Need Brake Help

[DANW]

Guys
After 3,500 miles on my Cobra i have never been happy with the braking. Non Power 12.88 Wilwood front and 12.19 Wilwood rear, .75 in Wilwood front master and .625 rear master. I have never driven a cobra set up like mine or any Cobra for that matter so not sure how it should perform. My pedal seems soft and I need to really, really put a lot of pressure on the pedal to even come close to locking up the wheel a wheel. I have bled the brakes the old way with two people that i have done for years on other cars, i have dried speed bleeders, I have tried vacuum bleeding from each caliper and build a pressure bleeding system which I have attempted many times on this car without any change. After all these different ways to bleed I don’t have any air bubbles bubbles while bleeding. Today i bench bled both masters while installed in the car hoping this would do it, no luck. I have Stainless steal brake lines front to back and check the fittings, none are leaking. How do you know if one or both Master Cylinders are bad? Should this system lock the brakes up fairly easy? Below are some pictures.
Thanks much Dan

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[Bob Cowan]

It should be fairly easy to stop the car on a dime. You have all the right equipment in place.

Measure the pedal ratio. It should be 6 or 7'ish. I know you have all the parts supplied by FFR, and they should be correct. But measure anyway and move on.

What pads do you have? Did you bed them in according to instructions?

[Papa]

Not sure I can offer any help as my brakes (same Wilwood setup you have) are working really well. I'd like to complement you on the very nice looking setup on your lines and reservoirs. One thing I haven't seen mentioned is to check the runout on the calipers. The rotor should be right in the center of the caliper. Mine required a few shims to get things to line up perfectly.

[DANW]

I did double check the calipers to make sure they are centered, I did bed the pads per Wilwood instructions. The pads are what came with the kit from FFR. If a master cylinder is bad shouldn’t it have an exterior leak you can identify or can the fluid stay in the cylinder with a leaky seal??
Thanks

[edwardb]

With the system properly bled, you should get a hard pedal. You're describing it as seeming to be soft. But that can be subjective. It should stop a couple inches after being pushed down, and when held hard at that spot for a couple minutes at least, shouldn't move. If it doesn't, chances are the MC's are OK. I suspect not everyone will agree with this, but how well your car stops is more important than when it will/will not skid the tires. We run big and often very sticky tires, so some variation there. More importantly, how does it feel? Like you have good stopping power? Especially when pulling down hard like a panic stop? With everything else being OK, you may end up needing more aggressive pads to get the feel and performance you're happy with.

[Itchief]

Dan

From my experience if you’re pedal is soft then there’s air in the system and you will have to stand on the brake pedal to stop the car

I love your work on the master cylinders and the brake lines but looking at your brake reservoir they do not have a diaphragm and a vent to allow air into the reservoir when you use the brakes and as the pads wear. This setup will cause a vacuum in the system and air will enter at the weakest point the master cylinder shaft seal. Over time you will notice that the pedal keeps getting softer as more air is sucked into the system.

I replaced my reservoir with one of the newer style from FFR about 10k miles ago and my brake pedal is still rock hard and the brakes work great I can lock up all four wheels without much effort

Hope this helps

Rick

[DANW]

Edward good to hear from you. I don’t drive the cobra hard more pleasure driving, I’m not uncomfortable driving it but the pedal always seems soft. I decided this fall to hit the brakes hard at 30MPH did this a few times just to see what would happen. I had to exert huge amount if brake pressure to get the tires to come close to locking up, almost feels like an ABS system. Not sure if this matters but when I have the reservoir caps off and but very lite pressure on the brakes the fluid raises out 1/8 inch in both reservoirs, no bubbles just moves the fluid up and down..

[edwardb]

Edward good to hear from you. I don’t drive the cobra hard more pleasure driving, I’m not uncomfortable driving it but the pedal always seems soft. I decided this fall to hit the brakes hard at 30MPH did this a few times just to see what would happen. I had to exert huge amount if brake pressure to get the tires to come close to locking up, almost feels like an ABS system. Not sure if this matters but when I have the reservoir caps off and but very lite pressure on the brakes the fluid raises out 1/8 inch in both reservoirs, no bubbles just moves the fluid up and down..

Just doesn't sound right. Manual is always going to have a heavy pedal compared to power that we're all use to. But you should have good stopping power and not feel like you're describing. I've had good success with pressure bleeding using caps on the reservoirs with a Schrader valve. CNC for the first builds, and modded a Tilton cap for my Coupe build. 6-8 PSI in the reservoir and going around the brakes farthest to closest, have always been able to get the air out and have a firm pedal and good brakes. I've never tried observing the level in the reservoirs while the brakes are operated, so don't know if that's normal or not. I would be very surprised if you have two bad MC's.

