Braking Bad: Upgrading the 128i for Track Duty

Like many of you, I enjoy driving fast—revving the engine to redline, nailing the perfect driving line, and feeling the car rotate through a corner. It's one of the best feelings in the world.

You know what’s not? Brake fade. That heart-dropping moment when the pedal goes spongy, the car doesn’t slow down as quickly as you expected, and your stomach knots up while your eyes lock onto a barrier you’d rather not meet—at any speed.

Before taking the 128i to the track, upgrading the brakes was a must. Because the only thing better than going fast is knowing you can stop when you need to. On the street, I’ve never had any real complaints about the 128i’s brakes. For a set of single-piston, modestly sized calipers, they perform surprisingly well—easy to modulate, confidence-inspiring, and providing solid stopping power for daily driving. However, like most OEM setups, I knew they wouldn’t stand up to the heat and abuse of an aggressive track session.

With plenty of brake upgrade options available for the 128i, I debated swapping to a larger setup but ultimately decided to stick with the stock calipers—at least for now. I wanted to see how they handled track duty before scouring eBay and local junkyards for a fancier set from one of the 128i’s bigger brothers.

For my setup, I picked up a set of Hawk ER-1 endurance pads, a budget-friendly set of Centric rotors from RockAuto, stainless steel braided brake lines from ECS Tuning, and a couple of bottles of the notoriously pricey Castrol SRF Racing brake fluid. I chose the ER-1 pads based on past experience—back when I tracked my old 1988 Honda CRX Si, they took all the abuse I threw at them without fade while still being easy to modulate. We won't get bogged down with the fact that the CRX was over 1000 lbs lighter than the 128i, which might have helped contribute to fade resistance with the ER-1 pads. And while Castrol SRF is expensive, I liked the idea of extending brake bleeding intervals while running a fluid I knew wouldn’t boil under track conditions. If the pedal goes soft, at least I’ll know it’s not the fluid.

Even though I was swapping out pads, rotors, brake lines, and fluid all in one go, I treated this as two separate jobs—installing the pads and rotors first before tackling the new lines and another fluid flush. More on that later.

First up: getting the car in the air, pulling the wheels, and removing the stock pads and rotors.

Before touching the calipers, I went around to all four rotors and removed the 6mm hex screws to ensure I wouldn’t run into any surprises later. These screws tend to rust and seize over time, so instead of wrestling with them by hand, I saved myself the hassle by using an impact gun to zip them off quickly and easily. A little bit of preparation can go a long way in avoiding headaches.

Next, I moved on to removing the calipers. Each caliper is secured to its bracket with two 7mm Allen key guide pin bolts, which are somewhat hidden inside rubber sheaths on the back side of the calipers. While they’re easy enough to break loose, they tend to get a bit "stuck" inside their rubber housings. A simple trick to walk them out smoothly is to apply light pressure on the threads with a thin plastic tool—I used a plastic interior panel tool, and it worked perfectly. Once the calipers were free, I used a set of caliper hangers to keep them out of the way while I continued working.

Next up: the caliper brackets. The front brackets are secured with two 18mm bolts, while the rears use 16mm bolts. If you have a high-powered impact gun, this is a great time to use it—especially for the fronts, which are torqued down pretty tight. Unfortunately, I couldn’t fit my impact in the available space without a swivel, but rather than stacking a daisy chain of swivels and extensions, I reached for my trusty 24-inch 1/2" drive breaker bar. It made quick work of them.

With the brackets removed, it was time to tackle the rotors. Luckily, the front rotors were already loose and slid right off. The rears, however, were still a bit seized in place. Pro tip: make sure your parking brake is disengaged before attempting to remove the rear rotors.

To free the rears, I used a wheel bolt to hold them in place, then—like a toddler throwing a tantrum—I took my trusty mallet and gave them a few solid whacks. A couple of swings later, they both popped loose. Using a wheel bolt to keep them from flying off was definitely the right call.

With the rotors removed, the exposed wheel hubs were now ready for the next step.

Wheel hubs can get pretty crusty over time, and while I wasn’t aiming for showroom perfection, I figured this was a good opportunity to clean them up a bit. A little preventative maintenance now could help minimize rotor seizure headaches down the road.

