Kboi12

Ya true, the car is still a s**t box. This brake issue has been making me question why I turned a perfect 10,000 miles NA into my racecar rather than selling it making double the profit and purchasing a new BRZ. I saw you guys make Xidas for those things. After I saw that I really got depressed.

Anyways, Ill ignore the idea that I feel that I am hitting the bottom of the MC. Maybe that's when the booster doesn't provide sufficient power to aid me in the pedal effort anymore. If you can answer this question, fabulous. How low can you press the brake pedal before bottoming it out with this MC? On my car its just a little bit lower the the level of the gas pedal. But I got to say I really do feel like I am hitting the bottom of it, like I feel like the pedal is hitting a solid wall.

Kboi12

Your comment had me thinking this. I will go in a little bit more detail here.

I ran my first Wildwood MC for 2 track days at Sonoma. I did set the pushrod on the pedal pretty close to the MC for a very aggressive brake pedal feel. There was still a little play but it was less than .2 inches. I had caught covid and lost my sense of taste/smell for weeks. So I could not smell if my brakes were fading. I was getting some pad knockback and being stupid and not thinking I decided to adjust the rod even closer so it would be easier to heal toe. I only ran it like that for one session. Then I went to Laguna Seca, at Laguna Seca that is when I felt that the pedal go soft and I was hitting the bottom of the MC and getting horrible braking. My friend did not smell any brakes. I went home, bled my brakes with the engine running. Pedal still spongy, then I checked wheel bearings, everything was good. I checked my brake pads, no difference.

Contacted Goodwinracing, they sent me a new MC. I bench bled it, threw it on. I didn't even bother bleeding the lines. Pedal came back everything felt good. I went to Buttonwillow pedal felt real solid first session but there was no bite. I thought maybe I need to bed the new pads in. I did that let the car sit for an hour and went out. Second session I was real hard on the brakes and the pedal just started getting lower and lower. Till it felt like the first MC.

Supermiata got the story and told me to add more dead play with the push rod and the MC. I went ahead and gave the pedal lots of dead play. I went for a drive on the street with race rubber and while the pedal was really low, it was enough to lock the wheels. I noticed the car was rolling back on hills more easily and the car required less gas on the highway. I do trailer a 4x4 paddock trailer though so my feelings may be off. However, when I was at the track I noticed something. When I was driving around the paddock my brakes were making the faint brake rubbing noise every rotation that it always used to when everything used to work right. Then during the sessions the pedal felt like **** but I was able to lock them a couple times. But I was mostly bottoming it out.

So I am thinking maybe the pushrod was dragging and that caused the MC to break. What you all think? I hope you have a smooth recovery LeoNA.

LeoNA

I’m running the gloc pads as well and they make a bit of noise when driving slowly. They are just moving around and contacting the rotor. The smaller pistons in the multi-piston calipers don’t retract much. It is determined by the cross section area of the square piston seal. I think we’re talking about two different op-rod adjustments.

Kboi12

Yes and I never heard that noise until I gave the rod more dead play with the MC. It used to always make that sound before I installed the MC and adjusted the rod to be more aggressive. I now am more convinced that the brakes were dragging but I still never smelled cooked brakes. So it possibly could me the MC is bad but I still have my doubts.

Looks like we are talking about two separate adjustment points. However both essentially do the same thing. If you adjust the rod at the pedals underneath the dash it effectively changes the rod length when the brake pedal is fully released.

LeoNA

Their two different rods. They are separated by the booster. The booster has a neutral position when energized. It can apply pressure to the piston in the mc even if the peddle op rod has clearance. In your case I don’t think it’s enough to keep the calipers applied but enough to not expose a port or ports to allow fluid to flow into the piston of the mc. If the calipers were not releasing you would not make one lap a Laguna. Your rotors would be cooked. I went to Laguna to dial in my system, had 1/2 a turn to much bias to the rear and the rotors were dead by the end of the day. Grooved and blue.

Kboi12

Huh, I never new that. Maybe its a good idea to install a MC when the booster has sufficient vacuum.

Grooved and blue? These were my rotors after laguna.

LeoNA

My rear rotors were much worse. Although pictures don’t really show depth well, but they do look like they were working hard. What do the rear rotors look like?

Kboi12

No good photos. Just a one a while after the day of buttonwillow. Excuse the mud, I went off bad at buttonwillow and there had to be a mud pit. ha!

emilio700

iTrader: (3)

Trying to be analytical.

