Well at least I have half of it figured out. Today’s part is the brakes — the rear brakes, since the fronts are still stock. I haven’t quite decided what I’m going to do with the fronts yet, but the rears are in the bag, and I think they look pretty cool. These are zinc-washed Wilwood disk/drum brakes with vented, slotted and cross-drilled rotors, and four-piston calipers.

I ordered these brakes many months ago and so I’ve had them for a while. Since I bought them I’ve learned a few things and have realized that if I were to do it again, I’d make some choices differently. I’m not upset at all and I think these brakes will be more than adequate, but there are some features that are suboptimal, of which I wasn’t aware at the time. I’ll explain here in case it helps anyone who is in the same position as I was in, knowing little about the subject and making a decision based on available information.

First, these brakes have single-piece rotors, which means they’re cast as one unit. This is the way OEM brake rotors are made, and it’s certainly a very cost-effective way to do it. The problem is that this is one of the primary causes of rotor warpage over time — the uneven heat transfer from the disk to the “hat”, which can be eliminated by manufacturing the rotor as two pieces which are then bolted together. Most premium brake rotors are made in two pieces for that reason.

The second feature I’ve come to disagree with is the rotor crossdrilling — the holes you see in the rotor surface. These holes were popular a decade ago, as they allow heated gases to escape from between the pad and the rotor surface, which increases friction. They also provide an additional path for cooling air to get pulled in as the rotor spins. The problem is that under extreme duty, the holes can cause the rotors to crack — a difficulty which has seen the technique all but eliminated in racing and high-performance vehicles today. Drilled rotors are sold today to people who prefer the appearance, and won’t be pushing them hard enough to risk this kind of failure. Slotting (the grooves you see between the groups of holes) is the preferred method, and even that feature is not universally agreed upon as a good thing to have.

Now this isn’t to say that these aren’t high-performance brakes, far beyond what ships with most vehicles on the road. The cross-drilled holes have rounded chamfers to smooth the transition and reduce the chance of cracking, the rotors are vented to promote cooling, and the four-piston calipers provide more pressure, more evenly for some incredible stopping power. The rotors are also larger in diameter — in fact, they barely fit inside my current 15″ wheels, with less than a quarter inch to spare once everything is bolted together.

Now you might be curious — why have I gone out of my way to provide beefy brakes in the rear? Shouldn’t the big brakes be on the front, like with most vehicles sold these days? There are two reasons why I wanted to provide really good rear braking.

• The rear brakes not only have to stop the truck, they also have to stop the motor. Recall that the motor is intended to be connected to the driveshaft via a yoke that slides on the motor’s splined output shaft. This means there’s no torque converter, no transmission, and no clutch to disengage the motor. The motor is permanently connected to the wheels. Now consider all that rotating inertia — the armature on the motor is about as massive as an entire 9″ motor used in many high-performance EVs. And all of that mass is going to be spinning with a greater than 4-to-1 gearing advantage via the rear end ratio. The best way to deal with this would be regenerative braking, but for reasons I’ll discuss in a future post, this isn’t an option for me, at least given currently available technology. As I want to slow down, the motor will want to keep going like a huge flywheel. The brakes must deal with this extra load.
• Skinnies. Yes, this may sound somewhat amusing, but it’s something I’ve considered. Skinnies are narrow (usually 3.5 inches or so wide) wheels you put on the front for reducing weight while drag racing. They’re worthless on the street since they can’t handle cornering side loads and tend to be somewhat fragile. They also make a very small contact patch with the road, which means if I end up getting a pair for use at the strip, the rear brakes would be more responsible for slowing the vehicle at the end of the run.

Link to today’s part.