A few readers, however, have replied to my updates that I should consider E9X 335i brakes. That was especially true after I briefly raved about driving my buddy Rob's E92 M3 with its massive OEM single-piston calipers and accompanying rotors. 335i brakes aren't quite the same size, but they're still noticeably larger than the base 128i equipment. In my constant daze of memorizing BMW's massive parts potential and aftermarket, I for some reason thought they meant the multi-piston Brembo units that came with the E82 135i. Stuff that's a bit much for my bank account. But nope, these are far less fancy, and therefore far less expensive. Like, several hundred dollars less expensive.

Here's how much bigger and heavier front E9X 335i-sized rotors are, how much of them get chomped on by the much-bigger calipers, and what kind of difference this upgrade made on the street. Spoiler alert: I bought two calipers in excellent used shape for $120 shipped.

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The calipers are only one part of this three-variable equation. Since I got them for so cheap, I thought it'd be wise to select fancier rotors and pads. Well, comparatively cheap, I know your cousin's neighbor's dog's brother upgraded his C5 'Vette's for $30/pop at their local O'Reilly's. But just over a c-note is mild in the realm of BMW taxation.

I went with Zimmermann drilled rotors and Ferodo DS2500 pads from FCP Euro, as both had good overall reviews. The Zimmermanns are especially well-reviewed, as it seems to be known as OE-level quality. Even M539 Restorations rocks them on his projects. The Ferodos appear to be a good dual-duty street/track pad, which normally means mediocre at track duty. I'll reserve judgment until I put them through their paces.

All said and done, the total came out to $670 all day. Then, since it's an OEM upgrade, all I had to do was bolt it all up.

The 128i's rotors are 11.8 inches, whereas the 335i's are 13.7 inches. They're also much wider and feature bigger vents. Surprisingly, pad size isn't that much of an increase, though overall caliper size is. Yet, both calipers weigh the same at 13.5 lbs. I'm thinking the larger overall caliper and rotor package will not only take the heat better, but also do a better job at dissipating it. Even if the pad size isn't much larger.

However, there is a downside to going larger: more weight. When I weighed each combo of rotor, caliper, and pads, the 335i setup was five pounds heavier per side. Considering my track wheel and tire setup is just over five pounds lighter than OEM per corner, the brakes eat up a lot of that benefit, though will hopefully make up for it in substantially improved braking performance.

Plus, they fill out the wheel well so much better. Aesthetics don't mean a whole lot for performance, but in terms of improving that walking-up-to or walking-away-from aspect of car ownership, these bolster both quite a bit.

Brake jobs on most cars are incredibly easy, but it's especially easy on BMWs. All of the 335i parts bolted up perfectly in the 128 parts' place. Even the caliper swap is simple enough, as all you need to do is first disconnect the flexible brake line at the hard-line, then at the caliper, unbolt the caliper, and do the reverse for reinstallation.

Because I originally tightened down the stainless steel lines a tad too much on the old OEM 128i kit, though, removal was a little tougher. Lesson learned, keep them on just snug enough. California living also makes brake swaps especially easy as old, mildly corroded rotors pop off with a light smack of a rubber hammer.

However, because I was doing this job entirely solo, I decided to invest in a power bleeder so that I could bleed all four corners with ease. This is where I mildly messed up.

The kit I went with was Schwaben's Premium 3-Liter European Brake Bleeder with Aluminum Adapter, and its operation is just as simple as everything else about a proper brake job. If I had just swapped rotors and pads, I wouldn't have needed to bleed the brakes. But I definitely had to since I swapped the calipers. It's important to ensure that there's nothing but fluid between the caliper piston and the master cylinder reservoir.

An "upgraded" aluminum reservoir cap adapter sounds like it's a strong, quality item, therefore I started off by using that. It promptly leaked brake fluid all over that corner of the BMW's under-hood area, even after tightening it down carefully and quite hard. Luckily, I had plenty of fresh Castrol SRF on hand.

After doing my best to clean everything off, I switched to a plastic adapter. It held the seal perfectly. Turns out the less-sturdy-looking option was the best and a full bleed of the system went off without a hitch.

This setup is great on the street, and my original rear brakes are still in great shape with plenty of Hawk HPS pad life left. It feels strong; the brake pedal is just firm enough and is confidently progressive. The pads don't squeak either, which is kind of a miracle for street-slash-track pads. Modulation is easy as well, and they're in no way grabby. So far this is a big net positive, however, the next step will be to see how they fare on track...

Stay tuned.