Brakes don't lock even with high pedal force, possible causes:
- Insufficient booster assist? Leaking vacuum check valve or booster? But that would make pedal harder, not softer. Rule out anything booster related. It's hydraulic.
- Fade? Every symptom and condition points to fade, despite having R10/R8 BX11 on a stock power HPDE Miata which should be enough pad. Laguna Seca is hard on brakes. He'd have to be an advanced driver on 225/45 Super200's to find the limits of that hardware. So that's possible.
If the pedal comes back firm after they cool off, but then sinks as they get hot, that's fade. In such case, I'd find a way to get some 3" duct hoses to the gap under the calipers.
- Hydraulic failure? The pedal height would be erratic, not the gradual sinking with heat. Not outright failure.
- Incomplete bleeding? It would start mushy and stay mushy. Wouldn't be affected by heat. It's probably bled fine.
- Issue with pushrod preload not letting calipers and/or master reset properly. Symptoms point to this to some extent. A test would be to back off pushrod and pedal adjustment, run a session and see if brake maintain enough bite to lock wheels.

That's it, I'm out of ideas.

Forgot to ask, is this car ABS or non ABS?

Kboi12

Car does not have ABS.

Ill consider your points in the same order:
- Confident the booster is not the issue, so agreed.
- Yes, it feels like fade. Going into the first several braking zones, the pedal is nice and hard but the pads feel like they are rubbing but not biting. This is fade. Couple sessions later, the pedal begins to feel like mush. It does not come back after everything has cooled. Pedal continuous to feels like mush even after a full-bleed. Pedal only came back after replacing MC.
- Pedal height does just drop for the first 75% of travel. Then the last 25% builds some pressure. I could take my pinky finger and push down the pedal until I hit that last 25%. Little to no hydraulic pressure is built during that 75%. So maybe something hydraulic is going wrong but as a symptom of a constantly engaged pedal???
- I know how to bleed brakes. So yes, we can rule that out.
- I ran 2 days without fading issues with this setup, but I was not that hard on the brakes. I adjusted the rod on the last session on my second day at Sonoma, then took it to Laguna and immediately got the fade/pedal-mush symptoms. Changed the MC, felt fine. Went to Buttonwillow at first the pedal felt good but was fading during the first session. The pedal then became as I describe at point 3. Went home and then I backed off the pedal pushrod. I was able to lock the wheels driving around the street on the race rubber. But at Thunderhill 5 mile, it wasn't locking. Though, I only had the bottom 25% of the pedal. I then bled the car between sessions and the pedal didn't change. Possibly the hydraulics in the MC could have broken.

Now saying that the issue is in fact the MC is constantly engaging causing drag still leaves us wondering why I have little to no pressure gain for 75% of the pedal after several sessions. Bleeding doesn't fix it either. Possibly the seals of the MC got damaged because they constantly rested on the ports of the MC.

If no other suggestions come up, once I get my new MC kit from SM. I will install it and make sure there is enough clearance with the pedal and the booster pushrod.

thebeerbaron

iTrader: (1)

Have you throughly inspected your hard lines for kinks, dents, or blockages? How is the pedal feel in each corner with the one bleeder open?

turbofan

iTrader: (1)

I don't understand how you all are so confident the booster is not an issue. This sounds like booster to me. Stiff pedal, no braking power. Sounds like unboosted brakes.

Kboi12

I gave a entire inspection of all the brake lines. No kinks everything looks good. My brake pedal slave(dude who pumps the pedal) says everything feels normal.

I don't think its the booster for the following reasons:
- After turning the car off I have about 2-3 pumps before the pedal starts stiffening up. Even if I leave the car for couple days.
- If I apply constant and equal pressure to the brake pedal while the car is off and then turn the car on the pedal will sink normally as soon as the engine starts.
- If I relieve all pressure from the booster and try to brute force the pedal, the pedal actually still feels like it has little pressure for the first 50%. Still a lot harder to press.

I should be more clear with my explanation. When I say the pedal is stiff, I mean its stiff as a good brake system feels when everything is working well. Its not like I cant push further. I can, the pedal just bottoms out. I believe I think I am hitting the bottom of the MC. I even hear it hitting it if I listen closely. If I had another car with the same MC it would be nice cause I could compare pedal travel distance. Not sure if your car has the same MC, but if so, we can compare. My pedal will bottom out little bit below the level of the gas pedal.

