Weak rear brakes

JDMac34

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I have a 2002 Mustang V6 that I'm turning into an autocross car. My ABS system has always seemed to kick in way earlier than expected and required me to really lay into it to actually get better braking. I tried removing the ABS fuse and did some testing the other day and the front wheels would lock up a lot easier than I expected. I tried to get the rear tires to lock up and couldn't. I bought this car last year and the guy before me put new pads and rotors (generic parts store pads) on right before he sold it. I have not dug into this issue that far yet, but everything seems like it's in good condition.

At the race, I rode with another guy who had a similar car, exact same tires, autocross brake pads, and he was able to stop so much better than I was. I understand that autocross pads will have more bite, but his car was much more composed and was able to slow down much quicker without locking up the front wheels as easily. I checked my rear rotors and they were definitely hot, but I'm convinced they aren't working as well as they should.

My plan right now is to flush the brake system and maybe install new rear pads. Is there anything else that I should look for?
 

delling3

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The calipers in the rear these cars are not known to be be the best. They also have fairly small diameter rotors. You can improve things by swapping out to better brakes, but remember that due to weight transfer during hard braking, the front brakes are doing a much larger percentage of the work. Always a good idea to flush the brake system on a 20 year old car if it hasn't been done. You will likely have some moisture in the brake lines, and this will not help your braking performance either.
 

chithead

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Might want to check the hoses too - if they are cracked, could possibly be from swelling when the pressure is applied, decreasing the caliper's clamping strength. Make sure to bleed from the furthest caliper working your way up towards the front driver's side. Had a similar issue after swapping out brakes on our 98 - replaced all the hoses and started bleeding at the driver rear, then passenger rear, then passenger front, then driver front because the brake lines in the rear split over on the passenger side.
 

white95

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So.. They both hit on excellent points. The LAST thing you want is the rear brakes locking up under hard braking because you may wind up heading in a different direction. Abruptly. Ask me how I know?

5F16E76F-E0C0-43E3-9843-52B218B0ED07.jpeg

My rear brake package consists of Baer +1 rotors [13"] 43mm caliper pistons [stock is 38mm] and track day pads. The rear brakes lock up on hard braking and at a recent, rainy HPDE event my car impacted the inside wall of the track.

Moral? Too much of a good thing ain't always good without proper execution. I'm adding an adjustable proportioning valve and eventually GT500 ABS to prevent a repeat occurrence. Overkill? You bet.
 
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JDMac34

JDMac34

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So.. They both hit on excellent points. The LAST thing you want is the rear brakes locking up under hard braking because you may wind up heading in a different direction. Abruptly. Ask me how I know?

View attachment 16496

My rear brake package consists of Baer +1 rotors [13"] 43mm caliper pistons [stock is 38mm] and track day pads. The rear brakes lock up on hard braking and at a recent, rainy HPDE event my car impacted the inside wall of the track.

Moral? Too much of a good thing ain't always good without proper execution. I'm adding an adjustable proportioning valve and eventually GT500 ABS to prevent a repeat occurrence. Overkill? You bet.
Dang. Hope everything was okay with that crash.

I'm not looking to have too much rear brake so that they do lock up often, it was just an example to show that they might not be working. I'll try to flush the brake system (with high-performance DOT 4) tonight and see if I get any change.

By the way, I'll be checking out your youtube channel!
 

white95

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Dang. Hope everything was okay with that crash.

I'm not looking to have too much rear brake so that they do lock up often, it was just an example to show that they might not be working. I'll try to flush the brake system (with high-performance DOT 4) tonight and see if I get any change.

By the way, I'll be checking out your youtube channel!

It was mostly cosmetic and a great learning experience. You’re doing the right thing but I’d recommend changing those lines prior to doing so. That way you only bleed the system once.

Thank you, in advance, for checking it out. I’m still learning how to drive my car fast and I love sharing my journey. Check out @Warhorse Racing channel while you’re at it. There is a wealth of knowledge to be gained there and he will help you with your quest. He also autocrosses a “Mustang ST” as it’s affectionately known.
 
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JDMac34

JDMac34

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It was mostly cosmetic and a great learning experience. You’re doing the right thing but I’d recommend changing those lines prior to doing so. That way you only bleed the system once.

Thank you, in advance, for checking it out. I’m still learning how to drive my car fast and I love sharing my journey. Check out @Warhorse Racing channel while you’re at it. There is a wealth of knowledge to be gained there and he will help you with your quest. He also autocrosses a “Mustang ST” as it’s affectionately known.
Yep. He is the one who convinced me that I needed a New Edge!
 

