MK7 PP Brakes on Track
No. You [probably] don’t need a big brake kit.
The factory Performance Pack brakes are actually really good. For reference, the C6 Z51 package Corvettes have a 340mm front rotor (albeit 32 vs 30mm wide). In most cases you just need GOOD pads and good fluid.
These calipers have now seen a solid 15 days on track in the last ~18 months. Most of that at VIR which has 3 notable braking zones inside a roughly 2:15 sec lap:
Entering T1 on the front straight (approx 130mph to 46mph)
Entering T11 “Oak Tree” (approx 105mph to 45mph)
Entering T12 “Rollercoaster” (approx 130mph to 48mph)
One VERY important note is that to get the most out of your brakes, you need to not abuse them. Though it sounds counter-intuitive, braking harder over a shorter distance puts less heat into the system than softer over a longer distance. Novice drivers tend to brake starting way earlier and far too softly. This comes from years of driving on the street and slowing down way ahead of time. You want to squeeze (not stab!) the brakes quickly but smoothly, and compress the braking zones as much as possible.
The reason that this is easier on the brakes is because more time is spent OFF the brakes, allowing airflow between the pad and rotor to cool everything off. On a 2 min road course, if you’re extending the braking zone by spending an extra [unnecessary] 3 seconds on the brakes in 3 hard braking zones, you’ve eliminated 7.5% of the available cool-down time.
I run the following setup on track for reference:
Ferodo DS3.12 front pads
Ferodo DS1.11 rear pads (custom ordered from Essex, normally not available for the GTI mechanical e-brake calipers, must call to order)
Endless 650 brake fluid (used to run Motul 600)
RS3/TTRS brake deflectors with backing plates completely removed (UPDATE: recommend trimming the backing plates rather than complete removal: melting of ABS speed sensor wiring is a potential problem. Also while I’ve not experienced issues with OEM ball joints, any plans to run aftermarket ball joints may bake the boots prematurely, like these 034 ball joints after only three 20 minute sessions)
GTI cosmetic caliper plates removed
Also worth noting is that because I have the VAQ differential, I have the “XDS” turned “off” entirely. It is a murderer of brakes, and really unnecessary with the VAQ. The traction control button is also coded to allow “full off” with a long press. Both of these settings will help to avoid putting excess heat into the pads and rotors.
Factory brake hoses - These cars do not have a known issue with brake hose sudden failures (such as S2000 rear hoses). Stainless doesn’t flex very well. I went through (3) separate sets (Goodridge, Technafit, and Stoptech) front hoses on my last track car in only 2 years and 30k miles. The outer sheath splits, which can potentially allow sand/dirt/grit to get in and slowly abrade the SS liner. If the GTI turns into a track-only trailered car, I’ll probably consider changing hoses, but there’s zero need for them in the foreseeable future. They’re 100% unnecessary to get your car on track.
Moving on: I was curious about just how hot they were getting, so finally broke down and purchased some Genesis temperature indicating paint from Don at TMI Racing the last time I went to VIR.
So what was learned from this? The pads perform well even at the top of the Ferodo indicated limits. The caliper dust boots are still in perfect shape as well.
When should rotors be replaced? Well I pushed one set 14 days on track, plus a bunch of autocross and daily use as well and they look like this. If any of the cracks go to the edge of the rotor, it’s time to toss them.
Minor rotor “crazing” has worsened to the point that you can grab a fingernail on all the cracks visible, with several getting very close to the edge. I retire them as spares at this point.. not worth trying trying to save a buck at the potential expense of shattering a rotor at speed.
Lowering brake temperatures via either more airflow or perhaps 2pc Girodisc rotors should help extend both brake pad and rotor life (which is honestly very good already, details in the first video above). I will likely be re-checking again in cooler weather at some point to verify I’m still getting the same results. It was 90-95F ambient temps when the above temperature samples were taken.
I’ve since played around with the temperature indicating paint a bit more - with Ferodo DS2500 pads on the street you’ll almost never see anything over about 500-600F (based off of IR temp gun after repeated 90-30 stops, as the temp indicating paint doesn’t start to change color until 679F+).
At autocross (again with DS2500s) I never experienced anything over 804F based on the paint with zero indication of problems there.
Ferodo temperature vs friction coefficient (Mu) - added Fahrenheit notations for reference
Big brake kits are great - larger rotors buy you more thermal mass to deal with the heat (and surface area to get rid of it faster), lighter calipers are great for dropping unsprung mass, etc… but the fact is they’re not an absolute necessity to get out on track.
I’m personally quite leery of the many “Chineseum” big brake kits out there for the simple fact that QC, spare part availability, or even just knowing if the brackets etc were even properly designed [with an adequate safety factor] is a huge no-go in my book. I intend to milk the factory calipers along for a bit longer, as frankly I haven’t found a “need” to do anything about them just yet.
