Brake Issues?

[Alphamacaroon]

Took my Coupe out for its first relatively long test drive yesterday. Everything went really well, but the brakes don't seem right to me. I'm running the 11" brakes in the front and the 13" brakes in the rear (this has always seemed weird to me, but FFR says it's the way). They certainly do stop the car, but I was able to push the pedal all the way to firewall without locking them up. Keep in mind I had to press with all my might to get it to the firewall, and the car did come to a relatively quick stop, but certainly much less than I expected— I expected at least some tire squeal if not a partial or complete lockup. I did do a few low-speed bedding procedures (30+MPH followed by quick deceleration to almost a stop), and it did seem to help a little, but certainly not to the level I expected. I feel like I've seen from others that their brakes felt fairly soft for the first few rides, but got better as they bedded, so I'm wondering if maybe I'm just in the same boat.

So I guess the question is: is this normal until the brakes get bedded in a bit more, or do you think I still have a small amount of air in the lines? I've done (what I think) is a fairly good job of bleeding them at least twice, but maybe it's just not enough. Maybe my pedals need to be adjusted to give more throw until they hit the firewall? Thoughts?

[Gordon Levy]

What pedal assy and masters?

[Alphamacaroon]

What pedal assy and masters?

It's pretty much the standard Wilwood setup they include with the Gen III complete kit (only modification/upgrade I've made is a hydraulic clutch, and I use the Tilton racing three tank reservoir). I believe the bore size is 3/4" front and rear.

[NAZ]

Jim, Wilwood makes great brake components but I'm not a fan of their pads. You should ensure your system is installed correctly, you can get full range of travel with the pedal, and that the brakes are bedded following the Wilwood procedure. If you can get 1,000 PSI out of your front & rear and can't lock the tires, change the pads to a different compound. I've tried a couple different Wilqwood compounds and could not get the results I was looking for. Went to Hawk pads and am happy with their DTC-50 compound, it has an aggressive initial bite with lots of torque on cold pads -- just what you need for a street car (or drag racer).

[Gordon Levy]

I am assuming you have the Mustang brakes all around. In either the IRS or live axle rear and the complete kit PBR fronts. The first think to check would be to make sure the calipers on are on the correct sides. They are marked L and R, R being passenger side. next would be to make sure they are fully bedded. the easiest way to tell is to see you have full contact marking on the rotors and not just a shiney stripe. Where is the balance bar set and the master push rods? those can have a determination on how things work and can be adjusted. If all this is correct and the stops but not as well as you like you can upgrade pads such as hawk XP or XP+. A bit of a warning, carbon ceramic pads like these while stopped really well with a high coaficiant of friction dust really bad. The next upgrade from here would be into one of my 4 or 6 piston brake systems. These will stop every time on the street or track.

[AC Bill]

Did you do the step by step break-in procedure for new brakes, when you first put it on the road?

https://brakeperformance.com/bedding-in-rotors.php

[edwardb]

I've never had a setup where the brake pedal was remotely close to the back wall. Mustang or Wilwood brakes. Mustang or Wilwood pedal box. Doesn't sound right to me. I'd want to sort that out before starting to change parts.

[Alphamacaroon]

I am assuming you have the Mustang brakes all around. In either the IRS or live axle rear and the complete kit PBR fronts. The first think to check would be to make sure the calipers on are on the correct sides. They are marked L and R, R being passenger side. next would be to make sure they are fully bedded. the easiest way to tell is to see you have full contact marking on the rotors and not just a shiney stripe. Where is the balance bar set and the master push rods? those can have a determination on how things work and can be adjusted. If all this is correct and the stops but not as well as you like you can upgrade pads such as hawk XP or XP+. A bit of a warning, carbon ceramic pads like these while stopped really well with a high coaficiant of friction dust really bad. The next upgrade from here would be into one of my 4 or 6 piston brake systems. These will stop every time on the street or track.

Correct— Mustang brakes all around with IRS rear brakes. I don't remember an L & R stamped on them, but fronts are installed with bleeder on the top, and rears are installed with e-brake springs and levers pointed towards the rear. It all looks 100% right according to manual.

In terms of being fully bedded, I am almost sure they aren't. And that's mostly what I'm asking— maybe I'm just not giving them enough time? I have probably done 15-20 hard stops (well not stops, but near stops to prevent the pads from sticking to the rotor), but nothing over 30-40 MPH. I just don't want to start stepping up the speed if something is fundamentally wrong to start with.

Balance bar is pretty much right in the middle (to start with), and I assume that probably wouldn't matter too much at this point— no matter where it is, wouldn't at least the front or the rears lock up?

I'm fairly certain everything is installed correctly, but I guess it comes down to:

a) Am I just judging them too early— i.e. they aren't bedded yet? I've replaced brakes probably 10 times in my life and I've never really felt a huge difference between nicely bedded and brand new pads & rotors, but almost all of that is on cars with brake boosters and under normal driving conditions, so maybe I just don't know what it should feel like.

b) Do I need to bleed them yet again? I know how to bleed brakes pretty well, and have never seen a leak, but are these brakes especially difficult to bleed in general?

c) Should I be able to lock up the tires with the standard Mustang brakes? Feels like a dumb question because I can't imagine these brakes aren't sufficient to lock up the tires in a car with this weight, but maybe I'm wrong. The car is actually stopping fairly well, but with extreme brake pressure I would assume it would be very violent and sudden with tires making all sorts of noise.

