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Tyre pressure


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35 minutes ago, firstone said:

Seems simple enough. Recommended 225/40/18  29psi front

265/35/18  36psi rear

Just had 2 new ps4s fitted and tyre guy gave them 40 front and rear.

Tell me your thoughts.

Not much else goin on atm.

Must admit I've previously run at higher pressures, but since getting the new race / road tyres on the GT3 I've become more aware of the need to monitor pressures based on the driving at the time.  I'm actually about to drop the road pressures in my fronts down a couple to PSI to pretty much what your label shows.  We've also dropped the pressures we have been running on the 981 as well........  But, @MFXhas been giving his PS4s  on his 996 C2 a real test and wringing them out pretty well - Jeff, what pressures have you been running???

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I dropped the pressure on the track from the 29/36 to from memory 26/29 (but don't quote me). It made a small difference, but I found the PS4 was very linear in it's slip, in the wet and the dry. Very predictable and easy to control, but the traction in the dry was not amazing. In the wet they were fantastic. Not far off from the performance in the dry and still communicated well with a nice linear slip.

The grip of the PS4 (note that there PS4 and PS4S which are different), was much better than the Dunlop junk that was on my car when I got it, but I am definitely going to change to PSC2's and test the difference. They may not last as long, but @Pork Chops now swears by them, wet and dry.

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As the sidewalk stiffness has a huge bearing on the pressure you need to run,the Pressure placard on your car is only relevant if you run the same or similar Tyres that were original fitment.Cup 2 or similar track Tyres have stiff sidewalls and on GT3 rec pressure is 29-31 which gives the Michelin recommended 10% increase between hot and cold pressure, which isn’t written in stone, but a good place to start. Too much pressure and you don’t get 10% increase and too low a pressure and you get more. As PS4 and 4s are road Tyres the best place to start is what is written on the car if your car came with road Tyres and check the increase between hot and cold, Direzzas are not as stiff as cups, but stiffer than road and from experimenting with them on my 993 I went from recommender 36-36 Down to 31-33 to get the 10 % and they worked perfectly, as they all work reasonably well at a wide range of pressures and it’s pretty hard to decipher feedback with constantly variable conditions I  have found that by sticking to the 10 % rule they always work and wear evenly 

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21 hours ago, firstone said:

Just had 2 new ps4s fitted and tyre guy gave them 40 front and rear.

He probably just pumped till the popped the beads on to the outer rims and left it that.

I ALWAYS check my pressure after the tyre guy does his thing as they don't know or care what pressure you want.

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47 minutes ago, Airhead said:

 

I ALWAYS check my pressure after the tyre guy does his thing as they don't know or care what pressure you want.

My tyre guy is a car guy so i take his advice mostly.

I have also played around with pressures myself and found that the better the tyre the less playing i have to do, i run about 36 in the rear and around 34 in the front, i have PS4's fitted on my 996 and will be sticking to these in the future, i was running lower pressure in the rear and one day caught the edge of a pothole and put a tiny crack in my rim, the tyre started losing pressure and i thought it was a screw or something. I would only run lower if i was at the track.

22 hours ago, firstone said:

 

Just had 2 new ps4s fitted and tyre guy gave them 40 front and rear.

 This is what my guy recommended as well.

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