Paul Bakker

Hi,
I want to switch from original 16" flat disc rims to 17" CUP 1 (or 2) rims.
In my rims I now have tire-pressure sensors. I'm not sure if (and how) these sensors can be re-used on the new CUP rims. I've heard these sensors are very delicate. I do'nt want to mess up! Any thoughts ?

Thanks,
Paul
'90 S4 (with tire pressure monitoring system)

Paul Bakker

Is there some kind of sender/receiver technology involved ? Do I need to keep my own original sensors ? If not, does the computer has to be reprogrammed by dealer ?

Just curious.

Thanks,
Paul

Rob Edwards

Each wheel has a pair of sensors and a detector mounted on a bracket on each hub. If you go from 16" wheels to 17" wheels you will need the longer GTS-specific brackets, or the extra 1/2" clearance will be too far away for the detector to work.

Cup1's had RDK sensors throughout 1992, 1993, and very early in 1994. I don't think that Cup 2's were ever made with RDK sensors but I could be mistaken.

Unless you really really want the system to still function, the easier option is to just find any 17+-inch non-sensor wheels and jumper the RDK computer connection so that you don't get the warning on the digital dash.

Thread on jumpering the RDK connector:

https://rennlist.com/forums/928-foru...to-repair.html

Vilhuer

ROW '94 GTS did not have RDK. Its just first 19 US model made which are in fact exact same as '93 MY US models and thus they have all the features '93 should have including Cup I wheels and RDK.

Only other 17" wheels with RDK possibility besides 7.5", 8" and 9" Cup I's made for '92-93 GTS I'm aware of are OZ Mito 3 wheels made for TechArt. Have seen two sets for sale in recent years.

There is also difference between rear 16x8 Flat Disk and D90 sersors vs 17x9 GTS summer and 17x8 winter Cup I. 16" rear wheels use 3.0 bar sensor while 17" has same 2.5 bar version as in front in all RDK wheels.

Rob Edwards

Erkka-

Thanks for filling in the gaps!

I've never seen (unless they're buried in the wheel thread and I've forgotten) OZ Mito 3's- got any pics?

Vilhuer

Meant to say 17"+ set and only 18" RDK available ever AFAIK. This is possibly only unused set around. Used 3/4 complete RDK set was for sale in Sweden recently. IIRR 4th wheel did not have sensor holes. Don't know if it sold or not.

Paul Bakker

Everything is much clearer now. Due to the complexity I'll stick to the flatdiscs.
Maybe I'll polish them to get a nice chrome like shine.... Any pictures anyone ?

Greetz,
Paul

jon928se

Just my opinion but I would abandon the RDK and thus permit yourself the opportunity to use a much bigger selection of wheels. RDK is completely pointless on a 928, if the wheel alignment is good then it is possible to tell that a tyre is at the wronng pressure well before it gets bad enough to be dangerous.

Tails

Interesting to note that the RDK is interlinked with the ABS and the PSD and differential tyre pressure is seen by Porsche as priority 1 safety issue as shown in the Owners Manual with cars fitted with RDK, even though Porsche discontinued the RDK system in the last few models of the GTS.

They produced two models of the RDK system, and the 1st system as installed in the 928 is a little difficult to maintain. There is a very good Technical Article in the latest Porsche Excellence magazine in which the RDK is given a full write up on how the system operates and also how to do a simple test and how to conduct a full test to set the system up correctly.

Personally I have two sets of disk S4 wheels that I use on my 928S4 and the RDK system operates fully with both sets of wheels and I would prefer to keep the RDK system operating to ensure vehicle safety, because there is not too much rubber area between the car and the road.

The safety of tyre pressure monitoring can be seen as one of the safety system on later cars as it is being introduced on more models and there are may after market tyre pressure monitoring systems now available.

I anyone wants to fully appreciate the technical aspects of the RDK system, its modus operandi and how to maintain it, it is fully described in Porsche Service Information Technik Booklet for the 1990 MY S4 & GT models on page 4-9 through to 4-16 and also in the Excellence Magazine article they recommend yearly full checks of the system, IIRC.

Tails 1990 928S4 Auto