Disc Brakes

Okay, I'm having trouble getting a good pedal on my recent disc brake installation. Alan suggested a 2 lb Residual Pressure Valve for the rear, which makes prefect sense. I'm ordering said valve now from Summit and I'm wondering if I should order two, one for the rear and another one for the front?

Another question: I haven't installed a proportioning valve on this car, (looking towards Alan) do you think I should order one of those too. I haven't notice any locking in the rear or front? But instinct tells me that I would want the rear to do most of the work (thinking about most of the weight being in the rear), but I'm open for suggestions.

I haven't broke in these new pads enough to really test the brakes and right now, I've got the car at the uphostry shop, so I can't test it now; but I can order parts :-)

You only need just the one 2lb. residual valve for the rear line this maintains a bit of in line pressure ( not enought to actuate the brakes though)so as not to allow for the line to back feed and empty into the master cylinder.
A proportioning valve is not necessary but would allow to you to dial the brakes in.... BTW your front brakes do 70% + of the stopping.
I also make sure that the drum/ disc surfaces are super clean and I scuff these surfaces with agreen scuffy pad then lightly scuff new shoes/ pads with 220 paper to remove the factory glaze, this is my own old school thing i.e. for peace of mind. ~Alan

Disc brake pads are very close to rubbing up front so no extra pressure needed there. I have always heard most of braking done by front brakes. Makes "engineering" sense for front engine cars but not so much for our rear heavy (engine), very light front cars. Locked up skidding front brakes don't help much in stopping on a dime. I suspect your thought of a proportioning valve might be way to go.

What parts did you get to join the SAE valves to your metric lines/fittings? Metric valves seem real hard to find.

Dave, what do you mean getting good pedal? If you mean it is spongy, you need to bleed the lines. Once you do that, go out see if the brakes work right. I installed a residual valve in the rear line of my Beck, but I am not sure it helped all that much. My problem was that the front discs seemed to work much better than the rear. Anyway, Alan is right, all it does is hold a little pressure in that part of the line. Can't hurt and their inexpensive.

I appreciate the advice;

Alan, I did clean the pads during installation, I agree, it's always a good idea, I still like to drive them a bit before I really clamp down on em. I'll get the 'wildwood' residual pressure valve ordered tonight.

Wolfgang, I agree, I don't want the front brakes to bite so much that the rear decides to come around. I have a hunch that once that engine heavy rear starts moving, it 'may' be a bit stuborn and keep on coming. Yet again, as Alan stated, it may not need it, it is a light car and hopefully it will stop great.

Warren, I've bled the brakes in every way I can think of, even blocking off the rear rotors, and not only is the pedal mushy but it only has about an inch and a half of pedal. Per Alan's suggestion, I looked up the above stated residual valve, note the description: "if your master cylinder is mounted lower than your brake callipers....will keep your brake fluid from draining back into your master cylinder" sounds like the situation to me. BTW, even with the described pedal I do have, they work great. I just feel more comfortable with a pedal that gives me back a little pressure before it goes 2/3's of the way down.

So as of now, I'm only ordering the one valve, after I get it back to play with it, I'll see if I need the proportioning valve, but I'm guessing that if I do go for it; it may be more to play with it than maybe I really need.

Wolfgang, the only valve I saw was in the Summit catalog, I was hopeful that my local (not a chain) auto parts store could give me the fittings I need (they have a machine shop). Now you've got me thinking about the SAE/Metric situation. Any suggestions?

Thanks,
Dave

I wonder if larger displacement master cylinder might be a better solution for "decreasing pedal push distance" before brakes grab? No SAE/Metric adapters to mess with either.

http://www2.cip1.com/ProductDetails.asp?ProductCode=C13%2D16%2D9554

Hi Wolfgang,

The kit (bought from Moore, made for Empi) came with a master cyclinder; it looks identical to the one your link hooks up to. I installed the one with the kit, the volvo reservoir I had on the previous one fit right on it. I thought that would fix the problem too, but no cigars!

