Stopping is Just as Important as Going

The older I get the more concerned I tend to be with safety. Now that I have children to cart around in my vehicle, my car has to be as safe as possible, and for me that means it turns, accelerates and most importantly, stops well. I bought a 2011 Ford Flex last year to replace our undersized midsized sedan (back seat was too small, not enough cargo space for our needs). It's a great car with the twin-turbocharged 3.5L V6 turbocharged engine, it handles quite well for the big heavy car that it is, but I find that it doesn't have particularly good brakes.

In fact, on a recent family trip to Arizona, I had to do an emergency stop on the interstate that gave me even less confidence in the brakes than I already had. I literally stood on the brake pedal and I could not get the brakes to lock up the front tires and engage the ABS system. What this means is that the tires have more grip than the brakes do, which is a first for me. Even my 60's sedan with manual 4-wheel drum brakes could lock up the wheels for one or two successive stops. Granted, the Flex has 245mm section width performance summer tires while the old sedan probably had 165 all seasons and weighed a ton less, so it's apples to oranges, but it still doesn't instill confidence that the brakes are the limiting factor in the stopping power, even while not overheated.

I found out that in 2013, Ford began offering a "heavy duty" (HD) brake package on the Flex and other vehicles built on this same platform (Taurus/Explorer) to remedy the small brakes originally included with this heavy car. That's almost 5000lbs in the case of this big Flex wagon. Lucky for me parts availability is quite good in the aftermarket (read inexpensivde) and the HD brakes simply bolt right up to the earlier cars. I decided last week to order the parts from RockAuto after doing some research and pricing them out. Since the front brakes do most of the work in a panic stop, I decided also to do only the fronts. The rears on the non-HD brakes are close in size to the HD version and the only advantage I can see is for heavy towing or track use (due to the added cooling vents to prevent fade), neither of which I plan on doing any time soon, so it's a moot point. This car is strictly a family hauler for now and will do just fine without vented rear discs.

As you can see from the picture above, there's a lot of extra room inside the big 20" wheels for bigger brakes.

I pulled the passenger wheel off first and wanted to compare old vs. new. An extra inch doesn't look like that much, but every bit of extra leverage counts when braking, thus the bigger-is-better mantra for brakes. It also helps that the swept area is larger along with bigger caliper pistons for more hydraulic force as well:

Doing this job requires the removal of the old calipers, caliper brackets, rotors and splash shields and replacing them with the upgraded versions. While I was assembling I noticed that (doh!) the surface where the banjo fitting screws into the caliper was damaged and the copper crush washers would not be able to seal:

Sorry for the out-of-focus pic, I'm still getting used to my new phone ;)

I often find that manufacturers miss things like this in their QC processes. I'm assuming this actually happened between QC and packaging though because it looks like it was dropped on something that damaged it after the machining was done. Normally a bum part like this would cause the job to grind to a screeching halt (pun intended), but lucky for me I'm an amateur machinist and I had this piloted milling tool lying around that I could chuck up in my hand drill to resurface the gasket surface with:

In order to avoid getting cast iron chips into the hydraulics of the brakes, I blew the chips back out of the banjo fitting hole by fitting this blow gun to the bleeder screw hole:

Here's how the resurfacing turned out:

The surface finish is a bit chowdery because of the use of a hand drill (I was too lazy to chuck the caliper up in the Bridgeport), but it was good enough to get the copper crush washer to seal (vs. the 1/16 inch maw that was there before). The next step after screwing together the banjo fitting and torquing down the bracket bolts and sliders was to move on to the other side and repeat the whole thing again. Luckily the driver's side caliper had no damage and that install went off without a hitch. I finished up this relatively simple job (barring the banjo fitting fiasco) and bled the brakes with this handy tool I picked up from Harbor Freight years ago:

Due to my chaotic schedule, I have to do most of my automotive work alone, so tools like this compressor-powered vacuum bleeder come in very handy. The business end of the vacuum bottle attaches to the outlet of the bleeder screw and sucks fresh, air-free fluid through the line when you crack open the bleeder with the trigger engaged. Sometimes it won't work if you have a bleeder screw with loose threads because air will be sucked down through them, introducing air into the caliper cylinders, but these new calipers had nice tight fittings on them, so the setup worked brilliantly. I exchanged all of the old fluid with DOT 4 just for good measure. DOT 4 fluid, while being the same basic chemical as DOT 3, and so backwards compatible, has a higher boiling point, which helps with fade resistance under repeated heavy braking.

My favorite part about this tool pair is the refill bottle, which sits upside down in the master cylinder reservoir and solves the problem of having to constantly refill it during the fluid bleeding procedure. As the level gets below the neck of the bottle, it bubbles in just enough brake fluid to seal it off again and keep the reservoir topped off at all times (as long as there is fluid left in the bottle that is). It saves a lot of mess from the inevitable pour spills using the manual method. Here it is in action:

Once the bleeding procedure was done, I torqued down all of the bleeder screws and put the wheels back on for a test drive. At first I wasn't super encouraged that there was any improvement but as I bedded the pads into the rotors the stops got progressively stronger. After the bedding procedure and letting the brakes cool down a bit, I decided to simulate some panic stops to see if the fronts would lock up, and sure enough when you stand on the brakes, tire squall emits from the front tires just as the ABS system kicks in . I drove it around for a little while after that and now it seems to have a lot more initial bite in addition to the ability to overwhelm the tires. Overall I'm very happy with this brake upgrade, especially since I was able to do it while maintaining OEM reliability. I highly recommend this upgrade for anyone with an older Flex or Taurus who isn't happy with their braking power.

Here's a pic of the upgraded brakes sitting in their native habitat, filling up that wheel space ever-so-slightly more so than before: