Tow Hook Question - Rennlist - Porsche Discussion Forums

Notices
928 Forum
Sponsored by:
Sponsored by: 928 Specialists

Tow Hook Question

Old 09-12-2013, 09:48 AM
  #1  
Jetdriver69
Addict
Rennlist Member
Thread Starter
 
Jetdriver69's Avatar
 
Join Date: Apr 2013
Location: Humble, TX
Posts: 850
Default Tow Hook Question

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!
Jetdriver69 is offline  
Old 09-12-2013, 11:09 AM
  #2  
WallyP

Rennlist Member
Rennlist Site Sponsor

 
Join Date: Jun 2001
Location: Acworth, GA
Posts: 6,469
Default

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...
WallyP is offline  
Old 09-12-2013, 11:30 AM
  #3  
Courtshark
Addict
Rennlist Member
 
Courtshark's Avatar
 
Join Date: Apr 2007
Location: Baltimore, MD
Posts: 1,854
Default

Have you tried removing the tow hook cap? Good luck if you haven't!
Courtshark is offline  
Old 09-12-2013, 11:39 AM
  #4  
davek9
Super User
 
davek9's Avatar
 
Join Date: Jul 2006
Location: Bloomfield, MI
Posts: 4,460
Default

Originally Posted by Courtshark View Post
Have you tried removing the tow hook cap? Good luck if you haven't!
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.
davek9 is offline  
Old 09-12-2013, 01:35 PM
  #5  
Alan
Electron Wrangler
Lifetime Rennlist
Member
 
Alan's Avatar
 
Join Date: Mar 2002
Location: Phoenix AZ
Posts: 11,893
Default

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

Alan
Alan is offline  
Old 09-12-2013, 01:38 PM
  #6  
Courtshark
Addict
Rennlist Member
 
Courtshark's Avatar
 
Join Date: Apr 2007
Location: Baltimore, MD
Posts: 1,854
Default

Originally Posted by davek9 View Post
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.
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.
Courtshark is offline  
Old 09-12-2013, 02:06 PM
  #7  
davek9
Super User
 
davek9's Avatar
 
Join Date: Jul 2006
Location: Bloomfield, MI
Posts: 4,460
Default

Originally Posted by Courtshark View Post
Rubber? Mine was all metal, and it bonded itself to the eye.....
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
davek9 is offline  
Old 09-12-2013, 03:01 PM
  #8  
M. Requin
Addict
Rennlist Member
 
M. Requin's Avatar
 
Join Date: Mar 2007
Location: Central Virginia
Posts: 3,304
Default

The thread size is indeed an oddball: RD20 x 1/8ö 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...
M. Requin is offline  
Old 09-12-2013, 05:49 PM
  #9  
Alan
Electron Wrangler
Lifetime Rennlist
Member
 
Alan's Avatar
 
Join Date: Mar 2002
Location: Phoenix AZ
Posts: 11,893
Default

He wants a bolt with this thread....

Alan
Alan is offline  
Old 09-12-2013, 05:59 PM
  #10  
auzivision
Super User
 
auzivision's Avatar
 
Join Date: Jun 2006
Location: Indianapolis Area
Posts: 2,588
Default

Originally Posted by Alan View Post
I think Carl at 928 Motorsports has a license plate solution that adapted to the front tow thread - check with him.
http://www.928motorsports.com/parts/...g_tow_hook.php
auzivision is offline  
Old 09-12-2013, 06:02 PM
  #11  
Alan
Electron Wrangler
Lifetime Rennlist
Member
 
Alan's Avatar
 
Join Date: Mar 2002
Location: Phoenix AZ
Posts: 11,893
Default

That's the one!
Alan is offline  
Old 09-12-2013, 08:00 PM
  #12  
M. Requin
Addict
Rennlist Member
 
M. Requin's Avatar
 
Join Date: Mar 2007
Location: Central Virginia
Posts: 3,304
Default

Originally Posted by Alan View Post
He wants a bolt with this thread....

Alan
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.
M. Requin is offline  
Old 09-12-2013, 09:17 PM
  #13  
jpitman2
Addict
Rennlist Member
 
jpitman2's Avatar
 
Join Date: Dec 2002
Location: Australia
Posts: 4,497
Default

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
jpitman2 is offline  
Old 09-12-2013, 09:44 PM
  #14  
Jetdriver69
Addict
Rennlist Member
Thread Starter
 
Jetdriver69's Avatar
 
Join Date: Apr 2013
Location: Humble, TX
Posts: 850
Default

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?
Jetdriver69 is offline  
Old 09-12-2013, 10:05 PM
  #15  
jpitman2
Addict
Rennlist Member
 
jpitman2's Avatar
 
Join Date: Dec 2002
Location: Australia
Posts: 4,497
Default

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
Attached Images  
jpitman2 is offline  

Thread Tools
Search this Thread
Quick Reply: Tow Hook Question


Contact Us Advertising Cookie Policy Privacy Statement Terms of Service

© 2018 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: