F

flyingbanana

Member
Hi all
I've a RRC 1990 v8 I'm changing the axels to 300tdi disco ones which have solid brakes and single
Pipe fitting callipers can I join the two brake pipes that go to each calliper with a tee piece then
One pipe out to the disco calliper. the reason is I'm fitting 24 spline set up
Thanks andy
 
flyingbanana said:
Hi all
I've a RRC 1990 v8 I'm changing the axels to 300tdi disco ones which have solid brakes and single
Pipe fitting callipers can I join the two brake pipes that go to each calliper with a tee piece then
One pipe out to the disco calliper. the reason is I'm fitting 24 spline set up
Thanks andy
Click to expand...
There's two pipes only to the front calliper, not each calliper, so still single at the rear.
The best procedure would be to retain one pipe and remove the other as far as the master cylinder and fit a blanking plug , better sill is to fit a 300 series disco's non ABS master cylinder.
 
Well as u have dual circuit braking u need to retain that, therefore two out of the four pistons in each front calliper are part of the rear braking system (primary), this is the system to remove, If you in the Haynes manual you can find the two two braking detailed primary and the secondary (front) with the pipe layout and how they are split.

As for which port at the master cylinder, the rear of the cylinder is primary, the front is the secondary and have two pipes to each, so u need to remove the pipes from the front callipers that go to the rear of the master cylinder.
It's possible the the brake balance valve is also involved so will need to be modified/changed

Lucky I know where my 30 year old Haynes manual was, so did a 5min refresher on what's what. :)
 
The two pipes to a RRC's front calipers are there because the top and bottom pistons on the front calipers are worked on seperate systems. The RRC abs works two of the four pistons on each front caliper and the back caliper off of the high pressure electrically pumped ABS system, and two of the pistons off an integral master cylinder that is built into the abs valve block mounted onto the pedal box. Two pipe front calipers are essentially two seperate calipers on one casting and there is no internal communication between the top and bottom sets of pistons.

AFIK you can bolt the RRC front calipers onto the discovery front axles thus retaining ABS / dual pipe. To go to a single pipe system and do away with the ABS you can either fit a 300tdi discovery master cylinder and front calipers, 300tdi disco master cylinder and Tee the two lines to the front calipers into one and join that to the brake hoses.
 
This is intriguing now, two pipes to each caliper as has been said by me and discool denotes the calipers belonging to an abs setup which works as I described, if your motor doesnt have ABS I wonder why it has dual pipes to the calipers...? Pics of the calipers and pipework and master cylinder would be appreciated.
 
Jayridium said:
This is intriguing now, two pipes to each caliper as has been said by me and discool denotes the calipers belonging to an abs setup which works as I described, if your motor doesnt have ABS I wonder why it has dual pipes to the calipers...? Pics of the calipers and pipework and master cylinder would be appreciated.
Click to expand...

Intriguing it is, it's a 'Heath Robinson' of a system the RR ABS equipped had, the Mk1 of ABS, compared with the simplicity of the disco 1 & 2 s ABS system.

The non ABS equipped RR like my 3.5 had the dual circuit front callipers, which was carried over to the first Discovery's the so call 200 series.
 
Jayridium said:
This is intriguing now, two pipes to each caliper as has been said by me and discool denotes the calipers belonging to an abs setup which works as I described, if your motor doesnt have ABS I wonder why it has dual pipes to the calipers...? Pics of the calipers and pipework and master cylinder would be appreciated.
Click to expand...
twin pipes on rrc isnt necessarily abs , the top front caliper pistons were fed by the primary circuit, the bottom pistons by the secondary circuit ,the rear were also fed by the secondary circuit by a pressure reducing valve
 
I stand corrected... Genuinely thank for your enlightenment gentlemen I have learned something new this evening :)
 
As the doctor (above) says, not ness ABS with 2 pipe. My info reads that RRC was 2 pipe front calipers from word go. My 87efi V8 is non ABS and is 2pipe
 
shocker said:
As the doctor (above) says, not ness ABS with 2 pipe. My info reads that RRC was 2 pipe front calipers from word go. My 87efi V8 is non ABS and is 2pipe
Click to expand...

Who is the Doctor?
ABS came in with the 3.9s so you won't have it on a 1987 3.5. The 3.9 from the VIN GA 1990MY if equipped with ABS, as it was an option, still had the two pipe dual circuit front callipers, see post#5, single pipe to each calliper ABS system wasn't introduced until the disco with ABS arrived. I was there and nearly bought one when my 3.5 was in for service.:)

As far as my ABS equipped disco goes ABS is non operational all year, only until I'm heavy on the brakes on an ice covered road then it does.
 
Last edited:
jamesmartin said:
twin pipes on rrc isnt necessarily abs , the top front caliper pistons were fed by the primary circuit, the bottom pistons by the secondary circuit ,the rear were also fed by the secondary circuit by a pressure reducing valve
Click to expand...
No quite right, the rear callipers are on the primary not the secondary circuit.
 
discool said:
No quite right, the rear callipers are on the primary not the secondary circuit.
Click to expand...
not that it really matters but rears are on the secondary circuit on both ap and girling systems ,with primary circuit been the one nearest the servo
 
flyingbanana said:
Do the brake pipes use the same pipe thread on the disco calliper as my RRC calliper
Andy
Click to expand...
So what is the thread on your RRC? my RR was imperial if I remember correctly as it's a long time ago, the disco was imperial to start with, but then quickly then moved on to metric, all the 300 series callipers are metric.
 
Last edited:
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