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HELP - Series brakes driving me mad


Nikolai_V

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Hopefully someone on here can help with this:

I`ve been knocked back on my WOF because my brakes need adjustment. The power and balance are there, but the first pedal push goes to about 2' off the floor, with the second being sweet as a nut.

It`s a 1967 88" with standard 10" drums all round. All shoes are good (4mm thickness), both front drums have been replaced (and backs were within spec with plenty of adjustment left).

I know about the proper location of the return springs - they`re all good. Fluid is fine... Pulled the wheel cylinders apart and all look fine (clean bores, seals nice).

Only wierd thing is a funny almost whine noise from back brakes after releasing pedal??

Its almost like the springs in the wheel cylinders aren`t seating the shoes out far enough, and the first pump is seating the shoes, with the second engaging them from the proper location. This is probably it, because if I leave it after the second pump its back to normal (too much travel). But the springs on the trailing shoes arent strong enough to pull the cylinder back in without the assitance of the spinning drum...

But why???? and how do I fix it?

Answers gratefully appreciated.

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Hopefully someone on here can help with this:

I`ve been knocked back on my WOF because my brakes need adjustment. The power and balance are there, but the first pedal push goes to about 2' off the floor, with the second being sweet as a nut.

It`s a 1967 88" with standard 10" drums all round. All shoes are good (4mm thickness), both front drums have been replaced (and backs were within spec with plenty of adjustment left).

I know about the proper location of the return springs - they`re all good. Fluid is fine... Pulled the wheel cylinders apart and all look fine (clean bores, seals nice).

Only wierd thing is a funny almost whine noise from back brakes after releasing pedal??

Its almost like the springs in the wheel cylinders aren`t seating the shoes out far enough, and the first pump is seating the shoes, with the second engaging them from the proper location. This is probably it, because if I leave it after the second pump its back to normal (too much travel). But the springs on the trailing shoes arent strong enough to pull the cylinder back in without the assitance of the spinning drum...

But why???? and how do I fix it?

Answers gratefully appreciated.

You haven't mentioned the adjusters: have you jacked the wheels up one by one and adjusted the hex head on the brake back plate until the wheel locks, then backed it off two clicks? Not doing this would explain all the symptoms you describe. There will be one near the front on each rear backplate, and two on each front backplate. There are no springs in the wheel cylinders. The whine is probably the brake fluid being forced back into the brake lines by the springs.

There is virtually certain to be a guide in the archive.

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You haven't mentioned the adjusters: have you jacked the wheels up one by one and adjusted the hex head on the brake back plate until the wheel locks, then backed it off two clicks? Not doing this would explain all the symptoms you describe. There will be one near the front on each rear backplate, and two on each front backplate. There are no springs in the wheel cylinders. The whine is probably the brake fluid being forced back into the brake lines by the springs.

There is virtually certain to be a guide in the archive.

Thanks for the quick reply - I did check the archive, but nowt in the index on series brakes, nor did a search turn anything up.

All the drums have been adjusted right up, i.e. as you say locked, then two clicks back. My backing plates only have one adjuster per (being bog-stock 10" drums - single leading shoe). When I pulled the wheel cylinders apart there is a spring between the two opposing seals (and pistons). Had a mechanic mate have a look on friday night and we`re both baffled.

One thing I just noticed is that both sides have the same part no. on them - arent wheel cylinders handed?

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two things you might want to try...

make sure the bleed nipples are on top on the wheel cylinders.

put a g-clamp on each wheel wheel cylinder and make sure the cylinder is fully compressed while bleeding, This should mean there is no chance of any air in the system.

I had the same problem and you describe while helping a friend. it was on a s3 88" with a non-servo assist system. should be the simplest system in the world :huh: But I replace every thing shoes, flexes, copper wheel and master cylinder/s, and still could not get a good pedal on the first pump second it stopped a dream.

Lots of people had a go at fixing it but never got to work properly my mate then got bored and sold it on ebay.. :o

good luck.. will be watching this thread with interest as to how you get it fixed...

Paul

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Hopefully someone on here can help with this:

....

Its almost like the springs in the wheel cylinders aren't seating the shoes out far enough, and the first pump is seating the shoes, with the second engaging them from the proper location. This is probably it, because if I leave it after the second pump its back to normal (too much travel). But the springs on the trailing shoes aren't strong enough to pull the cylinder back in without the assistance of the spinning drum...

But why???? and how do I fix it?

Answers gratefully appreciated.

Some of this doesn't make sense to me, but I'll come back to it.

First thing is to identify which wheels are at fault.

Yes, if you have to make two strokes, and the second one gets a firm pedal, I'm sure the first stroke is 'merely' pushing the shoes close enough to the drum for the second stroke to be effective.

I assume you have normal rubber flexible hoses, not the braided stainless steel type (which should NOT be clamped).

Clamp off all three flexible hoses, one for each front wheel, one for the rear axle.

Try the pedal, it should be short travel and very firm when it stops.

Release one clamp and re-try the pedal. Travel will be longer, but the pedal should still be firm when it stops.

REPLACE that clamp, release another clamp, and retest.

Replace that clamp, release the third clamp, and retest.

Hopefully you will now know what to concentrate on, one of the front wheels, or the pair on the rear axle.

Release all three clamps, simply because there is no point in leaving the hoses distorted under the clamps for longer than necessary.