I guess it's more of a question of what I should expect— should I be able to lock up the brakes in the first few test drives with extreme pedal pressure, or is that not something to expect until they've been properly worn in?

[egchewy79]

I'm experiencing this exact issue with my stock brake setup on my roadster go kart. I've bled a few times. Several hard near stops from 30mph. Nice bluing of the rotor with even pattern, but still can't lock them up by standing on the brake pedal. I'm thinking of swapping to hawks pads. I assume that I shouldn't even mess with the balance bar until the pads are changed, correct?

[Gordon Levy]

a) they are probably bedded or close if you have that many stops on them. Manual brake do take more effort but they should stop well and be controllable without having to "stand" on them. You may never really lock them up unless the pads start getting hot and unto their sweet spots.
b) breeding again never hurts
c) see last half of a.

[Fman]

Correct— Mustang brakes all around with IRS rear brakes. I don't remember an L & R stamped on them, but fronts are installed with bleeder on the top, and rears are installed with e-brake springs and levers pointed towards the rear. It all looks 100% right according to manual.

In terms of being fully bedded, I am almost sure they aren't. And that's mostly what I'm asking— maybe I'm just not giving them enough time? I have probably done 15-20 hard stops (well not stops, but near stops to prevent the pads from sticking to the rotor), but nothing over 30-40 MPH. I just don't want to start stepping up the speed if something is fundamentally wrong to start with.

Balance bar is pretty much right in the middle (to start with), and I assume that probably wouldn't matter too much at this point— no matter where it is, wouldn't at least the front or the rears lock up?

I'm fairly certain everything is installed correctly, but I guess it comes down to:

a) Am I just judging them too early— i.e. they aren't bedded yet? I've replaced brakes probably 10 times in my life and I've never really felt a huge difference between nicely bedded and brand new pads & rotors, but almost all of that is on cars with brake boosters and under normal driving conditions, so maybe I just don't know what it should feel like.

b) Do I need to bleed them yet again? I know how to bleed brakes pretty well, and have never seen a leak, but are these brakes especially difficult to bleed in general?

c) Should I be able to lock up the tires with the standard Mustang brakes? Feels like a dumb question because I can't imagine these brakes aren't sufficient to lock up the tires in a car with this weight, but maybe I'm wrong. The car is actually stopping fairly well, but with extreme brake pressure I would assume it would be very violent and sudden with tires making all sorts of noise.

I guess it's more of a question of what I should expect— should I be able to lock up the brakes in the first few test drives with extreme pedal pressure, or is that not something to expect until they've been properly worn in?

FWIW, I rode in a forum members mk4 back in June who is running a 427 with Mustang brakes... I actually asked him to do a hard stop so I could see how the Mustang brakes worked... he locked them up with no issues. He had no special pads or rotors, Wilwood pedal box, no power brakes and all Mustang parts that were sent with the car.

[Alphamacaroon]

Looking at the front rotors, the machining score marks don't appear to have changed at all— there is no wearing, smearing, or bluing yet. I would assume there would be some wear by now after a few stops? I think I'm just going to try bleeding them again. I'm going to try a reverse bleeding this time and see if that helps. Will let you know how it goes.

[NAZ]

Bleeding won't hurt but if you have a solid pedal it ain't gonna help either. Put a pressure gauge on the front / rear systems and see what you can get on each with a firm push like a panic stop. There are a variety of ones to choose from, here's just one example: https://www.speedwaymotors.com/Wilwood-260-0966-Brake-Caliper-Pressure-Gauge-0-1500-PSI,138768.html

Stop guessing and start troubleshooting.

[ggunter]

I have the same issue of poor braking only I have a hard pedal when I push it. If you can push it to the firewall you almost certainly have some air still in the system. With the Wilwood dual master cylinders I had the same problem with air and someone on the forum said to open one front and one rear at the same time to make sure all air was expelled then the other side and that part worked to give me a better pedal. I haven't done enough bedding to make a determination of changing pads yet but so far they are not good. 12 miles around the neighborhood. Where I live it is hard to go go karting without drawing too much attention from the cops. So when I put the body on firmly I'll make another attempt to bed the brakes.

[Alphamacaroon]

Bleeding won't hurt but if you have a solid pedal it ain't gonna help either. Put a pressure gauge on the front / rear systems and see what you can get on each with a firm push like a panic stop. There are a variety of ones to choose from, here's just one example: https://www.speedwaymotors.com/Wilwood-260-0966-Brake-Caliper-Pressure-Gauge-0-1500-PSI,138768.html

Stop guessing and start troubleshooting.

