[Larry Currie]

I changed to 17" wheels a couple of years ago, and I have continued to run 36 psi in all 4 tires. I have just bought a set of Pirelli PZero Rosso tires. I'm running 205/50-17 front and 255/40-17 back. Is the 36psi still the correct pressure? <img src="/forum/images/smilies/968/dry.gif" class="smilie" alt="" /> <img src="/forum/images/smilies/968/dry.gif" class="smilie" alt="" />

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[flash]

pirellis tend to be softer sidewalls, that means a couple of pounds more than a tire with stiff sidewalls - usage is the key here though - autocross settings are not anywhere near street settings - also, you have a slightly narrow tire on the front - that would have me setting the front tires a pound lower than what i would set the correct size



again though, the chalk or shoe polish method works very well at determining what you are using



but, for street, yes, 36 all around will serve you well

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[Langley968]

I was searching around the Forums for info as to why my rear / passenger-side tire (POTENZA 255) would be showing premature wear as compared to the driver-side. [img]style_emoticons/<#EMO_DIR#>/mad.gif[/img]
The wear is down the center. Would that type of wear be indicative of running the tire pressure too low? I thought initially that the pressure would be too high. I checked yesterday and it read 30.5 PSI. I see in this thread that Flash recommends 36 PSI for street.
Could an improperly balanced wheel cause wear down the center?
I am now looking to replace the rear tires. Last Saturday I went on the local Porsche Breakfast Run and was a little aprehensive about a tire failure. I will replace them before I try those speeds again! [img]style_emoticons/<#EMO_DIR#>/mellow.gif[/img]

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[flash]

sounds odd

http://www.procarcare.com/includes/content...adtirewear.html

might be a thrust angle problem

measure across the tire for an accurate assessment

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[ds968]

I have the OE 17s, PS2 tires ( relatively soft wall ) did the chalk thing, we also tested the temps when hot - my most even wear, and best PSI settings for the right hot temps are when the inflation is at 29 front and 30 rear ( cold ).

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[Tom030]

Jake,
Center wear is not unusual on rear tires on Porsches. If they are non limited slip the right rear will wear faster than the left. Center wear is not necessarily caused by under or over inflation. Torque is transferred to the tire via the wheel center out to both sidewalls of the tire down to the shoulders and across to the tread which is dragged across the pavement in order to provide traction. Wear will vary depending on belt type, rubber compound and right foot pressure among other things.
~tom

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[flash]

lol - i'm gonna measure dan's tire temps the next time he's down here - i have a very hard time imagining those tires getting to 40 (the hot target temp for street) from 30 - i'm willing to bet the outsides are hotter than the center, and not due to camber - i think that's too low, especially on mushelins - they usually need an extra pound or two over most other tires

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[Langley968]

Thanks for all the feed back guys.
I am glad I have three less mouths to feed over the past two months. With one daughter getting married and my son and my eldest daughter moving out, I should have some "extra" cash around for tires (rather than groceries!). [img]style_emoticons/<#EMO_DIR#>/biggrin.gif[/img]

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[flash]

tell me about it - with all the house projects, and the supercharger, my "expendable cash" has run out - i just had to buy tires for the 968 - a whopping $1400

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[ds968]

" i'm gonna measure dan's tire temps the next time he's down here "

you did, last time. and as a result, we lowered the front by 1psi and increased the rear by 1 psi.

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[biotechee]

Lil' bit of a thread revival here...

Two questions-

1) The chalk method - what is it? I presume you take chalk and draw across the tread, in as much of a straight line as possible, from sidewall to sidewall. Then drive the car. Chalk missing from the center but still visible on the sides indicates too much pressure whereas chalk missing from the sides and present in the center indicates too little pressure. Is this correct?

2) I have Goodyear F1 GS-D3 tires on my cab. 36 psi cold all around seems a tad high to me. I do not drive the cab aggressively - no more than say 5-6/10's of the car's potential. Is 36 cold still a good starting point?

Thanks in advance.

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[94SilverCab]

I did a search for information outside of this website (shivers in horror) and discovered this little gem, hope you enjoy.

http://www.automedia.com/Optimizing_Tire_P...ccr20010801tp/1

Jay

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[biotechee]

Thank you Sir!

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