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Tyre pressure logic ...


Arkaneslayer
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Neutral Newbie

sorry not tonite bro. gotta prepare for Hari Raya Haji or else wifey will slaughter me instead of sheep. hopefully next week...or after WRXGal got her tattoo [sly][sly]

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Neutral Newbie

Thanks bro.

 

laugh.gifCant wait to see huhsly.gif.

 

laugh.giflaugh.gifdon't we all??sly.gif

 

 

 

oh ya, some questions on tyres pressure. I noticed that if i pumped 33-34psi, steering wheel will wobble and jump at >120kmh, but not at 30-31 psi. is it due to tyre pressure or is my balancing out. fyi i've gone for balancing and rebalancing about 3-4 times liow.

 

and i've also noticed that at 33-34psi pickup is better. i deduced that at a higher pressure, straights are better but not for bends. am i wrong?? i've tried different pressure and what i've found is such:

 

29-30psi= handlingthumbsup.gifbounce2.gif, FCthumbsdown.gifbigcry.gif, pickupthumbsdown.gifPosted Image

 

31-32psi=handlingPosted Image, FCPosted Image, pickupPosted Image

 

33psi+ =handlingPosted ImagePosted Image, FCPosted ImagePosted Image, pickupPosted ImagePosted Image

 

 

 

so i think maybe the optimum pressure for my tyres, taking into account ride comfort, handling, FC will be somewhere between the two extremes. am i right? comments please.

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huh.... i drive a swift GTI 1.3 which is barely 900kg and i weight around 60kg...

then the psi should be around 15-18... isn't the figure a bit ridiculous ?

 

 

 

wrong calculation!

 

960kg = 2116lbs

185/60-14 carries 1047lbs @ 44psi

 

tyre pressure

 

(2116/4188)*44 = 22 psi

 

recommended pressure should be 26 psi from the following site :

 

http://members.ozemail.com.au/~crawfy/swift.html#mass

 

i presume the car manufacturer assumes that the car carries 4 adults on the average. so making adjustments for another 3 adults ...say 50kg avg per adult :

 

(2447/4188)*44 = 25.7 psi

 

 

 

close enuff - dun you think?

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Saw your argument and there seems to be some logic in it. Tried applying to my car but result doesn't seem to match.

 

KW = 1250kg, Load = 200kg assuming 2 pax + petrol + stuffs. Therefore total wt = 1450kg.

 

Tyre rating Max 1356lb (615kg) @ 44psi. Therefore, max load = 2450kg@44psi.

 

Now, using the formulae,

 

(1450/2450) * 44psi = 26psi

 

That's a long way off from manufacturer's recommendation of 32 psi for normal load and plus 3 psi for full load. [dizzy]

 

For myself, I'll just go with the manufacturer's recommendation as mean and +/- 2 to 3psi, depending on my driving needs.

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hmmmm...... just sidetrack abit:- for a parked car which is subjected to vibrations in the dark corner of a isolated carpark, which tyre pressure is good?? tongue.giftongue.gifwink.gifwink.gif

That one depends on suspension system liao. rolleyes.gif

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Neutral Newbie

Your findings on FC and handling thumbsup.gif different tyre pressure do have impact and since you have found the optimum psi good for u thumbsup.gif

 

Picture paints a thousand words.....

 

____________________________________________________________

 

Correct Air Pressures

 

Setting and maintaining the correct air pressures is the first step to obtain optimum performance and life from tyres. Incorrect Inflation

 

Over inflation reduces the ability of the tyre to absorb road shocks resulting in a much harsher ride. Excessive over inflation may lead to impact fracture or other casing failures. Over inflation will also cause excessive wear of the centre of the tyre.

 

Under inflation allows excessive flexing of the tyre, causing excessive internal heat to build up, eventually weakening the casing and causing damage. Under inflation will also cause excessive wear on the shoulder of the tyre resulting in heavy steering and poor handling.

 

Excessive pressure on the shoulder area will increase wear and reduce stopping distance

 

62.gif Diagnosing problems from tyre wear.

 

 

Tyre wear patterns can tell a lot about problems with the wheel/tyre/suspension geometry setup. The first two signs to look for are over- and under-inflation. These are relatively easy to spot:

 

17.gifUnder-inflation Correct Over-inflation

 

 

 

http://www.orbweb.net/autoshop247/tyre_tal...afety_tips.html

Edited by E36UDM
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