RE: 105 brake rebuild

[Mark Battley <M.Battley@xxxxxxxxxx>]

Anthony wrote:
 ----------------------------
	I'm still wondering about how to reduce pedal slack in a floor
mounted pedal 105.  One of the options I'm considering is the installation
of 2psi residual pressure valves in the brake lines.  Wilwood makes these
specifically for circumstances where the brake master cylinder is below the
level of the callipers:
http://www.wilwood.com/products/master_cylinders/rpv/rpv.asp
<http://www.wilwood.com/products/master_cylinders/rpv/rpv.asp>
<http://www.wilwood.com/products/master_cylinders/rpv/rpv.asp
<http://www.wilwood.com/products/master_cylinders/rpv/rpv.asp> > 
	 
	Someone over on the Alfa Racing list suggested that this may lead to
brake drag, through not allowing the pads to retract sufficiently after
application.  He also suggested that, so long as the system was sound with
no leaks, there shouldn't be any slack in the system.  While I agree with
this based on principles of hydraulic theory, anecdotal evidence suggests
that it's very rare to have a floor mounted pedal 105 with a firm brake
pedal.  (Or is this just because they're all over thirty years old now, and
the brakes have concomitantly deteriorated?)  
	 
	On these grounds, I'm still considering the residual pressure
valves, and also a 24 mm master.  The large master will result in less
travel and greater pedal effort, but it seems this should also translate to
less slack in the system.  
	 
	I'd welcome any views, advice, or effective solutions tendered.   
  ----------------------------

My 2 cents (NZ), a little more than 1 cents US.....

Don't make the system any more complicated than it is already, particularly
to solve something that I don't believe is really a problem. In my limited
experience there is nothing wrong with these systems when they are in good
condition.

What do you mean by firm anyhow? - in my mind there is a difference between
"slack/freeplay" before you start to apply pressure to the system (which
partly comes back to wear and adjustment in the mechanical pivots and
pushrod), and a "soft" pedal, implying air in the system, soft hoses etc.

Given that you are starting from a system in pieces I would strongly suggest
that you put it back together "standard" (but renovated where it needs it),
make sure it works as Alfa intended, before trying to modify the system.
Otherwise if you have problems, you won't know whether they are due to your
changes, or some original part that is not right. Brakes not releasing
properly is not an uncommon fault with these systems (often due to booster
problems), I wouldn't want to give them another possible reason to do it!
:-))

Some hints: Buy some "speedbleeder" nipples, I have found them a great help
to get a well bled system. Also - do the final bleed with the engine
running, this seems to help the remote boosters bleed properly. This has
made quite a difference to my car.

Have fun....

Mark.

Mark Battley
Auckland, New Zealand

1973 Alfa Romeo 2000 GT Veloce (with sad booster)
1989 Fiat Uno Turbo
1999 Fiat Marea Wagon, 2.0 20V
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