UrS6 AAN simple brake question

[Giacomo]

Hi,

my S6 brakes in a "strange" way. For example: 100 mph, strong hit to the pedal, the pedal has a long stroke and brake's action is not so stong. If I hit the pedal a second time the stroke is short and brake action very strong.
Everything is OEM (discs, pads, pipes, bomb...), the car is 100'000 miles old and the discs/pads are not new but also no need to replace yes.

My question is: what's wrong? The bomb is tired? There is air inside the brake pipes? So need to bleed? Brake pump need's to be replace?

Thank you!

[UrS4boy]

How the C4 UrS Power Brake System Works

You probably have some worn braking components, perhaps the master cylinder (as opposed to the brake servo).

What you have described is a classic "pumping the brake" scenario, more common with classic non-brake servo cars with worn (leaking internally) master cylinders.

How the C4 UrS power brake system works: http://forums.quattroworld.com/s4s6/msgs/25095.phtml

[Giacomo]

I understand. What do you suggest? Replacing the master cylinder? Is it possible to refurbish it?

[UrS4boy]

I understand. What do you suggest? Replacing the master cylinder? Is it possible to refurbish it?

There were two brake master cylinders for the UrS4s and UrS6s (and RS2s, for example). This diagram is for the RS2 but it works for the UrS4s and UrS6s too. The UrS4s used the 441611021B brake master cylinder and and the UrS6s used the 4A0611021C. Both are tandem (2 channel) with 25.4 (1 inch) x 13 / 22.5 mm piston.

So far, I've only found a kit that would only work for the smaller 23.8 mm diameter piston (used on the non-AAN, non-V8 UrS cars). See the second diagram. The search will continue.



http://www.ebay.com/itm/Audi-A6-Brak...item41792cd89c

[fourringsofhappiness]

Greetings,
I would release the rear bleeder screws to allow the rear piston to be re-adjusted. Reset the ebrakes and then re-bleed the calipers. A short 20-30mm's of ebrake arm on caliper travel is good before pads grab. After when doing speed the calipers are tighter on the first pedal application. This is all easy to do before replacing any items..
My $0.2

[chris]

brakes

agree with the bleeding first , i have also found it is better to bleed the rears with the wheels on the ground , so as no to upset the rear bias valve, also give it a lube and work it manually ,,
it is cheaper to bleed than renew

[Giacomo]

"Reset the ebrakes", what does it mean? What are "ebrakes"?

[Zoig]

"Reset the ebrakes", what does it mean? What are "ebrakes"?

Ebrakes is the US English word for Handbrake. Check also windshield vs windscreen


This gets me all the time when I try to write BBcode instead of selecting it from the menu: [colour="Red"] text [/colour]

[Giacomo]

Does UrS6 AAN calipers/discs (both front and rear) fit on A6 C4 AEL car?
Plug and play or not?
I have a spare set of new S6 discs, and a full set of OEM UrS6 calipers.
My AEL needs brakes refurbish, so...

[UrS4boy]

Wheel Bearing Housing 101

Does UrS6 AAN calipers/discs (both front and rear) fit on A6 C4 AEL car? Plug and play or not? I have a spare set of new S6 discs, and a full set of OEM UrS6 calipers. My AEL needs brakes refurbish, so...

Not plug and play unless you also change the struts/wheel bearing housings to which the calipers are attached.

The AEL and V6 C4 A6s use the 4A0412025AA (and 026AA) wheel bearing housing whereas the AAN and AEC (V8) use the 4A0412025AC (and 026AC) wheel bearing housing. Subtle deferences in the mounting locations/ears for the caliper brackets.

Wheel Bearing Housing 101: http://forums.quattroworld.com/s4s6/msgs/33797.phtml

[Giacomo]

So, if I also have S6 wheel bearing housing I can do it.
So my question becomes: seen that URS6 front wheels are wider (mean more far away each other than normal A6), will swapping the struts make the wheels lean out from the body of the car?
Did anybody make this job already?

[UrS4boy]

Did anybody make this job already?

Yes.

The Audi Neckarsulm factory.



IF there was an issue, you could run ET45 wheels instead of ET37 or ET40 UrS wheels.

[Giacomo]

Yes.

The Audi Neckarsulm factory.

Do you mean UrS6 front brakes were available on UrA6 cars?

[UrS4boy]

Do you mean UrS6 front brakes were available on UrA6 cars?

No. I mean that the C4 chassis can handle either the UrS6 or the C4 A6 struts/wheel bearing housings without any modification. Your concern about the wheels sticking out of the fender/wings after swapping UrS6 strut/wheeling bearing housings into a C4 A6 will either turn out to be a non-issue *OR* one that is easily solved by going to ET45 wheels instead of the ET40 (or ET 37) UrS4/S6 wheels.

[Giacomo]

ok, I understand what you say. So I think I can do the job.
My doubt comes from the fact that the UrS6 has front fenders wider than normal A6 (and in Italy extra fenders were forced to be supplied by Audi due to law approval), and it make me guess that something should be longer (arms?) or wider (front subframe?) in the chassis under the car.