new rear disks, need more "bite" - any suggestions?

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MRGTX

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My car is a non-power disk brake car. While I know what comes along with non power brakes, something still doesn't fell quite right as it sits.

Along with my 8.75" axle, I went with Ford Exploder rear disks. I also replaced the front rotors, calipers, flexible lines, all with OEM style parts...I'm not expecting hypercar braking performance...but the brakes feel just kinda weak. It's extremely hard to get them to lock...and no, it's not for lack of leg strength. :p

With the old stock drums, the rears would lock up pretty easily...so it's hard to say if the fronts have actually lost any performance.

I've bled the system a couple times, pedal feels pretty good...any other suggestions?
I get that upgraded pads and steel brake lines would probably help but that can't be the only cause....right?

Thanks for any tips.
 
The problem could be the wrong proportioning valve, or the Ford calipers need a larger volume of fluid than your master cylinder provides. There is a balancing act between the right amount of fluid volume and the right amount of line pressure. Sometimes when you swap in something quite different than what the original system was designed for, you can run into these sort of issues. Baer and Wilwood both make a brake bias adjuster valve that allows you to dial in the front to rear balance. You might consider adding something like that.
 
You don't want the rear to lock up before the front. 70% of your braking capacity is in the front.

What tires? They go a long way for braking performance.

What Garry said on the hydraulic side. What size master? Are you running an adjustable proportioning valve?

As you move up in "performance" pads they require more heat to work. So again you have a teeter totter of heat for a performance pad to work over the initial bit but early fade of a general pad.

Did you bed the pads and rotors? As in break them in? this is very important.
 
Did you bed the pads and rotors? As in break them in? this is very important.

This right here. I can't stress enough how important it is to bed in the brakes. It makes a massive difference

I follow this method EXACTLY. I suggest giving it a shot before changing anything.

  1. From 60mph, gently apply the brakes a couple of times to bring them up to operating temperature. This prevents you from thermally shocking the rotors and pads in the next steps.
  2. Make eight to ten near-stops from 60mph to about 20 mph. Do it HARD by pressing the brakes firmly, but do not lock the wheels or engage ABS. At the end of each slowdown, immediately accelerate back to 60mph, then apply the brakes again. DO NOT COME TO A COMPLETE STOP! If you stop completely, with your foot on the brake pedal, pad material will be imprinted onto the hot rotors, which could lead to vibration and uneven braking.

  3. The brakes may begin to fade after the 7th or 8th near-stop. This fade will stabilize, but not completely go away until the brakes have fully cooled. A strong smell from the brakes, and even some smoke, is normal.

  4. After the last near-stop, accelerate back up to speed and cruise for a few minutes, using the brakes as little as possible to allow them to cool down. Try not to become trapped in traffic or come to a complete stop while the brakes are still hot.

Here is the full write up:
Bedding in Brakes, Zeckhausen Racing
 
i replaced my front discs and the braking was also quite weak.A friend suggested bedding the pads as JoeSBP suggested,hauling it down a number of times from highway speeds.After bedding they worked fine!
A large master cylinder piston could also be your problem
 
Need to consult the Ford Explorer Factory Service Manual, or some other service manual, for the proper installation and adjustment of those brakes. I bought a rear disc setup from The Right Stuff for a Nova; their kit was from a Cadillac DTS. The calipers adjusted similar to drum brakes - had to ratchet. Not sure what Ford does.

Like others have stated, could be proportioning valve. Might need a different MC.
 
Need to consult the Ford Explorer Factory Service Manual, or some other service manual, for the proper installation and adjustment of those brakes. I bought a rear disc setup from The Right Stuff for a Nova; their kit was from a Cadillac DTS. The calipers adjusted similar to drum brakes - had to ratchet. Not sure what Ford does.

Some Ford stuff the piston threads back in and some (and I think the Explore 8.8 does) have an integrated parking brake shoe in the rotor. Picture a small drum inside the hat of a rotor.
 
Thanks, guys.

Yeah, the rear drum lockup was a nasty trait of our cars. IIRC, it was a pretty consistent problem for '73+ front disk cars. Right after experiencing this for the first time (as an 18 year old in the 1990s) I felt so vindicated when I read a complaint about this exact problem in a review of a '73 Duster in one of the old car magazines from the family library. So yeah, definitely want the fronts working harder than the rears. :)

After the install and before driving around normally, I did some basic testing of the brakes with a few hard-ish stops and but after reading the instructions from @JoeSBP I'm sure that I didn't bed in the pads properly. Is it fair to say that starting over with fresh pads would be necessary or is there any way to salvage the ones I've been driving on? Can the rotors be salvaged?

As for proportioning valve, MC, etc, it's all stock '73 Mopar stuff. I'll look into some upgrades there.

The advice is greatly appreciated.
 
As for proportioning valve, MC, etc, it's all stock '73 Mopar stuff. I'll look into some upgrades there.

The advice is greatly appreciated.

You very LIKELY have wrong proportioning, and may not want ANY prop valve to the rear. My setup is Duster front disk, rear is Ford/ Linc Versailles factory disk. Using the original 67 cylinder, no prop. It is not that hard to lock up the tires on the freeway, you "do" have to push. My legs are very weak from arthritic related problems, just turned 70
 
you can just do them now, don't have to be fresh
 
A smaller bore master cylinder will produce more brake pressure with less leg effort but have a longer travel. I run a 15/16 bore master cylinder on my manual brake car works great. I believe I ordered one for '73 duster power brake car. Direct bolt in. I also run EBC red pads too.
 
I also run EBC red pads too.

I don't have them on my Duster, yet. But I've use red stuff on all my cars and they make a big difference versus the cheap stuff you get at autozone.
 
Adjustable proportional valve will do it to the rear.

This isn’t necessarily true, it depends on how you install the adjustable prop valve. If you just install an adjustable prop valve behind the stock combination valve it might not help at all.

Del is right on, the stock combination valve may be reducing the pressure to the rear by too much already. If that’s the case, adding an adjustable prop valve behind the stock combination valve won’t help, the adjustable valve can only reduce the amount of pressure to the rear brakes, not increase it.

If that’s the case, you’d want to ditch the stock combination valve completely and use some kind of adjustable valve.

Summit Racing® Adjustable Brake Proportioning Valves SUM-G3906
 
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