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  1. #1
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    Default tyre pressure - higher or lower for better grip?

    I use 215/45/17 yokohama AD07 tyres on my car.

    Recently i added air, to 34 psi all around. And i noticed that i'm taking the same turns at same speeds but now my car is no longer making skidding noises. Before my air probably was on 31 or 32 psi and it would make slight skidding noises.

    So.... what is better? I thought higher pressure would usually yield better fuel economy but the car will be more "bouncy" meaning less grip?

    Why is it that after i increased my pressure my car is no longer skidding?

  2. #2
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    Default Re: tyre pressure - higher or lower for better grip?

    Quote Originally Posted by Dilip
    I use 215/45/17 yokohama AD07 tyres on my car.

    Recently i added air, to 34 psi all around. And i noticed that i'm taking the same turns at same speeds but now my car is no longer making skidding noises. Before my air probably was on 31 or 32 psi and it would make slight skidding noises.

    So.... what is better? I thought higher pressure would usually yield better fuel economy but the car will be more "bouncy" meaning less grip?

    Why is it that after i increased my pressure my car is no longer skidding?
    Think of the fact that the side walls are stiffer, and therefore the tires are working the proper way, in addition to the "sweat spot" of tyre inflation, your suspension now also works better. These are just the smallest adjustments that can make a big impact.

    As far as where the "sweet spot" is for tire pressure, that is difficult to say, there are too many variables as well as too many different tyres.

    The common thnking lower pressure makes the tyre sag alittle therefore increaseing surface area thus increases grip is not so clear cut.

    Just as it amazes me how a motocycle tyre sticks to the road on a high speed turn with nothing more than the surface area of the palm of your hand if it is that much. Friction and todays special polymer compounds do wonderfull things. Sticky, sticky.

    Max inflation for my tyres is 42 psi, I like to keep them at between 36-38 psi.

  3. #3
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    Thats why it puzzles me. I would think a higher inflation (to a point) would yield worse results, but in fact i skid less with higher inflation....

    I think my sweet spot would lie between 32-34 psi?

  4. #4
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    Quote Originally Posted by Dilip
    Thats why it puzzles me. I would think a higher inflation (to a point) would yield worse results, but in fact i skid less with higher inflation....

    I think my sweet spot would lie between 32-34 psi?
    Well if you over inflate toooo much, then you take away from the tyres foot print and again the tyre does not work correctly. You can bump it alittle more and see what results you get.

  5. #5
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    I've been keeping my tires well over-inflated (85%-90% of max sidewall) to boost fuel economy and haven't noticed any handling issues. The shape of modern belted radials is very well constrained and up to a point you shouldn't see the contact patch decrease too much. The only drawback that I can feel is a slightly harsher ride since the tires are harder than they used to be. (This could be bad for suspension components.) I would suggest that you inflate your tires in small increments (1 or 2psi at a time) to see what you like best. If the manufacturer recommends a bias front to rear (e.g.32 front 34 rear) you should keep the 2psi or whatever bias so as to limit any negative impact to handling. Be very careful as you experiment, though, especially since you are a "spirited" driver. Engineers design cars to understeer as an intentional warning that the driver is near the limits of handling. No tire sqeal could mean that you are doing fine or it could mean that you won't get any warning before swapping ends!

  6. #6
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    My vehicle 's door has printed the recommended tyre inflation of 32 front and back. Now i'm trying 34.

    Yes.... i am very worried that i may not get squeeling to warn me and i may just lose the end without any warning... but i'll sure be careful.

  7. #7
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    Forget about what is printed on car door and manual. What is the max inflation pressure on the sidewall of the tire. Also another considering point is load rating... general relates to how stiff the side walls are. I once had Pirelli that had max 50 psi, so I had them confortable at 40 psi, anything more was just too harsh of a ride. My Michelin are rated max 42 psi, I adjust them every so often up to 38 (note the rear are less because all its load is the empty trunk), I have 215/45 17 93V, I will be going 225/40 17 for my next set, Yoko avs es100, they will not last as much as my Mich but they are dirt cheap in comparison.

    Anyways here is a spectacular site that give you more than enough information.

    http://www.tirerack.com/about/techcenter.jsp :wink:

  8. #8
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    Hey amoney, you really do use high psi's for your accord which is similar weight and layout to my car.....

    anyways, that is a very very useful site, i'll be sure to take my time to read it.
    thanks for your help!

  9. #9
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    It all depends on the car, tires, and driving style.

    I run staggered tire pressures on my cars based on if I want them to handle neutral or oversteer some (I never want understeer). Changing the pressure on the rear (either lower or higher to the right point) achieves this.

    You want to have enough pressure in your tires so that when you take a corner the side wall does not roll over.

    But you do not want so much that the edges of the the tread never touch the road.

    And if you're not into changing your tire pressures often for daily driving and sprited driving then you also have to find the right compromise for air pressure. Something that doesn't ride bad but that doesn't allow the tires to roll over.

    I think the tires you have have a fairly stiff sidewall, so insanely high air pressures won't be needed. No more than 37 or 38 for the hardest driving. If ~34 is working good for you, I'd leave it about there. That should not wear the tires out any sooner or give you a really harsh ride.

  10. #10
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    Quote Originally Posted by Kremithefrog

    You want to have enough pressure in your tires so that when you take a corner the side wall does not roll over.

    But you do not want so much that the edges of the the tread never touch the road.
    At open track events, it's common to see someone place marks across the tire and up the sidewall before going out onto the track. When you come back in after some hot laps, you can look and based on the wear off of the mark, get an estimate of the tire's contact patch. You find a good pressure based on driving style and your car's particulars.

    Ed

 

 

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