You can short circuit this complete test, guess that it's the rear axle at fault, and just clamp off that hose to prove it, but this guessing (and any subsequent misleading conclusions) are your responsibility.

If you are looking for a Tech Archive type article you could review the one on the Series 2 Forum http://www.series2club.info/forum/index.php?topic=6606.0 which confirms the existence of the 'springs inside the wheel cylinders'.

These springs are only there to keep the pistons against the shoes, the springs play NO part in keeping the shoes close to the drum, which you seem to have assumed in the comment I've quoted at the beginning.

Also, use the pictures on that page to confirm you have the pull-off springs mounted correctly.

Note also that the wheel cylinders do have different part numbers, but the only difference appears to be around which direction the brake pipes face. They should both face the same way, forwards or backwards, but it doesn't appear to matter which way they face, apart from how the direction affects the neatness of the pipe run.

The number on the cylinders you see could be a casting number, and you will see that the castings are identical, the difference comes about when the holes are drilled.

Once you have identified which wheel is at fault, without touching the adjuster, remove the drum and look closely at the adjuster, and how it's resting against the pin in the shoe.

My guess is that one or more of the adjusters are not holding the shoe against the drum.

Don't have a false confidence because you have fitted new parts, the pins may be too short, and 'falling off' the adjuster snail the first time the brakes are applied.

Note also that the shoes are handed; have you got them fitted to the correct sides?

But the springs on the trailing shoes aren't strong enough to pull the cylinder back in without the assistance of the spinning drum

I don't know why you say this, you don't appear to have identified a problem with the brake shoe staying in contact with the drum.

HTH

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Hi

The rear wheel cylinders are 1" bore and the front are 1 1/4" bore iirc and as David says LH/RH angling the flexi. If you have too much slack (should be a small amount) in the pushrod in the pedal box this can give the same symptoms, also a failing master cyl too.

Is the return spring ok on the brake pedal?

cheers

Steveb

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Some of this doesn't make sense to me, but I'll come back to it.

First thing is to identify which wheels are at fault.

Yes, if you have to make two strokes, and the second one gets a firm pedal, I'm sure the first stroke is 'merely' pushing the shoes close enough to the drum for the second stroke to be effective.

I assume you have normal rubber flexible hoses, not the braided stainless steel type (which should NOT be clamped).

Clamp off all three flexible hoses, one for each front wheel, one for the rear axle.

Try the pedal, it should be short travel and very firm when it stops.

Release one clamp and re-try the pedal. Travel will be longer, but the pedal should still be firm when it stops.

REPLACE that clamp, release another clamp, and retest.

Replace that clamp, release the third clamp, and retest.

Hopefully you will now know what to concentrate on, one of the front wheels, or the pair on the rear axle.

Release all three clamps, simply because there is no point in leaving the hoses distorted under the clamps for longer than necessary.

You can short circuit this complete test, guess that it's the rear axle at fault, and just clamp off that hose to prove it, but this guessing (and any subsequent misleading conclusions) are your responsibility.

If you are looking for a Tech Archive type article you could review the one on the Series 2 Forum http://www.series2club.info/forum/index.php?topic=6606.0 which confirms the existence of the 'springs inside the wheel cylinders'.

These springs are only there to keep the pistons against the shoes, the springs play NO part in keeping the shoes close to the drum, which you seem to have assumed in the comment I've quoted at the beginning.

Also, use the pictures on that page to confirm you have the pull-off springs mounted correctly.

Note also that the wheel cylinders do have different part numbers, but the only difference appears to be around which direction the brake pipes face. They should both face the same way, forwards or backwards, but it doesn't appear to matter which way they face, apart from how the direction affects the neatness of the pipe run.

The number on the cylinders you see could be a casting number, and you will see that the castings are identical, the difference comes about when the holes are drilled.

Once you have identified which wheel is at fault, without touching the adjuster, remove the drum and look closely at the adjuster, and how it's resting against the pin in the shoe.

My guess is that one or more of the adjusters are not holding the shoe against the drum.

Don't have a false confidence because you have fitted new parts, the pins may be too short, and 'falling off' the adjuster snail the first time the brakes are applied.

Note also that the shoes are handed; have you got them fitted to the correct sides?

But the springs on the trailing shoes aren't strong enough to pull the cylinder back in without the assistance of the spinning drum

I don't know why you say this, you don't appear to have identified a problem with the brake shoe staying in contact with the drum.

HTH

Thansk for the detailed reply. I`ve tried the hoseclamp on the line method of isolating the fault - it appears to be the front right wheel at fault, however, clamping off the rear alos improves things (as I guess there is less fluid to move etc). My backing plates only have one adjuster per plate, which acts on the leading shoe only - the trailing shoe is left to do its own thing. From observation - the leading shoe is fine (adjusted right), while the trailing shoe slowly moves away from the drum. The initial pedal press seems to 'seat' the trailing shoe, with the subsequent presses fully engaging the brakes.

This is why i mentioned the spring tension being insufficient to pull the shoe away from the drum, because the trailing shoe is coming back away from the drum surface under whatever mechanism. if the trailing shoe had an adjuster this would be simple, but there is no mechanism for setting the 'pre-load' on the trailing shoe. It appears that fluid pressure is all that holds the trailing shoe in the correct location...

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