I have troubleshooted— that's why I'm asking for other people's experiences to understand if I do have a problem, or if it's actually normal. Seems like I've heard valid opinions on both sides. Either the brakes are not installed correctly— they are. Or there is a leak— not that I can see. Or there is air in the line— maybe, maybe not. I can't think of anything else, other than bad pads and rotors (which I don't suspect). I guess one other possibility is that there is junk in the line— but I assume that a softer than expected pedal would not be a symptom (probably exactly the opposite).

I could definitely try one of those pressure gauges, but pardon my ignorance— how does that actually work??? I don't see any sort of bleeder on it, so how do you evacuate the air from the nipple and gauge inlet? I guess I can read about it online, but it doesn't make logical sense— I guess they sell them, so I guess they work?

[Alphamacaroon]

I have the same issue of poor braking only I have a hard pedal when I push it. If you can push it to the firewall you almost certainly have some air still in the system. With the Wilwood dual master cylinders I had the same problem with air and someone on the forum said to open one front and one rear at the same time to make sure all air was expelled then the other side and that part worked to give me a better pedal. I haven't done enough bedding to make a determination of changing pads yet but so far they are not good. 12 miles around the neighborhood. Where I live it is hard to go go karting without drawing too much attention from the cops. So when I put the body on firmly I'll make another attempt to bed the brakes.

Yeah, I think I'm exactly in the same boat. The ability to press it into the firewall seems like the main villain here. Even though it takes a lot of effort to get it there, I don't think it should be possible. I've read others who have mentioned open the front and rear at the same time as well, but it didn't quite make sense to me— since they operate on separate MC's why would that make a difference? Is it because of the balance bar and you can't fully depress the pedal if one MC is pressurized and the other isn't?

[NAZ]

Mechanical brakes require more foot pressure than power brakes BUT it's not like you have to push excessively hard to get the brakes to lock up. Brakes turn kinetic energy into heat energy by way of friction. Friction is increased by the clamping force of the calipers and by the pad compound coefficient of friction. Caliper clamping force is a product of the pressure times the total piston area and easily calculated.

If you have sufficient clamping force and can't lock up the brakes on one of these light cars using OEM calipers and rotors, then the most likely suspect is the pad compound. The best compounds for street cars are those that don't requiring building heat to get enough torque to lock the wheels. If you have high temp racing pads they may not provide enough torque to lock the wheels when cold. So if you have systematically troubleshooted your poor brake performance and everything checks out -- change to a pad compound that provides high torque when cold.

Both Gordon and I have provided a recommendation for pad compounds that will work on a street car.

[Alphamacaroon]

Mechanical brakes require more foot pressure than power brakes BUT it's not like you have to push excessively hard to get the brakes to lock up. Brakes turn kinetic energy into heat energy by way of friction. Friction is increased by the clamping force of the calipers and by the pad compound coefficient of friction. Caliper clamping force is a product of the pressure times the total piston area and easily calculated.

If you have sufficient clamping force and can't lock up the brakes on one of these light cars using OEM calipers and rotors, then the most likely suspect is the pad compound. The best compounds for street cars are those that don't requiring building heat to get enough torque to lock the wheels. If you have high temp racing pads they may not provide enough torque to lock the wheels when cold. So if you have systematically troubleshooted your poor brake performance and everything checks out -- change to a pad compound that provides high torque when cold.

Both Gordon and I have provided a recommendation for pad compounds that will work on a street car.

Thanks NAZ! I think I have at least confirmed that the brakes aren't operating as they should (or at least how I think they should)— first step is admitting you have a problem :D Next easiest step (I think) is to confirm they really are bled properly— I'll do that either by just doing a more thorough job or trying some different methods and seeing if it improves and/or getting one of those pressure gauges like you mentioned. If that doesn't work, then I'll certainly look at upgrading pads as a next step.

[NAZ]

Jim, just to give some contrast to the subjectivity around evaluating brake performance -- I just calculated the pedal pressure to achieve 800 PSI line pressure on my front brakes and it's all of 80 lbs of foot force which I consider moderate. 800 PSI locks the tires on my car and the clamping force is 4,040 lbs on the pads. With Wilwood pads (I tried a couple compounds) I couldn't lock the wheels up with 1,200 PSI when the brakes were cold and that was 120 lbs of foot force which is not acceptable to me.

Update: I saw a note from my initials testing of the Hawk DTC-50 compound and before bedding I could lock up the brakes on the street at 400 PSI line pressure. So, read that as "pad compound makes a significant difference".

[Alphamacaroon]

Jim, just to give some contrast to the subjectivity around evaluating brake performance -- I just calculated the pedal pressure to achieve 800 PSI line pressure on my front brakes and it's all of 80 lbs of foot force which I consider moderate. 800 PSI locks the tires on my car and the clamping force is 4,040 lbs on the pads. With Wilwood pads (I tried a couple compounds) I couldn't lock the wheels up with 1,200 PSI when the brakes were cold and that was 120 lbs of foot force which is not acceptable to me.

Update: I saw a note from my initials testing of the Hawk DTC-50 compound and before bedding I could lock up the brakes on the street at 400 PSI line pressure. So, read that as "pad compound makes a significant difference".

