Wondering which aluminum lug is correct for a 993, the silver is from the 94 968 has a longer bevel, and matches the taper of the Cup2 wheel better, the black one is off of a 96 993, same size Cup2 wheels. The black one seems to meet only at small area and may be "galled". What is best, can either one be used? Part number 999.182.003.36 lists for all Fuchs 1967-1998

 

Hard to tell on the one that has lost its anodizing what its contact patch was for comparison.

 

all oe lug nuts/wheels used R14 ball seats, I know next to nothing about the water cooled cars from that era but guess that the stud exposed lengths may have been different from that of the air cooled

 

did porsche ever run conical ?
I know ours are ball seat..

 

After a little thought, I believe there is only one type of nut. This is validated by a single part number over all the application years as you note. Manufacturing differences may result in differences in the area of the convex contact face of the nut even if the area of the contact patch is the same when mounted. One could paint a little black nail polish on the nut that is missing its anodizing and then mount it and remove it to see the patch area. My concern about using it for comparison would be to use a nut that is so worn that the anodizing is completely gone may no longer meet the geometry specifications from when it was originally made,
ANdy

 

The black nut above looks suspicious to me

here are 3 from my cars all have the R14 ball

TI, Al, Fe

 

The black lug nut seems to only really tighten up in the thin band, where the black it worn off. Later today I am going to try "blueing" the wheel bevel and then check the contact. Both the 968 and 993 have the same wheels, Cup2 with the same hub and studs. But the 968 has natural aluminum finish lug nuts, and the 993 has the black. Will post later today my finding.

 

Yes, that's what seems off, it appears from here to be too shallow to be R14

 

Original Porsche rims are all made for R14 'round' ball fit.
Some aftermarket rims require 'conical' fit, looks like the upper nut is exactly for such rims ...

 

R14 refers to the radius of the ball

Porsche lugs are M14 x1.5 w/ an R14 ball seat
M1.4 x1.5 is the thread spec R14 means the radius of the seat is 14mm

Audi uses M14x1.5 R13, the black one looks to me like an Audi nut, the ball just isn't as deep as the Porsche ones

 

just to clarify ...



And of course, the radius on a 'ball' nut has to fit too ...

Beside a possible different ball radius on the shown upper nut, the shown contact area would likely look like this if you screw a ball nut into a conical seat ...

 

Agreed. The radius of the ball seems to be a bit small, which would cause the center of the radius to touch the wheel before the rest of the radius, thus wearing the anodize.

If it were a "conical" nut, it would not touch in the center, instead it would make contact at both edges instead.

 

Several of you are correct in saying the the black nut is wrong, I took all of the ones off the 993 and found 6 that were wrong and 14 that were good. I took all of them off the 968 and they were all good, and met the seat perfectly. I just ordered a set of Rennline lugs and will replace all of them just to be sure. Thanks to everyone who responded and solved another 993 puzzle.
Steve

 

Same thing with a 'smaller' radius ...

 

Only ever 1 nut used by Porsche as mentioned, came in black and was alluminum and not magnesium as is often quoted, difficult to see after years of use but there are many aftermarket alluminum nuts available, Bimecc, HTech, Boothe Design etc

I would guess the OP has a mixture!