Jim Chambers

Do the sensors in the wheels sense the actual pressure, ie, 36 lbs in front, or do they simply sense the change. I am totally frustrated with my TPS. I get the light off and it lasts for about one trip to the store and the dash reports one or more corners to be low. I have the best luck when I cold inflate a couple of pounds above spec. My concern is compounded by the fact that my car came with 4 new Toyo tires (would not have been my choice) and they are rated at 44psi max. To even temporarily turn off the warning lights I have to start with the rears at about 46. I am not comfortable with tires at their max when cold.

Marine Blue

I've been running at or slightly above the recommended pressures on my Toyo's for the past couple of years without any problems. The sensors are set to a certain pressure and when the tire pressure falls below the setting it lights up the dash....literally!

Often when the tires heat up and you stop/start the car the tire pressure is high enough that it meets the low pressure setting and the warning doesn't show.

Rob Edwards

Though it violates every purist impulse in my body, I would just pull the connector to the RDK brain above your left foot and jumper pins 2 and 13. You've now been conditioned to check your tire pressures so often that you will never run the risk of your tires getting too low a pressure. And it'll free you to experiment with tire pressures that will optimize your tail-out cloverleaf powersliding pleasure.

pcar928fan

They are notoriously picky and frequently just broken and they cost a fortune to fix but will still fault AT and certainly below the factory recommended tire pressures. Most people just disable the function these days...

Jim Chambers

Yes, they are holding pressure. A little more detail on the jumping process please Rob (I too have to fight my entrenched purist nature). Pull the connector on the RDK, then jump pins on the
RDK or on the connector? Then reconnect the plug? What to use as a jumper? As you can tell I am not familiar with the process. Not eve sure I will know the RDK when I see it.

edit: I am aware of the temp. factor and have inflated all to spec at about 70 degrees in the garage, even using multiple gauges.
I am wondering if altitude is a factor for me. I live at 3800 feet in Bend, OR.

Rob Edwards

Jim:

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

Bertrand's pic in post #2.

Marine Blue

Altitude may not affect but if you're leaving the car outside or if temperatures drop the pressue also drops as you know.

I didn't think that the pressure sensors also accounted for temperature, is that right?

Jim Chambers

So the RDK (what do those letters mean?) is left disconnected. I assume the RDK component is only for the tire pressure system.
I think I will do the low pressure, drive, high pressure, drive, deflate to spec. thing one more time. If that fails, jumper 2-13.

docmirror

Reifen Druk Kontrol.

I've been told that the RDK setpoints can be modified through some various pushing and pulling of the stalk. I don't know how to do it but you may want to check your cars manual.

RKD in OKC

The first thing I would recommend is getting out your manual and set the tires pressures according those instructions. IE. air the tires (Or tire that is a problem) to a lower pressure, I think it is 32, and drive around the block. Then air them up to a higher pressure, I think it is 44, then drive around the block. Then bleed them down to the correct pressures, 36 front. On my GT the rear tire low, high, and set pressures were different than the fronts.

When my dealer, or a mechanic used the hammer to set my RDK it would go off all the time, Only when I followed the manual and did the low, drive, high, drive, bleed thing did they work properly. After setting them this way they would only go off when the pressure fell at or below 30psi. Only once did they false in two years and doing the setting procedure on all four fixed it.

And I think it would be great if I could have the RDK system on my non-stock wheels and my 94 GTS. It worked fantastic on my 90GT and the stock wheels. Saved me twice from coming out to a flat tire after picking up nails. I was able to drive to a tire shop and get the holes fixed, no putting a spare on.

Marine Blue

This is odd, I have never had any problems with the RDK unless the tire pressure are truly lower than spec. If I fill the tires while the car is off and make sure they are at or slightly above (.5 PSI) the setpoint I never have a problem. Of course after two or three months one of the tires will get low but I simply add more and they're fine again.

Jim Chambers

OK, just did manual procedure...8 lbs under, drive; 8 lbs over, drive; deflate to spec. The warning lights performed as prescribed, all 4 arrows flashing when under inflated, nothing when over inflated. Now off for a drive. I will report back.

Tails

I have two sets of rims with RDK and no problems for the last 11 years.

As stated above there is a procedure to set the pressure in the owners manual and if you have Jim's Technical CD there is a more comprehensive procedure for setting up the RDK, IIRC.

Tails 1990 928S4 Auto

Jim Chambers

I just drove the car for about 20 miles and the lights stayed off! First time ever. Clearly just inflating the tires to spec is not sufficient, but maybe it will be now. Hope I don't have to do the under/over very often but problem solved for now.

Marine Blue

I personally think the technology is just too accurate. The first few times I inflated the tire pressure I relied on the crappy gas station gauges and or the gauge on my walmart inflator. Needless to say that neither gauge was very accurate and when I finally found my digital gauge I realized that the tires were not fully inflated. I've never bother with the under/over adjustment and it works fine.