Technical Brake Woes

[stefanwest]

Hi all,

I’ve got a little 1970 L and recently I did a full overhaul on the brakes. Unfortunately I ended up snapping one of the old hard pipes. Tried having a go at making new ones myself but ultimately ended up getting a local garage to fix it. However the brakes never seem quite right.

Before the overhaul if you pressed hard on the pedal you’d easily lock up the wheels and there was proper feeling to the pedal. Since the overhaul the pedal does travel quite a long way, and I wouldn’t say it brakes, it more gently retards the speed.

Now the garage have taken a look a few times now and each time they’ve ensured the system is fully bled with no leaks and they’ve been happy with it. But I don’t know it just doesn’t feel like it did before and certainly doesn’t feel safe. But 100% there is no air in that system so I’m stumped

 

[StMarks]

Hi all,

I’ve got a little 1970 L and recently I did a full overhaul on the brakes. Unfortunately I ended up snapping one of the old hard pipes. Tried having a go at making new ones myself but ultimately ended up getting a local garage to fix it. However the brakes never seem quite right.

Before the overhaul if you pressed hard on the pedal you’d easily lock up the wheels and there was proper feeling to the pedal. Since the overhaul the pedal does travel quite a long way, and I wouldn’t say it brakes, it more gently retards the speed.

Now the garage have taken a look a few times now and each time they’ve ensured the system is fully bled with no leaks and they’ve been happy with it. But I don’t know it just doesn’t feel like it did before and certainly doesn’t feel safe. But 100% there is no air in that system so I’m stumped

Whilst it does sound very much like trapped air, in the lines or master cylinder, there may be another culprit worth checking.: On some older motorcycles, usually from around 70's - 80's I have come across situations where the rubber sections of the brake pipes loose their integrity. Instead of transferring pressure within the hydraulic system they "inflate" slightly, so the brake system appears "soft" even with a 100% perfectly bled fluid present.
Fwiw my money would still be on trapped air somewhere, but it may be worth checking out your rubber hose sections.?

Hth.

 

[bugsymike]

When you say a full overhaul of brakes, did that include new shoes with self adjusters etc.?
If so how good is the handbrake, did you have to take up a lot of adjustment?
Reason being, even fairly good quality pattern brake shoes and adjusters are often not effective at holding the shoes in close contact with the drums, resulting in excessive brake travel which is even more noticeable when new shoes haven't quite bedded in also.
If you have enough brake pipe clamps and are careful not to damage the rubber hoses then by clamping all four hoses at the wheels, if you then have a good brake then you know the fault is in the drums, possibly as I suggested.
There are different ways to improve that, but try the clamping first.
However if brake is still poor then as garage has thoroughly bled the system the only other likely cause is a dodgy brake master cylinder.

 

[Goldnrust]

If the shoes have been disturbed, the self adjusters on the 500 brake shoes sometimes need a bit of help settling back into place, and if wrong will cause a long pedal travel.

I was told to drive forwards in 1st, then brake hard to a stop. Then do the same in reverse. And to repeat that 5/6 times to get the shoes to adjust fully.

 

[bugsymike]

If the shoes have been disturbed, the self adjusters on the 500 brake shoes sometimes need a bit of help settling back into place, and if wrong will cause a long pedal travel.

I was told to drive forwards in 1st, then brake hard to a stop. Then do the same in reverse. And to repeat that 5/6 times to get the shoes to adjust fully.

My preference is to manually adjust with a screwdriver levering the shoes out a bit wide and then taping the drum on gently, once screwed down /bolted on then give the drum a gentle bang with a copper mallet which then centralises the shoes and they spin free , but with minimum clearance, so best minimum pedal travel.
There is also the issue of strong brake springs overcoming pattern quality brake adjuster friction pads.
Always assuming the brake pedal is good with four pipe clamps on.

 

[stefanwest]

Whilst it does sound very much like trapped air, in the lines or master cylinder, there may be another culprit worth checking.: On some older motorcycles, usually from around 70's - 80's I have come across situations where the rubber sections of the brake pipes loose their integrity. Instead of transferring pressure within the hydraulic system they "inflate" slightly, so the brake system appears "soft" even with a 100% perfectly bled fluid present.
Fwiw my money would still be on trapped air somewhere, but it may be worth checking out your rubber hose sections.?

Hth.