[DANW]

This is the pressure bleeding setup I have, it works great to push fluid through the lines. I start with the rear master cylinder on the passenger rear caliper, push about 10 fluid oz’s of brake fluid then to the same on the drivers side. Then pressurize the front master cylinder, start bleeding the passenger upper inside bleeder then the upper outside bleeder, to the same on the front drivers side. Done this many times this weekend with no bubbles in the clear lines and no change in the soft pedal.118002118003

[Gordon Levy]

Do you have a single piston rear caliper or 4 piston?

[Papa]

DANW,

Interesting setup and definitely looks like it would do the trick. Here is the procedure I used to bleed my Wilwoods with perfect results the first attempt:

1. Bled the master cylinders (MC) by disconnecting the output line from the MC and running a piece of tubing from the MC output to the reservoir. Fill the reservoir and pump the brake pedal until no air in the stream of fluid entering the reservoir. Do this for each MC separately or can be done together.

2. Reconnect the output lines to the MC.

3. Fill the reservoir.

4. Pressurize the reservoir for the rear system with 3-5lbs of pressure. I have the CNC reservoir with the pressure cap, but if you buy an extra cap that fits your reservoir, you can put a Schrader valve in it to make your own pressure cap.

5. Once pressurized, start with the right rear. Attach a catch bottle with a piece of clear tubing to the top bleeder valve and slightly crack the valve open. Ensuring the reservoir doesn't run dry, repeat this process until no bubbles are seen. and then move to the left rear caliper and do the same.

IMPORTANT: Do not pump the pedal at any time with the reservoir pressurized or this can cause damage to the seals in the MC.

6. Repeat for the front starting with the right front and then moving to the left front.

7. Once you have all four calipers done, I repeat the cycle a second time starting with the right-rear again.

8. After depressurizing the MCs and replacing the caps, check for pedal firmness. The pedal should be firm after a couple of inches of travel and stay firm if held for 30-60 seconds or more.

I'm suspicious that pushing fluid through the Wilwood calipers is really getting all the air out.

Dave

[DANW]

Gordon
I have a single piston in the rear and 6 piston fronts
118004118005

[DANW]

PAPA
Did exactly like you described, I bench bleed both brake cylinders on the vehicle at the same time, made sure the clear lines always stayed submerged in fluid..

[edwardb]

This is the pressure bleeding setup I have, it works great to push fluid through the lines. I start with the rear master cylinder on the passenger rear caliper, push about 10 fluid oz’s of brake fluid then to the same on the drivers side. Then pressurize the front master cylinder, start bleeding the passenger upper inside bleeder then the upper outside bleeder, to the same on the front drivers side. Done this many times this weekend with no bubbles in the clear lines and no change in the soft pedal.118002118003

That should work, and your process is exactly right. Now wondering about whether you have a defective MC. They're easy to rebuild if just seals. Wilwood has a kit. But obviously a pain to get in and out. I was wondering about Gordon's question too -- whether you have the single or 4-piston rears. Although you still shouldn't have a soft pedal.

[DANW]

Edward
I have the part number for the wilwood repair kit, but I don’t understand if one of the masters is bad shouldn’t it be leaking under the boot???

[Gordon Levy]

I have a 4 piston setup for that rear. The master with that caliper should be fine. I can't tell from the pick whether the front caliper hase a single bleeder or dual. If it has duals you need to bleed inside then outside then in.
Another thing I have run into is a soft pedal can but up until the time you drive it and bed in the brakes. I have had the pedal come up and feel fine afterward. Other time we drove it and bled the brakes again and there were fine after that.

[Jeff Kleiner]

Dan,
As you no doubt recall I drove your car a few miles when you came to pick it up after I painted it and commented on the brakes then. I've driven others with the exact same setup and there is no problem getting them to stop with authority! I don't know what you have going on but I can assure that you don't need to change the configuration to achieve excellent braking---you just need to sort out what you have.

Jeff

[DANW]

Good to hear from you Jeff hope all is well for you and your family. I have tried everything except rebuilding the master cylinders. I just would like to know if it is a bad master cylinder and that is the is the reason for the soft pedal shouldn’t they be leaking brake fluid?

[Murd]

I’m no expert but a couple things not mentioned you could try.
Does the pedal allow the MCs to return fully? Is the pedal hitting the cross member of the frame or does it have some play at the top?
Is your balance bar set up correctly? Both for front and rear bias (side to side) and the front/rear push rod length. One needs to be longer (think front but can’t remember) when fully extended, should appear even at moderate pressure and offset again at pull depression. Should all be in the manual.

