Hydraulic to vaccum brake conversion Urs6

[Wrath]

Have anyone don this to get a better response in braking or is just to get rid off the brake bomb?

Have read this brake conversion pdf but I don´t know if that apply more for the S2 family

Would really like to have som guidelines of making this to my Urs6 (this winter) So I can get a more modern feel to the braking... faster response and so on.

Have looked at the A8 master cylinder and I don´t know but it feels like a better option then an old Audi 100/A6 cylinder. Do you still need extend the rod of the "new cylinder" and is it possible to change this without spilling brake fluid everywhere in the Engine bay

Also if you don´t change your PAS pump for the steering, do you just rip out the springs and Everything under the X cap and what do you do with the brake bomb? rip it out completley and cut the lines to it?

[RichLV]

My master cylinder was leaking, and knowing the reputation of brake bombs i just swapped in vacuum booster from 2.8 C4. Its a straight swap, just need to tap vacuum from nearby lines.

I ripped the bomb off completely, all lines which go to it got blocked.

For the PAS, just get the pistons and springs under the x-plugs. And block the unnecessary line.


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[Wrath]

Is The 2.8 diaphragm a single or dual? I guess you need a dual to get things working as it should.

[popdemonic]

All C4 is single diaphragm Goeran.

[Wrath]

Aah thanks pop, then A8 pump is the only alternative I guess... but then I need to change mastercylinder with attached vaccum plate, then I probably will need to extend the rod that seem to have a shorter axle. I don´t have any problem today with my brake system only want to upgrade the feel to a modern feel like say any modern car with brake assist. Short travel in the brake pedal with fast response.

[RichLV]

I'm running a single diaphragm and its completely fine. There's absolutely no need for a dual one, especially considering the "sex" you have to go through with the extension of the pedal rod. Russians drive standard C4 units with Cayenne brakes and it's very good. Brake Cylinder stays the same, the UrS one.

[popdemonic]

i had single diaphragm but not quite happy with the assists.i still need to give more foot effort when depress the brake pedal.

[RichLV]

Swap for a larger brake disc and it will be better. I'm very satisfied with my vacuum assisted HP2's, considering that I will never have to worry about brake assistance again (damn brake bomb).

[popdemonic]

I have Cayenne 6 pots on my HP2 but decided to swap it back to hydro system.
the single diaphragm is fairly good but i would love some even more lighter
pedal feel.Just my 0.02.

[RichLV]

There's no contention to the hydro assist. It can muster twice the pressure a vacuum assist can. Too bad it's not that reliable and is very expensive in maintenance. :/

[popdemonic]

Talking about the Hydro system,some likes the pedal feel but some decided to get rid of them due to the "Sponge" pedal feel.
if my Hydro system ever broken down again,i'd consider vacuum booster but only me.i would get the dual diaphragm booster
once i'm there.

[Wrath]

I feel that my pedal is quite stiff as it is now, and you have to press hard to get taking force but when you do you stop like you throw out an anchor maybe my brake bomb
Is getting tired i don't know.

[RichLV]

When brake bomb starts to die it usually shakes or vibrates the brake pedal when you press it. Pressure fluctuations start in the hydro assist brake lines. After some time you lose the assist completely, that means that the membrane in the brake bomb is non existant.

If you do not experience these symptoms then your bomb is still functioning.

[popdemonic]

Goeran,
Check your high pressure and scree line on each banjo bolts.if they're clogged up,you will lose all the assists.
Just like Rich said if bomb failed,the system will generate the assist directly from pump and you feel the pedal
Pulsating all the time.

[Wrath]

Rich, Pop:

I´ll check that as soon as I get my waterconnection for the turbo so I can start the car and get a feel to it, I remember that I have had some (!) warnings in the past but it was self healing and disappeared and I have felt this before that the pedal is rocksolid or just harder then I believe it should be but brakes works good, now I haven't drived the car for 2 years and have new brakelines/calipers (cayenne 6-pot) so on... The brakes are good but have been driven my other car that´s 20 years newer so maybe this is just how they feel these old gems Therefor I was interesting if the vaccum conversion could be a better option or if it´s just a fix to get a cheaper system if the hydraulic one brakes down...