires, some truck tires are notorious for blowing up...
    sir i use a yokohama geolandar ht... 245 70r16 tires... its max. inflation reads 51psi... and the sticker on my front dr. reads 45psi unladen, and 55psi laden...
    sir can i use 55 psi on it?

    sir may nakausap po ako dati na technician or engineer ata yung sa isang tire factory... ang sabi kasi nya sakin ... mas mataas ang hangin mas matibay pa nga daw ang tires... ang dahilan daw po nito eh... para daw po kasing filler ang air... so mas maraming filler mas matibay.... im not sure pero ang pagkakatanda ko yung gulong nga daw na may max inflation ng 60psi.. kung i-test nila eh they put up to 95psi on it... to check kung may leak daw... or force ply ata yun... then may nabangit din po sya na meron daw 5psi na allowance pa daw yun sa max na recommended na naka indicate sa tires... sir again im not sure po ha.... at may 13years na po ata yun... sir i want to know if it is true...?

  8. Join Date
    Jun 2011
    Posts
    4,509
    #88
    Quote Originally Posted by uls View Post
    para lang makatipid konte mag o-over inflate kayo?

    there are other ways to save fuel

    don't know about you guys but i'd rather have more rubber on the road for traction than less rubber on the road just to save a few pesos
    sir hindi po makatipid ang talagang habol ko... kung may tipid na kasama ill take it as a bonus... the reason sir... the tires that is fitted on may van read max 51psi... na yokohama na geolandar ht 245 70r16... pero po ang naka indicate sa door ko eh... 45psi unladen, 55 psi laden... right now i use 44-45 psi... yung isang tires ko naman nag nakalagay max 44psi hankook ra07 245 70r16... ang gusto ko po malaman eh kung pwede ko lagyan ng 5psi over dun sa max psi na naka indicate dun sa tires... someone once told me that there is still an allowance of over 5psi on what is indicated on the tires... maybe the best thing is ill over inflate it first at 2-3psi over the recommended tire pressure indicated on the tires and see what happens after month.. then dagdagan ko nalang kung pwede pa... up to a max of addl. 5psi...

  9. Join Date
    Feb 2009
    Posts
    5,009
    #89
    Quote Originally Posted by glenn manikis View Post
    sir hindi po makatipid ang talagang habol ko... kung may tipid na kasama ill take it as a bonus... the reason sir... the tires that is fitted on may van read max 51psi... na yokohama na geolandar ht 245 70r16... pero po ang naka indicate sa door ko eh... 45psi unladen, 55 psi laden... right now i use 44-45 psi... yung isang tires ko naman nag nakalagay max 44psi hankook ra07 245 70r16... ang gusto ko po malaman eh kung pwede ko lagyan ng 5psi over dun sa max psi na naka indicate dun sa tires... someone once told me that there is still an allowance of over 5psi on what is indicated on the tires... maybe the best thing is ill over inflate it first at 2-3psi over the recommended tire pressure indicated on the tires and see what happens after month.. then dagdagan ko nalang kung pwede pa... up to a max of addl. 5psi...


    the tires were overinflated when the car left the assembly plant after the slide slip tester station. the extra pressure was an added allowance just in case the tire has a slow leak while in transit from the shipping yard to the dealership. this was also slightly overpressurized to eliminate or reduce the tire having a flat spot from shape memory retention of the tire. the recommended pressure is the balance between comfort and fuel economy just like the air fuel mixture, it is set at stoichiometric to balance power and economy and produce the least amount of pollutants

  10. Join Date
    Jan 2009
    Posts
    4,873
    #90
    You can over-inflate, not under-inflate. Under-inflating causes more sidewall flex and hence, heats up the rubber which under certain situations, can overheat to destruction.

    Tires are more resilient when over-inflated. However, as with the law of diminishing returns, if a slightly over-inflated tire gives you slightly better fuel economy, adding air beyond a certain point is not necessarily better even if it is way below the maximum pressure allowed for the tire.

    The road conditions where the car will be primarily used should be one of the things to be considered. The suspension would probably take most of the blunt out of the imperfect roads that we have here. Bushings, ball joints, tie rods, rack ends, etc. will all be exposed to additional forces and likely will not last quite as long. And because most passenger cars are of the unibody construction, the added strain of the road bumps that makes it past the tires and suspension makes the whole car susceptible to rattles. What's worse is that the daily pounding on the unibody can also cause it to flex more and eventually weaken due to fatigue.

    So a few cents of fuel savings per Km may not be enough for the repairs later.

    The tire pressure specified by car manufacturers provides the best compromise for fuel economy, comfort and reliability.

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Increased fuel economy from over-inflated tires