JET951

Actually , when you think about the new prices ( now ) and consider these Forged / anodised Fuchs wheels that were always expensive to make new in Germany some 26 + years ago & have been stored in individual boxes ( which take up a lot of storage shelf space ) ever since , so in essence the return on investment from Porsche buying these new from Fuchs & storing them in a warehouse that someone has to pay for & this also includes the airfreight to anywhere in the world as well .

Then on top of that I am amazed there are any 928 parts at all , most other car manufacturers , delete old stock ( write off within tax rules ) and get this stuff destroyed within 11 years in some cases

JET951

Just out of curiosity , I typed the part number for a rear wheel for Carrera GT into Pelican Parts & the 980 362 174 12 rear wheel is $ 7,458.50 US Dollars ( thats for one wheel ) , now thats an exotic price

Red Flash

Well, thanks to the knowledge of a couple of you very special people (notably but not exclusively Rob, Bruce and Roger) I am moving forward on this project. The publicity of the thread also provided in some areas a meaningful cost reduction in the project. :-)

I got the GT out from winter sleep today and after an exhilarating drive started the work. The project will proceed like this:
1.) Cleaning and equipping very dirty and rather beat up D90s with used 2.5 bar RDK sensors in all corners. (Doesn't it seem like all 928 projects start with cleaning?)
2.) Then I will re-install the RDK controller and undo the bypass done by the (very responsible by the way) previous owner.
3.) Then I will test all the sensors and system.
4.) After the first 3 steps, I will transfer everything to the new rims. I am hoping that by doing this I will avoid multiple mounts and demounts on the new rims.

Some notes on step 1: the D90s came with the 2.5 and 3.0 bar sensors of course and they are indeed tan and black respectively. I covered the inner surface with tape (see picture) during the cleaning process to avoid getting water in there. I have no idea, if it would hurt them or not...

Given the fact that I have Eibachs, people have advised me that I should stick to the stock tire width, but, which model tires to finally select? I am thinking to go with the Potenza S-02 or the Continental SportContacts in all corners in the specified factor sizes 225/50 and 245/45. These tires seem to me to be a good balance between performance in wet and dry weather with the correct speed rating for the car. Note that these tires ARE available in the correct front and rear sizes, but I will have to import the rear ones from Germany. Why don't they just sell them in the US too?

Attached a picture of the cleaning stage... don't we all love that part?

FBIII

I don't understand what running Eiback springs has to do with running stock tire sizes. I think you will find running the 225 on the front will really leave the edges of your rims vulnerable. On my car it appears under tired. I don't see the factory's logic in why an 8 inch rim used on the back of the S4 received a 245 and when you put an 8 inch rim on the front of a GT it receives a 225.

Red Flash

OK, so we finally made more progress today. The test rims were completely degreased, the 3bar sensors were switched out on the back rims and all sensors got new seals.

Two problems came up:
1.) The RDK sensors have an anodized aluminum housing. On 2 of the sensors the threads were highly corroded. What should you do to avoid this corrosion in the future? Could you put a small amount of anti-seize compound?
2.) The second observation was that in the WSM it states to always replace the seals AND the mounting nuts? Are they for real with the mounting nuts? Why do you need to do this?

Any suggestions on these points?

John

Red Flash

FBIII,

Somewhere you are probably right here. I am going to have dig into the question of offsets, scrub radius', clearnace, etc. now. Currently, I've got 17" rims with 255 on the front and 265 on the back (with the Eibach springs.)

Regarding the front, I am rather worried that the 225 tires in front will be utterly too skimpy... which is why I originally wanted to run 9" ROW CS in all corners. On the other hand, if you look at the picture attached, the rims I have now stick out way too far for my taste. It just looks like a problem waiting to happen. That having been said, these rims and tire sizes have been on the car at least 10.000 miles!

Rob Edwards

Replacing the seals, yes. Replacing the mounting nuts, NFW, unless they got all munged up in the process of removing them. The nuts (928 361 203 01
) are absurd, like $25, and only take 15 ft-lbs of torque.

FBIII

"Regarding the front, I am rather worried that the 225 tires in front will be utterly too skimpy... which is why I originally wanted to run 9" ROW CS in all corners. On the other hand, if you look at the picture attached, the rims I have now stick out way too far for my taste. It just looks like a problem waiting to happen. That having been said, these rims and tire sizes have been on the car at least 10.000 miles!"

If you want I could shoot you a picture of the 8's with stock 225's. They do look very skimpy and the edge of the rim protrudes out from the tire.

dr bob

You are investing a lot of time restoring the RDK function. Here's the good news-- tire technology has advenaced some in the 25+ years since our cars were built. The 2.5 and 3.0 bar pressure recommendations won't apply to your modern tires. Running the new tires at their correct pressures will have the warnings showing. Running the higher pressures needed to satisfy the RDK will give you tire wear and ride issues you won't like. You'll need to reseal the sensors to keep air from falling out of the tire, but don't lose the bypass jumper for the controller plugs.

Red Flash

Dr. Bob

Please feel free to expand on these points. I am thinking that due to the newer technology, the 3.0 bar sensors are for sure not needed in back, this is why I am "upgrading" the back sensors to 2.5 bar. Are 2.5 bar sensors in all corners so far off the mark though? I resealed the sensors with new seals according to the WSM, is there anything else you are hinting at here?

Thanks and regards,

John

jcorenman

John, the 3.0 bar sensors were never needed in the back, but somebody in the late 80's thought it would be a good idea. I don't think it was the engineers.

Fitting the 2.5 sensors and getting it working is absolutely the right choice, but don't be surprised if you find that a bit less pressure suits you better. We run 33 psi front and rear, plus/minus a pound or two depending on the tire. And in that case the RDK may show an alarm. But you always have the jumper option, and a working RDK if you or someone later chooses to use it.

I also think it would be pretty simple to convert the sensors to 2.0 bar. "All you gotta do" (tm) is take them apart, cut a bit off the spring, and reassemble without leaks. I don't need another project but if you are going to toss the 3.0's then shoot me a PM.

Mark Anderson

Jim I have a few " less than desireable" sensors you can play with . Remind me and I'll toss one in with your next order.

jcorenman

Cool, thanks!