Disc Brakes . . . Completely Utterly Frustrated

[horseballz]

One issue that I've seen time and again, is that all the different parts and kits came from different vendors. Many vendors feel that their method of "re-inventing the wheel" is superior, but not always compatible with other vendors' methods! It's been my experience that getting all parts from one vendor helps ensure compatibility all the way around. Not always the most economical approach, but once you factor in time, effort and aggravation, in addition to the $$$, it's often the best. On the other hand, some vendors are simply in the weeds and full of BS! For example, the concept of a vendor providing a "kit" with calipers that were designed for a particular thickness rotor, that is intended/assumed to be used with a thinner rotor is simply asinine! It is, after all called a brake "SYSTEM" for a reason!

Just My $.02 & Likely Worth Even Less!
Gene

 

[D Durden]

I've got the MC for 4 wheel discs, so I'm supposedly good there.

Today, I DID learn that I have a whopping 500 PSI at the front calipers (should be 900-1,200), so . . . I think we're narrowing down the problem.

 

[D Durden]

Latest update:

We put a pressure gauge on the fronts, rears, and directly at the master cylinder. Max on the rear was 500 PSI. Max on the fronts was 800 PSI, but it was both feet on the pedal and breaking the seat back. Pressure at the master cylinder wasn’t different, so there’s no blockage.

Wilwood states they need 900 to 1100 PSI for relatively normal operation, so I’m not even really close there. And I figure the rears aren’t going to be much different. So, long story short, the master cylinder isn’t even close to working with my setup EVEN THOUGH it's advertised as exactly what I need.

So, we call ABS Brakes (they make the units for Scott Drake), and they say that the unit has a dual diaphragm booster, and I should be making plenty of power. After about 30 minutes of on the phone troubleshooting, I send a picture of what I have to ABS. Low and behold, it’s a single diaphragm unit, which is wrong for the part number I ordered. That’s actually the good news. The bad news is that I bought it through Summit, so I had to return it to them and HOPE they send me the right part. ACTUALLY, they did . . . the marking on the box was wrong, so either Scott Drake mislabeled it or it was made wrong at ABS.

We decide to send the unit back to Summit for credit (it really WAS the wrong part number, so nothing dishonest there), and we’ll buy the right unit from ABS.

All is well with the world.

NOT EXACTLY!

As we’re wrapping things up, a little detail comes to light. While, YES, the pedal will feel much lighter and be more pleasant to drive, the right unit WILL NOT have more hydraulic pressure. So, we just spend 45 minutes to go from “the pedal is hard and the car won’t stop” to “the pedal will most likely be very pleasant . . . but you still can’t stop the car”. *sigh*

ABS said they can custom fab me a system with a dual diaphragm booster and a 1” instead of a 1 1/16” master cylinder, and that should do it. Wilwood recommended a 1” MC so I’m encouraged here.

We’re in process of removing the MC/BB and sending it to Summit. When my card is credited, we’ll order a “custom” unit from ABS. I’ll let you guys know how that works.

We have a path forward, but I’m disturbed by one thing. I bought a MC/BB that was designed to work with a ’65 Mustang with both 4 wheel discs and a manual transmission (which I have). It didn’t . . . at all. I asked ABS “so, if this is designed for what I have, what components would I need to change to make it work?” I didn’t get a clear answer . . . or one at all. So I’m still left with the question of “why didn’t the one I bought work . . . at all?”

Guys, I can’t tell you have frustrating this is because I can’t be the only person doing this. If anyone else has this MC/BB and can put a pressure gauge on the outputs, I’d be curious to see what you get.

 

[bdepedro]

Been following your progress and I'm not sure if this will apply to you as well but when I called Wilwood, they recommended a non power 1" MC and a combination distribution block/proportioning valve. I'm not sure this was part of my problem, or yours, but apparently there are different pedals for power or manual brakes. I haven't measured mine yet but since my car was originally a manual system, my pedal may not be pushing the piston of my power MC enough. I have to do more investigating but hoping the pedal is right for a manual system and with a larger MC and proportioning valve I can get enough braking power to the front and rear equally.

 

[D Durden]

Excellent observations my good man!

Wilwood recommended that setup to me, as well.

I found out the same thing i.e. there are different pedal setups for a manual and power system. The power systems have something like a 3:1 ratio while the manual systems are 5.5:1. I REALLY wish this would have been addressed somewhere in the part description before buying it, but I digress.

I, like you, have the manual (5.5:1) setup.

What I’m about to do is go in a different direction. I had a friend I work with put me on to Baer brakes. Now, there brakes are top of the line, but way out of my price range (right now), plus, eh, what I just put on is pretty good. So I called them, and they talked with me a good 15 minutes on how to address what I already had . . . AND DIDN’T TRY TO SELL ME ANYTHING! They really were trying to help me get all of this non-Baer stuff working together. That was impressive. I told them that I wanted to drop the current MC/PB and put in one of their manual “Remaster” setups, and they pretty much told me that it would put out way more than I needed and a 1” or 15/16” piston was in order. It’s pretty much a direct bolt up, and the price was right. So, the current plan is to pick up one of those when Summit gets the Scott Drake unit back. I’ll let you guys know how it goes.

The guys from Baer and from Wilwood were aces, though . . . great response.

 

[Tim65GT]

I'm having a similar issue with my '65.
...So I read through this entire thread... NO Resolution?!

 

[rbohm]

all too often when people recommend brake swaps, they usually also recommend too large a master cylinder as well, under teh idea that bigger is always better. they forget though that disc brakes operate on pressure rather than fluid volume. i would have to find my brake math handbook, but i thin the recommendation of the 15/16" to 1" master cylinder would be about right for your combination D. and if you still have the stock manual brake pedal on the car, you might get a hold of mustang steve and have him send you his kit that changes the pedal ratio as necessary.