Wow— yeah that is very surprising and unexpected difference. I'm on the stock included pads and standard Ford front and rear (IRS) brakes. So I guess I'm wondering what is "normal" for those? Fman mentioned that the Ford calipers and the stock pads will lock up on an MKIV, so I would assume it would be somewhat similar on the Coupe (granted it probably weighs a bit more)? So I guess that's what I'm basing my "normal" on at the moment— unless someone has a different experience with this specific setup? NAZ, am I understanding correctly that you have the Wilwood calipers?

(P.S. I'm calling them Ford calipers (not sure they are actually made by Ford), because I think at least the rears actually come from the T-bird instead of the Mustang. At least that's what FF told me.)

[NAZ]

Yes, I have Wilwoods all around. 12.88" front rotors and 12.19" rear, and the car weighs a but over 2,500lbs in race trim with me in it.

[Nigel Allen]

Hi Jim,

I posted a version of this on the other forum for a member with the same problem-

Once the pedal is firm, then you can tick off the bleeding as done. No amount additional bleeding will improve braking performance. Getting the balance correct certainly will squeeze any last bit of braking efficiency out.

In my case, Hawk HP+ solved my problem. Although now I have a dust problem. You can even smell the dust when driving. I swear if brake pads still had asbestos in them, I would be dead in a month. Seriously though, the Hawks ended my woes. They are still manual brakes that require more than a big toe, but are now very effective. There are other options besides Hawk. It is possible that FFR has sent different pads with some kits. That would certainly explain how some seem to have acceptable brakes and others not. Mine were so woeful that I really needed a wider pedal so that I could put both feet on it at once (reminded me of Elwood from the Blues Brothers)

Another option is experimenting with smaller bore master cylinders. My expectation is that a smaller bore would suffice. A smaller bore = more braking pressure and better modulation/ feel, but with more pedal travel (pedal travel is bugger all on the standard 0.75 MC). This is only my theory and realistically is a lot more work then changing the pads to a more suitable compound, especially with the body on.



Helping you spend your money.

Cheers, Nigel

[ggunter]

I just ordered a pressure gauge and will measure line pressure at the calipers when it gets here next week. I have the three link rear. What brakes do FFR supply with the kit? Are they Mustang or T Bird and what years. I have to tell you the first time I stepped on the brakes I almost panicked because they were almost non existent. They have gotten better and I have 12 miles on the chassis with emphasis on bedding the brakes on the last six miles. But they still suck and no matter how hard I push that pedal they will not lock up. I hand checked the heat in the rotors and they were all about the same, so, barring any pressure restriction it looks like pads are in my future so that's why I would like to know what aftermarket car they will fit. Thanks again for all your help.

[AC Bill]

If there is air in the system still, the pedal should get firmer, and not travel as far, after pumping it several times in a row.
There is also the rare case of fluid in the m/cylinder actually bleeding past the internal seal, as pressure is applied.

[Ducky2009]

I had the FFR supplied (Ford) front calipers and equivalent rear, with the dual Wilwood master cylinders. After bedding the brakes and continuous driving (600 miles) I still couldn't lock up the wheels. When I pulled the body to paint, I added vacuum power brakes and a single Ford master cylinder. I hadn't see any posts about replacing the pads with Hawk HPS up till that point. Still have the supplied pads but get a lot of brake dust on the front wheels. Getting ready to change pads now, only because of the dust.

EDITED: I always had a firm pedal from the start.

[Erik W. Treves]

Like others have stated you still have air in the line - I have the exact same set up and the pedal is FIRM... the supplied pads are, well, not great - I swapped to yellow stuff EBC pads and while dusty brings the car to a stop in no time at all.

[sread]

I see nobody has mentioned the importance of quality rotors yet. The rotors are just as much of the friction equation as the pads. Different metallurgy and machining techniques can also make a huge difference in brake performance. While you certainly need to be sure the system is installed, adjusted, and bled properly I bet you will see a big change with a pad/rotor swap. A number of people on here have reported outstanding results using the Powerstop rotor and pad packages which are priced very reasonably.

[ggunter]

I see that there are quite a few car owners who complain about the poor stopping ability of the supplied pads. Curious as to whether FFR is taking note of this and why they would supply a brake combination that is inadequate in my eyes. They seem to be much better than that. I will check my line pressure at the calipers once my gauge arrives, but I'm betting its pretty high with the amount of force i have put on it to try and lock the wheels. I have installed many sets of brakes in my lifetime and know and understand bedding the brakes but I never had any brakes that were as wimpy as the ones on my car. We shall see.

[Erik W. Treves]

the stock pads are ...ok ... I track my car and drive a bit aggressively so I upgraded - but it does come at a cost - high dust and wear...the stocks pads are not unsafe by any stretch. The bigger thing is that they are manual brakes vs power - so there is that perspective.

[Nigel Allen]

I really am convinced that there must be variations in the brake pads that FFR sends out with the standard braking package. Like others have reported, mine were terrible to the point that I cant think of another light or heavy vehicle I have driven with brakes as poor. How can one person have a good experience with the stock pads and another not?