Ill try to look for any leaks next time I see the car.

turbofan

iTrader: (1)

Perhaps the check valve going to the booster? But yes all your tests indicate a properly working booster.

Ed

LeoNA

The last time you bled the system did you see any air come out? Bleeding can be a challenge especially on the clutch system on these cars. For that reason I recently purchased a motive kit to test out. Not a huge fan of the fact that it does not separate the pressurized air and fluid but thought since their made in Gilroy I would try it.

Here is my process and system specs. I will usually do a slight bleed before every track day and a full flush once a year so I do it a fair amount. My system is a home brew because when I put it together the SPM box mount kit was not out yet. Surely the way to go and would have saved me a bunch of time. I’m using the 4 piston dynapro, r10 pads with the aluminum hat 11” wilwood disc’s and their adjustable proportioning valve. Rear brakes are the na8/nb1 with powerstop track day pads. The MC is a rabestos Na6 replacement, not the bestos part and that’s what originally drew me to this thread. Fluid is just pentosin dot 4. Currently the system works good has run in the 1:40’s at laguna with me driving 400mi round trip to the track.

I use the two person method but have had to shore up it’s short comings to make it consistent. The worst issue is closing late and air being introduced around the threads of the bleeder screws. First fix is to Teflon tape the threads of the bleed screws. It should not be below the threads, not over the ports or the conical sealing surface. It doesn’t last long before the tape is ineffective. The little willwood bleeders do wear but are relatively inexpensive. The bleeding hoses get hard over time so I use new ones often. I secure them with safety wire.

I open the proportioning valve all the way when I bleed on new fills. Here is a little disclaimer about this because a mis-adjust PPV is one of the fastest ways to get you killed on the track. Make sure you can and do return it to it’s proper location. Mark the **** and count the turns from closed first. With the reservoir caps off I will slightly overfill the res with fluid. Make sure there are no air bubbles in the res from the pour. A little finger tap for good measure. I set the car up on stands usually level or with the back a touch higher. I used to just go corner to corner with the tools but now I install a wrench at each corner with a hose that is safety wired on the bleeder screw running into a clear jar.

Start at the corner which is furthest from the MC which is the driver side rear. I have the operator pump the pedal 2-3 times between bleeds to make sure fluid is entering the system from the reservoirs. Many pedal jockeys are erratic with the pedal movement which should be smooth with a light to medium pressure and the screw should be closed before the pedal bottoms. If the screw is not open enough the fluid speed in the lines can be too low. Open too far and you will not be able to close it in time. A tap tap from a small dead blow before hand is always a good idea and pay attention to the ambient temp. Cold temps make bleeding harder. I always inspect everything visually and check mounting fasteners at this time. If your MC has an internal leak you will not be able to bleed out the air and it will be obvious. There may also be fluid leaking down the booster. Good luck.

Kboi12

I started investigating on the car itself. If I remove the Master cylinder and connect my old one without it being connected to any hydraulics the pedal has so much more travel, like we’re talking 3x the travel.

so either bad booster/or kink or clogged lines.

edit: well actually if a line was kinked then any other caliper would lock its wheels. I’m leaning towards bad booster. I will check it rn.

afm

iTrader: (3)

Or bad adjustment of the pushrod just as LeoNA suggested. A quick test for this is to see whether you can easily push fluid through the system with a Motive bleeder, since bad pushrod adjustment will block the transfer port.

Kboi12

I believe the rod is fine. I test fit it. Same issue. Pedal just stops at a certain point doesn’t want to go further. Rather then adjusting the rod cause I think it’s fine, just put some spacers between the MC and booster. Same issue pedal just doesn’t want to go further past a certain point.

afm

iTrader: (3)

I think the worry is that bad adjustment broke your MC (it can easily destroy the seals). I would try this after replacing the MC.

Kboi12

That was one of my thoughts. Not that I’m disagreeing, but, I want to know why you say the seals would break. I can only think of it as it’s always resting on open port rather then a smooth surface.

So this is where the car stands:
- Brake travel feels limited to just a little lower then the gas pedal. If I open a bleeder and push the pedal drops a lot lower. If I hookup a MC to the booster without connecting hydraulics the pedal just can drop to the floor.
- With everything connected the pedal just feels extremely difficult or impossible to press passed the gas pedal.
- I did not hear any visual leaks with the booster.
- I turned the engine on and the adjustment rod seems fine. I can easily press the MC against the booster to be flush.