Armed with a cordless drill, a circular steel wire brush, and a bit of WD-40, I went to work.

A few passes later, while far from perfect, the hubs were looking significantly better.

With the hubs cleaned up, I installed the new rotors and brake pads. Before installing the pads, this is the perfect time to reinstall the caliper mounting brackets. The rear brackets, which on my 128i use 16mm hex head M10 bolts, should be torqued to 48 ft-lbs. The front brackets, on the other hand, require a much beefier 81 ft-lbs—so be ready to put in a bit more effort.

When installing new pads, keep in mind that if your old ones were fairly worn, you may need to compress the caliper pistons quite a bit. It’s a good idea to open the brake fluid reservoir while doing this, as the fluid level will rise. If your reservoir is already near the max fill line, now is the time to drain a little fluid to prevent it from overflowing—and inevitably seeping onto the backside of your engine bay. Ask me how I know.

There are plenty of ways to compress the caliper piston, but I’ve found that spending a few bucks on a simple brake caliper compressor tool is well worth it. It makes the job easier and eliminates the need for, let’s say, more “creative” methods of making room for the new pads.

The inside pads can be a bit tricky to remove due to the three-pronged spring that secures them to the caliper piston. Three out of the four pads I was replacing came out with just a bit of finagling. The fourth, however, put up more of a fight—requiring a screwdriver, some leverage, and a few choice words—before ultimately snapping one of the springs off.

At this point, you can reattach the calipers to the mounting brackets. The guide pin bolts on the rear calipers can be torqued down (22-26 ft-lbs, depending on the bolt head type), but I’d hold off on torquing the front calipers until after replacing the brake lines. More on that below.

Installing the Upgraded Brake Lines

I don’t know about you, but I’m not a big fan of being covered in brake fluid. That’s why I split this job into two parts—installing the new rotors and pads first—so I could avoid drenching myself in brake fluid in the process.

Before removing the OEM brake lines, do yourself a favor and wedge something between the seat and brake pedal to keep the pedal depressed. This helps minimize fluid loss while you work. I used a piece of PVC pipe cut to length, but anything sturdy enough to hold the pedal down will do the trick.

You might be asking yourself: "Aren't we replacing the fluid anyway? Does it really matter if some spills out?" Yes, we're replacing the fluid, but the last thing we want is for the brake fluid reservoir to run dry. If it does, air could get into the ABS module, which would make the bleeding process much more complicated later on. Plus, who wants brake fluid dripping down onto their face while they’re lying on their back? Before we get started, you should know that the E8x and E9x chassis don’t have just four rubber brake lines like most cars—they have six. In addition to the lines running to each caliper, there are two extra ones located above the rear subframe on the driver’s side. I can only assume these were added to make subframe removal or installation easier, but I have no idea why they didn’t just run hard lines above the subframe to eliminate this “feature” altogether.

To the engineer responsible for mounting these lines in such an infuriatingly inconvenient spot—who hurt you, and why did you take it out on the rest of us?

It’s hard to see, but here’s a photo of the upper two connections. They’re tucked behind the upper control arm, forward of the sway bar, and mounted to the chassis. This view is from the driver’s side rear wheel well.

Here’s a photo of the lower connections for both lines, taken from beneath the car.

And here’s a photo of the lines from underneath the car, showing them running up to the upper connections mentioned above.

See how rusty some of these connections are? It’s a good idea to soak them with PB Blaster or your preferred penetrating oil before attempting to break them loose.

Now, before you dive into this job, do yourself a huge favor—seriously, for the sake of all that is good and holy—buy a ratcheting flex-head 11mm wrench. A 14mm is also a smart addition, but the 11mm will make removing the upper connectors of these two rear lines from underneath the car significantly easier. This will save you a ton of time and frustration.

Yes, you can get the job done with a regular open-ended wrench from the top/through the fender well, but be prepared for a long, uncomfortable day. Just get the right tool—it’s worth it.

Ratcheting wrenches can be a bit pricey if you buy them individually, and they're not always easy to find. Since the inside line connections were 11mm and the outside connections were 14mm, instead of buying two separate wrenches, I opted for a whole set from Amazon. There’s something to be said for “buy once, cry once.”

