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My TPMS wasn't active for almost a year (didn't have time to buy and change new sensors). Now after changing the tyres and TPMS sensors it works great...
Unfortunately there is strange behaviour from the system itself. When setting up the tyre size etc. (275/40 R20 Summer) it says that tyre pressure should be 2.6 front and 2.9 rear (for partial load). So I have inflated the tyres to this level and TPMS system after learning phase reads correctly 2.6 front and 2.9 rear, but... it says that I need to inflate tyres 0,3 bar more (to 2,9 front and 3,2 rear) which is not correct pressure neither for any of the wheel setups and not listed even for Full Load in the manual.
The TPMS sensors measure absolute pressure in the tire, and not the ambient pressure of where you live. In the Denver area I put 37 lbs Front and 41 lbs Rear in my Cayenne due to the lower air density, where the Owner's Manual calls for 35F and 39R partially loaded. Adding the extra air brings the TPMS sensors up to where the Cayenne wants them to be.
The TPMS sensors measure absolute pressure in the tire, and not the ambient pressure of where you live. In the Denver area I put 37 lbs Front and 41 lbs Rear in my Cayenne due to the lower air density, where the Owner's Manual calls for 35F and 39R partially loaded. Adding the extra air brings the TPMS sensors up to where the Cayenne wants them to be.
So when you check pressure in the Main Menu, does it force you to put 37 Front/ 41 Rear or like in owners manual - 35 Front / 39 Rear?
If I put 37F and 41R in, it usually reads 35F and 39R at 68 degrees F. I suspect I would simply use 35F and 39R if I lived at sea level. My home in the Denver area is at about 6000' in elevation.
I run 38F / 43R on my 09 TTS with the 22" wheels and 315/30 tires that I've told the system are the regular 21" summer tire setup and don't have any issues so I wouldn't be concerned about running a few extra psi if it makes the system happy. I even printed a label with these pressures on it and adhered it inside the fuel filler door so I don't have to remember what to use when I'm checking / adjusting the pressures.
Mine gets road tested up above 100mph regularly and usually with a full passenger and cargo load since it's out vacation trip vehicle.
Probably a better idea to inflate to what the tire says. The door sticker is more to do with limiting Porsche's liability rather than performance or fuel economy. With this in mind, I go the opposite direction and go 45F and 40R
Probably a better idea to inflate to what the tire says. The door sticker is more to do with limiting Porsche's liability rather than performance or fuel economy. With this in mind, I go the opposite direction and go 45F and 40R
Surely that combination can't do the handling or tyre wear any good? The figures on the tyres themselves are usually only generic and bear no relation to the Cayenne's weight or handling characteristics - I would strongly recommend that you stick to tried and tested pressures. Personally I use 38F 42R with my 20" summer tyres.
The max tire pressure cast in rubber on the tire sidewall is a spec based on the tire only. It is truly a MAX value. Made with no idea about what car it will be mounted on. So don't ever exceed that pressure (unlike the speed limit signs on the freeway, these are max values that are not intended to be exceeded, ever). And also like speed limit signs, you should not assume that it is bad to be below it.
The Porsche numbers are probably intended to optimize safety, handling, etc. while providing them with sufficient insulation from legal liability.
Some good threads on here discuss these in more detail with good numbers - people will generally come to different answers depending on multiple variables and optimization goals. Performance, comfort, tire wear, fuel efficiency ...
But hey, I've been wondering since post #1, but waited for others to answer the OP's question ... I've got a 2004 S too, and as far as I know, I don't have TPMS. Can that be right? Was it an option that I did not get?
My TPMS wasn't active for almost a year (didn't have time to buy and change new sensors). Now after changing the tyres and TPMS sensors it works great...
Unfortunately there is strange behaviour from the system itself. When setting up the tyre size etc. (275/40 R20 Summer) it says that tyre pressure should be 2.6 front and 2.9 rear (for partial load). So I have inflated the tyres to this level and TPMS system after learning phase reads correctly 2.6 front and 2.9 rear, but... it says that I need to inflate tyres 0,3 bar more (to 2,9 front and 3,2 rear) which is not correct pressure neither for any of the wheel setups and not listed even for Full Load in the manual.
Does anyone had similar issue? Cayenne S 2004
You should be able to change settings on the instrument cluster to select partial load and whatnot
Surely that combination can't do the handling or tyre wear any good? The figures on the tyres themselves are usually only generic and bear no relation to the Cayenne's weight or handling characteristics - I would strongly recommend that you stick to tried and tested pressures. Personally I use 38F 42R with my 20" summer tyres.
Max pressure for the tires are listed at 51psi. Running high 40s makes them handle and wear much, much better than running them 20% underinflated, as it appears most do.
Manufacturers also configure suspension settings that influence vehicle dynamics based on the pressures they recommend. It's usually very important to keep roughly the same pressure Differential front to rear even if you modify the absolute pressure numbers a bit based on individual use cases (load, driving style, etc) and on the Cayenne they want a 5-6 psi different front to rear with the rear being higher. You've completely reversed this making your front higher. Even in a light load situation, that's going to create significant understeer compared to balanced handling.
Manufacturers also configure suspension settings that influence vehicle dynamics based on the pressures they recommend. It's usually very important to keep roughly the same pressure Differential front to rear even if you modify the absolute pressure numbers a bit based on individual use cases (load, driving style, etc) and on the Cayenne they want a 5-6 psi different front to rear with the rear being higher. You've completely reversed this making your front higher. Even in a light load situation, that's going to create significant understeer compared to balanced handling.
Porches primary concern when establishing tire pressure guidelines is liability, not performance.
Lower rear tire pressure will cause a slight oversteer, not understeer.
Most trackday enthusiasts tend to run their tyres at lower pressures to get the correct handling and grip at racing speeds when the tyres are hot. If you run higher than stock pressures then you will risk overheating the tyres even more with even less grip.
During track days, if you’re using standard road tyres, a good starting point is 2-4 psi below the car manufacturers recommended pressures with a target hot pressure of 2-4 psi above.
If you’re using a track day tyre like the Yokohama A048 or Toyo R888 then you want to run them at the tyre manufacturer’s recommended ‘hot’ pressures.
That not my own theory - it is common knowledge in racing. My own pressures often rise around 4 psi when hot and I keep an eye on them with my TPMS, however if you really want to get the pressures to the perfect level then use a Lazer thermometer to measure the temps across the width of the tyre - the more even between centre and outsides the better.
Just sayin 🙃
06-17-2019, 08:53 AM
TPMS requesting high tyre pressure