As part of the licencing process, my Mk4 was put on a brake performance testing machine that tests all wheels independently. I was pressed back in my seat to apply enough pressure to stop the rollers. Not a good look, but just passed. The testing guy let me off as he expected that I hadnt bedded them in. I had. The brake testing machine also confirmed that the balance was satisfactory. I vacuum bled my brakes and have not had to bleed again as I have always had a rock solid pedal.

If everyone is running the same components in the pedal assembly, and calipers, then in my mind it can only be the pads or rotors. During the build, I first de-greased and then washed my rotors in hot soapy water to remove protective oils. Then finished off with brake clean. I have no experience in metallurgy, so cant comment on material used to manufacture the rotors. The finish on them looked like any other rotor on new cars I have purchased, and they definitely had no oil / protective coating on them.

Is it possible for brake pads to deteriate with age? Mine sat for 7 years whilst I built the car.

Otherwise, I can only see pad compound as the variable. Thoughts?

Nigel

[NAZ]

There are literally a couple thousand commercially available brake pad compounds and changing the amount of one constituent by as little as 1% can make a difference in performance. It's not good enough to simply say that my pads are the stock pads or OEM pads as there may be different compounds for different model vehicles from the same manufacturer even when the same calipers are used across two or more models. The best way to compare pads is by the DOT edge codes. A service tech that replaces brake pads is supposed to ensure the new pads match the same code as that originally supplied by the manufacturer. Substitutions can affect brake performance and balance. Edge codes can give an idea of cold and hot braking performance. Similar to how tire tread wear codes give an idea about traction.

If you're not familiar with edge code (they've been around for a long time now) here's a chart that helps to explain them. If this is exciting then you'll want to learn about the latest change in codes that are important to those who live in CA and WA. http://faculty.ccbcmd.edu/~smacadof/DOTPadCodes.htm http://www.safebraking.com/decrypting-brake-pad-edge-codes/

[ggunter]

So continuing the brake performance issue. What year ford product are the pads on the MK IV? I see 88 TBird for the rear is that correct? I assume some Mustang for the front. Can anyone tell me what they are ? I'm probably going to change out to something more aggressive because I see Ducky above he has 600 miles on his and still not thrilled. I don't care about dust, I want this baby to stop when the binders go on. I don't want sphincter constriction when I need the brakes to work.

[Alphamacaroon]

This has been a really amazing discussion— super interesting to hear all of the differing (and similar) experiences, and I have learned a lot! Update on my end:

Pulled off the wheels and have noticed some interesting wear on the front rotors. It only seems to be wearing on the outer half only:

139479

I guess it confirms that my pads are not being fully utilized (regardless of their compound). So I guess this means that the brakes probably aren't quite bedded yet, right? But then the next thought becomes— are they not properly bedded because I still have air in the lines? Anyway, I re-bled them and will see if it makes a difference. Any other thoughts or ideas?

[Alphamacaroon]

One other interesting thing I have noticed is that there is a fair amount of play in the sliding portion of the caliper— like the slide pins are slightly undersized when compared to the holes. The slide pins themselves are properly torqued, so I know they aren't loose, but they don't seem to have a very tight tolerance within the holes. My guess is that this is probably one of the reasons for the uneven wear. Is that something I should be concerned with? I feel like a small amount of play is normal, but maybe I'm wrong. Here's a video if you're curious:


https://youtu.be/i3il7jQ_E6w

My new theory is that these brakes are probably on the cheap-side with low tolerances, and because of these low tolerances, the caliper doesn't engage perfectly square to the rotor (i.e. the play in the pins and holes causes some deflection when it's put under clamping force). And because of this uneven clamping force, that maybe these brakes take an especially long time to bed, because the pads need to be worn down to the point where they become square to the rotor surface. Thoughts?

[Ducky2009]

Are both front rotors this way? Can you see a gap between the pads and rotors on the inner area?

Measure the rotors at the outer edge and inner (smallest surface near the hub/lugs) edge. If they measure differently, replace the rotors. If they are the same, inspect the pads and calipers. Are the pads the same thickness across the entire pad. Are the calipers mounted squarely? Is the caliper bend?

[Alphamacaroon]

Are both front rotors this way? Can you see a gap between the pads and rotors on the inner area?

Measure the rotors at the outer edge and inner (smallest surface near the hub/lugs) edge. If they measure differently, replace the rotors. If they are the same, inspect the pads and calipers. Are the pads the same thickness across the entire pad. Are the calipers mounted squarely? Is the caliper bend?

Measure as-in width, like with a micrometer? Not sure I have one with a large enough throat. Checked, re-checked and triple checked the calipers— they are properly torqued, and mounted as square as can be (they had a perfectly clean mating surface). From all outward appearances the calipers look fine (other than the slide pin tolerances I mentioned above). I thought maybe I screwed up and switched the inner and outer pads, but I checked and they appear to be correctly installed. Happy to post pictures if someone wants to double check my work.

Any thoughts on the slide pin tolerance?

