alistairolsen
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| posted on 6/5/10 at 08:12 AM |
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Brake circuit layout
Starting with calipers on the front, and drums on the rear, a non servo'd master cylinder with two ports the same bore and no lines at all, what
is the best way to lay the system out?
Ive seen many systems with one port to the rear, divided on the rear axle, and oe port split on the bulkhead for the fronts?
Modern cars however are all diagonally split and this would demand I guess two dividers in the bulkhead region and two lines run back along the bottom
of the car?
Which is best and why? Any other layouts to consider?
Cheers!
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coozer
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| posted on 6/5/10 at 08:14 AM |
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I have a similar setup you describe there, One pipe to front middle and a 3 way T, same to the back.
Mine has a 4 way jobbie at the front with a hydraulic light switch.
1972 V8 Jago
1980 Z750
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matt_gsxr
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| posted on 6/5/10 at 09:39 AM |
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If you do the diagonal splitting thing, then the front and rear wheels are getting the same brake fluid pressure. This isn't bad, but it means
that you have to size the brake calipers very carefully.
If you do the front to rear split, then you can tweak the pressures front to rear using various means (different masters, balance bar, etc.).
The diagonal split is probably better in failure (i.e. you always have one front brake if you lose one braking circuit) which is probably why the big
boys use it.
Matt
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alistairolsen
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| posted on 6/5/10 at 09:41 AM |
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My understanding is diagonal split has been a legal requirement for a number of years.....
Ill be on the same master cylinder size anyway as I have a non stepped tandem cylinder. I suspect Ill be overbraked on the front however so it will be
"safe" you can get restrictors to fit inline (common on many Oe setups) but I'm not sure how they work, as surely they can only
restrict port size, not pressure :S
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blakep82
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| posted on 6/5/10 at 10:06 AM |
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quote:
Originally posted by alistairolsen
My understanding is diagonal split has been a legal requirement for a number of years.....
noooooo, a split system is a legal requirement, but diagonal is not.
front/rear split is fine, and i can't think of anyone on here whos gone to s/iva with a diagonal split
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IVA manual link http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1081997083
don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
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alistairolsen
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| posted on 6/5/10 at 10:19 AM |
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Even for type approval for mass manufacture?
I guess on a single bore master cylinder it doesnt really matter....
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blakep82
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| posted on 6/5/10 at 10:26 AM |
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ah sorry, i don't know about mass produced actually. thought this was going to be in a kit car?
________________________
IVA manual link http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1081997083
don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
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britishtrident
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| posted on 6/5/10 at 10:35 AM |
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Simple front rear split.
Proably eaiser to use two lines to the front and just a single line tee the rear, although if you have a live axle you can get away without the
tee and just run a pipe across the axle between the wheel cylinders.
Any unused ports on the master cylinder can be blocked with a bleed nipple --- actually quite handy for priming the system.
To be 100% in compliance with Road Traffic Acts the brake light switch should be in the front hydraulic circuit, although as far as I am aware no
Locoster has ever failed SVA or IVA for having the switch in the rear circuit.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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britishtrident
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| posted on 6/5/10 at 10:45 AM |
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quote:
Originally posted by alistairolsen
My understanding is diagonal split has been a legal requirement for a number of years.....
Ill be on the same master cylinder size anyway as I have a non stepped tandem cylinder. I suspect Ill be overbraked on the front however so it will be
"safe" you can get restrictors to fit inline (common on many Oe setups) but I'm not sure how they work, as surely they can only
restrict port size, not pressure :S
Diagonal split is a can of worms, it would require a differential pressure warning switch for circuit failure. This type of switch needs re-centering
if the brakes are bled.
The restrictors you mentioned are simple pressure cut-off valves although other variations exist including proportioning valves and dual rate
proportioning valves.
Some cars (notably the poverty spec BMW E46) have actual damper restrictor in both front brake hoses to slow down the initial fluid flow in rush
prevent the front brakes snatching but that is a special case.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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alistairolsen
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| posted on 6/5/10 at 11:04 AM |
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Dont think any car Ive ever had has had a differential pressure switch fitted, just a diagonal split with 4 separate hard lines and inline restrictors
int he rear ones.
Pressure cut off? So when they reach a certain level they just stop allowing any more pressure to be applied? effectively limiting the max rear wheel
cylinder pressure, not the distribution of pressure?
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