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Tundra Brake Break-in and First Impressions

October 28, 2017

New brakes nearly installed, I waited anxiously to see how the replacement brake line that Steve @Wheeler's Off Road sent was mailed - was it fast, or would it be slow?

It was great - he sent it 1-day and I had it Saturday morning. Not only that, but he sent an entire brake line kit, so now I've got an extra line and set of crush washers to throw in the trail kit, in case something goes wrong on my or a buddy's truck! Thanks Steve!

Installing the line was pretty straight forward, especially as I'd done the other already. One interesting thing to note - and the reason that new lines are required - is that the stock Tacoma brakes use a line with a little "registering beak" on it (which fits into an indent in the caliper); the 13WL Tundra brakes don't. Additionally, the circumference of the interior of the banjo fitting is ever-so-slightly larger for the Tundra brakes (I hear).

At any rate, with the line installed, @mrs.turbodb came out and helped bleeding the system. A straightforward process, I started in the rear passenger, then moved to rear driver, front passenger, and front driver to ensure that the system was properly bled. Of course, the rear was good-to-go from the start since I hadn't messed with anything there, and the fronts had lots of air (needing to fill up the new lines, etc.). I made sure to keep the reservoir topped off as I went.

The process went without a hitch, mostly. One thing I discovered was that the bleeder valves on the 13WL calipers I'd gotten from Napa used a different size wrench than the old Tacoma bleeders (which are 10mm). In fact, they turned out to be 8mm, which extra-sucked, because I didn't have an 8mm flare nut wrench. Unfortunately, I'd already returned my Tacoma caliper cores, so I couldn't just grab the old bleeders and re-use them. I'll need to see about getting some different bleeders at the local Napa. Or Toyota. Or get another wrench.

System bled, it was time for the ultimate test - head out on the freeway (I-5), risking life and limb - to bed the new rotors and pads. At least I'd know quickly if I'd really screwed something up!

The bedding process, I'd learned, is a process by which you deposit a layer of pad material evenly across the braking surface of the rotor. This minimizes squealing, increases braking torque, and maximizes pad and rotor life.

Bedding in Advantages:

  1. Gradually heat treats the rotor and eliminates any thermal shock in the rotor.
  2. Burn off volatiles and moisture from the resin that is near pad surface. This will eliminate “green fade.”
  3. Establishes a layer of transfer film about a few microns thick on the rotor surface. Shearing of the film during friction is an effective source of friction force. Otherwise, when using a freshly ground rotor without the transfer film, the main friction force would come from cutting, plowing, or scoring the asperities on the rotor surface. This leads to inconsistent braking effectiveness.
  4. Mate the two surfaces to a near perfect geometrical match, so that the contact area is high, and therefore the friction force is increased.
  5. The performance of a fresh rotor/fresh pad system would be inconsistent. This is due to ever-changing structures and properties of the two mating materials. Bed-in of pads and rotor will form a stable transfer film.
  6. If bedding in procedure is not applied, a stable transfer film may not be established for a long time. In other words, the rotor surface would have to be constantly regenerating a film that is not quite stable for a long time. This effect would reduce the performance and increase the wear.

Bed-In Procedure:

  1. Make a series of five gentle slow-downs from 60 to 45mph. Do it GENTLY to bring the brakes up to operating temperature. This prevents you from thermally shocking the rotors and pads in the next steps.
  2. Make a series of eight near-stops from 60 to about 10 mph. Do it HARD by pressing on the brakes firmly, just shy of locking the wheels or engaging ABS. At the end of each slowdown, immediately accelerate back to 60mph. DO NOT COME TO A COMPLETE STOP!

Note 1: With less aggressive street pads and/or stock brake calipers, you may need to do this fewer times. If your pedal gets soft or you feel the brakes going away, then you've done enough. Proceed to the next step.

Note 2: During this process, you must not come to a complete stop because you will transfer (imprint) pad material onto the hot rotors, which can lead to vibration, uneven braking, and could even ruin the rotors.

Note 3: Depending on the pads you are using, the brakes may begin to fade slightly after the 7th or 8th near-stop. This fade will stabilize, but not completely go away until the brakes have fully cooled. A bad smell from the brakes, and even some smoke, is normal.

  1. After the 8th near-stop, accelerate back up to speed and drive around for as long as possible without using the brakes. The brakes will need at least 10 minutes to cool down.Note: Obviously, it's OK to use the brakes to avoid an accident, but try to minimize their use until they have cooled.
  2. Repeat steps 1-3 for a second break-in cycle. This may not be entirely necessary in all cases, but is good insurance to ensure a good break-in. Additionally, if you've just installed a big brake kit, the pedal travel may not feel as firm as you expected. After the second cycle, the pedal will become noticeably firmer.

After the break-in cycle, there should be a blue tint and a light gray film on the rotor face. The blue tint tells you the rotor has reached break-in temperature and the gray film is pad material starting to transfer onto the rotor face. This is what you are looking for. The best braking occurs when there is an even layer of pad material deposited across the face of the rotors. This minimizes squealing, increases braking torque, and maximizes pad and rotor life.

How'd it go?

Since I decided that the only place I could get eight, 60-10mph slow-downs, and then 10 minutes of "no brakes" was on the freeway, we headed out on I-5 at 11:00pm, hoping to find light traffic. We did, but only once we got ~45 minutes north of Seattle, near Marysville.

As we put on the hazards and started our series of slowdowns, everything seemed to be going well. The truck was stopping fine (not pulling one way or the other), and no one hit us from behind.

We did have one State Patrol pass us, and then pull over a car just ahead of us - but they didn't seem all that interested in my hazard lights being on, or my erratic driving.

Strange. Or maybe people do this all the time. (No.)

After the second bedding cycle, I pulled over to take a look at the rotors. As I got out of the truck, the smell of brakes, and wisps of smoke greeted me. Guess that's a good sign. A flashlight on the rotors, and they had a blue tinge to them - another good sign! And, there was that film of pad material. Pretty cool, guess it worked.

At that point, we headed straight back home. It was 1:00am, and way past our bedtime.

First impressions of normal braking

When I got a chance to take the truck back out again for normal braking, I can only describe the braking as "completely normal," which I view as a good thing. The brakes don't lock as soon as I hit the pedal, but it's easy to lock them with additional pressure. To me that means that I've got more braking power than before (larger rotors, pads), but that it won't affect my day-to-day driving in any way.

The thing I don't notice is any squishiness. That's apparently a common complaint of folks who own 1996-2000 vintage Tacoma's, where we have a larger master cylinder (1'' bore) vs. the 2001-2004, with a 13/16" bore. Monte (@Blackdawg) talks about this in his post here.

My guess is that he's correct in his analysis. Perhaps the bedding process helps a bit, but I don't know how it could make too much difference - after all, the same amount of fluid (and thus pressure) is in the system. Therefore, more likely is that I don't notice anything out of the ordinary because I'm used to my larger master cylinder already.

An interesting test will be for Monte and I to trade trucks. I bet the brakes in Igor are more sensitive, and will feel strange to me. And Monte will wonder if my truck is even stoppable.

And then we'll both be happy to go back to what we're used to!

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