[NAZ]

They seem a bit loose and may cause some noise but I doubt they will cause uneven contact with the pad / rotor. That's more likely to happen if the pins lock up and are not free to move (usually caused by lack of lube, rust, dust, etc.). But if you truely are not getting even pad to rotor contact on both sides that's something you'll want to address. It's sometimes hard to tell on new rotors but if you take a jumbo size magic marker to the rotor you can easily see how well the pads contact the rotor. The marker only leaves a very thin film on the rotor and will quickly wear by simply dragging the brakes while driving halfway down a typical city block.

[Alphamacaroon]

They seem a bit loose and may cause some noise but I doubt they will cause uneven contact with the pad / rotor. That's more likely to happen if the pins lock up and are not free to move (usually caused by lack of lube, rust, dust, etc.). But if you truely are not getting even pad to rotor contact on both sides that's something you'll want to address. It's sometimes hard to tell on new rotors but if you take a jumbo size magic marker to the rotor you can easily see how well the pads contact the rotor. The marker only leaves a very thin film on the rotor and will quickly wear by simply dragging the brakes while driving halfway down a typical city block.

Okay, I'll try the marker and let you know, but just by feel I can tell that part of the rotor is starting to smooth out (the outer edge) but the inner portion is still rough to the touch from machining. If it is wearing unevenly, what should I check for next? Pins have been lubed with caliper grease and retaining clips appear to be installed correctly.

[Erik W. Treves]

are you sure you have the pads in correctly? not sure which pads you have but there is normally an outboard and an inboard - just asking is all... with the caliper off I would be interest in seeing if the disk is centered in the bracket

[Alphamacaroon]

Yep, I just checked that yesterday— pads appear to be installed on the proper sides of the caliper. The disk appears to be nicely centered in both axis. The wheel turns very smoothly when the brakes are released (no excessive dragging or contact at any point), and the pads do cover most of the rotor from an overlap perspective (i.e. they overlap the rotor from about as close as you can get to the center of the rotor, all the way to the outer edge) so from all outward appearances the pads look like they should be evenly contacting the rotor across the entire surface. But in practice they don't appear to be applying the same pressure equally from center to edge.

Been reading more online about other people who have reported similar problems (on different cars), and the answer almost always seems to be: wait a bit longer for the brakes to bed. And that seems to resolve most people's problems. So maybe I'm back in the "give it more time" camp. I suppose it literally could be an issue with some cheaper brands of pads (or even certain manufacturing runs) where the pad compound isn't perfectly parallel to the backing surface— you just need more time for the pads to get worn down to become perfectly parallel to the rotor. ¯\_(ツ)_/¯

I'm definitely not a master mechanic, but I've done different brakes on different cars enough times in my life where I consider myself "relatively experienced" and in most cases I've found there isn't a lot of wiggle room— they either work pretty well, or it's blatantly obvious you did something wrong. Still haven't 100% convinced myself I haven't messed something up ;) but after checking and re-checking, and using my past experience as a guide, they look like they should be very happy brakes. That's why I keep going back to this "what is your experience?" question — it seems like maybe there are some general "issues" if not idiosyncrasies with these standard brakes that need to be resolved or at least documented. It looks like I'm not the only one to have had some head-scratchers with these puppies.

[NAZ]

Jim, I've changed a lot of brakes over the last half-century; mostly street cars when I was a Ford Service Tech and race cars, off-road vehicles, motorcycles, even industrial applications outside of Ford. While bedding the brakes improves performance I've never ever seen it make a night and day difference or fix a problem where you couldn't lock the wheels on cold brakes (which is absolutely essential on a street car). But again, without knowing what pressure your front and rear is operating at it's hard to compare what you're experiencing to what you should expect. Remember, we're here on the other end of a computer and you're there dealing with a problem so it's hard for us to help diagnose the issue from afar. But if you are sure everything is assembled correctly and no mistakes, my prime suspect is pad compound.

[Alphamacaroon]

Couldn’t agree more NAZ— that’s the whole reason I came here. I’ve never seen a big difference between bedded and brand new brakes either, so what I know and what I can see doesn’t add up to what I’m experiencing. That’s why I’m hoping to find some answers.

It may very well end up being pad compound related, but right now what I’m seeing is that only half of my brake pad seems to be doing any real work. Wouldn’t it make sense to try to understand that problem first? Any compound that is only working at half its capacity is probably going to be considered unsatisfactory.

I think this thread started as “my problem” but what I’m starting to see is that this may actually be a common problem with these brakes. Maybe I did end up installing something incorrectly, but if I did, I’m not the only one. So maybe there’s an opportunity to help others in the future? And that future might be to convince FFR that the included brake pads aren’t sufficient and to move to something better. But they’ve been doing this for a while and my inclination is to give them the benefit of the doubt until all other ideas have been exhausted.

I will order a pressure gauge and let you know what I find.

[NAZ]

It may very well end up being pad compound related, but right now what I’m seeing is that only half of my brake pad seems to be doing any real work. Wouldn’t it make sense to try to understand that problem first? Any compound that is only working at half its capacity is probably going to be considered unsatisfactory.

Jim, did you use the Magic Marker trick and after dragging the brakes for a couple hundred feet did the pad contact show most of the pad on each side of each suspect caliper was contacting the rotor? If so, go to the next step – pressure check.


