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Posted By : Ben Watson, 10-Aug-2004,
11:43pm
hello all
im still confused about this bloomin great big master cylinder,
heres a picture of it next to the standard clutch master cylinder(painted green, mmm great!) both have 5/8" written on the side this i believe is the
piston bore, so in theory im thinking both will behave exactly the same when fitted, is this right?
is there any advantage with using the bigger one?
cheers
ben w
master cylinder type
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Posted By : Jonathan Pashley, 11-Aug-2004,
08:17am
Hi Ben
The reason for the Larger reservoir on the brake master cylinder over the clutch master cylinder is that the brake system needs subtantially more fluid
to compress the calipers wheel cylinders etc than the clutch system which only has the one operation to perform therefore you need a bigger reservoir
to hold the greater amount of fluid
Just changed mine with one from Canleys with a nice plastic reservoir on it. What a difference!!
my brakes work!!!!!!!!
Jon P
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Posted By : Paul Bodiam, 11-Aug-2004,
09:27am
Hmm.. interesting analysis.
Overall, the braking system holds more fluid than the clutch system, agreed, but when you actually press the pedals, the clutch displaces more
fluid than the brakes (think how far each pedal travels).
So why the larger reservoir? Some speculation:
1) to try to reduce the risk of running dry and getting air into the top of the system when bleeding the system?
2) to provide a safety margin of fluid in the system to help you stop the car in the event of a wheel-cylinder seal failing?
This second scenario happened to my brother-in-law. He had to make an emergency stop in a knackered Chrysler Sunbeam and in doing-so aparently
popped a seal on a rear-wheel cylinder, which only came to light a few minutes later when travelling at 70+ on a dual carriageway he found he had
no brakes. Pumping the brake pedal produced some result, and he managed to stop the car safely, but in doing so, he completely emptied the
reservoir of the brake circuit.
Paul
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Posted By : William Davies,
11-Aug-2004, 09:34am
Being self adjusting, the disc brake system requires a larger reservoir as the fluid level in the system will drop as the calipers wear. On
drum braked Heralds the clutch and brake master cylinders are identical, the disc braked models use a cylinder with a larger reservoir,
Cheers,
Bill.
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Posted By : Christopher How,
11-Aug-2004, 11:04am
As the calipers wear?
Do you mean as the 'pads' wear?
I can see sense in that, if a pad is half an inch thick, times 2 that's one inch (excluding wear on the back). If your pads are worn right
down to the calipers, that's and extra inch of travel for the pistons, hence, more fluid is needed in the reservoir. That doesn't happen on
a clutch, there's no need for more fluid than will be needed in one pump of the cylinder.
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Posted By : Philip Brammer,
11-Aug-2004, 11:23am
The big problem for me was that the customer kept 'topping up' the master cylinder to its 'upper' level. All fine and dandy until its
time to fit new pads. push back 4 pistons and you have brake fluid everywhere! I quickly learned to keep a big plastic syringe in my
toolbox to remove excess brake fluid to the 'lower' level.
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Posted By : William
Davies, 11-Aug-2004, 02:56pm
Blame it on my (lack of) proof reading! I di of course mean that the pads wear, rather than the calipers.......
Cheers,
Bill.
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Posted By : William
Davies, 11-Aug-2004, 02:57pm
Blame it on my (lack of) proof reading! I did of course mean that the pads wear, rather than the calipers.......
Cheers,
Bill.