60 Veloce two shoe Brake Problems

[AR58SprintV]

Dear George,
After lurking a while, I suggest that you test for free movement of the pedal in the pedal box FOR FULL STROKE by opening a bleed screw with a bleed tube at a front wheel and by hand (not foot) slowly push the pedal to the FLOOR! If you can easily and smoothly, let me know. If not then find out what is hanging up or rough. Pedal shaft cotter bolt? Coins on the floor at the shaft? Junk master cylinder? Keep a sharp lookout!
While the pedal is to the floor, have your faithful helper close the bleedscrew, then let the pedal fully up by itself. Don't touch it (!), have a cig or a beer or watch the birds for 2 minutes, then go back to the pedal and you should have your usual hard brake pedal at its usual height. If not post the result.
If so, Please then retry it on the road. Please post your results-don't deviate from the ritual! You are missing something basic and I know that you know it!

Cheers, After you have brakes like mine, then Keep the revs up!
Laurence

[alfabits]

Quote:

Originally Posted by AR58SprintV Dear George, After lurking a while, I suggest that you test for free movement of the pedal in the pedal box FOR FULL STROKE by opening a bleed screw with a bleed tube at a front wheel and by hand (not foot) slowly push the pedal to the FLOOR! If you can easily and smoothly, let me know. If not then find out what is hanging up or rough. Pedal shaft cotter bolt? Coins on the floor at the shaft? Junk master cylinder? Keep a sharp lookout! While the pedal is to the floor, have your faithful helper close the bleedscrew, then let the pedal fully up by itself. Don't touch it (!), have a cig or a beer or watch the birds for 2 minutes, then go back to the pedal and you should have your usual hard brake pedal at its usual height. If not post the result. If so, Please then retry it on the road. Please post your results-don't deviate from the ritual! You are missing something basic and I know that you know it! Cheers, After you have brakes like mine, then Keep the revs up! Laurence

[AR58SprintV]

Dear George,
Did you keep the old shoe-return springs? You appear to have Gorilla-sized shoe return springs with fresh plating (HARDENING) on the Front shoe pair, which may keep the shoes from Bendix self-servo type (sprag) self-application as normal. Try your old return springs if possible.
I see the backing plates are on the correct sides of the car, as designed, to be double leading-shoe. There ARE different bore wheel cylinders(!) double check. I know, but it is back to checking basics. Aren't you glad that you aren't diagnosing at the side of the road (yet?).
Please post an update.
Laurence

[alfabits]

Quote:

Originally Posted by AR58SprintV Dear George, Did you keep the old shoe-return springs? You appear to have Gorilla-sized shoe return springs with fresh plating (HARDENING) on the Front shoe pair, which may keep the shoes from Bendix self-servo type (sprag) self-application as normal. Try your old return springs if possible. I see the backing plates are on the correct sides of the car, as designed, to be double leading-shoe. There ARE different bore wheel cylinders(!) double check. I know, but it is back to checking basics. Aren't you glad that you aren't diagnosing at the side of the road (yet?). Please post an update. Laurence

[alfazagato]

This is a long shot, but have you established that the snail adjusters have worked the correct hand? Again embarrassed experience.

[alfabits]

Stuart, I did have one adjuster that wouldn't stay adjusted. Turns out the spring was busted. So I had to drill out the rivet end and disassemble the unit, install a new spring, tap the drilled out end and bolt it back together. Now it holds fine.

G

[AR58SprintV]

Dear George,

A long shot, but put the motorcar off the ground, preferably on a professional lift with an assistant in the cab to apply the brakes, and a lever arranged on the hub nuts to have about a 6-foot torque arm. apply the brakes and move the arm down and rearwards below the carwith a 100-lb hook scale, and see that the brakes all apply evenly side-to-side rotating in the forward direction, and that the front brakes apply with at least twice the retarding force as the rear brakes.
What do you think? Learn something?

Here's to getting on with driving,
Laurence

[redblk63]

George,

As I remember, your question has to do with the fact that you have to push too hard on the brake padal for a given level of deceleration. For a given brake design, that is a function of two things:

1. the ratio of the cross sectional areas of the wheel cylinders divided by the area of the master cylinder.

2. The coefficient of friction of the material used.

Racing shoe material acts as you describe until up to temperature, but you ruled that out by trying standard material.