Warhorse Racing

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It's always great to see another New Edge V6 being built for autocross! I appreciate you checking out my videos. White95, thanks for mentioning my channel. I was sorry to see the damage to your car. I'm glad everyone is okay.

As for JDMac34's brake issue. There's a lot of good advice in the previous posts. Inspect the calipers, hoses, and fluid to make sure they are all in good shape. If the hoses don't need changing, bleed the brakes properly to see if that's the issue. If the hoses need changing, consider SS brake hoses (if they are legal in your SCCA Category/Class).

Keep in mind that several things factor into braking performance outside of pads, rotors, calipers and fluid. Weight transfer, chassis stiffness, strut stiffness, tire pressure, and braking input degree, timing and duration are also part of the equation. The "similar" car you rode in might have had some important differences that made it more composed under braking. How cold was it when you tested the brakes? If your Falkens were cold, they would slide easily, triggering ABS.

I use OEM 03-04 Cobra brakes front and rear on all my Mustang autocross cars. None of them use ABS. I'm not a fan of the OEM GT/V6 ABS system on these cars, and pads with aggressive initial bite tend to trigger ABS the second you touch the brake pedal. I switched to the Cobra brakes because my 2000 GT (when it was an SRA car with OEM GT calipers, cross-drilled/slotted rotors, and Hawk HPS pads) tended to lock up the front brakes easily out on course (with ABS disabled). I currently run HP-Plus pads in the front and Hawk HPS pads in the rear. The HP-Plus pads have more initial bite. The HPS pads have less initial bite, but a good consistent feel.

I use the HP-Plus/HPS combination on my 1992 GT too (SRA). My 2004 IRS-swapped V6 has HP-Plus pads front and rear. All of my cars will lock up the brakes if I brake too hard, but that just lets me know I need to brake earlier on the next run.

Different pads will have different levels of initial bite. It often takes some experimenting to decide which pads work best for your driving style. Remember, you want to use the brakes as little as possible out on course.
 
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JDMac34

JDMac34

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Ah crap, I never updated this thread. My brakes felt about the same after a brake bleed (not flush).

I've been having issues with the parking brake sticking on my rear calipers, and that's been a thing since before I bought the car. I ordered Powerstop (rebuilt OEM) calipers for the rear to fix the sticking caliper. They looked so nice that I ended up ordering the fronts too. My thoughts then were that if I have the system open then I might as well switch to stainless lines, so I ordered those too.

I just had the idea that maybe the rear pads have been glazed over by driving with the parking brake partially applied. There have definitely been times when I've smelled hot brakes after a casual drive. The pads looked funny last time I had them off, which now makes sense as to why they don't perform well. I glazed a set of pads on my mountain bike, and it seems like a similar situation.

Tire Rack had a good deal on HP+ pads with the enhanced compound, so I ordered a set of those. I then thought that I might as well get a set of rotors while I'm at it, so I ordered a set of Powerstop rotors too - a classic example of the snowball effect.
 
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JDMac34

JDMac34

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I'm not a fan of the OEM GT/V6 ABS system on these cars, and pads with aggressive initial bite tend to trigger ABS the second you touch the brake pedal. I switched to the Cobra brakes because my 2000 GT (when it was an SRA car with OEM GT calipers, cross-drilled/slotted rotors, and Hawk HPS pads) tended to lock up the front brakes easily out on course (with ABS disabled).
Hopefully I don't run into this issue. Would ABS cars have different brake biasing when the ABS system is disabled when compared to a non-ABS or deleted car?
 

Warhorse Racing

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Ah crap, I never updated this thread. My brakes felt about the same after a brake bleed (not flush).

I've been having issues with the parking brake sticking on my rear calipers, and that's been a thing since before I bought the car. I ordered Powerstop (rebuilt OEM) calipers for the rear to fix the sticking caliper. They looked so nice that I ended up ordering the fronts too. My thoughts then were that if I have the system open then I might as well switch to stainless lines, so I ordered those too.

I just had the idea that maybe the rear pads have been glazed over by driving with the parking brake partially applied. There have definitely been times when I've smelled hot brakes after a casual drive. The pads looked funny last time I had them off, which now makes sense as to why they don't perform well. I glazed a set of pads on my mountain bike, and it seems like a similar situation.

Tire Rack had a good deal on HP+ pads with the enhanced compound, so I ordered a set of those. I then thought that I might as well get a set of rotors while I'm at it, so I ordered a set of Powerstop rotors too - a classic example of the snowball effect.
It is possible that the pads got glazed and weren't working as well as they should.
 