[Jacob McCrea]

Dan,

For what it's worth, here is what I posted in another thread, which dealt with a clutch bleeding problem:

"I had a similar problem, albeit with a Wilwood rear brake master cylinder on a balance bar setup. I could never get a firm pedal. I tried every bleeding process and half of the bleeding devices out there, with no success. I eventually disassembled and totally cleaned the offending master cylinder. As far as I could tell, the problem was machining debris in the orifice that allows fluid to pass into the bore. Sounds like your problem is it won't "stay bled"; my problem was I could never get it bled in the first place. Nevertheless, hope this helps."


The line routing and reservoirs are as good as I have seen, by the way.

[mosh1999]

Is it possible it is something simple like glazed pads?

[DANW]

Murd
You got me thinking about the balance bar, I read the Wilwood manual again and it said that the master cylinder pushrods should be screwed into the clevis at different lengths. The rear .625 inch master should be screwed into the clevis 4 turns more than the .75 inch front. Mine are set equal, maybe that is the answer, would this causes a soft pedal?? I will give it a try.. Thanks all and Happy thanksgiving...

[Murd]

Makes sure after you adjust it that the pedal isn’t against the crossbar. The MCs need to return fully to expose the port to the reservoir. If it hits the crossbar first they may not fully extend.

[edwardb]

Improperly adjusted balance shouldn't cause a soft pedal. Would affect bias, but you should still have a hard pedal. Agree the MC's need to be free to return against their internal stops (snap rings). Can't be hanging up on the frame. I had those single piston rear calipers on my #7750 build and for my street driving were fine. The four piston Gordon is describing, which are what the 2015+ IRS Wilwood upgrade uses, is no doubt technically superior. But you should be able to get what you have working OK. And yes, the main piston seal in the master cylinder could be leaking and no fluid leak into the boot.

[DANW]

I called Wilwood tech service today. I told him I have a 5/8 inch Master Cylinder "Part#260-6087" for the rear brakes and a 3/4 inch Master Cylinder "part#260-6089" for the fronts. I was looking for a repair kit for both, he said they do not have repair kits for these masters. He said the only way they go bad is if they start leaking out the rubber boot. He also ask why I have a 5/8 inch going to the rear, it should be 3/4 inch and if anything the 5/8 inch should be for the fronts but recommended 3/4 inch for both.

[Avalanche325]

Like is stated, the equipment that you have is tried and true. Not sure why they now supply different sized M/Cs. It does take significant pressure on the pedal if you have sticky tires. However, the soft pedal means that you have a problem. The fact that Jeff drove your car and said that your brakes don't feel right take the subjective opinion out of it.

I didn't read every word of the thread. Did you unbolt the rear calipers and move them up to 10 and 2 when bleeding and keep the pads fully on the rotor? I also would check all of the physical stuff that Murd mentioned. Especially that the M/Cs are being allowed to fully retract.

If those are all good, I would bite the bullet and change the M/Cs.

[edwardb]

I called Wilwood tech service today. I told him I have a 5/8 inch Master Cylinder "Part#260-6087" for the rear brakes and a 3/4 inch Master Cylinder "part#260-6089" for the fronts. I was looking for a repair kit for both, he said they do not have repair kits for these masters. He said the only way they go bad is if they start leaking out the rubber boot. He also ask why I have a 5/8 inch going to the rear, it should be 3/4 inch and if anything the 5/8 inch should be for the fronts but recommended 3/4 inch for both.

Interesting. Not what is traditional with MC's. But assume they should know about how they leak. But having said that, that's the same advice (5/8 in front vs. rear) that I've heard them give multiple people that have called. Going to trust Factory Five on this one, since they did it that way for a number of years. All of my builds with the Wilwood pedal box were set up that way and worked fine. The part numbers for the MC's get's a little wonky too. Agreed you won't find those part numbers. I haven't and others have reported that too. But the kit number (e.g. 260-13619) has what appears to be that same exact 3/4 MC, for example. I had to rebuild the 260-14297 MC on my Coupe build because it was leaking into the boot. I found the front seal right behind the boot was damaged. Either a defective part or damaged during Wilwood assembly. Wilwood Master Cylinder Rebuild Kit 260-10514 fit perfectly and had every part except the actual housing and fixed the problem. So not sure what to believe...

[Hurman]

Have you ever thought of using a brake bias pressure gauge kit?
Smiley's racing supply has the QuickCar Mini Brake Bias Gauge Item # 61-10 and when I built my GT3 racer I had a soft pedal and found this gauge set to be invaluable when working on my brakes. It helped me diagnose the faulty area and then was a good check before hitting the track.

[karlos]

Based on what I think I know (dangerous) brake systems in high performance cars like the roadster should be designed to provide a front brake pressure that’s about 70% of the rear pressure, and provide for a braking ratio (front/rear clamping force vs total clamping force) of about 60/40. I have the exact same setup that Dan has, and I also have some calculations that I put together previously to help me understand the range over which it’s wise to mess with the balance bar adjustment.

