Rear Disc Brake Upgrade

[tuko]

The hybrid is going through a brake upgrade phase where I'm changing the rear drums to disc's to complement the from disc's.

On the hybrid I have the standard 110 master cylinder that is basically plumbed into the series 3 brake lines with the PDWA valve.

The plan is or what I'm doing is installing an early RR rear axle that I will use 110 rear disc's and brake calliper's on. I've already done a dry run with everything installed and I can report that everything fits perfectly. The only thing that I needed to do is to drill and tap out the calliper mounting bolt holes on the axle so that I can use the original Defender calliper bolts.

So at this point I'm thinking about brake pressures between the front and rear. Some places you read that you can bypass the brake pressure reducing valve (BPRV) and others saying that you need it because of the short wheelbase. Either way, I'm installing one.

The confusion that I'm encountering now is what BPRV to install? Weighing my hybrid last year, she topped the scales at 1745kg and that was without the recovery gear, external roll cage, front winch bumper and finally the winch. I'm willing to venture a guess that she's nearer to 2000kg today ??

Bearing that in mind, I've been searching for which BPRV to source to the hybrid.

NRC8215 is for 110/130 Vented front/solid rear,

ANR1415 is for 110/130,

SJD500020 is for 90 from 2007 onwards,

NTC8836 is for 90,

ANR3194 is for Disco less abs,

NTC6868L is for Disco/RR.

These are just a few of the numbers I dug up today and I was planning to go with the 90 variant, but searching around I see that they are rather dear on the wallet. But then I found this site DBrakes and it's written there that you can use the more commonly found NTC6868L on a 88" landy that has 4 wheel disc brakes.

So here is the questions;

Do I follow what was written at that site about NTC6868L?

Do I use a 90 BPRV instead?

Should I consider an adjustable BPRV that are plentyful on eBay?

Or is there a BPRV from another make of car that I could use in place of the "original" LR stuff? ie:Saab or Volvo

Todd.

[Jon White]

I'm running disks all round on my SWB series and you dont need the PRV at all. Simply repace it with a T piece for the front brakes and re-run the lines to suit. Job done.

I run the series dual circuit master (50:50 bias) which I find about right. tonk ran his with a similar setup with the 110 master which has something like a 60:40 bias IIRC which made the front dip nicely under braking and the front wheel locked first.

We both ran with the early 110 servo setup.

Jon

[tuko]

I'm running disks all round on my SWB series and you dont need the PRV at all. Simply repace it with a T piece for the front brakes and re-run the lines to suit. Job done.

I run the series dual circuit master (50:50 bias) which I find about right. tonk ran his with a similar setup with the 110 master which has something like a 60:40 bias IIRC which made the front dip nicely under braking and the front wheel locked first.

We both ran with the early 110 servo setup.

Jon

Thanks Jon,

Thats very interesting information that leads me to another question, the 110 rear callipers and disc's are larger than those found on a 90, the disc's anyways and I'm "told" that the callipers are to but if the callipers are larger will it cause the brakes to come on sooner?

I've never seen any information that states the bias ratio for the master cylinders, but the above figure looks appealing as the 110 master is already installed.

Todd.

[zim]

When i first got my truck done, i was running discs front n back with a series servo and a 110 master. But to be honest the brakes were horrible

I swapped out the pedal box, servo and master for a defender td5's and now they're awesome

Gordon

[tuko]

Thats good to know Gordon with the series servo and 110 master.

I should have made myself clearer in my first post that I have a 110 master/servo complete, I even think that the pedal box is 110 as it still has the yellow pencil making from the breakers.

hmmm......td5 stuff.

Todd.

[Jon White]

there should be a plastic tag (king of like a zippy tie) around an original master cylinder which tells you the bias ratio.

I'm running wilwood front calipers with range rover rears.

Jon

[zim]

Thats good to know Gordon with the series servo and 110 master.

I should have made myself clearer in my first post that I have a 110 master/servo complete, I even think that the pedal box is 110 as it still has the yellow pencil making from the breakers.

hmmm......td5 stuff.

Todd.

Todd, i made a mistake in my post... i meant i had a 109 master (not 110) and the brakes were horrible. Sorry.

[Daan]

I wouldnt use any of these valves. the problem is that your wheel base isn't correct for any of the setups these are calibrated for. I dont think you can adjust them either, which may well result in a lot of money spent to find out it isn't right. There is also not much point in looking at the zeus comments, since their piston dia wont be the same as what you are running.

I run a 300 TDI brake pedal and master cylinder, 46 mm piston calipers at the front (the large 110 ones), and standard 90 calipers at the back. I dont use the series brake switch valve, which is completely pointless in my opinion.

This worked well, however on the SVA test resulted in a fail due to the rears locking up just before the front (on 35" simex).

To combat the problem I fitted this:

http://www.tiltonracing.com/content.php?page=list2&id=38&m=b

you can adjust this untill its right.

Daan

[tuko]

there should be a plastic tag (king of like a zippy tie) around an original master cylinder which tells you the bias ratio.

I'm running wilwood front calipers with range rover rears.

Jon

Jon,

I just checked the plastic strap on the master cylinder and I can't make heads or tails of the numbering, maybe you can decipher this for me; 6391 02/ 29AZ

Thanks,

Todd.

[Jon White]

That doesnt make any sense to me - are you sure there is nothing else written on it? The ones I've seen have 50:50 or 60:40 or something like that written on them!

Jon

[tuko]

Jon,

thanks to your reply, I have done some research on what I have on the hybrid. What I "thought" I had and actually have are two different things. I have a pedal box with brake servo from a 110 and a series dual circuit master cylinder from a series 3. Based on your first post I'm going to try this setup for the time being. (If I find that I have any issues then I'll buy an early 110 master cylinder.)

By myself I bled the brakes, which didn't give the performance that I was expecting. I guess pumping with your hand, wedging a 2 by 4 between the seatbox and pedal then running around to the back to crack the bleeder screws just doesn't work as one would expect. The brakes felt no different than with rear drums.

But once an able body came home from the cottage we were able to properly bleed the brakes that gave and impressive result. The pedal is much more firmer with no signs of pedal fade. Another big bonus is that when I hit the brakes, the hybrid actually tracks straight.

So far so good, I'll keep you posted if there are any issues.

Thanks,

Todd.

[tomaco1]

anr3194 out of a Disco,

ntc8836 for a Defender.

Anyone know the difference in these 2 valves?

Other than the different trucks they seem to be the same, to me anyway. Many thanks

anr3194 out of a Discovs ntc8836 for a DefenderAnyone know the difference in these 2 valves?Other than the different trucks they seem to be the same, to me anyway. Many thanks

[tuko]

ntc8836 non ABS

anr3194 with ABS

That's the difference that I found.

[Snagger]

The rear brakes should be at a lesser pressure than the front on a swb, and especially if you have larger rear brakes than normally matched to the front system. If you were using a Defender/Discovery master, then I'd say you need the reducing valve for sure, but if you have the older 110 master which is set up for drums on the back, then that will be producing less pressure on that circuit and I wouldn't want to reduce it further with the valve. So, incorporation of the valve depends on the master in use...