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Tyre pressure??

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Old Mar 10, 2008 | 01:54 PM
  #1  
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happy dude
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Default Tyre pressure??

Hi everyone,

Does anyone know what the correct air pressure I should have in my tyres?? (my scoob has 17" wheels)
Also how would low tyre pressure effect the handling of the car??
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Old Mar 13, 2008 | 06:40 AM
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Plenty of posts on this already - so do a search and you'll get any number of views.

For road use the rough equivalences are: lower pressure=less grip & more wear, and higher pressure=better grip & less wear.

A good starting point is to run the recommended pressure for high speed/ load that is shown in the car user manual and often on a sticker on the car somewhere (in Oz on the driver door B-pillar). Do not ever exceed the maximum pressure that is molded onto the sidewall of the specific tyre you are using.

The trade-off for grip is harsher ride, but that's always the choice when you want performance and safety over comfort. Start with all tyres at that same pressure (typically 36-38psi) and then play around in small increments if you need to change the balance of the car.

If you have understeer (ie: front wheel slip) then a little less in the back tyres/ more in the front (eg: F38-R36) if you have oversteer then try F36-R38). If your have loaded up for trip with driver & 3 passengers & luggage then increase the rear tyres by 2-4psi (eg: F36-R40).

With modern steel belted radials there is little bowing out of the tyre centre at higher pressures (to the maximum rated psi), but low pressures will increase wear on outer edges.

Higher pressures will generally increase grip, reduce tyre wear and give improved fuel consumption (due largely to reduced rolling resistance). I have suspension mods that makes the handling pretty neutral so for daily use I run 42psi all round.

Some different rules apply for rallying (surface dependent) and for driving on sand - but few drivers do either very often. Pressures should be measured 'cold' ie: not after a long drive. Usually best to check them at the service station after a short drive from home or work. Or check them using your own gauge once a week in the morning before you drive off.

Upping your tyre pressures to the max is the most effective handling mod you can do and since air fills are usually free - the cheapest too. This is so for pretty much any car and any tyre.
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Old Mar 15, 2008 | 01:25 AM
  #3  
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renny
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I usually go between 36F 34R & 35F 33R on my 18's.
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