Dave

Dave, here's the adjustable proportioning value that I bought for my track Miata.
http://www.flyinmiata.com/index.php?deptid=4539&parentid=0&stocknumber=14-76240
It has NPT to metric flare adapters.
Before you order one give your brakes a good workout in the rain. Your front brakes should always lock first. If the fronts do lock first I wouldn't order the proportioning valve.

I've been thinking about this for a while too, but was unclear about the residual valve. i have discs up front and drums in the rear. adjustable proportioning valve on the front, but the front still locks up first. is it the 2psi one that is needed on the rear line? or the 10psi on the rear line?

Dave: on the brake bleeding:
i've done pressure bleeding and it it's a piece of cake and no help is required.

here are a few examples:
http://faculty.ccp.edu/faculty/dreed/campingart/jettatech/bleeder/index.htm (this is the one i did, but used my compressor and regulator to bring the pressure to 5psi)

http://www.e38.org/brake_bleeding.htm

Ron, I like that proportioning valve, but I'm with you, I'm going to try it out before I buy one, I'm just not sure if I need it.

Mango-Smoothie, I don't think you'll need the residual pressure valve with drums on the back, I believe this is a disc all the way around problem, do you have a good pedal now? But if you do decide to use one, I believe the 2 lb is the one you want. I like that do-it-yourself pressure bleeding system, I may use it.

I'm thinking the bleeding problem centers around the location of the back calipers and the back lines reaching over the IRS in comparison to the 'lower' location of the master cylinder.

Dave, what is a residual pressure valve and where does it go? I have four wheel discs on my IM and I'm pretty sure there is nothing extra added to my braking system. Henry did the bleeding and the brake pedal is firm.

CB Performance has the adapters you need.

http://www.cbperformance.com/catalog.asp?ProductID=1265

A couple of things here to interject into this conversation.

If you have Disc/Drum, then a 10 lb residual pressure valve is desirable for the drum brakes.

If you're having problems with the back brakes locking up first that's because 70 to 80 % of your vehicles weight is being pushed forward thus lightening up the rear and causing the brakes to lock. This is where a proportioning valve come into play. You can reduce the pressure to the rear and produce even braking.

In regard to scuffing up pads and rotors, It's NOT NECESSARY and doesn't produce significant results .

ALL new brakes should be burnished.

This process is as follows:

Find a large parking lot with no obstructions. Accelerate to 60 MPH and SLAM on the brakes but don't skid the tires.

Immediately repeat this 3 more times in rapid succession.

Hopefully, the brakes should be producing a lot of smoke. If not, then do another 60 to 0 stop.

Let them cool, with your foot off the brake pedal for 3 minutes.

Repeat the 60 to 0 stops 3 more times.

Let them cool for 5 minutes with your foot off the brakes then 3 stops from 40 to 0.

That's usually enough to burn off all the glue resins and the outcome is this,THE BRAKES WILL WORK BETTER AND, LAST LONGER.

This procedure is done to all race cars and vehicles operated in any kind of high performance situation.

Brake technicians (if you want to call them that) don't do it because it takes time and, your brakes will last longer.

They usually tell you to take it easy for a couple of hundred miles. This is wrong and bad for your brakes. Often times they will glaze and then vibrate causing that annoying squeal and if the brakes glaze they don't stop as well as they should...

When I was working, I performed hundreds of brake tests and in every case, the brakes stopped the car in far less distance once they were burnished and, they lasted longer than non burnished brakes.

Trust me!!!!

Thanks Larry, good info! It makes sense that you would need the 10 lb for drum brakes.

Ron, if you have a good pedal (firm with reasonable distance to travel) you more than likely, do not need the residual pressure valve (or maybe you already have one installed), but if you don't, it would go on the brake line that supplies the fluid to the rear brakes, I intend to install it up close to the master cylinder. In my situation, I'm having trouble getting a good pedal; when I bypass the rear calipers, my pedal is fine, this leads me (with Alan's help) to believe the fluid is draining back into the master cylinder which in my car is mounted lower than my rear calipers. The above said valve will prevent that from happening.

Jeff, thanks for the link, if my local shop can't help me, I'll know where to go. I appreciate it.

Guys, I appreciate all the help, this is a great site.