So I believe the only rubber hose that wasn’t replaced was the one that goes from the reservoir to the master cylinder. But I have ordered a new one of those anyway. The garage have bled the brakes each time they’ve worked on it, and test drove it and said they were happy with it, so I’m not sure if maybe the brakes are actually firming up straight after bleeding but when the cars been sat for a few hours waiting for me to collect it air is getting in somehow

 

[stefanwest]

If the shoes have been disturbed, the self adjusters on the 500 brake shoes sometimes need a bit of help settling back into place, and if wrong will cause a long pedal travel.

I was told to drive forwards in 1st, then brake hard to a stop. Then do the same in reverse. And to repeat that 5/6 times to get the shoes to adjust fully.

I shall give this a try! Can’t hurt!

 

[stefanwest]

When you say a full overhaul of brakes, did that include new shoes with self adjusters etc.?
If so how good is the handbrake, did you have to take up a lot of adjustment?
Reason being, even fairly good quality pattern brake shoes and adjusters are often not effective at holding the shoes in close contact with the drums, resulting in excessive brake travel which is even more noticeable when new shoes haven't quite bedded in also.
If you have enough brake pipe clamps and are careful not to damage the rubber hoses then by clamping all four hoses at the wheels, if you then have a good brake then you know the fault is in the drums, possibly as I suggested.
There are different ways to improve that, but try the clamping first.
However if brake is still poor then as garage has thoroughly bled the system the only other likely cause is a dodgy brake master cylinder.

It did, I also replaced the handbrake cable at the same time. The handbrake works really well now. Better than the brake pedal! The master cylinder was my thought. It’s new, but I never bench bled it, instead I bled it on the car, so maybe there’s air trapped in it or maybe it’s faulty. Either way for the sake of £20 I’ve bought another one and will have the garage do it instead of me! I’ve also bought a replacement T piece that goes at the back where the brake line splits between the rear wheels as I did have to re tap that so maybe that’s letting air in. When the garage worked on it they were happy with the brakes on a test drive so I don’t know if they’ve then gone soft after they’ve parked up

 

[bugsymike]

I do usually prime master cylinders, both clutch and brake. Though mainly as it makes the job quicker.
If garage has bled the system then I doubt if any air is remaining in the master cylinder.
If it was me I would just do as I described earlier, as it has worked for me for over 50 years in the motor trade.
The only other point is the master cylinder, which if poor quality or old, can let air into the brakes from the back seal.
Anything after the master cylinder would cause a leak of brake fluid out, rather than allowing air to suck in, as it is on the pressure side of the pump.

 

[the hobbler]

I do usually prime master cylinders, both clutch and brake. Though mainly as it makes the job quicker.
If garage has bled the system then I doubt if any air is remaining in the master cylinder.
If it was me I would just do as I described earlier, as it has worked for me for over 50 years in the motor trade.
The only other point is the master cylinder, which if poor quality or old, can let air into the brakes from the back seal.
Anything after the master cylinder would cause a leak of brake fluid out, rather than allowing air to suck in, as it is on the pressure side of the pump.

When you overhauled the brakes did you fit new shoes and 'shoe-return'springs? I ask this because there a number of reasons causing you not to have a very good brake pedal. Any 1 of these reasons, or a combination of them will cause a long brake pedal. (1)a lot of the 'pattern'brake shoes have a slightly thinner lining than the 'factory-original'. Tony Castle-Miller at Middle Barton has had 500 shoes made for him by (I remember correctly) Ferodo to the original specifications, (2) the little 'friction-pad-washers' on the self-adjusters (on the 'pattern'shoes) are, I am convinced, not at 'grippy' as the factory-original and, (3) the 'pattern' shoe-return springs are shorter that the original. The outcome of the shorter springs is that when they are extended (when the brakes have been applied) they are too strong and then, combined with the "not-so-grippy" friction pads on the self-adjusters, the shoes are pulled too far back from the drum when the brake pedal is released. The simplest way round the spring problemis to either retain the original springs (if they are in a good enough condition to do so) OR, stretch the 'pattern' springs out to the same length as the originals. The easy way to do this is to hold one end of the new spring in a vice, and then using a bar in the other end of the spring (a screwdriver will suffice) GENTLY and CAREFULLY pull out the new spring so that it length matches the original.
I will happily concede that a problem with your master-cylinder MAY be the cause of your woes. It is not unknown for a "working OK" master-cylinder to fail when bleeding the brakes.This is because a fine film of corrosion can build up on the un-swept-by-the-seals section of the cylinder-walls of the master-cylinder, which causes no problems when the brakes are 'originally' being used. BUT, when the brake pedal is FULLY depressed when bleeding the brakes, the seals inside the master-cylinder go over the slight corrosion, causing slight tearing of the edges of the master-cylinder seals, and therfore, internal leaking.

