Track Testing on Different Tire Pressure - 2013 Porsche 911 Carrera Cabriolet Long-Term Road Test

2013 Porsche 911 Carrera Cabriolet Long-Term Road Test

2013 Porsche 911 Carrera Cabriolet: Track Testing on Different Tire Pressure

May 20, 2013

2013 Porsche 911 Carrera Cabriolet

As you've read before, finding the correct tire pressures for our 2013 Porsche 911 is no easy task.

We're currently running our tires at 31 psi front and 34 psi rear according to the "comfort, part load" specifications. In conversations with Porsche, they suggested that we use this tire pressure for our testing as well as it should give us the best results.

We could take their word. Or we could try it out for ourselves.

Our first track test, which we published on Tuesday, didn't report the numbers at 31/34, but rather 31/39 — a pressure suggested in the manual for less casual driving and the one that our driver liked the best.

2013 Porsche 911 Carrera Cabriolet

See the numbers in the chart below, and the driver's comments below that.

  31/39 31/34
0-30 (sec.): 1.8 1.9
0-45 (sec.): 3.1 3.2
0-60 (sec.): 4.7 4.8
0-60 with 1-ft Rollout (sec.): 4.4 4.5
0-75 (sec.): 6.6 6.7
1/4-mile (sec @ mph): 12.9 @ 108.4 13.0 @ 107.9
30-0 (ft): 25 26
60-0 (ft): 102 102
Skid Pad Lateral Accel (g): 0.99 1.00
Slalom (mph): 71.3 70.5

Comments on 31 psi front, 39 psi rear:

Acceleration: I only did one run with Launch Control and it was essentially the same as before with the higher rear-tire pressures. Same amazing launch and lightening shifts. No measureable feel or difference.

Braking: Once tires and brakes were hot, the best stop was the second and matched exactly our previous best 60-0 stop. No measureable feel or difference.

Skidpad: Like before, zero intrusion from PSM as the limit approaches and is even surpassed. If I was forced to point out a difference with the lower rear pressures, I would say the rear slip angle was slightly greater, but we can't verify this with the instruments we have.

Slalom: Here, however, the car felt more lively and loose. The turn-in was just as quick, but the car itself felt less stable and trustworthy. Sure, the ultimate slalom speed is slightly lower, but more or less comparable (down by 0.8 mph) , yet it required more vigilance and concentration on my part. I'm confident I could match the previous best, but it would take a bunch of runs to knock off the mere 0.06 seconds that separate my previous best to today's best.

Mike Magrath Features Editor

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