Warhorse Racing

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Hopefully I don't run into this issue. Would ABS cars have different brake biasing when the ABS system is disabled when compared to a non-ABS or deleted car?
The decision to disable ABS should be made carefully, especially if you daily drive the car. My 2000 GT has the ABS sensors removed, but the module is still in place. The brake bias feels the same as my non-ABS 2004 V6. The V6 is lighter and better balanced, so you might be less likely to lock up the front brakes on course. But pads, rotors, hoses, and braking input timing and degree will all still be important.
 
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my recommendation for you is get some cryo treated, slotted stoptech rotors and run the most agressive hawk street pad paired with either the most agressive hawk front pads, or some ebc orange stuff front pads. youll enjoy the set up. also run some dot 4. pentosin is usually the highest you can get commonly at autozone or oreillys. i personally run wilwood exp600+ , or whatever its called, but i used the pentosin for a long time before i upgraded to the wilwood fluid
 
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JDMac34

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Well, that turned into way more of a project than I was hoping for. I was adding stainless brake hoses, Powerstop rotors, Powerstop rotors, Hawk HP+ pads, and flushing the system with Prestone DOT4 Max fluid. My plan was to flush each corner with the OEM calipers before adding the new ones.

I started with the driver-side rear corner and everything went great. It flushed fine, everything came out relatively easy, and went in easily...one might say too easy. I moved to the passenger-side rear corner and the flush goes fine. I then go to remove the brake line from the rubber hose and the steel line starts to twist inside the fitting. It was too late by the time I noticed. After it snapped off, I finished removing the stuff and installed the new parts and called it a night.
IMG_5864.jpg67642511595__69267774-5B99-413F-AD01-239D7C63A175.jpgIMG_5866.jpg

Our master mechanic at work came over the next night to try and fix that. The plan was to cut and flare the old line and put a 3" elbow section in its spot. While he was working on that, I moved to the front and started to remove and replace those parts while leaving the calipers hooked up so that I could flush the system before hooking up the new calipers. I let the old calipers dangle while I waited for him to finish up.

The rear pads definitely looked used, but the fronts seemed to be in worse shape. One rotor was starting to get some hot spots and I had a pad (on another corner) with a decent crack in it. I'm not an expert with brakes, but I'd bet that's not a great thing.
IMG_5874.jpgIMG_5875.jpg

Once we thought that everything was good to go on the line fix, we did a quick bleed for the rear and checked for leaks. The driver's side bled great. The passenger's side went fine for the first couple of pumps until I heard the master cylinder run try. I was confused why it sucked so much fluid in, but added fluid and went on with the job knowing that we would have to rebleed everything again anyway. The next pump resulted in a leak from the new union fitting that was just put in. On the next pump, we heard something hit the ground that sounded like a socket was dropped. Neither of us were using sockets, so we were confused and decided to look around the garage. Sure enough, I forgot to put something in the old calipers and the pistons over-extended and one shot out.
IMG_5876.jpg

After calling myself an idiot a few times, I removed the old calipers and hooked up the new ones with new hoses while he tried fixing the new fitting. When finished, we tested the fitting again with the same result. After multiple attempts, we finally agreed that the OEM steel line was too difficult to flare and it was better to make a new line. We did that and it worked. The whole system was bled and good to go. I followed the break-in instructions and considered the project done.
 
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JDMac34

JDMac34

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Before, I had a weird spot in my braking with the old setup that was a little difficult to work with. Braking would feel fine as I pressed harder on the pedal, but there would be a spot (right as ABS would kick in but I wasn't laying on the pedal yet) where braking would get worse. If I laid into it, braking would get better and act as one might expect. At events, I'd have to commit to either lightly press the brake and stay above that threshold or slam on the brakes and let ABS do its thing.

The new setup will take a little bit to get used to, but I already like it so much more. The pedal still feels soft for the first quarter of travel, but hits a wall and has a much stiffer feel from the stainless hoses. The braking power is much better now. Best of all, I'm finally able to modulate the brakes! They feel much more linear and I can control how much braking force I want. The ABS kicks in at a predictable time and feels composed. Another small bonus is that I finally have a functioning parking brake in this car.

The Hawk HP+ pads do squeal a little bit when coming to an easy stop but are quiet when stopping harder than usual on the street. It doesn't bother me on this car, but I could see how somebody might not want the noise on their daily driver.

Overall, I'm a very happy camper. Unfortunately, I finished the brakes at 2:30am Saturday morning and the deadline for registration was 11:59pm Friday, so I was not able to test them on track yet.
 

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