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Brakes and proportioning valve tech...

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brake
5K views 10 replies 6 participants last post by  grnthng 
#1 ·
Browsing the parts catalog for brake part numbers to place my order and running into a small bit of confusion.
I have the RRC axles going under the 109, and as they are disc/disc, there are a wide variety (it seems) of brake pipes and valves to choose from.I have both types of MC at my disposal, but leaning towards the 50 type servo with the late S3 type MC only cuz the servo is smaller and will be easier to fit it under the 2A wing.
Now both MCs have dual circuit, so I'm good there. The confusion is in regards to the rear brakes which show something called a G Valve as well as a "valve brake-29PRF43" Can anyone help me sort out whether I need either/or or neither?
There also is listed a PDWA connection listed for trucks with disc/drum.
 
#2 ·
There's no real breaking issue that requires a PDWA. It's more of a "feel good" thing. If you loose a circuit you'll know it. And since your setup is entirely custom, it's likely to cause you more grief than anything else.

As for the proportioning valve, unless someone has done the same setup as you and can offer advice I think it's going to be a crap shoot.
I'd probably either try it without one and see how it does, or try one from a 110 and see how it does.
 
#3 ·
I'm also toying with using the ABS from the RRC. Actually more than toying, really want it. Gotta see if I can make it work, then go to plan B, the regular dual circuit system.
 
#6 ·
I will tell you how I really feel and that is that the RRC ABS is a fucking abomination and by all accounts works great "until it doesn't" and then it is a nightmare of chasing faults etc. Not to mention parts to repair and replace failed items are $$$$. The failure mode for the system is to give you one pair of pistons on each front caliper working with NO BOOST so any kind of stop on a downhill is a two foot situation (experience talking). Its a fucking stupid overly complicated system that you just don't need. I ripped mine out and replaced it with a normal vacuum boosted setup and never looked back.

Now, with that out of the way, I would avoid trying to combine the series M/C with a disk brake setup. You're probably better off using a non-ABS RRC M/C adapted to the Series booster, or better yet a RRC or D1 booster adapted to the Series pedal tower. Or, perhaps one of those will fit the defender pedal tower and you could use that. or, get an early defender booster from before they went to the larger diameter setup.

As for the proportioning valve, when I built Rich Biby's coiler 88 we used RRC brakes all around but we split the system front/rear instead of diagonally/front/rear as on the RRC. I guess our setup was more like the typical US spec late IIa or SIII in that respect. Which, FWIW, I can personally attest works just fine in an emergency situation as I have BTDT when a front flex hose on my drum-braked SIII failed on the Roosevelt Bridge during rush hour.

On the Biby truck we used a G-valve as supplied by ECR along with the rest of the designa-chassis "kit." I installed the g-valve using the factory bracket that puts it at a particular angle. I don't know how much difference it made but the brakes seemed fine. On my RRC when I removed the ABS I used the little inline proportioning valve that came off the donor truck that supplied the non-ABS system parts. That also worked fine even descending the slickest slip-n-slide downhill that Uwharrie's Daniel trail (in the rain, trying not to rear-end Galpin in his manual V8 110) had to offer. The back end never broke loose though my frantic stabbing at the pedal probably had something to do with that too. BTW those proportioning valves are also used on the RRC ABS system, it is mounted right on top of the electronic valve block.

Hope that helps, sorry for the rant but I really think the RRC ABS system is total crap. I know you like to futz around with stuff like that but deliberately installing into another vehicle in lieu of a simple, reliable solution? Not to mention, the parts off of that LWB you are using as a donor have been sitting up for awhile. Who KNOWS what is growing inside that Wabco chamber of horrors...
 
#4 ·
I hope the RRC ABS is more reliable than the D1 ABS. I don't think anyone could pay me to install it to mine.
 
#5 ·
Use the valve from an 87-89 RRC without ABS or a 94 and up 110 with rear discs. As far as running pipes, I would think you would want to use a 110 rear pipe and the front you would have to choose between early RRC and 110. Note the valve moved around between the cars and years so you really need to figure out what you need.

Honestly, recreating a 94 and up 110 brake system will probably be cheaper and safter than making something work.
 
#7 ·
get an early defender booster from before they went to the larger diameter setup.
Have that. Looks very much like the later S3. The dual MC also looks like an S3. Needs a cleanout. I think it will fit better than the later 60 style booster.

K, I guess i'll do the right thing and go with a regular old dual circuit system, without any g valves or anything, and be done.

The back end never broke loose though my frantic stabbing at the pedal probably had something to do with that too.
Yes, that what ABS does, except really fast.
 
#9 ·
Do I need to replace the ABS front calipers with non ABS from an earlier RRC? These ones are two line, and I think I don't want two line calipers, do I?
 
#10 ·
I've seen people put a "T" at the caliper and use the dual line rrc calipers. I'm using disco calipers and adding the spacer from rrc calipers so I can have single line and vented front rotors.

Have you considered an adjustable proportioning valve for the rear? http://www.jegs.com/c/Brakes-Drivetrain_Proportioning-Valves-and-Balance-Bars/10165/10002/-1

I haven't bought one yet for my rig but intend to use something like the above choices.

I'm interested to see how you handle the front axle installation.

Daniel
 
#11 ·
Having read these posts, I'm convinced I need to convert my Lwb! After driving an '83 RR for 5 years....w/a vacuum leak at the booster I actually didn't mind it! It is a noticeable difference in braking power (when its working) on my LWB.....it actually brakes better than our '09 Touraeg!

However...I am done with it, 3 TIMES I have been left with no brakes! I am ordering the booster and Mcyl... and converting!:icon_peace:

Just as with the Elec. Air Suspension......see yaa!!:thumb:
 
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