As for pad contact area (the highlighted sentence above), that has no real effect on locking up the brakes. I know that is counter intuitive, but trust me on this for now and I can explain later. However, a significant amount of the pad contact void at the top or bottom edge points to a possible problem of the pads or pistons binding and not applying full clamping force to the rotor, and that WILL make a difference. So, if that’s what you find, that needs to be addressed now.


The caliper is held in alignment with the rotor by the mounting bracket(s) and in your case, the slide pins. A bent bracket or debris between the bracket mating surfaces can affect alignment. The piston(s) usually have enough clearance that they can cant slightly in the bore to allow the pads to contact the rotor squarely with a small bit of misalignment of the caliper, but this is a limited range of misalignment adaption. And the clearance in the slider pins will also allow some freedom of movement to adapt to slight misalignment to the rotor. So very small misalignment with the rotor is usually not an issue. But if a piston is binding in the bore it may cant and apply unequal pressure on the pad and diminish the total clamping force. This may show up as a pad not being square with the rotor and on in-service brakes you will see uneven wear.

[Nigel Allen]

Hi Naz, Jim,

FWIW, I had the same partial contact issue with my supplied pads as Jim describes. More driving / braking did increase the contact area as the pads wore to match the disc, however the braking performance was still very ordinary. This was exactly the same issue for a colleague who built a Mk.3 at the same time. We switched both cars to softer Hawk pads and confirmed the correct bias front to rear. No more problems.

It will be cool to know what brake pressures the 0.75 Wilwood MC's exert.

Regards,

Nigel

[Alphamacaroon]

Update: I'm still waiting on the pressure gauge, but I already had the wheels off and figured I would just do another bleed while I was at it (I tried a reverse bleed this time). I was also able to get the car to a place where I could do a serious job of trying to bed the brakes at higher speeds. Both of those things seem to have made a big difference. I haven't had a chance to check closely but it appears to have fixed the partial contact issue— I don't see the marker line anymore (at least at first glance).

I still wouldn't call them "race car" brakes, but they feel on the acceptable-ish side— switching to a new compound would probably seal the deal.

So where does this leave us? Honestly I'm not quite sure. I didn't see any noticeable air come out from the latest bleeding session, so it's hard to say how much that helped, but with the reverse bleed I wasn't in a position where I could see things very well. My guess is that the high-speed bedding probably did more to wear the pads down parallel to the rotors and that made a big difference. But who knows.

My theory is that there is still a general "issue" with these pads and calipers in that they take a much longer time to bed than what most people will be used to. And also unlike other brakes (and even worse) they are borderline dangerous until they are bedded— like another poster mentioned, I also experienced a moment of sheer panic when I tried to stop the first time and it's a good thing I was going very slow, straight and level, and nowhere near anything I could hit. I've track raced cars with completely manual braking systems before, so I don't think it was a case of not understanding how different they feel from assisted systems. And while my system might not have been 100% air-free (still not entirely sure) I certainly didn't have a glaringly soft pedal that would have caused me any concern before trying my first stop.

I guess I would end with this: I feel like I have enough knowledge about what a safe manual braking system should look like, feel like, and act like (at least as much as your average builder) and I was extremely surprised and shocked at how bad they were at first. And it seems like other builders have come forward to express similar experiences. So it's probably safe to say that many new builders will also probably be taken by surprise when they try to stop the first time.

At a minimum it might be nice for FFR to address this as a warning in the manual (i.e. these brakes might take much longer to work than what you're used to)? I exercised an extreme amount of caution with a wide safety margin in my first go-kart test and I was still pretty spooked by the experience. Things have definitely improved today, but it worries me that there is no smoking gun.

[Alphamacaroon]

Update #2:

Well, even though the brakes feel a lot better, I can confirm that they are definitely not working at full capacity. I finally took the wheel off today and noticed my pen mark is still there (must have been hidden behind a spoke). It's hard to tell from the picture (the HDR camera captures a lot of detail), but the pen mark on the inner portion of the disk is much darker (i.e. most of the brake pad seems to be contacting the outer edge of the disc). I did get my pressure gauge, but of course it has the wrong threading for these bleeders (made for Wilwoods), so it will probably take some more time to get that ironed out, but again, the pedal feels very firm now. (Incidentally, does anyone know what the thread size is for these bleeders?)

Was able to get a clear shot of where the pads contact the disc and can't see any sort of gap or anything else wonky. Does anyone else notice anything strange?

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[NAZ]

Jim, if that thin light black line is you magic marker line, that's not the way I do it. I use a extra large chisel point marker like this: https://www.amazon.com/Marks-Chisel-Washable-Marker-24158/dp/B000N47FGK/ref=pd_lpo_229_img_0/147-8454190-1048748?_encoding=UTF8&pd_rd_i=B000N47FGK&pd_rd_r=85e74ffb-6ffc-4e3c-b0b0-c70912d9d0cb&pd_rd_w=yeHCH&pd_rd_wg=S8mo5&pf_rd_p=7b36d496-f366-4631-94d3-61b87b52511b&pf_rd_r=YMQPS9T5DVGD15VXHRYZ&psc=1&refRID=YMQPS9T5DVGD15VXHRYZ I put a thick band of ink about an inch or more wide on the disc surface, You can also use Dykem but only machinists and fabricators seem to use this or even some spray paint will work but is hard to control overspray. However, from your photo it appears you have burnish marks on at least half the surface of the disc on the side you can see in the photo. If the other side looks the same, burnished on half the surface favoring to outer diameter then it's not likely you have anything binding.

