Jetdriver69

Does anyone know the thread pitch and diameter size of the tow hook? Can you find a generic bolt that would fit the towing attachment hole in the front say from Lowes or Home Depot? Reason Im asking is that I want to make my own license plate holder since Texas is getting serious again about giving out fines for no front plates and putting them in the front window will not cut it. I DO NOT want to drill holes in the front bumper on my 82. It has never had front plates installed. Thanks!

WallyP

Very uncommon metric thread similar to an Acme thread. The thread size (which I don't remember) has been discussed at length here, in regards to cleaning/repairing the threads in the chassis. There is a special tap that is being passed around. A search on here should give you the info that you need. Good luck, and there will be other folks who want to know how you get on with this...

Courtshark

Have you tried removing the tow hook cap? Good luck if you haven't!

davek9

I heat them up with heat gun to soften the rubber, else like you said "... Good luck.." caution don't burn your paint.

Don't know the thread size, but like Wally suggested "search" as this has been covered.

Alan

I think Carl at 928 Motorsports has a license plate solution that adapted to the front tow thread - check with him.

Alan

Courtshark

Rubber? Mine was all metal, and it bonded itself to the eye. My brother spent a few hours trying to drill it out for me before conceding defeat.

There's a thread about the tow eye tap you'll need once you get it free. (I'm assuming the OBs have the sae tow eye and metal cap S4s do). The tap is currently in Europe. I'm looking into getting one to keep stateside, but it went on a US tour last year.

davek9

Thought they were speaking of the black cap in the bumper, they get really hard especially in the winter.

Thanks for clearing that up,

Dave

M. Requin

The thread size is indeed an oddball: RD20 x 1/8” knuckle. A knuckle parallel tap (European, probably Polish made, so I am sure high quality) in this thread is available from e-taps.com . When I checked, though, the single quantity price was $293, so I deferred. There is at least one loaner available here- search is your friend. For those of us who are **** about details, this is from the e-taps.com web site:

SPECIFICATIONS:
- material of tap(s): HSS (M2) steel
- ground thread and shank
- thread tolerances per DIN 405-1
- straight fluted
- taps linear dimensions per DIN 376 or DIN 352 standard
- tools are manufactured in our mfg. plant in Europe
- prior to ordering please provide application (quoted tap is for standard material and standard depth):
1 = TYPE of MATERIAL BEING TAPPED.
2 = THRU OR BLIND HOLE.
3 = HOW DEEP IS YOUR THREADED HOLE.

And BTW they were very friendly and fast in getting back to my inquiry.

IIRC there are two different thread sizes, I think this is the later and more common, but I wouldn't send them $293 based on my research...

Alan

He wants a bolt with this thread....

Alan

auzivision

http://www.928motorsports.com/parts/...g_tow_hook.php

Alan

That's the one!

M. Requin

I read the post, but if looking for a bolt, it might be helpful to know the thread size, pitch, and type (which he requested)... I was only trying to give some possibly useful information, in the broad sense.

jpitman2

Sometime around 86 the thread changed from what Porsche call 15mm x 8 threads per inch (knuckle type RD14 - 14.318mm, 9/16" OD) to 20mm x 8 tpi (Knuckle RD20, 20.318mm, 0.8" OD x 8 tpi). An 82 should have the 15mm thread (my 83 has this). The hole is under the right hand removeable cap in the front bumper, and in the centre (angled upwards a bit) of the license plate area in the rear bumper. You will really be pushing to find a bolt for this. Buy the proper item from Porsche, not expensive when I last bought one. They will NOT tolerate side loads at all, much too brittle, so be careful how you use them - BTDT.
here is a link to the specs:-
http://www.gewinde-normen.de/en/knuc...d-din-405.html

I have looked at Carl's stuff in this area, and had some email correspondence with him on it. He talks of a fine or a course(coarse) thread here - on a 928 both towing eyes have the SAME thread pitch in my experience ! If there is/was a fine thread used on Porsche towing eyes, my guess is it would have been on 911s. My car has the "15mm" towing eye, and as some will know, I had a "20mm" tap made to help S4 onwards people clean their corroded threads (around 25+ users so far, currently in Europe I think), so I know of what I speak from first hand experience.
jp 83 Euro S AT 55k

Jetdriver69

I called a bolt specialist in Irving, TX and they said it is called an Acme thread. Similar to the gear thread in a table vise. Anyway, they have the item, but they sell it in three foot sections for over $250. Then you have to either weld on a bolt cap or have someone machine a thread for a bolt to attach. Forget it. I'm thinking of getting a Texas antique license plate which you get only one. There is a limitation on how much you can drive your car, but who is to say how much you actually drive your 928?

jpitman2

Wrong. Acme is a square section thread, knuckle has a rounded form, very like a sine wave.
See:-
\http://en.wikipedia.org/wiki/Trapezoidal_thread_forms
for acme details. Almost square section - 29Degree sides.
jp 83 Euro S AT 55k