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Discussion Starter #1
What should the brake fluid pressure be at the calipers on the Wilwood system provided on the mk3.1?
 

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FFCobra Craftsman
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I have no idea. Does your car stop OK? I am curious why you are concerned. I have read a few threads over the years where some have put a gauge in the system but I don't think it is very worthwhile other than in diagnosing some weird problem.
 

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Discussion Starter #3
The braking on my Cobra has never been good. I've always been afraid someone will pull out in front of me and I'll hit them. My health has not been great the few years so I've driven it very little and quit worrying about it. Feeling better and staying home because of the virus I've been drawn back to working on the Cobra.

The other day I ran across my brake pressure gauge. It got me thinking that I should make one final try on getting good brakes. I purchased the gauge years ago after I ran across an article/post that talked about the amount of pressure that is needed to be placed on the pads in order for them to work well. It connects into the bleeder connection.

I found that my pressure was low because of modification I had made to the brake pedal geometry during the build to get more space between the brake and the gas pedal (automatic) because of my big feet. I changed back to a stock F5 brake pedal and the braking was better. Not great just better. I put on new high performance pads that didn't do much. I finally gave up and learned to live with the brakes. I don't drive it much so I can be pretty careful.

The other day, years after the above, I ran across the gauge and decided to do the tests again. I've got 600# on all 4 wheels. Problem is I don't know if that is good or bad. I have not been able to track down older posts on the old ffcars.com site and all my old documentation was destroyed in a garage fire. I do remember quite a few other guys complained about brake problems some of which installed power brakes. I don't want to go that far.

So this is my deal. Any help would be appreciated.
 

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FFCobra Craftsman
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Rich's link gives double your readings at 1200 vs your 600. So let's go back to the beginning of your system. What calipers, what MC, and what pads do you have? Has the pedal been modified for better leverage?
 

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Discussion Starter #6
I purchased the 3.1 complete kit in late 2008 I think. I used all the braking components provided with the kit. The calipers are Wilwood with 2 pistons in the front and 1 in the rear. The master cylinder and all tubing were as provided if I remember correctly. Later I purchased the Wilwood adjustment knob & cable that allows the balance between the front and rear to be adjusted. I played around with it quite a bit and never found a setting that made any difference. The knob is in the cockpit where it can be adjusted by the driver without taking the cover off the master cylinder. The current pedal is the stock unit from Wilwood.
 

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First thing I would do is call Wilwood about the pressure. According to Rich's link, you only have half the pressure. Second thing, you say 2 piston fronts and 1 piston rear. I have 6 front and 4 rear. It's almost like having powered brakes and stops great. I can't see a 2 piston non powered front working very well. I would also ask Wilwood about that while you have them on the phone. The current F5 kit has 6 piston front.
 

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FFCobra Craftsman
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Can you show us the calipers and what diameter are your MCs?
 

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Discussion Starter #9
I pulled the front wheels and found the calipers have PBR (K242-0470 10) stamped on them. No sign of Wilwood anywhere. I have no idea of where I came up of the brand difference except my Challenger has Wilwood calipers? From a quick search it looks like these are pretty standard replacement parts for 99-04 Mustang. I've called factory five to see if they have a technical sheet on the braking system used in the 2008-2010 era. The front calipers have 2 pistons. I'm sure the back are single caliper units, but I'll double check based on my Wilwood mistake. I'll also pull the master cylinder cover and measure the brake pedal. If PBR sheds any light on my issues please let me know... Jim
 

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Discussion Starter #10
There are individual Wilwood .75 master cylinders for front/rear. I could not get much out of Factory Five tech support other than replacing the master cylinders or going to a different brake pad. The FF guy said that as far as he knows PBR does not provide any technical support for the public. The aforementioned calipers are for 99-02 Cobra Mustangs. He said 1200 psi was for power brake systems. He didn't know the manual brake psi, but it would be quite a bit lower. Adding a power booster was another option he noted.
 

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FFCobra Craftsman
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PBRs were used for quite a few years on FFRs as the standard unit. Usually used w/ the single piston rears. I have been seeing some references to using same sized MC for both front and rear. But I 'think' more common is .75 (3/4) front and .625 (5/8) rear. A smaller rear would give you more hydraulic advantage for the rear brakes.
Do you know which pads you installed back when? Hawk has several compounds that will give more brake for a given pedal pressure.
I have used the HPS and HPS5.0. They are good grip w/ little dust or noise. I haven't experience w/ the PC compound but it looks good on the graph. I have also used the HP+ which have significantly more grip than the HPS or HPS5.0 but they do dust more too.
Breeze sells EBC which could also give more brake but I don't have personal experience w/ them.
A power booster would definitely give an easier pedal but I don't know any way to do that and still have the dual balance adjustable MC setup.
 

