[urq] V8 Brake swap for UrQ - saga continues..

[Robert Pastore]

Ben:

What did you do to solve the hydraulic booster problem you had?    
Despite all the good 'theories' about matching the MC and calipers, my 
experience is the same as Scott J's -- I've used V8/S4 rears and big red 
(stoptech) fronts with the stock 23mm MC without any noticeable 
difference in pedal travel.   Are you sure the booster isn't still the 
problem?

Bob

On 11/7/2010 11:23 PM, qshipq at aol.com wrote:
>
>> ----------
>> From: 	qshipq at aol.com[SMTP:QSHIPQ at AOL.COM]
>> Sent: 	Sunday, November 07, 2010 11:23:25 PM
>> To: 	benswann at verizon.net; urq at audifans.com
>> Subject: 	Re: [urq] V8 Brake swap for UrQ  - saga continues..
>> Auto forwarded by a Rule
>>
>>
>   Sounds like a bad master or bomb to me, or air/leak in the system  I've installed a couple dozen v8 rear brake setups on urq's over the years, with a wide variety in front from G60 and to Big Reds....  Most with the stock urq 23mm MC.  I routinely replace the prop valve with the Tilton 7 position adjustable, and normally set it almost full front, except when at the track, and/or locking the center diff.  For the G60 brake setup with 'v8' rears, you can use the euro 20vt stock brake prop valve, as the G60F/v8R setup came on that car from the factory.
>
>
> IMO, what you describe has nothing to do with the size of the rear brakes or the prop valve (36/38mm stock to 41/43mm v8 rear piston dia should yield little to no difference in pedal travel).  The stock MC can handle several different caliper setups with no significant difference in pedal travel, btdt.  Certainly if the pedal goes to the floor, one can be assured there is another problem.  IME with every audi hydraulic brake setup that exhibits this issue, I first go to the MC, then to the brake bomb.
>
> Scott J
> Stock urq MC'd
> 84 urq Big Reds Front/V8 R Tilton-7
> 83 urq Steamboat car G60F/V8R Tilton-7
> Sold
> 83 urq G60 F/v8R
> 83 urq G60F/v8R
> 83 urq G60F/v8R
>
>
>
>
>
>
> -----Original Message-----
> From: Ben Swann<benswann at verizon.net>
> To: 'Ben Swann'<benswann at verizon.net>; urq at audifans.com
> Cc: quattro at audifans.com
> Sent: Sun, Nov 7, 2010 7:08 pm
> Subject: [urq] V8 Brake swap for UrQ  - saga continues..
>
>
> The Brake saga continues on my '83 Ur Quattro.  I finally have a replacement
>
> booster
>
> installed to replace the one I botched.
>
>
>
> To recap., I installed V8 brakes in the rear and messed up the original
>
> hydraulic
>
> booster when trying to retrofit a V8 master cylinder.  That in order to proivde
>
> correct
>
> brake proportioning/compensating for the newly installed rear V8 calipers.
>
>
>
> After repetitively bleeding the system - I now think there is another problem or
>
> two.  I
>
> am fairly certain I have the air out of the lines, Master cyinder and slave
>
> cylinders.
>
> I have gone through no less than 4 full liter containers of DOT 4 in several
>
> attempts to
>
> remove the soft pedal.  Even though I got some air out in repeated attempts
>
> using power
>
> bleeding and manual ( foot and other techniques), the brakes still do not work.
>
> Seems
>
> no matter what I do, I still have the same end result - spongy pedal that
>
> provides
>
> little braking and continues to the floor with moderate pressure.
>
>
>
> I ordered a master cylinder since the pedal   is  not only spongy, but continues
>
> to go
>
> all the way to the floor when held.  The pedal can be pumped hard, but shortly
>
> after the
>
> slight braking, the pedal goes down, and then again until it bottoms out.
>
> Braking is
>
> almost non-existant, although will skid in rear  or lock up sometimes when near
>
> bottom
>
> of pedel travel.
>
>
>
> So., I think I need to replace the proportioning valve, and should do it with
>
> the new
>
> master, since I need to crack the system again.  I was going to get a stock
>
> proportioning valve, but since I changed the calipers, part of the problem may
>
> be that I
>
> need to adjust the bias for the rear V8 calipers.  That was the reason I
>
> molested the
>
> master and booster in the first place.
>
>
>
> Main reason for this post: Recommendations for adustable proportioning valve and
>
> any
>
> installation advice.
>
>
>
> Am I on the right track with this?   I will replace the rear lines, maybe front
>
> lines
>
> too.  So system will have new master, adjustable proportioning valve, V8 rear
>
> brake
>
> setup.  Presently the fronts are the dual caliper brakes from an '87 5000 turbo
>
> quattro.
>
> Except for the left rear caliper dragging and locking up  before all the work,
>
> the
>
> brakes worked great.  I had already swapped the rear calipers out too for the
>
> newer
>
> style which lasted several years.
>
>
>
> I have the option to install PORSCHE Monoblock calipers too - like I want to
>
> make more
>
> changes, but being I'm changing ther rears, master and proportioning valve,
>
> maybe time
>
> for these I've had on the shelf for sometime.
>
>
>
> So looking for advice on the proportioning valve as well as anything else that
>
> will keep
>
> me from digging this hole any deeper.  I have not ruled out booster problem, but
>
> no
>
> reason to suspect that - new booster, relatively new bomb, new bomb to rack
>
> hose, no
>
> leaks!
>
>
>
> I recall having a similar, if not identical problem on an '83 CGT that I did the
>
> MC-1
>
> turbo install.  I had pretty much installed "retro" brakes all-around. converted
>
> rears
>
> to disk and fronts to larger model 80 brakes.  I never was able to get those
>
> brakes
>
> right.  Same thing - spongy pedal, reduced braking, followed by pedal going to
>
> the
>
> floor.
>
>
>
> Ben
>
>
>
>
> _______________________________________________
> Audifans urq mailing list
> Manage your list connection: http://www.audifans.com/mailman/listinfo/urq
> http://www.audifans.com/kb/List_information
>
> Pictures/Polls/Database at: http://autos.groups.yahoo.com/group/urquattro/
>
>