Brake Caliper - Primary & Secondary Connections

Hi All, on my rebuild (landy 2a v8 hybrid) I am fitting Lockheed brake calipers that have both a primary and secondary brake line supply's.
The problem I have is which brake line entry on the caliper itself is which, i.e. which is Primary circuit and which is the secondary circuit?


(Some have mentioned that with the caliper in it's mounted position the top pair are the secondary circuit one's, this is unconfirmed at present).

all help and advise greatly accepted
Rich

shy7g said:

Hi All, on my rebuild (landy 2a v8 hybrid) I am fitting Lockheed brake calipers that have both a primary and secondary brake line supply's.
The problem I have is which brake line entry on the caliper itself is which, i.e. which is Primary circuit and which is the secondary circuit?
View attachment 51638

(Some have mentioned that with the caliper in it's mounted position the top pair are the secondary circuit one's, this is unconfirmed at present).

all help and advise greatly accepted
Rich

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They both work together, then if one fails you still have the other.....in theory

Is there not another inlet on the opposite side of the caliper? Not usual for a caliper to have two feeds. One is usually the feed and the secondary is for a pipe to couple the other side of the caliper. Either can be used as primary but obviously the one nearest to the other side will give a neater run.

early disco and defender's had twin feed callipers I have a pair sitting on a shelf in the workshop.

Pikey said:

early disco and defender's had twin feed callipers I have a pair sitting on a shelf in the workshop.

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Ok never seen them, but one line must feed the two top pots and the other the two bottom ones so it does not really matter which is used for primary.

wammers said:

Ok never seen them, but one line must feed the two top pots and the other the two bottom ones so it does not really matter which is used for primary.

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Would think so. Not even sure there is a primary & secondary Feed? AFAIK it's just twin feed. to each front caliper.

Pikey said:

Would think so. Not even sure there is a primary & secondary Feed? AFAIK it's just twin feed. to each front caliper.

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Would think it's two brake feeds from a dual master cylinder one fails the other is still live. Which way around they are does not matter a great deal.

pretty sure on a fender it's just a tee piece that feeds both sides same master cylinder as the 2pot calipers.

wammers said:

Would think it's two brake feeds from a dual master cylinder one fails the other is still live. Which way around they are does not matter a great deal.

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Never known a dual circuit braking system to work when a pipe fails

landowner said:

Never known a dual circuit braking system to work when a pipe fails

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You must have seen some pretty knackered dual circuit braking systems then. That is the purpose of them, to give braking if one circuit fails.

Pikey said:

pretty sure on a fender it's just a tee piece that feeds both sides same master cylinder as the 2pot calipers.

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Not a lot of point in having two separate circuits in the caliper then. Unless Land rover got them on a special offer buy one get one free.

wammers said:

You must have seen some pretty knackered dual circuit braking systems then. That is the purpose of them, to give braking if one circuit fails.

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Used to work a lot on classic Minis and if a pipe bursts the pedal goes to the floor, same with every car I've ever had, pedal to floor but just a little braking but not for long. Try taking a pipe off the master cylinder on the landy, all fluid will escape then no brakes

wammers said:

Not a lot of point in having two separate circuits in the caliper then. Unless Land rover got them on a special offer buy one get one free.

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Only difference between single feed and twin feed calipers is the extra line in and bleed nipple. caliper body is same on both calipers

landowner said:

Used to work a lot on classic Minis and if a pipe bursts the pedal goes to the floor, same with every car I've ever had, pedal to floor but just a little braking but not for long. Try taking a pipe off the master cylinder on the landy, all fluid will escape then no brakes

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That's because classic Minis did not have dual braking systems.

wammers said:

That's because classic Minis did not have dual braking systems.

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Yes they did, front / rears

wammers said:

That's because classic Minis did not have dual braking systems.

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And diagonal, depended on the year

Pikey said:

pretty sure on a fender it's just a tee piece that feeds both sides same master cylinder as the 2pot calipers.

Click to expand...

Fenders with single line brake pipes have front rear split brakes, there is a valve on the bulk head drivers side (from same parts bin as classic Mini) which also serves as a rear brake restrictor, there is a shuttle in it which shuts either front or rear off whichever is leaking

landowner said:

Yes they did, front / rears

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No they didn't later ones may have had, but the early ones 848 Mini, 998 Cooper, 1071 and 1275 S the only ones you can call classic, certainly did not.

wammers said:

You must have seen some pretty knackered dual circuit braking systems then. That is the purpose of them, to give braking if one circuit fails.

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Would you know if there is any truth in -
"Some have mentioned that with the caliper in it's mounted position the top pair are the secondary circuit one's"
Cheers
Rich

shy7g said:

Would you know if there is any truth in -
"Some have mentioned that with the caliper in it's mounted position the top pair are the secondary circuit one's"
Cheers
Rich

Click to expand...

I don't know you never answered the question i asked. Are there any more ports in the other side of the caliper? I can't see any reason there would be two coupled inlets supplying all the pots. Can you blow into one port and get air out of the other. Or are the two ports not connected? If there are only two ports, and they are not connected one inlet must supply one pair and the other inlet the other pair. Otherwise there is no point in having two inlet ports. Put a piece of wood between the pots with a slight gap to stop them blowing out and apply an air line to each port in turn and see which pots move with what port pressured. If one port supplies the top pair and one the bottom pair it is up to you which way round you put the pipes. Orientation does not really matter.