When I looked at this previously I concluded that Wilwood did a really good job of sizing the various components that make up the system (master cylinders, pedal ratio, calipers, etc). That’s evident by looking at the portion of the table below in the green box. The numbers in that box reflect the system exactly as Wilwood provided it: 3/4” front master, 5/8” rear master, centered balance bar. Line pressure in the front is 69% of the rear, and the overall bias is 58% front, 42% rear. Really close to the goals of 70% and ratios of 60/40.

Now look what happens when we do nothing more than swap the front and rear master cylinder sizes (red box): line pressure in the front is 144% of the rear, and the overall bias is 74% front, 26% rear. This would render the rear brakes basically useless.

The blue box shows 3/4” master cylinders in both positions. Line pressure in the front is 100% of the rear, and the overall bias is 66% front, 34% rear. Workable with some balance bar adjustment, but not an improvement.

I believe Wilwood did a nice job on the system design out of the box. Not sure what to make of the advice to swap or equalize the sizes of the master cylinders. I wouldn’t do it. Solve the spongy pedal and the brakes will work fine. Disclaimer: I changed out the BP 10 brake pads and messed with the balance bar a bit but was able to eventually get things working to my liking.


-Karl



https://thefactoryfiveforum.com/attachment.php?attachmentid=118113&d=1574797702

[DANW]

Karlos, that’s quite the spreadsheet, thanks for the info. We are going to get 12 inches of snow tonight so tomorrow I’m going to take everything apart and to some investigating.. thanks all for you help, I will keep you informed.
Happy thanksgiving Dan

[phileas_fogg]

Hey Karlos,

Just curious - did you measure the lbf & psi values shown in your table or find them from some other party? If you generated the data, how did you measure the lbf (psi is readily measured using the Wilwood gauge at the caliper)?


John

[karlos]

Hi John,

Pedal force is assumed but all the rest are calculated based on info from Wilwood, such as master cylinder bore size, caliper piston area, pedal ratio, etc. Since I'm only looking at the ratio of the front/rear line pressures and the front/rear bias, the pedal force can be any arbitrary value as it has no effect on the ratios. 100 lbf is easy to scale and it's pretty close to what I understand is commonly exerted on the brake pedal in normal day-to-day driving (80 lbf).

There are some interesting numbers in the tables. For instance, with a Wilwood footbox pedal ratio of 6.25:1, the 100 lbf applied with your foot ends up being 625 lbf at the balance bar. And this creates over 1000 psi line pressure. Which in turn produces 5000 lbf of clamping force at the rotors. Some pretty seriously big numbers!

As an aside, all this has inspired me to pick up a pair of the pressure gauges you and Hurman mentioned above so I can simultaneously measure the front/rear pressures and directly observe the effect of different balance bar settings. The numbers say the balance bar probably shouldn't stray more than 3 turns or so either direction from center. Be interesting to see if the measurements back that up. Winter break (brake?) project...

[CraigS]

IMHO pressure gauges can help verify a system design maybe but that's all. Example 1; Take a system that is working fine, is perfectly balanced front to rear, and change to grippier pads in the rear. Now what do you have? A system w/ the exact same pressure readings but now it locks the rear brakes first. Example 2; Same initial system as above but now put drag radials on the rear. Now what do you have? A system that still has the same pressures but now it locks the fronts first.

[Jeff Kleiner]

IMHO pressure gauges can help verify a system design maybe but that's all. Example 1; Take a system that is working fine, is perfectly balanced front to rear, and change to grippier pads in the rear. Now what do you have? A system w/ the exact same pressure readings but now it locks the rear brakes first. Example 2; Same initial system as above but now put drag radials on the rear. Now what do you have? A system that still has the same pressures but now it locks the fronts first.

Exactly! The coefficient of friction is as much of a player as pressure.

Jeff

[karlos]

Geez, you guys gotta take all the fun out of it ;)

Pressure's just an indirect way of measuring the front/rear bias. I'm interested in understanding how far I can push the bias toward the rear as compared to the 60/40 split your typical passenger car is set at. Our cars have a lower CG and a more uniform weight distribution to begin with, so more rear brake is theoretically possible. I've searched for but cannot find data that shows what's possible on the roadster. Using the pressure gauges, I can determine exactly where the balance bar is centered. I can then change the front/rear bias and confirm - by driving the car - how much rear brake is safely achievable. I can then compare to where I started and know exactly what bias I ended up with.

An academic exercise, I suppose, but I'm interesting in seeing where the numbers fall out.

Apologies to Dan for semi-jacking the thread. I'll stop now.

