Phil68

Does anyone know at what pressure loss the tire pressure monitoring system installed in the 2017 Audi S8 plus will display a warning? Is there a way to adjust the warning threshold?
Thanks for any help!

Mike911A8

I don’t know the precise pressure loss necessary to trigger the warning, but it’s not very much. The pressure drop associated with the onset of cold weather will trigger it. After you increase tire pressure, resetting is very simple. Select the CAR function button on the MMI, then go to Car Systems (lower left corner button), then rotate the control **** to Service and press. You will see the tire pressure monitor display, and be prompted to reset the parameters. Mike

uberwgn

I think the government/standard threshold is 25%, no? I feel that the dTPMS sets off earlier than that. It seems like the iTPMS sets off later than that. We have both systems on our cars.

Phil, it seems like your car would have the in-wheels sensors for the TPMS?

Mike911A8

The S8 Plus does , in fact, have the in wheel sensors which transmit for display both pressure and temperature. Mike

MP4.2+6.0

I don't think there is a lot of information around to answer the questions easily. Also note the OP is in Switzerland.

On the D3 with in wheel TPMS, you could find the pressure triggering points stored in the TPMS module using VCDS or similar tool. On D4 with in wheel TPMS, I don't know if that module still exists or it has been integrated into one of the others like the body control module. Audi has been combining some of the modules as electronic processing power has gone up and new car demands put pressure on reducing space used and cost. Anyway, that's where I would look, and then see if the parameters can be modified.

On the USA side, only the S8 Pluses will have in wheel TPMS. In other markets it may have been sold as an optional system for other various motor variants. For USA, because of the Ford Explorer roll over debacle the pressures listed on the door jamb sticker are also generally higher (since approx. 2008) than in other markets. They now tie to the pressure to support maximum load as opposed to what the vehicle manufacturer thinks makes sense for handling dynamics, comfort, varying loads, tire wear, etc. I don't know if that then means the minimum pressure parameters used for TPMS vary by country. The owner's manual has better info for recommended tire pressures than the USA door jamb sticker does. It also typically has the range of recommended pressures by motor and wheel size; the jamb sticker meanwhile has been dumbed down.

Finally S8 Pluses have higher baseline pressure settings IIRC. So high that to me in the USA context they seem excessive. I expect it relates to higher potential running speed, but the weights of the Plus and non Plus are the same, and not too many people I know in the USA even exceed 90 or 100MPH, let alone S8 155 MPH or S8 Plus 190 MPH.

For others in USA market or who switched wheel sizes, when I went from 21's to 20's I came down several PSI on the pressure settings. I decided on the pressure by looking at a tire load index table and cross checking from the original size to the replacement size. I also cross checked it against the owner's manual for 21's vs. 20's.

Phil68

Thank you guys for your answers. In fact my S8 plus have the in wheel TPMS and thanks to Mike for your guidance on how to save the reference values. But that is already clear to me. I'm really looking at the difference between the pressure loss at which the TPMS trigger an alarm and whether they take the temperature into account. @MP4.2+6.0: I didn't find anything in the VCDS in a very short time, but I'll do a more thorough search taking your advice into consideration. Thanks!

MP4.2+6.0

On D3 the pressures were in measuring blocks in the TPMS module if I am remembering correctly. But it has been years since I looked at it. I don't recall whether temps were in there.

Covered in depth in Audi USA's Self Study Program (SSP) 992203 from back in 2002 from looking at some old stuff--probably as a warm up for D3 intro. Copyrighted document as far as posting here, but you may be able to find it somewhere on web as a pdf.

I haven't looked in my D4 (or B8 Q5) for a TPMS module or function--since I have the indirect version. But from experience if you don't find it directly, also look at things like the body control and comfort modules. Those are among areas where Audi has been combining modules and functions in the newer models.

Mike911A8

Phil, I don’t think the system takes temperature into account, at least not in the sense that the system would determine what the pressure would be if a “normalized” temperature applied, rather than the actual temperature. I say this because I had a pressure warning recently when the temp dropped into the teens recently, and my indicated pressure was about 37 or 38, whereas I normally run at about 42 psi on the particular tire. In fact, I noticed that you were in Switzerland, and the cold winter temp sort of jumped out to me as the cause of the warning. I tend to believe that Audi is hyper critical about tires and tire pressure on the S8+ because of the potential speeds achievable, and it doesn’t take much of a pressure drop to trigger a warning.

But if Audi is indeed hyper critical about tire pressure, as I suspect, they do a lousy job of informing the driver as to the correct pressure. Specifically, my door jam sticker states 39/38 f/r, whereas the owner’s manual specifies 45/39 for a normal load, and 49/48 for maximum load. These are all 275/35-21 tires.

MP4, my owner’s manual (2018) lists the following pressure for the regular S8: 36/30 normal, 44/42 maximum load, same size tire. I’ve been running 46/42, normal load, and it feels good. I believe you run 20”, and the manual specifies 36/30 and 39/38 for 265/40-20’s.

mike