Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community - FT86CLUB - Stoptech, Brembo, AP Racing, Performance Friction, K-Sport BBK Comparison

A couple of thoughts from an insider viewpoint:

The article is based around track performance. My first question is: Why would they take a group of street big brake kits and test them on the racetrack, rather than evaluating each of the manufacturers' best available track brake kit (StopTech Trophy, AP Racing Competition Kit (either the AP Racing Factory one or our Essex one), a Brembo GT-R kit, etc.)? I'm assuming it's because the BBK's in the article are the only ones that are currently TUV approved? Street performance and track performance are evaluated under an extremely different set of criteria. Street performance is about pedal feel, seamless ABS interaction, Noise/Vibration/Harshness, and cosmetics. Track performance is about fade resistance, disc, pad, and caliper temperatures, component weights, available pad options, pad and disc wear rates, iron disc replacement costs, wheel fitment, etc. Excelling in one arena doesn't typically mean being the top of the heap in the other. If you're going to look at track performance by brand, it would make sense to put each manufacturer's best foot forward for the competition.

Pads are a critical piece of the puzzle, and variable elimination is at the core of the scientific method. My understanding is that the same pads were not used in all of the kits (you can see different color pads in the various calipers). To make the comparison as apple-to-apples as possible, it definitely would have been best to run the same pads in all kits. I can understand why they didn't use the same pad compound in each kit, but it is a variable that does unfortunately impact the results rather dramatically. Anyone running one of these kits their M3 on a track in Germany can easily toss the pads that came with their kit and likely get Pagid race pads at a reasonable price (Pagid is a popular brand in that region). As such, it seems a bit silly to insist that the pads remain "as delivered." Yes, I know that the pads are considered part of the approved kit in Germany, but I also know that people will run what they need to run on the track.

· That said, the magazine was working with what they were given, within the as-delivered specs including TUV approval (which is crucial in Germany). I'm sure the magazine editors also didn't want to add to an already costly test by spending an additional $2400 to buy identical race compounds for all of the kits in the various shapes (6 kits x $400 per pad set). It still seems like a very big missed opportunity to me.
· Comparing a street or semi-street hybrid pad against a track pad is a big no-no. Their characteristics are dramatically different (see my article on How to Choose Brake Pads). The FM1000 that ships in a Brembo kit is a slightly milder version of Ferodo DS2500. Pagid RS29 is an endurance racing compound. They're not even remotely similar.

As some others have mentioned, stopping distance is largely a function of tire choice. Using the same tires on all was an excellent choice. One would expect any solid aftermarket street BBK to have a similar or slightly better stopping distance than OEM under a one stop scenario. The Brembo results are definitely surprising in that regard. Again though, pad friction level when cold has an influence on this result, but the FM1000 pads in that kit should have good cold bite.

Now I'm not sure if I'm reading the data correctly, but it looks like every brake kit tested, including OEM, had very little fade over 20 stops from 200-0 kmph. The 20th stop on each was roughly within a meter of their first stop distance. That means none of them, including stock, exhibited any noticeable pad fade. The comments about the soft pedal on the OEM option indicates fluid fade. If I was analyzing the data for the article as presented, it would have been a single sentence article, "If you never plan to do anything more than 20 stops from 200 kmph, don't waste your money on a BBK!" Some of the kits showed a shorter 20th stop vs. the first, which is likely because the race pad compounds generate more mu with some heat in them.

· What they should have done first is to find the 'failure point' of the OEM system. If the OEM system wilted on the 27th stop from 200 kmph, adding 20 meters to the stopping distance, then from that point 'up' (more stops and/or from a higher speed) would have been the critical info to gather on the big brake kit stopping distances relative to stock and each other.
· To take this a step further…run each big brake kit until it wilts from overheating, be it pad fade or fluid fade. That would show how much torture each could take, and would give a better understanding of their value vs. the OEM brakes, their relative durability to each other, and a better approximation to the stresses inflicted upon your brakes at the track.

Taking disc temps would have shown how cool the discs were running after the series of stops. This could have been done with a pyrometer at the end of the stop, or for more accuracy, on-board via a thermocouple with data-logging (very simple with today's data acquisition…pedal travel and pressure can also be measured in that manner). Disc operating temps are critical when evaluating the efficiency of a brake kit (how much air the discs flow), pad and disc wear rates, the impact on the caliper and brake fluid temps, and the resulting likelihood of boiling that fluid. Without temps, you don't really know which kit is working best or smartest, or which is likely to last longest.

They could have taken a look at the discs in each kit after the test to evaluate heat checking/cracking, as well as pad wear (how many mm of pad remain, any taper, etc.). Again, that would give some great insight into how durable each kit is, and what a user could expect.

The weight of separate components should have been measured. Two kits may weigh the same, but one may have far more thermal mass in the disc, while the other is toting around four extra, unneeded lbs. in the caliper. The complete corner weight doesn’t mean much without knowing where that weight is!

How much do spare iron rings cost? How much do replacement race pads costs? Are there a lot of pad options for each kit? Does each kit fit the most common track wheels people are using? These are some of the most important questions when evaluating an aftermarket big brake kit.

Overall, I wouldn't go so far as to completely throw this evaluation under the bus, but I don't know how much valuable data actually lies within it. As far as I can tell we're looking at street big brake kits being tested for stopping distances under moderate usage conditions that barely even exceed the stock brake system's capacity. In such a case, feel and aesthetics will be the primary differences between kits, which are both somewhat subjective.