-Karl

[DANW]

Karl
You can keep on chatting, I am like a sponge when it comes to learning about these cars from the guys on this site. I have both masters out of the car, took them apart and all looked good. I might have had a fitting on the pressure side of the rear master that wasn’t as tight as I think it good have been. Maybe this was my problem.. I’m also going to follow the directions closer on the balance bar.
Happy Turkey day

[CraigS]

Since you can't really see where the balance bar bearing is inside the center piece, keep the exposed threads on both ends equal and you will be starting w/ it centered.
https://live.staticflickr.com/65535/49141190238_a72fd93124_z.jpg (https://flic.kr/p/2hSrrNE)Balance bar 2 (https://flic.kr/p/2hSrrNE) by craig stuard (https://www.flickr.com/photos/152454123@N04/), on Flickr
How does this work? the bearing is locked to the shaft w/ the jam nuts on either side. The shaft is threaded through the brass pieces in the centers of the black clevis. This bearing is a slip fit in the top of the pedal. With the bar/bearing centered you get equal pressure applied to both MCs. As you twist the bar you move the bearing toward one MC and away from the other MC. Which ever MC is closest to the bearing will get the most pedal pressure applied to it. You can tell where the bearing is (even though you can't see it) by looking at the ends of the shaft. The bearing is moved toward the side where the exposed shaft is longest. I am too lazy to go back and read the whole thread so I will add one thing in case it hasn't been stated yet. When bleeding the brakes by pushing the pedal, you must bleed both front and rear at the same time. The reason is that the cross shaft can only go to so much of an angle. So if you bleed just one MC, the MC will move some but stop as pressure builds. So you have the already bled MC stopping after it moves somewhat, the balance shaft then goes to it's max angle, and stops moving. Unfortunately, now the other MC stops moving well before it is completely compressed. To get all the air out of the MC it must be depressed completely. But, when it all stops moving, the MC you are trying to bleed has only moved to let's say, 3/4 of it's travel, and that last 1/4 of it's travel has air in it which will never be pushed out. This usually makes bleeding by pedal pushing a 3 person job. One at the pedal, and one at a front
caliper, one at a rear caliper.

[Richard Oben]

We did a car last fall that had the same issue. We had to remove and remount the rear caliper, top bolt in bottom hole to get it to bleed. We tried every form of bleeding there is. Once we moved the caliper three pumps and fixed, two on one side and one on the other. HTH, Richard.

[bobl]

Reading this thread brings up a question. If you install a pressure gauge at the caliper and a solid press on the pedal generates an appropriate pressure reading, could one assume there was no air in that leg of the system and full pressure was reaching the caliper? Conversely if there was air in the line wouldn't the pressure be low? Seems to me if the correct pressure was at the caliper it would rule out a m/c or installation problem. Granted I know little about brakes, so I look forward to some thoughts on this from those with a better understanding of brakes.

[CraigS]

Reading this thread brings up a question. If you install a pressure gauge at the caliper and a solid press on the pedal generates an appropriate pressure reading, could one assume there was no air in that leg of the system and full pressure was reaching the caliper? Conversely if there was air in the line wouldn't the pressure be low? Seems to me if the correct pressure was at the caliper it would rule out a m/c or installation problem. Granted I know little about brakes, so I look forward to some thoughts on this from those with a better understanding of brakes.

I think the key is what is an 'appropriate' reading. IE: think about when we used to use all the calipers etc from a Mustang. If you measured pressure while still on the Mustang, and activated through a vac assist, you might get readings you could compare against. But, as touched on above, you would want the rears to read significantly higher once all is installed on an FFR. Also, there would probably be different numbers because the FFR usually doesn't have a vac assist ( although some do). I do agree that air in the system would most likely result in lower pressures.

[karlos]

It does seem intuitive that air in the system would change the pressure reading, but that’s not actually the case. The volume of the trapped air will change as its compressed, but it will transmit pressure just the same as the fluid will. It may, however, limit the magnitude of the pressure that can be generated if the master cylinder were to stroke out before the column of air became fully compressed.

Unless you have some idea of what readings to expect, the gauge readings are gonna be somewhat hard to interpret. This explains the value of the calculations, BTW. Not as a be-all, end-all, but as a way to gain insight into how the system works and what its sensitivities are. In the case of the system Dan’s running, i would expect to see a pressure ratio of 7:10, front vs. rear with the balance bar centered. This is based on the ratio of the areas of the two master cylinders (0.307/0.442 = 0.69, or approximately 70%). If you push on them with the same force (centered balance bar), then the pressures will follow that same ratio. If a ratio of 7:10 can’t be achieved with the balance bar in roughly a neutral position then something’s amiss.

As a hypothetical, let’s say the measured pressures turn out to be 700 front and 800 rear (ratio = 7:8). This would mean the pressure in the rear circuit is lower than expected. If a reasonable adjustment on the balance bar doesn’t produce the expected result, then the gauge pressures indicate there’s a problem with the rears. Maybe the M/C ran out of stroke because it’s full of air, or maybe the seal is leaking backwards into the boot, etc.

