ABS Self-Test Noise (when pulling away)

[Scott.T]

Now this thread is either going to put my mind at rest or not......depending on your responses.
I have a noise that I can't seem to reliably reproduce, in order to demonstrate to the dealer, that is a rotational click/crunch/clunk as you pull away slowly after the car has been parked up for a while.

I thought it was wheel bearing, CV joint or differential. But driving round and round in tight circles either backwards, forwards, left or right does not do it.
However if I park up at work in the morning, then drive out slowly I get the noise as I trundle through the smooth car park (which probably helps me hear it), on what appears to be the 1st and 2nd rotation of the wheel. I can also feel it through the pedals.
But this does not happen, or at least it's not audible/noticeable every time.

If it is going to happen the car doesn't necessarily have to be left for long, because it done it the other day after just 20-30 mins stop.

I then found these links, which seems to explain it as part of the ABS Self-Test. So I was wondering if anyone else experiences it

http://www.honestjohn.co.uk/forum/post/index.htm?t=30969

http://www.pistonheads.com/gassing/topic.asp?h=0&t=571601

http://www.airliners.net/aviation-forums/non_aviation/read.main/2135436/

http://tech.bentleypublishers.com/thread.jspa?threadID=478

http://www.tyresmoke.net/forum/topic/48502-a4-tdi-problems/

Fix ? : http://www.audiworld.com/forums/s4-rs4-b5-platform-discussion-6/abs-self-test-brake-noise-"fix"-sorta-1368781/

 

[ub7rm]

Yes - had it on all ABS equipped cars. If you lightly cover the brake pedal with your foot you can just about feel it as well.

 

[Scott.T]

I've driven plenty ABS equipped including 2 VAG group (Audi A4 Quattro & SEAT) as well as 3 Subaru's over the last 15 years and this is the first time I've noticed it.
But it does sound like it's normal from what I have read/heard.

I drove out the car park under 5mph and it didn't do it, so it would be good to find the trigger point.
I might have a sniff round in VCDS to see if there are any clues.

 

[ub7rm]

Its so subtle you won't notice until one time you do then thats it. I first noticed it with a golf I parked in a narrow lane and with the windows down in such a confined space it amplified the noise. I've noticed it on every car since.

 

[Scott.T]

Looked into this a bit more over the last couple of days and I can confirm (by setting the DIS to display MPH) that it occurs at approx. 6-8mph every time you start and pull away.
I even stopped the car and pulled out the key, then started again once everything had shutdown (approx. 45 seconds). The same noise/ABS check was felt.

A lot of other makes/model forums seem to have discussed this, but it doesn't appear to be noticeable on all cars, even of same make a model. It probably depends very much how quick you pull away after starting, as to how noticeable the noise becomes.

Strange though that there is no reference to this on Audi-Sport, that I could find.