The amount of pad contact will not affect the amount of friction and if the contact patch is favoring the outer diameter that will not affect the brake torque. Friction is not dependent on surface area contact -- clamping force and pad coefficient of friction determine the friction (see Amontons laws of friction). The pad contacting the outer diameter gives the greatest mechanical advantage so you're not loosing brake stopping effectiveness even if you don't have full pad contact. So in short, uneven pad contact will not keep you from locking your wheels. The pads will wear in with time and having more pad contact will help heat transfer and increase the life of the pad.

Once you get your pressure readings you'll be able to determine with certainty what the problem is.

[Alphamacaroon]

Got it. Thanks NAZ— I'll see if I can find the right adapter and report back.

[mswisher]

One of you pictures seems to show a gap between the pad and the rotor. This may be an optical illusion, but I do have one more suggestion: Measure the thickness of the rotor in three places on the same radial line. Once near the hub, once in the middle and once near the edge. If the rotor wasn't machined properly it might act as you are describing.

[CPThack]

My Roadster has been on the road for 6 years but I had the weirdest brake problem this summer. It's an MK4 Complete Kit with all the stock brake components that come from FFR, PBR in the front and mustang brakes in the rear. Only recently did I discover that if I gently rest my foot on the brake, it will slowly compress all the way to the floor. However, if I push it with a normal pace it will firm up and stop quickly. This even happens when parked so I can recreate this action over and over. I know it's not an air/bleeding issue because I have the CNC Reservoirs with the pressure cap and I've pushed a ton of fluid through them just to be sure. I even took the calipers off to point the bleeder valve straight up and still no bubbles. Could I have some weird issue with the master cylinder? I'm all out of ideas, but need to fix it this winter.

[Alphamacaroon]

My Roadster has been on the road for 6 years but I had the weirdest brake problem this summer. It's an MK4 Complete Kit with all the stock brake components that come from FFR, PBR in the front and mustang brakes in the rear. Only recently did I discover that if I gently rest my foot on the brake, it will slowly compress all the way to the floor. However, if I push it with a normal pace it will firm up and stop quickly. This even happens when parked so I can recreate this action over and over. I know it's not an air/bleeding issue because I have the CNC Reservoirs with the pressure cap and I've pushed a ton of fluid through them just to be sure. I even took the calipers off to point the bleeder valve straight up and still no bubbles. Could I have some weird issue with the master cylinder? I'm all out of ideas, but need to fix it this winter.

That is really weird... First thought would be a tiny leak in the seal of one of your MCs, but then I think that'd be pretty clear because your legs would be wet with brake fluid. When this happens I assume you can see fluid being pushed back into the reservoir? The next thing that popped into my mind was "check valve???".

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Not sure if this is how Wilwood MCs look internally, but it sounds like what might be happening is that maybe the seal to the "Inlet (Reservoir)" isn't fully closing off unless there is a certain amount of force on the pedal? It seems weird to me, but maybe it's normal?

[ggunter]

Took my car out last saturday and put 65 miles on it with many high speed stop, probably30, and the brakes improved about 50% of what I think they should be. Still cannot lock them up but under very hard pedal pressure they do stop much quicker than in the beginning. Iv'e never seen pads take so much to bed in. They may come in over time but I'm not waiting for over time. I would like to try hawg pads but can't find them for the Mustang brakes.

[Alphamacaroon]

Took my car out last saturday and put 65 miles on it with many high speed stop, probably30, and the brakes improved about 50% of what I think they should be. Still cannot lock them up but under very hard pedal pressure they do stop much quicker than in the beginning. Iv'e never seen pads take so much to bed in. They may come in over time but I'm not waiting for over time. I would like to try hawg pads but can't find them for the Mustang brakes.

Sounds pretty much 100% like my same experience. Good to hear I'm not the only crazy one! :D

[johnnybgoode]

ggunter. Not sure what your rears are but I've got the 88TC 45mm/10" rears and could not find HPS (D347) pads to fit (have HPS on front single pot 60mm GT calipers) so went with EBC Green Stuff which I have had very good luck with. They have a special break-in compound that helps them bed in quite quickly and have good initial bite. I tried a set of Porterfield but had less bite so went back to the EBC GS. Once I got the rears sorted out I was much happier with the overall braking performance. There was a really good thread on brakes on the other forum a few years back that you might want to do a search for. Good Luck. Scott

https://ebcbrakes.com/product/greenstuff-brake-pads/

found it.

https://www.ffcars.com/threads/brake-bias-concern-and-a-warning-for-safety.245120/