I think pressure gauges can be a useful, if limited, diagnostic tool. Taken by itself pressure doesn’t really mean much. And to get to what’s actually informative (ratio of front to rear) you really need to use two gauges simultaneously. I have a pair of gauges on the way. I’ll take some measurements and report back once I have something to look at. Particularly interested to see how close to center the balance bar actually is compared to where I originally set it, and in seeing the measured effect of adjusting the balance bar.

[DANW]

Here is an update over the past few days.
1. Pressure bleed all reservoirs to push all brake fluid out the four calibers.
2. Removed the triple reservoir, removed front and rear master cylinders from the pedal assembly.
3. Disassembled both master cylinders checked for problems, cleaned and reassembled.
4. I had a new .75 inch master cylinder so replace the one I was using with the new one.
5. Reinstalled both master cylinder and adjusted the balance bar according to forum and Wilwood directions.
6. Check all fittings front to back for tightness or leaks.
7. Bench bled both masters after installing back on the pedal assembly, pumped until no bubbles.
8. Pressure bled the right rear then the left rear.
9. Pressure bled the right front inside bleeder then the outside bleeder then the left.
10. Pedal seems to be the same, soft. I may order a new .625 inch master.

Dan







7. Pressure bled the right rear then the left rear

[Itchief]

Dan

Just for s—-s and giggles try bleeding the passenger rear one more time and open the bleeder so that you get a good flow to the point you have used most of the reservoir and then test the brake pedal.

For me getting the air out of the passenger rear line was a real pain.

Just an idea you may want to consider

Rick

[rich grsc]

I have no idea how a pressure gauge would give you any helpful info. The harder you push on the pedal, the higher the pressure would be. How are you going to be sure the same force is applied at the pedal each time you check a caliper? That and you have the mess of attaching and removing the gauge at each caliper, plus then introducing air into the system and re-bleeding the system AGAIN.

[karlos]

The pressure gauge talk is a separate discussion going on inside the discussion. I'm sure it's all very confusing if you don't bother to read/understand the entire thread.

[Ducky2009]

Dan,
Here's a video from Wilwood. Important point, do you have two bleeders per wheel?
https://www.google.com/search?q=how+to+bleed+wilwood+brakes&rlz=1C1SQJL_enUS833US833&oq=how+to+bleed+wilwood+brakes&aqs=chrome..69i57j0l7.10481j0j8&sourceid=chrome&ie=UTF-8#kpvalbx=_gkfpXfmONs_s_QaQl6iYAw46

As others mentioned, the balance bar setup is also very important.

[bobl]

Here was my experience with a pressure gauge. My rear brakes worked very poorly. So I installed a pressure gauge and determined I was getting over 1000 PSI to the caliper(power brakes). The pedal was firm with no air in the system. Therefore I decided the problem was mechanical within the rear brake system and not the master cylinder. So, I replaced the mustang brakes with 4 piston Wilwoods and they work great, with the same operating psi.

[Richard Oben]

Did you re locate the rears to be sure they are getting bled fully. See my other post about this on this thread. JMHO.

[DANW]

Richard
I looked at my rear Caliber, it seems my bleeder is almost at the 12:00 position or strait up. I have a picture on this post showing the rear. Did you have the same setup as I do? How important is it to level the Masters by lowering the rear of the car, I have read this a few times but thought bench bleeding the Masters on the car would take care of any air in the Masters.. my new 5/8 inch master comes today..
Thanks Dan

[Richard Oben]

Looks like the same rear set up. We had a 3 link but it appears to be the same caliper. The bleeder pointing up may not get it bled, the air has to get to the bleeder. In the old days a LOT, I mean a whole LOT, of people put the fox front caliper on wrong and the the bleeder pointed up, which is logical, when it needed to point back. Because pointing the bleeder up the caliper was still half full of air. (there was a really good pic of this somewhere, could not find it) If the caliper is rotated either up or down the bleeder is at the top of the piston circle it will get the air out. We went through a lot of fluid trying but until we moved the caliper it was a no go. Right now the bleeder looks like about 10 o'clock on the piston circle not 12. JMHO. Richard.