Sounds as if the problem is either from 1., or else both sets of shoes you tried have bad friction characteristics. (It must be pretty bad for you to swap shoes!)

By the way, self actuation of brakes just refers to the fact that with the shoes arranged as in your picture (thanks) of the left front brakes in your first post, the drag of the drum on the shoes moves them in a direction to increase the braking force. The rear brakes have a single "leading shoe" with this effect so that you have some of this effect from the "trailing shoe" in reverse, and don't roll backwards when you stop pointed uphill. I have a 1963 Honda Super Hawk with double leading shoes on both front and back (trick technology in the early 60s), and I can tell you it is a mixed blessing as it is hard to prevent it rolling backwards on a hill.

Please tell us that the image is reversed, and that pic is actually of the RIGHT front brake, and we can solve your problem in a snap.

Larry from Pasadena

[Andrew]

From the look of the apparent sway bar coming in from the left, looks like the left front.
Andrew

[redblk63]

Andrew,

Yeah, to the naive observer. But what if the digital image got flipped as a mirror image? Hey, I'm grabbing at straws here, inspired by the apt comment by Laurence on self-energizing properties. With my feeble ability to picture the geometry change under a partial parity operator, it seems as if the right/left components could be switched, with a really hard pedal the result.

But I agree, if that photo is really of the left side this hypothesis is wrong.

Larry

[alfabits]

Quote:

Originally Posted by redblk63 By the way, self actuation of brakes just refers to the fact that with the shoes arranged as in your picture (thanks) of the left front brakes in your first post, the drag of the drum on the shoes moves them in a direction to increase the braking force. The rear brakes have a single "leading shoe" with this effect so that you have some of this effect from the "trailing shoe" in reverse, and don't roll backwards when you stop pointed uphill. I have a 1963 Honda Super Hawk with double leading shoes on both front and back (trick technology in the early 60s), and I can tell you it is a mixed blessing as it is hard to prevent it rolling backwards on a hill. Please tell us that the image is reversed, and that pic is actually of the RIGHT front brake, and we can solve your problem in a snap. Larry from Pasadena

[alfabits]

Quote:

Originally Posted by Andrew From the look of the apparent sway bar coming in from the left, looks like the left front. Andrew

[GTD]

George
This brake dilemma of yours has made for some fascinating reading and has generated more than just a little cranium scratching amongst board members.
It would seem that the vital clue to the solution should have been readily discovered using the combined experience of all the AlfaBB’ers assisting you.
Perhaps the resolution is to be found by reviewing what is being assumed as functioning properly rather than by pinpointing a distinct malfunction.
Following this train of thought, two things come to mind:

1) You have mentioned that rather than replacing your brake lines, you have re-plated them. Have you done this in a manner which precluded any plating of the inside of the brake tubing? Any reduction of the inner diameter of the tubing would have a negative effect such as you are experiencing.

2) You have pictured your restoration quite thoroughly; amongst the pics is one of a truckload of parts in boxes indicating your Veloce was something of a basket case when purchased. Was the pedalbox amongst the boxes or was it already installed on the chassis? Is it the correct (36mm) length lever arm for your brake system?

[Andrew]

Has it been firmly established that the front brake assemblies are not reversed, side to side? That would make them work better backwards than forwards.

Andrew

[alfabits]

Quote:

Originally Posted by GTD George This brake dilemma of yours has made for some fascinating reading and has generated more than just a little cranium scratching amongst board members. It would seem that the vital clue to the solution should have been readily discovered using the combined experience of all the AlfaBB’ers assisting you. Perhaps the resolution is to be found by reviewing what is being assumed as functioning properly rather than by pinpointing a distinct malfunction. Following this train of thought, two things come to mind: 1) You have mentioned that rather than replacing your brake lines, you have re-plated them. Have you done this in a manner which precluded any plating of the inside of the brake tubing? Any reduction of the inner diameter of the tubing would have a negative effect such as you are experiencing. 2) You have pictured your restoration quite thoroughly; amongst the pics is one of a truckload of parts in boxes indicating your Veloce was something of a basket case when purchased. Was the pedalbox amongst the boxes or was it already installed on the chassis? Is it the correct (36mm) length lever arm for your brake system?