pajsh
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 posted on 22/5/05 at 06:32 PM |
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Brakes driving me nuts!
Can anyone give me some advice on brakes. My car (started by someone else) is fitted with a sierra master cylinder, sierra front discs and 9"
rear drums on a capri live axle. Trouble is the brakes don't work. I have fitted new discs, pads and shoes, freed everything and bled them but
still have no real stopping power. Should I suspect the master cylinder or is the basic principle of using a servo master cylinder without a servo
flawed.
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theconrodkid
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| posted on 22/5/05 at 06:38 PM |
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think you got it in one,using a smaller dia master would help or fit a servo,had one on my locost and brilliant brakes,my current hasnt and crap
brakes
who cares who wins
pass the pork pies
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pajsh
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| posted on 22/5/05 at 06:50 PM |
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There seems to be enough travel and the pedel is firm but stamp hard and the car stops eventually! No chance of locking a wheel at all. The guy who
built it (used to build stock cars) said with a servo it would lock up. Being a Pinto it's a bit conjested on the drivers side so a servo would
be alot of work. I'm not sure about the pedel rotation. Lever arm seems quite good, probably about 3:1 maybe. Do you know where I can get a
non-servo SVA master cylinder.
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britishtrident
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| posted on 22/5/05 at 07:50 PM |
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Pedal ratio should be between 4:1 and 5.5:1 for use without a servo. You are going to need a smaller master cylinder --- trouble is very few dual
circuit non servo cylinders around, the most suitable would be one the Girling from a late Triumph GT6, late FX4 taxi -- this is an expensive item
new however any of the Triumph Spitfire secondhand spares such as "The Spitfire Graveyard" should be able to supply one which you can fit
new seals to.
Two things to watch on this cylinder -- the mounting bolt holes are a different patern (vertical instead horizontal) and I am not sure if its has
metric or imperial pipe fittings.
[Edited on 22/5/05 by britishtrident]
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phil m
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| posted on 22/5/05 at 08:08 PM |
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had the same thing on my locost , using a sierra master cylinder. It was caused by the master cylinder not being bled properly.
It was positioned very low down and took a hell of a lot of playing around to get it to work.
I disconnected the brake pipes at tyhe cylinder and tried to get the master full of fluid before connecting it all up again
Keep playing wityh it !!!!!!!!!!!!!!! 
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pajsh
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| posted on 23/5/05 at 06:49 PM |
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Thanks chaps.
At least I am alot wiser now as to what the problem is and what to look for.
I've renewed everything except the drums [which I'm struggling to source cos there off an old Capri] and the master cylinder. I was going
to get an old one from the breakers, but I don't think I'll bother now.
I might just ditch the whole pedal set up and buy one from MK or Luego iwth cylinders attached, to solve my problems. I've practically redone
everything the first bloke did. Don't know if I can fit it in around the 4:1 though?
As Arnie said "I'll be back"
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theconrodkid
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| posted on 23/5/05 at 08:10 PM |
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i made a new brake pedal,3 times the length of the original,its a lot better but still no brilliant
who cares who wins
pass the pork pies
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Avoneer
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| posted on 23/5/05 at 10:28 PM |
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Have you tried using an Ezi-Bleed?
Pat...
No trees were killed in the sending of this message.
However a large number of electrons were terribly inconvenienced.
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pmc_3
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| posted on 24/5/05 at 07:47 AM |
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I take it the front callipers are fitted the right way round with the bleed nipples at the top? Otherwise you wont get the air out.
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andkilde
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| posted on 24/5/05 at 12:21 PM |
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quote:
Originally posted by pajsh
The guy who built it (used to build stock cars) said with a servo it would lock up.
Hmmn, sounds fishy -- a servo helps reduce effort under moderate braking but AFAIK doesn't really provide more braking power in a panic stop
(wheel lockup).
I would suspect air in the system or a duff master.
Cheers, Ted
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britishtrident
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| posted on 24/5/05 at 06:59 PM |
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quote:
Originally posted by andkilde
quote:
Originally posted by pajsh
The guy who built it (used to build stock cars) said with a servo it would lock up.
Hmmn, sounds fishy -- a servo helps reduce effort under moderate braking but AFAIK doesn't really provide more braking power in a panic stop
(wheel lockup).
I would suspect air in the system or a duff master.
Cheers, Ted
The level of servo over assist on modern cars is totally absurd as a result many drivers now feel uncomfortable with a brake pedal that needs more
than about 35 lbf foot pressure for an emmergency stop.
The early 60s generation of medium cars with disc brakes but no servo were a bit sore on the the leg but they did stop well if you pushed the pedal
hard enough. By the early 70s pedal pressures on small and medium cars even without servos like the Avenger Marina and Viva wern't to bad. But
since the later 1970s when servos became universal fitting even on the smallest cars pedal pressure have become much too low.
EBS GreenStuff brake pads have an initial coefficient of fricton of 0.46 even decent quality oridinary pads are usually only in the range 0.3 to
0.33, crunching the numbers that is a 1/3 reduction in pedal effort by just changing the pads.
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pajsh
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| posted on 24/5/05 at 09:11 PM |
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Bleed nipples are on the top which I guess is the right way.
I use a non return type valve fro bleeding btu am not sure of the condition of teh seals in the master cylinder.