With the 11mm ratcheting flex-head wrench, I was able to undo the top two connections from underneath. It wasn’t exactly easy, but it was definitely easier than using regular wrenches. Here’s a photo taken from the driver side wheel well, so you can see what I mean.

It took a bit of time, but I was eventually able to swap in the two lines from ECS Tuning.

The lines leading to the rear two calipers were a bit more straightforward. The inner lines are connected with an 11mm, while the outer lines connecting to the calipers use a 14mm. I’d recommend loosening the inner lines first, because if you try to unscrew the outer lines at the calipers first, they’ll twist- they need to be able to spin freely. Loosening the inside lines first allows the outer lines to spin freely.

Then, just install the new lines in reverse order: start by attaching them to the calipers (so they can spin/twist), then connect them to the inside fittings.

For the fronts, you’ll want to follow a similar procedure, with a couple of important caveats. First, you’ll need to remove the circular rubber mounts from the metal brackets that are mounted to the shock/strut. I’m sure there’s some fancy German tool for this, but if you’re like me and plan to just use your hands, I hope you’ve been hitting the gym lately—because those mounts are in there tight!

Second, since these lines are longer and curved, they’re a bit more involved. You’ll want to loosen the 14mm connections at the calipers while the calipers are still mounted. This will give you better leverage (it’s easier to loosen them when they can’t move). However, when it comes time to install the new lines, I found it much easier to remove the caliper entirely. Trying to thread those long, curved hoses while they’re flopping around inside the wheel well is a real headache.

When it comes to pushing those rubber grommets back into their metal mounts using your hands, all I have to say is: good luck and may The Force be with you. Once the new front lines are installed, torque down the calipers to 22-26 ft-lbs.

At this point, the brakes should be looking pretty good.

Feel free to toss the old rubber brake lines where they belong: in the bin!

Now it’s time to bleed the brake fluid. You’ll want to drain out as much of the old, dirty fluid as possible without completely running the reservoir dry, then fill it up with your new high-temp track fluid.

Next, I grabbed my trusty old Motive Power Bleeder and pumped it up to about 10-15 psi to start pressurizing the system.

When bleeding each individual caliper, you want to start with the caliper that’s furthest from the reservoir and work your way towards it. So, in this case, follow this order: right rear, left rear, right front, left front.

The Motive Power Bleeder did apply enough pressure to get fluid running through all of the lines. However, based on past experiences, I never fully trust the simple pressure method when installing new lines. So, I enlisted my wife to help with a round or two of the good old-fashioned two-person bleed method. Was it necessary? In my opinion, absolutely. As soon as we switched to the two-person method, I saw air bubbles coming out that the Motive Power Bleeder didn’t manage to flush out.

Since I was already in the garage with the Motive Power Bleeder, fresh Castrol fluid in the reservoir, and the car up in the air, I decided to take the opportunity to reconnect the Power Bleeder and quickly bleed the clutch line with the fresh fluid. You can check out my previous post for photos on how to access the transmission slave cylinder.

For reference, I’d plan on this job taking you a solid 5 to 6 hours, working at a steady pace and assuming there are no unexpected hiccups.

Once everything was buttoned up, I took the car out to bed-in the new pads, following the instructions on Hawk’s website. It’s a good idea to find a quiet, uninhabited road to get them properly bedded. Expect some smoke from the brakes during this process, accompanied by a less-than-pleasant smell.

After a cooldown period, I took the car for a spirited drive. My thoughts? With a bit of heat in the pads, the stopping power has been substantially improved. The brake pedal is solid as a rock, yet these pads are surprisingly easy to modulate. But man, they are loud! I’ve heard semi-trucks coming down from the mountains on I-70 that are quieter than these pads!

While I feel like the Hawk ER-1 pads will be a great match for track work, there’s a solid chance I’ll swap them out for a more street-friendly set once track season is over. I’ll report back on how they hold up at High Plains Raceway.

In the meantime, the car is almost ready to start ripping laps at HPR. I just need to do a bit of DME programming to turn off some of the nannies and finally get around to adding that extra grip I’ve been talking about. Soon. Very soon.