 

[bugsymike]

When you overhauled the brakes did you fit new shoes and 'shoe-return'springs? I ask this because there a number of reasons causing you not to have a very good brake pedal. Any 1 of these reasons, or a combination of them will cause a long brake pedal. (1)a lot of the 'pattern'brake shoes have a slightly thinner lining than the 'factory-original'. Tony Castle-Miller at Middle Barton has had 500 shoes made for him by (I remember correctly) Ferodo to the original specifications, (2) the little 'friction-pad-washers' on the self-adjusters (on the 'pattern'shoes) are, I am convinced, not at 'grippy' as the factory-original and, (3) the 'pattern' shoe-return springs are shorter that the original. The outcome of the shorter springs is that when they are extended (when the brakes have been applied) they are too strong and then, combined with the "not-so-grippy" friction pads on the self-adjusters, the shoes are pulled too far back from the drum when the brake pedal is released. The simplest way round the spring problemis to either retain the original springs (if they are in a good enough condition to do so) OR, stretch the 'pattern' springs out to the same length as the originals. The easy way to do this is to hold one end of the new spring in a vice, and then using a bar in the other end of the spring (a screwdriver will suffice) GENTLY and CAREFULLY pull out the new spring so that it length matches the original.
I will happily concede that a problem with your master-cylinder MAY be the cause of your woes. It is not unknown for a "working OK" master-cylinder to fail when bleeding the brakes.This is because a fine film of corrosion can build up on the un-swept-by-the-seals section of the cylinder-walls of the master-cylinder, which causes no problems when the brakes are 'originally' being used. BUT, when the brake pedal is FULLY depressed when bleeding the brakes, the seals inside the master-cylinder go over the slight corrosion, causing slight tearing of the edges of the master-cylinder seals, and therfore, internal leaking.

Fully in agreement with @the hobbler as same methods I practice also.

 

[stefanwest]

When you overhauled the brakes did you fit new shoes and 'shoe-return'springs? I ask this because there a number of reasons causing you not to have a very good brake pedal. Any 1 of these reasons, or a combination of them will cause a long brake pedal. (1)a lot of the 'pattern'brake shoes have a slightly thinner lining than the 'factory-original'. Tony Castle-Miller at Middle Barton has had 500 shoes made for him by (I remember correctly) Ferodo to the original specifications, (2) the little 'friction-pad-washers' on the self-adjusters (on the 'pattern'shoes) are, I am convinced, not at 'grippy' as the factory-original and, (3) the 'pattern' shoe-return springs are shorter that the original. The outcome of the shorter springs is that when they are extended (when the brakes have been applied) they are too strong and then, combined with the "not-so-grippy" friction pads on the self-adjusters, the shoes are pulled too far back from the drum when the brake pedal is released. The simplest way round the spring problemis to either retain the original springs (if they are in a good enough condition to do so) OR, stretch the 'pattern' springs out to the same length as the originals. The easy way to do this is to hold one end of the new spring in a vice, and then using a bar in the other end of the spring (a screwdriver will suffice) GENTLY and CAREFULLY pull out the new spring so that it length matches the original.
I will happily concede that a problem with your master-cylinder MAY be the cause of your woes. It is not unknown for a "working OK" master-cylinder to fail when bleeding the brakes.This is because a fine film of corrosion can build up on the un-swept-by-the-seals section of the cylinder-walls of the master-cylinder, which causes no problems when the brakes are 'originally' being used. BUT, when the brake pedal is FULLY depressed when bleeding the brakes, the seals inside the master-cylinder go over the slight corrosion, causing slight tearing of the edges of the master-cylinder seals, and therfore, internal leaking.

I did replace the springs so that’s a good point actually. I will definitely have a rummage through the garage as I’m sure I’ve got at least one of the old springs to compare it against. Thanks

 

[Fatcatvera]

See here for a video of the issue of the spring force of pattern parts that are too shorth overcoming the friction plates and retracting the shoes too far away from the drums:- https://www.fiatforum.com/threads/spongy-brakes.457736/page-2#post-4761330