I figured I would share this quick simple tip on setting the optimal tire pressure for our 997.2 Turbo/(S). Quick background, Porsche engineers designed the TPMS in their cars to be so sophisticated that it can be optimized for both the type of tire and the cabin weight! Once selected, the TPMS determines the optimal tire pressure based on a pre-calibrated ambient temperature (I am told this is 68 degrees F/20 degrees C). The TPMS then adjusts continually as you drive and temps change.

Using the lower left hand stalk, delve into the menu and select "TPM" (car should be turned off but ignition in the "on" position where the dashboard lights are on). You should see a few selection options (i.e., Info Pressure, Info tyres, Load, etc).

Info Pressure - indicates over/under inflation of each tire based on the pre-selected settings using +/- psi readings

Info Tyres - allows you to select between Summer or Winter tires

Load - allows you to select Partial Load (Best - assumes only two occupants in the car) or Full Load (assumes four occupants in the car and a fully loaded frunk! Yikes!)

Select Summer tires [Info tyres setting] and Partial load [Load setting]. Either early in the morning (Best) or after the car has been stationary for a while in the shade check the inflation measures by selecting [Info Pressure]. If you note + or -, you need to correct your tire pressure by the indicated amount to set the optimal tire pressure (i.e., a +2 reading means that the particular tire is +2 psi OVER-inflated thus reduce tire pressure by 2 psi; -3 psi means the opposite, under-inflated thus add 3 psi). The goal is to show ZEROES at each wheel..!! Optimized.

The car's handling characteristics are greatly improved when zeroed. When I initially got my car, it was on the Full load setting, Winter tires and readings of +3 to +5 psi across all four tires. The car felt fine under normal driving conditions but push over +100 mph and the rear seemed to have a slight shimmy that sapped confidence (to be fair the cold surface street temperatures in March didn't help, these babies need to be warmed up to bring out the best in them)! I thought I needed suspension upgrades! I was informed of these settings by my indie, made the adjustments (zeroed in) and WOW, what a difference! Nicely planted even in the cold!

Many of you may already know this, for those who don't, check your settings and ZERO IN!! Happy motoring! (tip: if you show +/- 1 psi I wouldn't make any corrections, ambient vs. current temp cause slight fluctuations, however I would remedy anything over +/- 3 psi)

TPM menu


Sample incorrect tire pressure (illustration purposes)


Zeroed in!

 

So by this you reduced the fronts by 1psi and increased the rears by 1psi to get it back to zero?

And does this somehow affect PASM or PSM?

 

For this illustration, yes (I actually inflated the front and let air out of the rears for demonstration purposes). When I initially performed this adjustment I had varying reading on all four tires between +3psi to +5psi at each! The car was set on winter tires and full load!

I don't think it has any effect on PASM, the suspension works exactly the same. To be honest, I've only driven my car with PSM off once, when I did a few launch controls so this comment is pure conjecture. Given that PSM is primarily a traction/stability management system, I would think "zeroing" and improving traction thus handling may cause PSM to engage less frequently.

 

I'll check my settings first thing in the morning. For all I know it could be set exactly the way yours was.... lol

Thanks for the info!

 

This works well for satisfying TPMS, unfortunately, I'd be willing to bet if you used an accurate gauge you'd be off. TPMS just isn't accurate enough.

I personally don't give a damn what my TPMS tells me. If I did I'd be riding on concrete blocks. Do it manually with a good gauge is the best way IMO.

 

Obi, this is enlightening for those that we're unaware just how sophisticated TPMS Porsche fits onto their cars. And it is remarkably accurate down to .5 a psi, but it's not meant to replace a manual check with a reliable gauge.

Whoever advised you in such detail before you spent a boat load on suspension upgrades was very wise indeed Make sure the car is set up the way the P engineering gods intended first.

 

The Man himself! What's up Gus!! I'm just trying to share it forward and hopefully help a fellow P-car owner! Folks listen to Gus, he's wise indeed!

 

It is definitely not within 0.5. Multiple people with reliable gauges have stated it is often 3-4 PSI off. It's designed to let you know you have a rapid leak/problem with a tire. That is it.

 

I wonder is the 997.1 has the same feature? I see the logic though. I mean you can zero out the meter. Then take a gauge to dial it it even better.

 

I wish I had never done this now. I "thought" that the reset would put the TPMS limits at my new (lower) pressure ratings but it doesn't.

I finally got the tire pressures where I wanted them and now it constantly gives me the TPMS warning lights and when I shut the car down, it shows -5psi and tells me to put air in the tires. I'm not going to put air back in the tires as it put the pressure higher than I want.

Anyone know how to reset the TPMS to a lower value over that of the factory preset?

 

Nick, maybe you're in full load? If so go to partial load, and summer tires.
You don't need to reset and learn the system--that's only when you get new sensors or tires.

 

No. I set it for summer tires @ partial load.

So now that I've done the reset and it constantly gives me the warnings, is there a way of fixing it?

 

Really? With partial load says -5 psi? All 4 tires? What are the actual dash readings when cold? Should be 33/39 front/rear cold? And verify with a tire guage.

If the readings are off by 5 psi compared to your guage then sounds like the batteries in the TPMS sensors are getting old and start to glitch. I think they have a 5 year life before they error.

I had a 2007 Cabrio and the TPMS was accurate to 1/2 a psi, as well as the '09 turbo I have now. My friend's '08 just started glitching recently and the dealer read out said 12 months left on the sensor batterys, but they told him it's estimated and they glitch after 4/5 years. Let us know...

 

Dash readings when cold are 31F/36R per the display in the dash.

Batteries are good per Durametric. I checked them this weekend and it showed they are good for 67 months.

 

Ok verify the 31/36 with a good hand held guage. On the dash should rear -2 or -3, if you're under inflated just a couple psi...