Dave

I recall reading that the Ghia master cylinders actually came with the valve installed on the master cylinder. Now 35 years later - the only master cylinders available seem to be generic T1 ones. All articles say to install the valve close to the master cylinder.

I finally got around to installing the 2 lb residual pressure valve on the rear line tonight; after bleeding the brakes again, I now have a pretty good pedal. :-) Thanks Alan and all for the advice!

Dave,
I don't remember where I got the 2 lb w/ metric ends...Where did you end up getting the from ? Tnx ~Alan

Hi Alan,

I took Jeff's advice above,

http://www.cbperformance.com/catalog.asp?ProductID=1265

especially since CP is located about 15 miles from my house. They have them in stock. I got the valve from sonic.

Dave

Thanks Dave !

We/CB sell a 4lb residual pressure valve dedicated for the VW master cylinder. You need a tandem style(1967) master cylinder when using front and rear disc brakes. Our residual pressure valve threads directly into the master cylinder. The valve should go to the rear brakes only, fronts do not need one. This is all that should be needed.

Also, depending on were your calipers are mounted, you might need to unbolt them so the bleeder screw is directly on top when bleeding your brakes.

CB Performance 4lb. residual valve (metric) part number 6609 = $31.95

Pat,

I wouldn't have thought about the need to unbolt the calipers for bleeding.

Would this be necessary for KG calipers at the 3:00 and 9:00 position?

It is nice to see you here.

Now they tell me (slaps head)!!

I had previously unbolted the real calipers, that was the only way I could get any pedal; but after I installed the 2 lb valve, I used a pressure bleeding system. I now have a pretty firm half pedal and I believe that's all I'll get. They feel good and stop on a dime.

The easy way to do a check valve, in combo with a proporting valve (PV) is to install the check valve on the output side of the proportioning valve as it leads to the rear wheels. The Wilwood PV valve is 1/8 NPT and supplied with NPT to US style flare adapters.

I usually install the PV on the tunnell next to the drivers seat so that it can be easily adjusted, and once done locked down to prevent fingering by admirers. Since the Wilwood PV is NPT/USA style flare, you will need to cut the steel brake line and re-flare to US style.

I always unbolt the calipers and raise them to a high position with the bleeder at the highest point possible. I like to use a vacuum style bleeder because my wife gets sick of pumping the brake pedal for me. Some calipers do not have sealing type bleeder screws for vacuum bleeders. You can wrap the bleeder screw with teflon tape so it seals the threads and it will work fine. On tandem master cylinders, alway bleed the closest wheel first. Driver front first, pass front, driver rear and then pass rear. If you use our 4lb residual valve with a tandem master cylinder you should get a very firm pedal. You might also need to adjust the rod that goes from the pedal to the master cylinder. Basicly you want to take out most of the free play between the rod and the master cylinder, alot like adjusting a clutch cable.
Dave, I see you are from Dinuba. I grew up in Dinuba, graduated from Dinuba High in 84.

Hi Pat,

I've lived here since 77', my wife, Debbie, is a fifth generation Dinuban, my daughter is a sixth. I was raised in the Bay Area.

Where are you now?

Dave

I live in Visalia, close to you. Still have many friends that live in Dinuba. My Mom still lives on her farm on Ave 400, just a little west of you. I have been with CB Performance since 1986. Next time you are at CB you should ask for me, I would like to meet you. What was your wifes maiden name?

I stopped by today, you were out. My home ranch is across from the new golf course on 64 and 416. My wife's maiden name is Newton, she's the broker of Newton and Sons Real Estate, est 1918.

I remember the Newtons, I used to walk by there house many times when I was young. My gradmother lived around the corner from them. My mom lives about 4 miles from you. I play golf often at that course next to you. Sorry about being out. I am home for the week after having surgery on my sinuses. Wonderful Centrel Valley air has taken it's toll on me.

Dave, is that huge grove your's??? If so, is that huge barn also yours and what's in the back yard??

I did all the steps Pat suggested 8 years or so ago and have firm pedal and great brakes. CB Roto-Hubs on the rear along with their res. valve work great! I bleed them out every other year or so to keep fresh "blood" in the veins. You'd be surprised of the crap that comes out of the lines after it's been in there awhile.

~WB