Super Brake Pedal Spec

[nochicken]

I finished replacing the flexible brake hoses on my '66 Super (along with the small, fixed hard lines at the front calipers). I did an initial brake bleeding--huge amounts of air had entered the lines--with an initial road test today. The brake pedal (floor mounted) seems to go in quite a bit before really taking hold--though it holds fine and I don't see any leaks.

Question: is there any kind of spec regarding brake pedal movement (e.g., how far can/should it go before brake action occurs)? Sort of like with the mechanical clutch--there is a spec for how far out the pedal should go before the clutch engages.

I posted this under the brake section but figured it may be getting lost in there.

Thanks.

[sprintgtc]

Hi Frank,
Beyond the usual stuff (IE trapped air in the lines, worn master cylinder and/or calipers, mis-adjusted rear Dunlop calipers) You may have excessive slop in the pedal pivot. Have someone work the pedal while you watch the movement from below. You might also try pulling the clevis pin and removing the boot & rod at the master to get a better feel for the situation.

[Andrew]

Individual MCs will have different feels too. My GTV has longer MC travel than my Berlina, which in theory have exactly the same MC. My Super's pedal (ATEs, so no potential for Dunlop lost motion at the rear) travels not more than maybe 1-1/5" til it firms up completely. It has a newish MC from Centerline, installed 3-4 years ago, and new rubber flex lines.

Andrew

[CN36]

If you have a lot of air in your brake system, then try bleeding it with the motor running; I has worked for me in the past.

[nochicken]

Thanks for the info and ideas. Interesting that there is that much "play" (1.5") in Andrew's pedal. That seems like about what I am getting. BTW, am assuming that running the engine has something to do with getting the brake booster in the loop--what's the theory behind that?

[Andrew]

I don't mean play; that's how much travel my brake pedal has total from off to on. I checked again yesterday and it's more like 1.5-2". But to me that's pretty short travel, and it firms up well.

Floor mounted MCs can be tough to bleed, in my experience, with the fluid going from the reservoir, down to the MC, back up to the booster, then down to the wheels. I've tried the bleeding-with-engine-running thing too but never had it make a difference. I think the theory is the vacuum generated puts the booster into play, moving its components and in theory helping bleed the booster.

Andrew

[Giulia67]

Hi,

When bleeding the single circuit brake I put a wooden block on backside of the brakepedal so it never reach the floor, that helped me with the same sympton you are describing and I got a much better feel and only about an inch of play in the pedal.

/Fredrik

[jarrington]

I'm going to be dealing with this in the next couple of months - the basket case has all of the hard brake lines removed, so there will be absolutely no fluid in the system. Any secret tricks as I plan to put it back together?

Frank, we may need to talk if you have any extras from the set of spare lines you bought. My outer front hard lines are OK, but one of the longer ones is in two pieces.

-Jason

[nochicken]

I checked my brake pedal again and discovered that it would basically go all the way to the floor. I could find no fluid leaks. I started another bleeding session and the pedal just would not pump up much (though fluid was being flushed and without a huge amount of air bubbles like the first session after installing the hoses).

At the driver front caliper, I think the bleed screw is not seating properly. As I made my second round, I noticed that after I did the "finger tighten", there was still some noticeable movement in the fluid in the bleeder hose when the pedal was pushed in.

Thus, I'm wondering if this bleeder screw is not seating correctly. Again, I didn't notice any fluid loss, but it may be that it is sucking air back into the system.

I'll probably replace these bleed screws--any issues wrt to fit on those? On my calipers, I apparently have mix of screws--need to use from a 7mm to 9mm wrench depending on which caliper I'm at.

Also, I checked the MC/linkage--no problems there. However, I could not find in the PO(s) previous paperwork (going back a good 10 years) that the MC had been replaced. Is there any kind of test to figure out whether the MC has gone bad? Just for peace of mind, I may just replace it. Any issues here with form/fit/function of replacement MCs? I'm finding with the Super that pulling on one thread unravels a few others

BTW, I did try putting a block under the pedal, but believe the above problem negated that.

Jason, I only replaced the two short, solid lines right at the front calipers--not the long lines that run out from the MC. My long lines seemed okay.

Thanks.

[Andrew]

Originally, 1750/2000 front calipers had 9mm screws and rear had 7mm. I can't recall if smaller 1600 fronts have 7 or 9. I've seen rebuilt ones come with 8mm so yes, you can have a mix.
Andrew

[gprocket]

If your pedal can go to the ground, pumping the pedal does not firm it up and there are no leaks then I would say that fluid is getting past the seals in the master cylinder. This could be worn seals, worn barrel, or mispositioned MC piston. I am assuming that the single circuit MC is similar in function to the dual system. If true, read papajam's excellent post : Tandem Brake Master Cylinder...how it works - Alfa Romeo Bulletin Board & Forums

I had a similar situation and it turned out that the piston was moving past the compensating port which allowed fluid to pass.

If your MC is no good, contact papajam - he rebuilds these guys and likely has stock.

If your bleed screw is bad I would think you would see fluid squirting out around it. If not, I doubt that is the source of the problem.

Good luck!

[nochicken]

I emailed papajam to see about a maser cylinder rebuild. I checked again and could not find any leaks--I probably have a bad MC on my hands. I also found no record of the MC being replaced in all the old paperwork,

I checked Centerline for an M--they have a note about potentially rebending brake lines for a replacement MC. I'd like to avoid this if at all possible. From the photos below, is there a way to identify what type of MC this is (and would a new replacement cause the need to modify the hard brake lines).

Just to add another question, what is the easiest way to identify the brake calipers? My Super had '73 Spider spindles installed about 10 years ago and I *think* all the associated Spider front brake parts (including the calipers). This is based on reading the old paperwork--thought I'd try to confirm this.

Thanks.

[101/105guy]

Some of the replacement masters have the lines coming out more towards the rear of the car so you would have to bend your lines and maybe come up with a little more length some where. I have seen the original type for sale at some of the euro vendors.

How about just taking yours in to be rebuilt? Took my '67 Duetto brakes to a local rebuilder with original kits that I had in stock. They did a beautiful job and even had all of the correct parts as my kits were too old.
Randy

[nochicken]

Good idea. I ended up calling Julio at Milano Motors nearby and he will do the rebuild. That way, I won't end up with any form/fit problems.

Of course, the way things are going, my next post will be about where to locate new hard lines from MC out These look like they have been attached a long, long time. I'm going to hit them with some WD-40 or similar for a few days before I try to remove them.

After that, about the only thing that can go south will be the booster and the calipers!

[101/105guy]

And.. make sure that you use a 'metric flare nut wrench", not an open end wrench on your lines!