Thread chaser for tow bar hook

[B7Tourer]

Can anyone tell me the tow bar hook thread size? I noticed in winter that I could not get my tow bar hook in when I got stuck in the snow, and I just tried it again yesterday with a new tow bar hook and it is rusted up - I could only partially get it in. I believe it's 18mm? But I'm not sure of the exact thread pitch, can anyone recommend a thread chaser for it? Obviously I do not want to replace the crash bar just for this.

 

[Matt275]

Is it a reverse thread maybe?

 

[B7Tourer]

No Matt, it's not in my case, either with the original hook in the toolkit, or the thread - I can get it partially in, so I know that the thread is corroded. I believe some Audi models, later perhaps are reverse threaded but I am sure all B7 A4s are like mine. It's M18 I believe and I have sourced a thread chaser in that size, but until it arrives, I am unsure of the thread pitch. I'd really appreciate it though if you get a chance to test yours?