Sounds to me like the pedal does not have enough leverage and the cylinder is too big for use witout a servo. My options seem to be, find a smaller
cylinder, fit a servo (big problem) and/or extend the pedel lever arm.
I am scouring ebay at present for options.
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indykid
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| posted on 25/5/05 at 08:36 AM |
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fyi, 3:1 is all i've got in the indy.
pedal is rock hard, and emergency stop feels good.
for the sake of a tenner, i urge everyone to get an easi-bleed, as it's as cheap as throwing brake fluid at it, and even cheaper than getting a
new master cylinder because the old one "might" be suspect
hth
tom
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britishtrident
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| posted on 26/5/05 at 10:33 AM |
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quote:
Originally posted by indykid
fyi, 3:1 is all i've got in the indy.
pedal is rock hard, and emergency stop feels good.
for the sake of a tenner, i urge everyone to get an easi-bleed, as it's as cheap as throwing brake fluid at it, and even cheaper than getting a
new master cylinder because the old one "might" be suspect
hth
tom
Individual pereceptions and experince of what it acceptable vary --- Like you a very solid pedal works for me, but the mastercylinders fitted to
cars with servos are a larger diameter the reduction in pedal effort switching from a .82" to a 0.75" mastercylinder is quite
noticeable.
[Edited on 26/5/05 by britishtrident]
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britishtrident
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| posted on 26/5/05 at 10:45 AM |
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Been thinking I seem to recall some everyday (ie non-cozzie) Sierra models have calipers with slightly larger piston ---- can anybody confirm ?
[Edited on 26/5/05 by britishtrident]
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saigonij
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| posted on 26/5/05 at 11:39 AM |
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im not 100% sure, but here is what i think.
there are two types of front disc size on the sierra - non cossie
240 and 260.
im pretty sure that both typres use the 60mm single piston caliper, although the 240 one MIGHT use a 53mm piston.
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britishtrident
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| posted on 26/5/05 at 02:00 PM |
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quote:
Originally posted by saigonij
im not 100% sure, but here is what i think.
there are two types of front disc size on the sierra - non cossie
240 and 260.
im pretty sure that both typres use the 60mm single piston caliper, although the 240 one MIGHT use a 53mm piston.
If it were so fitting both discs and calipers that would be another 1/3 reduction in pedal effort.
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NS Dev
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| posted on 26/5/05 at 02:47 PM |
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abs equipped sierras and 4x4's (abs or not) used a bigger caliper but I don't know the piston size. Certainly the caliper and pad are a
fair bit bigger.
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saigonij
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| posted on 26/5/05 at 03:51 PM |
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according to brakes international,
Sierra 1.3 and 1.6 > 86, and 1.6 87 onwards :
had a 53.9mm piston caliper running 240 discs
and anything with rear discs, inc 2.0 DOHC and 2.9 had 260mm discs with the 59.9 mm piston calipers.
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pajsh
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| posted on 26/5/05 at 07:35 PM |
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Discs are 240mm vented and I don't think the donor had abs as it was circa 1984.
Not sure about calipers but they look around 50-60mm one pot Teves type. Pretty standard I think as I got pads from a factors without any real
references.
Im not sure on the master cylinder dia but am going to change it for something less than 19mm and see if this helps.
I might also increase the pedel lever arm and then if all that fails fit a bloody servo!
BTW what is an eazi bleed is it just a non return valve because I've already got one of them.
Also where can I get bleed nipples cos the front ones are too worn to use an open ended spanner.
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britishtrident
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| posted on 26/5/05 at 07:48 PM |
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Is the pedal spongey ? if it isn't don't waste time bleeding.
If it is check the master cylinder mounting isn't deflecting when force is applied to the pedal.
Any accessory shop or motor factor will carry bleed nipples if in difficulty try LSUK or any of thier agents.
[Edited on 26/5/05 by britishtrident]
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pajsh
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| posted on 26/5/05 at 07:55 PM |
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The pedel is not spongey and I am pretty happy I have bled all the air out so I think it is the master and/or the lever arm.
Looking at ebay item 7976337083 to solve my problem. What do you think BT?
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britishtrident
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| posted on 26/5/05 at 09:01 PM |
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A 0.7" bore it should work
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DarrenW
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| posted on 27/5/05 at 09:27 AM |
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Eazibleed is basically a 1 litre bottle that you fill with new clean fluid. It has a pressure connection that attaches to spare wheel (not at 30psi
tho). Other end is a cap that fits onto the master cylinder. Fluid is then forced into the circuit under low pressure. You then just need to go to
each nipple and open to release air / old fluid. Nice and easy.
Word of warning - i didnt read instruction first time i used one. I didnt reduce wheel pressure. Opened first nipple, fluid squirted out into my face
and eyes. I panicked, ran into house. Front door was shut, hand slipped on handle (oily off the fluid) and i put my head thro the plate glass window
(6mm). Even tho a lump of glass fell on my head i was extremely very very lucky not to be injured. Read instructions, wear safety glasses.
(i maybe should have kept this secret!!! - i was a lot younger at the time (18)).
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pajsh
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| posted on 27/5/05 at 06:42 PM |
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Don't worry your secrets safe with me.
Guess I should have kept schtum about the ebay item as someone put a bid on straight after my post.
Live & learn!
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