As it turns out, Apple has been making brake pads for years and calling them phones. This YouTube user "EverythingApplePro" has put together a new video showing off the iPhone's prowess as brake friction material, subjecting them to a series of tests on his 996 generation 911. So how do they work? Should you be replacing your PCCBs with Apple's finest? Check the video to find out.
In the video, the host says a couple of things that don't quite jibe with what I know.
1. This 996 has been upgraded to "Turbo Brakes" in order to fit iPhone 5S in the front.
Based on the original black calipers, this appears to be a 996 Carrera 2, which uses the same calipers as a Boxster S. Turbo front calipers require a lot more than just the caliper to fit, including basically the whole front suspension from the Turbo. I suppose this was possible, but that's a lot of effort and money (something in the range of $3000 dollars) to prove a point about iPhones.
If he did upgrade to Turbo calipers, I'd like to know how he did it, and what his reasoning was.
2. The brakes were spongy on the first run.
Well, aside from the fact that the friction coefficient of an iPhone screen is practically none, the spongyness of the pedal is mostly due to the four pads not being mated up to the rotor yet after a fresh brake bleed. Your first couple of stops immediately after a brake pad change are always spongy, because the master cylinder hasn't pushed the pistons of all four calipers out all the way to the rotor yet. Those first few spongy stops are what you get before the fluid all finds where it's going to settle out.
3. The iPhone 4S fared better than the iPhone 5S.
Well, the 4S phones were placed in the rear, and the 5S phones were in the front calipers. Placement, in this case, has a lot more to do with the outcome of this test than does the construction of the phones. There is a lot more pressure exerted on the front calipers than there is on the rears. A few years ago I worked with some people who performed some brake bias calculations based on the piston sizes, rotor sizes, and master cylinder size of a 996, and I don't recall the exact numbers, but the outcome was something like a 70% bias toward the front. If the iPhone 5S on the front is getting most of the pressure of the braking system, chances are that will fare much worse.
The moral of this story is: Don't use iPhones as brake pads. That should probably go without saying, but it makes for a fun and entertaining video. Don't try this at home.