[DANW]

Just wanted to give you an update. I purchased two new Masters, .75 inch front .625 inch rear compact Wilwood masters. I bench bleed them off the car and again on the car. Dropped the rear if the Cobra so the masters were level in the car. Removed the rear calibers and milled out a pad size piece of aluminum the same thickness as the rear rotor, with the rears calibers removed i placed the spacer between the pads so I could rotate the calibers in any position so the bleeders are straight up. I pressure bled the system 4 times with no air bubbles coming out of the calibers. Pedal seem somewhat better but still not hard. I then had my wife help me pedal bleed, doing the front and rear rights side at the same time then the front and rear left side. Still no bubbles. I am going to replace all the Pads with Hawks “unless someone was better pads they can tell me” I am going to double check to make sure the Calibers are centered over the disks, I have read that can cause a soft pedal. Maybe the soft pedal is in my head and and I didn’t bed the brakes pads correctly when I first got it running. I attached a picture of a rear pad, it seems glazed what do you guys think? Also can any one tell me the part numbers for front and rear Hawk pads that fit my 12.88 6 piston fronts and 12.19 inch single piston rear? Would Hawks be the best pads? 118664118665

[karlos]

Some options, including Hawk, shown below. The BP-10s that come with the Wilwoods are pretty terrible. I'm currently running the choices shown in green, and find them to be a big improvement. Wilwood's website gives lots of additional info you can use to do some comparison shopping.

Also, on the soft pedal: as measured at the pedal pad on the brake pedal, I see 1-1/4" of travel when pushing as hard as I can with my hand. May be useful as a point of comparison for determining whether or not it's in your head.

Keep at it - you'll get it figured out.

-Karl



https://thefactoryfiveforum.com/attachment.php?attachmentid=118670&d=1575860078

[Richard Oben]

Dan the bleeder being up is irrelevant. The piston circle has to be at the bleeder exit, not the bleeder up. It could be up, but it could be at 10. Like I said on the old mustang front calipers the bleeder pointed straight back, not up. JMHO R

[Bill Waters]

This thread has certainly covered all the bases regarding bleeding and brake line pressure generation, etc.

So I thought I would offer a thought. Are you sure that the pads which shipped with the Wilwoods are street pads? If they are track pads, you will have much higher pedal pressure to stop effectively at the cold to moderate temperatures (relatively speaking) of street driving. Pad composition for street pads won’t hold up under track use and track-composition pads won’t perform effectively when cold. Ask me how I know......


After all you have gone through, will be interested to see the effect of pad replacement, which I take from your last post you are considering.

Brake woes and intermittent electrical problems are the least fun aspects of our hobby....

Bill

[DANW]

Karlos, i called the help desk with Hawk brakes he said the only brakes they have for the front calipers is the DTC-30 like you show on the above post. He told me the these brake pads will have way more stopping power than the BD-10 Wilwood pads that came from FFR, but will screech quite loud during braking and be dusty. I see the Wilwood pads you have on their website, are they loud and dusty during braking? Richard i will take a look at the rear calipers piston circle is up.

[karlos]

No noise, a bit more brake dust. Most noticeable difference is that they actually stop the car.

[rich grsc]

Just wanted to give you an update. I purchased two new Masters, .75 inch front .625 inch rear compact Wilwood masters. I bench bleed them off the car and again on the car. Dropped the rear if the Cobra so the masters were level in the car. Removed the rear calibers and milled out a pad size piece of aluminum the same thickness as the rear rotor, with the rears calibers removed i placed the spacer between the pads so I could rotate the calibers in any position so the bleeders are straight up. I pressure bled the system 4 times with no air bubbles coming out of the calibers. Pedal seem somewhat better but still not hard. I then had my wife help me pedal bleed, doing the front and rear rights side at the same time then the front and rear left side. Still no bubbles. I am going to replace all the Pads with Hawks “unless someone was better pads they can tell me” I am going to double check to make sure the Calibers are centered over the disks, I have read that can cause a soft pedal. Maybe the soft pedal is in my head and and I didn’t bed the brakes pads correctly when I first got it running. I attached a picture of a rear pad, it seems glazed what do you guys think? Also can any one tell me the part numbers for front and rear Hawk pads that fit my 12.88 6 piston fronts and 12.19 inch single piston rear? Would Hawks be the best pads? 118664118665

Something doesn't look right with the wear on those pads. A pad should not set above the rotor, the pad should make 100% contact on the rotor. It looks like you have maybe a 1/4"(?) above the rotor?

[Inman Lanier]

On page 1, someone asked about glazed pads - no one picked up on that. My very first set of pads I changed when I was getting into autocross back in 1984 with my TurboGT Mustang - I cooked my set of new bendix pads following what I though were the 'bed-in' instructions. It turns out I applied way too much heat in the first stops and although not 'soft' in my opinion - the pedal was definitely not hard and created no brake torque. After going round and round, some buds and I determined I had cooked the brakes in my method of curing. I took them in, swapped them out for an identical set of pads, then did a much more gentle break in and they were fine.

There are actually 2 things that need to happen with pads - they need to be cured (the glues and additives need to cook off), and the friction surfaces need to mate. The first part is potentially problematic based on method - the 2nd part takes care of itself with use.