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There are individual Wilwood .75 master cylinders for front/rear. I could not get much out of Factory Five tech support other than replacing the master cylinders or going to a different brake pad. The FF guy said that as far as he knows PBR does not provide any technical support for the public. The aforementioned calipers are for 99-02 Cobra Mustangs. He said 1200 psi was for power brake systems. He didn't know the manual brake psi, but it would be quite a bit lower. Adding a power booster was another option he noted.
Sorry but that isn't correct, it takes the same pressure at the calipers to create the friction to stop the car. Power boosted, just means that you don't have to apply as much force on the pedal, the booster does the work. On a manual brake system, you have to apply more force on the pedal to get an equal amount of friction. That is one of the reasons that the brake pedal needs to be modified on a manual system, to increase the leverage on the master cylinder.
I don't know what the correct pressure would be, that would be determined by piston size and number in the caliper, and diameter of the rotor, but the pressure needed would be the same regardless of who or how it was generated.
 

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Discussion Starter #13
Searched through my post history and found a 2012 entry noting I installed "Carbotech XP8 pads". 2012 sounds like a long time ago, but I've got less than 5,000 miles on the build.
 

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I don't but hopefully someone reading this will have experience w/ the Carbotech XP8s.
 

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Discussion Starter #15
I continued my research into the Carbotech pads on the forum history. In addition with discussions on different brands of pads there were lots of posts about various brake issues. Jack Wojack posted on 8/17/12 about his successful use of the Carbotech pads. He listed having the 1999 GT 2 piston PBR front calipers and the single rear caliper that is the same as my build. His series of posts mentioned contacting Tilton Engineering for help on determining the master cylinder sizes (front/rear). They recommended 15/16 master cylinders. As previously noted mine are .75. It looks to be a major issue on my build to get to both of the master cylinders.

Other posts noted the issues with the use of braking systems designed for the heavier Mustangs that are front heavy. Many resolved their issues with a few like me still dealing with issues. There were quite a few posts from happy users of the Hawk brake pads. I didn't see a real consensus on the ideal Cobra braking system.

Solving the problem with new calipers and pads would certainly be a lot easier than trying to get to the master cylinders. Anyone have thoughts on the easier solution?
 

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When I had a system similar to yours (my fronts were Fox single piston calipers which I remember have almost identical piston area to yours) I ran Hawk HPS front and Hawk HP+ rear w/ 3/4 front and 5/8 rear MCs. But before you spend $ on new parts let's talk about front to rear balance. FFRs needs much more rear brake than the Mustangs so Have you worked at adjusting your balance toward the rear? I know you need to put a lot of effort into the pedal but it may be worthwhile to adjust balance even if it doesn't provide the ultimate solution.
 

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Discussion Starter #17
I can't recall any previous efforts to adjust the balance to focus on the rears. Of course sometimes I don't remember what I had for breakfast yesterday. I don't mind the break pedal effort. It's just the emergency stopping power. There is a blacktop marina entrance (maybe 3/4 mile long) across the highway from our property that is a good place to play with brake adjustments. I've got the knob in the cockpit to adjust the brake bias. I'll have to review it again to see if it notes which way to turn the knob for front or back bias. Any suggestions would be appreciated.

I'm off to the city for two days for my 5th my annual pet-scan. Hopefully this is the last one if I show up cancer free again. The visits give me a good opportunity to visit my kids. My wife is shopping for carpet. That might be painful. Talk later this week. Jim
 

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Discussion Starter #18
I checked the Wilwood bias adjustment. It clearly notes the direction to turn the knob for front/rear bias. I'll try to get out this weekend and play with it.
 

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Discussion Starter #19
Hoping to get the rear brakes more into the plan I turned the Wilwood bias knob all the way towards rear and went for a drive. From 45 mph the front brakes lock up on a panic stop and the overall stopping distance is pretty good. I don't recall this happening in the past. I expected the reverse, getting the rear brakes more into the stop.

Getting back to the shop I again looked over the stock balance bar setup. There is the issue of adjusting the length of the rod going from the master cylinder to the mount on the regular balance bar that controls which brakes kick in first. On mine the rod for the front brakes has more threads showing (makes the rod longer) indicating this master cylinder will be dominate in the braking. This setting may be strong enough that the bias dial can't make much of a difference.
I was sure there were instructions on how to setup the master cylinders but I can't find it on the factory five, ffcars or other websites.

As a side note the inside of the front wheels (American Racing chrome mags) were really dirty with some oily stuff mixed with brake dust. I expected some dust but not the sticky stuff. I cleaned them well. I'm sure that must have had some impact on the increased braking. The old saying "Anything that looks better works better".

On the good news side I installed a new distributor cap and rotor to replace the one that had gotten corotated (sp) which solved some miss fire problems. On my drive today I got on it hard in 1st until the shift light came on and shifted to 2nd (automatic) and it almost broke loose. The heavy wiggle in the rear end woke me up. It was telling me it was still alive.

I called F5 tech support to see if they had some documentation. Jim
 

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On the steering rack tie rod ends, the grease, dust caps are real close to the rotors. Excess grease from them can get on the rotors.
 
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