Front brakes not locking up

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Some time ago I replaced the brakes at the four corners. In the front I installed Wilwood's 11.3" rotor kit with 4-piston calipers (140-13477). In the rear I installed a conversion kit that uses the ElDorado type of rear brake calipers. Recently, I replaced the master with a Wilwood tandem (260-8555) with a 1" bore. All the tubing and hoses are new. I also have a proportioning valve on the rear circuit. That said, everything has been replaced except the combination valve. However, I rebuilt the combination valve with the kit from Muscle Car Research and removed the integrated proportioning valve springs of the combination valve. My issue is that the car is not braking as I was hoping it would. With the proportioning valve all closed I am able to lock the rear brakes, but I have not been able to lock the front brakes. I expected that with the brake system that I have I should have been able to lock up the front brakes. I understand that I don't actually want to lock the front brakes for efficient braking, but the fact that I am not able to lock them when fully stepping on the pedal is telling me that something is not right. The only suspect I have now is the combination valve and I am wondering if I should eliminate it and go with a tee to the front. What else can be in the combination valve that could cause the front brakes to be inefficient or am I missing something? I guess that the only thing I will lose is the functionality of the idiot brake light.

 

Robsweden

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Hi

Did you benchbleed the new master cylinder ? Im suspecting air is trapped somewhere. Did you push the pads to far back when installing them ?

 
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Fabrice

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Air trapped sounds indeed like the bad guy as the kind of brakes you have installed should send you straight into your windshield if pressed to the max.

Did you noticed if the car wanted to go one side when you tried?

How did you bleed the lines? Personally, I do the expensive way, meaning, I use way more fluids than I should.

I usually set a plastic tube down a container pre filled where the tube hole is submerged, then put my wife to work, per side (first passenger then driver side) pumping fast, 4 or 5 times and then hold, close bleeder a tad, so I can refill the MC level, repeat till no air is seen in the tube, and on the final pass, while the brake pedal is under max load, I tighten te bleeders. Usually, the container, is then holding 1/4 quart per line and when done, end up with more liquid used than I should have, but totally sure to have 100% clean/new fluid and no air.

 
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I forgot to add that yes, I did bench bleed the MC. I actually bled it for a lot of reps even after there were no bubbles. I did bleed the brakes but it is very possible that I am not being successful on taking all the bubbles out. Something that bothers me about the system is that the loop of the tubing as it comes out of the MC is higher than the MC. Because of the loop, I can see it very easy for bubbles to get trapped at the top of the loop and expect that these bubbles wont travel too easily out of the system. That's why at some point I was asking if reverse bleeding would be more effective in getting rid of bubbles in the loop. These bubbles will have to somehow travel around the loop, then through the combination valve through the ups and downs of the tubing to the bleeder and out.

 
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I would suggest two things

1. test the pressure at the calipers as your system is set and see what pressures you are getting. If you don't want to buy the tool, shoot me a pm and I'll ship you mine for the cost of shipping.

2. Consider your pad compound. When I had ceramic pads on my front brakes, they just didn't get hot enough to perform. Semi metallic pads returned the braking to what I expected.

 
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I would suggest two things

1. test the pressure at the calipers as your system is set and see what pressures you are getting.  If you don't want to buy the tool, shoot me a pm and I'll ship you mine for the cost of shipping.

2. Consider your pad compound.  When I had ceramic pads on my front brakes, they just didn't get hot enough to perform.  Semi metallic pads returned the braking to what I expected.
1. Thank you Jeff. I will PM you.

2. The pad compound is the BP-10 from Wilwood which is supposedly recommended for Street High Performance. They have a compound with slightly better CF but I don't think this will be the big difference I am looking for. I am sure I could improve the rear's pad for a better one, but that won't help the fronts.

 
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Fabrice

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While you wait for the pressure tool,

if you have high lines, just pomp fast, air doesn't travel as fast as in water in brake fluid. Bubbles will be flushed by the incoming fluid. 4 or 5 times and hold it (your pumping friend that is). The bleeders, don't open them too much so you can just secure them in 1/4 turn to refill.

Did you also have the tube in fluid so no air can return or do you have one of these bleeders valve?

 
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While you wait for the pressure tool,

if you have high lines, just pomp fast, air doesn't travel as fast as in water in brake fluid. Bubbles will be flushed by the incoming fluid. 4 or 5 times and hold it (your pumping friend that is). The bleeders, don't open them too much so you can just secure them in 1/4 turn to refill.

Did you also have the tube in fluid so no air can return or do you have one of these bleeders valve?
I can try with 4-5 times. I have been using 1 pump of the pedal since from what I read, there is a school of thought that if you pump too many times you end up breaking the bubbles in more tiny bubbles. For the first time during the bleeding process the tube is in air and it eventually starts filling up with fluid. Since I shut the bleeder before my helper releases the pedal it shouldn't matter, right?

 

Fabrice

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That's why I do the expensive way. bubbles, tiny bubbles, micro bubbles, they all go using plenty fluid :)

You will see them in the tube (I use transparent one). make sure also that you open enough usually 1/4 from the point its loose to max 1/2 allows a great flow and a quick way to lock for refill. The pumping 3-5 times fast ( fast as my wife can pump ) and holding works for me every time. On my bikes always did same too and could tilt rear wheel up.

 
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That's why I do the expensive way. bubbles, tiny bubbles, micro bubbles, they all go using plenty fluid :)

You will see them in the tube (I use transparent one). make sure also that you open enough usually 1/4 from the point its loose to max 1/2 allows a great flow and a quick way to lock for refill. The pumping 3-5 times fast ( fast as my wife can pump ) and holding works for me every time. On my bikes always did same too and could tilt rear wheel up.
It is a good workout too :D

 

Don C

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Are you going to try to convince your wife that it'll be good for her? :)

 

Canted 393

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That's why I do the expensive way.  The pumping 3-5 times fast ( fast as my wife can pump ) .
Are we still talking about bleeding brakes. lollerz

 
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I am currently replacing the combination valve with Wilwood's proportioning valve. While doing this I figured I missed something critical when I installed the Wilwood master :shootself: . The Wilwood MC has the front brake system in the front which is the opposite as the OEM style. Since I didn't reroute the connections when I originally installed the Wilwood MC, that tells me that could have been part of the problem.

 
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That would do it!

Are you familiar with gravity bleeding?

If not it is my favorite method.

Here is a simple explanation

https://www.speedwaymotors.com/the-toolbox/gravity-bleeding-your-brakes/28681
Yes, I tried it once. My plan is to rebleed the MC, then gravity bleed through the new valve and distribution block before I connect the lines that go to each wheel. Then bleed each corner.

A concern I have with gravity bleeding is that I don't know how effective is it to push the air bubbles through the brake line loops near the MC. That's why I will first bleed the system at the engine bay before I connect the lines to each wheel.

 
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Fabrice

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Are we still talking about bleeding brakes. Haha

I just see that one now! Lol :D

 

Don C

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Another consideration, wider radial tires and better rubber compounds make it less likely the brakes will lock up, but still stop much quicker.

 

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