How did you 'bed in' your pads? The best way with new pads is to take the car up to 30 mph or so and do some 50% stops. You want to get them hot enough to where you just start to smell them off-gassing (that nasty brake smell when they get to temperature). When you smell them for the first time, stop braking at that point and let them cool (by driving around). Repeat this perhaps a half dozen times and you're done enough to where they will be fine (partially cured) and bed-in on their own going forward. The reality is that with pads and street driving you don't need to do anything at all! They will eventually get hot enough to off-gas, and the friction surfaces match the rotors with normal driving. Just recognize that early on, a panic stop on the highway with uncured brakes may actually fade them and you won't be able to stop as quickly. Generally, however you can get at least one decent stop on new pads before you overheat them.

If you think you may have really worked some energy into the pads at bed-in - go get some cheap pads anywhere - put them in and see if it makes a difference.

[DANW]

Thanks for the advice on bedding the pads, I purchased a set of pads that Karlos suggested. I am checking to make sure the calipers are centered. I did read on the Wilwood instructions about adjusting the parking brake for the first time. It said to apply the brakes about 50% then cycle the parking brake a few times. I don’t remember doing that, wondering if this is some of my problem. It’s hard to do a test drive in MN it is going to be 12 below zero tomorrow.
Dan

[Inman Lanier]

Not having applied the brake many times is NOT the problem (as I suggested most pads don't need any bedding considering the first panic stop caution). The only issue on 'bedding' is if you apply too much heat before they've properly cured.

From many, many, many years both on the street and racing (autocross first, later road racing) - trust me the parking brake does NOT contribute in any way. You can ignore that recommendation.

If you have the new pads in - did the pedal firm up? If no - it feels the same, then pads are NOT your issue.

I've not heard it mentioned yet, but conventional rubber brake lines can have localize defect areas where they will balloon slightly w/o bursting. This is a small percentage of failures but from what you've been describing you're at a small percentage issue! Just keep that in the back of your mind now.

Inman

[rich grsc]

Thanks for the advice on bedding the pads, I purchased a set of pads that Karlos suggested. I am checking to make sure the calipers are centered. I did read on the Wilwood instructions about adjusting the parking brake for the first time. It said to apply the brakes about 50% then cycle the parking brake a few times. I don’t remember doing that, wondering if this is some of my problem. It’s hard to do a test drive in MN it is going to be 12 below zero tomorrow.
Dan

Yes the parking brake needs to be adjusted. If the P brake isn't adjusted correctly, the pads have to move a greater distance to the rotor, and the master cylinder runs out of movement and can't apply enough pressure at the pads. ALMOST all performance pads have break-in procedure, if yours lists one, follow it. A break-in allows the transfer of pad material to the rotor to increase friction, very important for certain types of brake material.

[Jeff Kleiner]

...A break-in allows the transfer of pad material to the rotor to increase friction, very important for certain types of brake material.

And speaking of the transfer of material...Dan, if you change pads it would be advisable to freshen up the rotors to eliminate any embedded material from the old pads. Minimally give them an aggressive clean up by using 40 or 60 grit on a DA or better yet by having them turned with just a couple thousandths taken off.

Jeff

[DANW]

I did have the machine shop turn all four rotors just to be sure. I wanted to understand how the parking brake mechanics work so i took the puck out to look inside the caliper, by moving the parking brake lever on the caliper and watching the worm gear move inside the caliper was helpful for me to understand why wilwood’s directions say how to adjust the parking brake. Excited to see if this works. Jeff, i will buy you a cold beer and a steak if you come up here to MN and take it for a test drive, we are suppose to hit 10 above zero. Thank all for the help will keep you informed.

[DANW]

X-mas came early for me. I installed the new Pads today and checked everything over, I followed the directions on adjusting the parking brake and now the pedal is rock hard. It was a struggle but learned a great deal. Thanks all for your help, and Merry X-mas to you and all your families.
Dan

[totem]

Dan,

Great that you work it out. Still, check that the contact between the rear pad and the disk is right. Otherwise, the pad will wear wrong and might bring back the soft pedal.


Something doesn't look right with the wear on those pads. A pad should not set above the rotor, the pad should make 100% contact on the rotor. It looks like you have maybe a 1/4"(?) above the rotor?

[Mark Eaton]

Dan,

So in the final analysis what was the problem causing the soft pedal? Was it faulty or wrong sized MC's , the pads, or maladjusted parking brake?

[DANW]

Mark
I think it was the parking brake. I installed the brakes and the original hand operated parking brake doing the build, then a few years into the build when i was designing the interior I decided to install the electric E-Stopp parking brake and must not have followed the final Wilwood instructions telling me after bleeding the brakes to apply 50% brake pedal pressure and cycle the parking brake a few time. Dan