Another brake issue

[brewha]

Hi guys

I been away for a while waiting for my car to get finished by the painter. Well I’ve had it back for a couple months now getting it ready for vehicle inspection which should be next week.

Everything seems to be great and ready to go except for the brakes. Car stops fine but not like I would expect for a car with of this performance.

Brakes are 2000 Mustang Cobra Brakes ( front and rear)with the Wildwood dual master cylinders. I have Hawk HP+ pads in the rear and HP in the front.

My pedal is rock solid so I don’t think air is in the system. What I experience is that the rear heat up nicely to about 180 to 190 degrees, but the front only go to 135 and 145 degrees. I do not think I’m bedding the pads on the front at that temperature. The balance bar is set to be front aggressive. I have locked the rear a couple of times but just barely. I cannot lock the front at all.

Does anybody have a suggestions to try? I’m thinking that the front master cylinder may be faulty but I’m unsure how to validate that.

I’m having inspection skid pad nightmares…….help!!!

[Railroad]

I do not have much hands on experience for setting up brakes from scratch, but something not mentioned, are the master cylinders sizes.
Mine came with different sizes, front and rear.
Later F5 changed to same size, front and rear.
I have the Wilwood 6 piston front and 4 piston rear.
I put a softer pad on the front to stop with less pedal effort.
I could lock all 4 wheels with delivered Wilwood pads.
Just food for thought. I am sure some of the autox guys will have some better information.

[Rsnake]

Brewha,

Go to 5/8" master cylinders and the pedal will feel a lot better I promise.
I have a video on my channel as I did this a few months ago and it's a huge change.
I am assuming you are using the wilwood pedal assembly.

[Rsnake]

Plus you are running very high friction pads in rear hp+ and a lot less in the rear. Hp plus or hps all around.
I run hp plus and they take little pedal pressure to lock up the tires.

[brewha]

Thanks Rsnake. I watched your video and you describe the pedal effort identically to what I’m experiencing. I am running the Wilwood pedal assembly. I’m ordering a 5/8 master today and hopefully will install it on Saturday. That should give me enough time to get it balance bar adjusted before I go for inspection.

[CraigS]

Something else to look at is MC pushrod length. You may need a helper to push the pedal pretty hard while you look down on the MCs. Look for how much angle the bias adjuster shaft goes to at full pressure. The MCs will travel differently because of the different sizes and different caliper sizes requiring different volumes of fluid to operate. It is possible that, in your case, the rear MC stops moving while the front needs more travel. The balance shaft can only move to a certain maximum angle inside the top of the pedal, so w/ one MC stopped, max angle of the shaft is reached, and the other MC receives no more pressure. I have seen a couple of recommendations for pushrod adjustment. The one I like is you adjust so that at full pedal pressure, the cross shaft is at right angles to the pushrods. On my car w/ similar but different CNC MC setup, I had the cross shaft at a bit of an angle one way at rest and, as pressure was increased it went to 90deg and then past a bit to an angle the other way.
Another caution; when you drop the MC size down, be sure you have enough MC volume to actuate the front brakes. I had a situation where I went to larger rear calipers when I did the IRS retrofit. Turned out the 5/8MC, that had worked fine, couldn't fully actuate the larger calipers so I had to increase one size.
If this becomes a problem, you could go to HP+ at the front. I ended up doing that, HP+ front and rear. They dust more but wow, do they stop. I got a tiny shop vac w/ a brush tip on the end that I dedicated to cleaning wheels. I also used this which really helped the dust not stick as badly.
https://www.armorall.com/product/outlast-brake-dust-repellent/

[Hoooper]

You said you adjusted to be front agressive but youre locking the rears first. Sounds like it needs to be adjusted more front agressive.

[brewha]

Thanks for the reply Craig’s, I have check the throw so many times… I actually reset everything to be in the middle of the balance bar to see I could get the front to grab and heat up the pads more. The throws seemed to be full on both the back and front master cylinders. That’s why I was thinking the front master was possibly bad or had fluid stuck on the wrong side of the piston not letting it release enough. Rsnake’s video described the feeling of my pedal exactly which feels like you can’t push on the pedal hard enough…and I’m a big guy… The rear mc is a 5/8 already and I just ordered another one from Summit this morning. I have the front mc out already which is a 3/4 and did not see anything that would indicate a failure. I’ll know this weekend if I’m successful and will post the results here either way.

[brewha]

Well it took me about 4 hours to change out the front master cylinder. The old cylinder seemed to hang up on the return. I’ll probably get a rebuild kit for it just so I can take it apart and see what the issue was. Always nice to have spare parts. The smaller 5/8 master cylinder seems to work pretty good as I’m seeing a lot hotter temp(190 degrees)on the front rotors. I should be able to get the pads seated soon. It does take a longer pedal compression and it’s size may be borderline for use with cobra brakes in the front as it uses almost full compression. The pedal does feel much better then though. In the fall, I may install a residual pressure valve in the front line to help retain fluid near the calipers and reduce excessive pedal travel. The next step is DMV inspection.
Thanks to all who responded.