FredR

I guess individual experiences differ but on my S4 the system was a PITA and the only way one could keep it quiet was with stupid high pressures that left you with noticeably less grip driving around on Flintstone wheels. I was never totally sure whether it was our climate or the rating of the sensors but it seemed much less of a problem during winter time. Best thing I did was when Marc Thomas told me what terminals to jumper. And yes- the centre of the tire wore- surprise surprise.

I thought the GTS models did not have the system fitted but clearly it was jumpered [thank goodness] or was it deleted on 94/95 models with cup 2 wheels?

I like the system fitted on my Cayenne- presumably similar to that Allan alludes to although even that may be an expensive extra if one has to replace the sensors with each tire change if one wishes to change the valve assembly. Not sure on that one- yet.

Jerry Feather

Hi Nicole. My "requirements" are different. When I bought my first 928 and drove it home from Longbeach, several times I found myself hitting 100 or so without any effort. I even got a ticket doing 94 in Eastern Utah about 70 miles from home. That is about when I resolved to carry more pressure in the tires--about 44 psi. So I did.

Then over a short period of time, even though I occasionally glanced at the treads, at least on the outer edges where they are readily visible, I finally found that the tread was wearing very rapidly in the center, and to the point of wearing down to the air in at least one spot. I limped home on the spare; and then resolved to not use more than about 36 psi, unless I was intending to go 100 or more on any special occasion.

This was on an 87 S4 with 17 inch Cups, 7.5 and 9 inch.

So, I now "require" only 36 psi all around. I don't see any reason that an aluminum wheel that is 16 inches in diameter would require 44 psi when an aluminum wheel that is 17 inches in diameter might require 36 psi. On the other hand, there could be a good reason for differing pressure requirements, but based on the tires and not the wheels. So, if I require 36 psi on a 9 inch wide 17 inch tire I think I can also require 36 psi on a 9 inch tire that is 16 inches in diameter. I think the tread wear issue will be essentially the same.

Now, the RDK system "requires" 44 on the rears, for some reason, which I suspect has more to do with the tires than the wheels, but that is only because the sensors on the 9 inch rears are designed for that. If I change the sensors on the rears to 2.5 BAR my rear wheels will now require only 36.

I don't know how to measure the happiness of the car, but I think it and I will be quite happy with this project, if I can have 2.5 BAR sensors all around and still have the RDK system work at least up to the limited extent that that is was designed to work.

It might be that the factory is the source of the requirements, but I have found enough issues with what the factory has done over the years to put myself in the position of questioning things and then doing what I can to correct them or make them better. The examples are all the things that I have redesigned and fabricate for the 928 inluding the WW liners for the GTS, the Spare Tire Cover, the Windshield Gap Filler Strips, the Cowl Covers, to name some. All of these are based on what might be considered mistakes by the factory, at least at some level.