mipcar

Hello, installed the Radi-cals last summer on the .1 GT3 RS. Really like the performance on track vs the PCCB's.

Running Ferodo DS3.12's have found all pads have worn unevenly with the drivers side wearing much more substantially on the inside position with the bottom of the pad worn easily 50% more than the top. I had performed a second brake flush after install and was thinking I had air in the calipers. I bled the front tops using a pressurized master cylinder and found no air coming out. Did the bottoms and repeated the tops, no air.

I spoke to Essex who said they had customers report this and suggested rotating the pads. I am okay rotating going forward, just trying to understand what if anything is causing the drastic uneven pad ware. I do run with TC and ESC on. Is that causing the uneven ware or is it something else? I would believe TC may be causing some ware on the rears, but why would the front be so drastic, they look like triangles?

Thanks..

dsteding

Are you describing taper developing on them? Leading edge wearing more than the trailing edge? I see that on my 3.12s (AP radi-cal kit on a 991.1 GT3). Like 2 mm more wear on the leading edges. I’ve had to toss front pads prematurely because of it.

ir is somewhat annoying. I drive the car hard, and don’t really want to rotate pads every other track day, but that seems to be the only solution.

SDB

Had the APs on my last 911 with the same issue you mention and had to flip the pads after every track day. When I bought my current GT3 Essex wouldn’t sell me the brackets for my new car e enabling me to reuse the calipers.

That turned out to be a blessing when I installed PFC calipers on my 2018 GT3. The PFCs significantly out perform the radicals and pads wear perfectly even with considerably more pad life. Should have figured cup car brakes were the way to go from the start and ignored the marketing.

JRitt@essex

It would be extremely rare to have all the pads wear evenly in all the calipers under all conditions. We see some amount of pad taper wear at all levels of motorsport. We see it in NASCAR Cup, IMSA, as well as in HPDE and time trials. We also see it with all the top caliper manufacturers including Brembo, AP Racing, PFC, and Alcon. Pad taper today is typically not a function of some deficiency with the caliper, unless you're talking about a low-cost, flexible caliper. All the premier racing calipers from these brands are stiff and don't have any inherent penchant for spitting out tapered pads. The staggered piston bores help with end-to-end pad taper, but it's extremely tough to completely eradicate. Taper has a good deal to do with your track layout and driving style. We get reports of a little taper, zero taper, or moderate taper depending on the conditions under which the pads are being run. It's most common to see taper on the front outside caliper that's getting the most abuse on a given track. A good way to think about pad wear is just like tires. If you're running clockwise and making a lot of right-hand turns in heavy brake zones, you're typically loading up your front driver's side corner most heavily. Your weight shifts forward as you brake into the turn, and as you turn in through the corner, the front outside corner takes a substantial lateral load. It also depends on the characteristics of the pads that are being run. A softer pad that is easier on the discs is more likely to show additional taper wear vs. an extremely hard compound (which also chews up your discs). It's all about tradeoffs with pads.

Electronic nannies most often create uneven pad wear in the rear of the car, although they can impact the front as well. The car uses the brakes to slow down the wheels on the inside of the turn relative to the wheels on the outside of the turn, causing the car to yaw on what it thinks is your intended path. On rear wheel drive cars we most often see additional wear and taper on the inside rear wheel being used to help yaw the car through the turn. I have however had reports of odd wear up front on a front wheel drive car using some form of torque vectoring/yaw control (the Ford Focus ST comes to mind). Anytime you have electronics working their wizardry on altering the trajectory of the car, you have the potential for what could be considered unnatural or unanticipated component wear.

If you jeff.ritter@essexparts.com and I'll take a closer at your specific situation...happy to help.

I have more tips and advice on squeezing the most from your brake pads in our Essex Blog article. I talk in more depth about pad taper and electronic nannies as well: Track and Racing Brake Pad Owner's Guide

One of the great aspects of the AP Racing Radi-CALs, is that unlike some competing brands, it is incredibly easy to change pads. Our calipers feature a removable bridge, which pops out with two bolts in the front and one in the rear. Many other calipers have a fixed bridge, which means you need to remove the caliper entirely to swap pads.

JRitt@essex

I'm sorry we couldn't make an exception to our company policy to accommodate you. While I'm glad you're enjoying the brakes on your new car, your comparison to your experience with your last 911 isn't completely fair, as you're talking about two different vehicles. For years I tracked a C5 Z06, and subsequently a C6. While the C6 was an evolution of the same chassis, it was for many reasons a very different experience in numerous ways, including how it used its brakes, suspension, tires, etc. Again, I'm glad you found a solution that works well for you, but to insinuate that our product and presentation are based on marketing fluff is both unfair and unfounded. Porsche has won Le Mans on AP Racing Radi-CALs numerous times over the past several years, and they have equipped their premier racecar, the 992 GT3 R, with AP Racing Radi-CALs. The kits we offer our 991 GT3 road car clients are as close as one can get to the brakes on that car and leverage identical technology.

Also of note, we are now offering our CP9669 caliper option in our 991 GT3 Radi-CAL kits. It uses a 25mm thick pad and is perfect for those seeking the absolute longest pad life possible. Detailed differences between the CP9661 and CP9669 calipers can be seen here: Which AP Racing Radi-CAL is right for me?

mipcar

Jeff, thanks for the info. Essex has always been a great resource for me and appreciate the technical advice. As I am new to the Radi Cal it is nice to hear the experience from other users as it helps to validate observations and give confidence that I do not have an issue to sort out (air causing a problem/alignment/etc). Easy enough to flip the pads while rotating tires.

From a performance standpoint the capability of this breaking system in my opinion is far superior to the PCCB's for HPDE. The raw stopping power is remarkable, have not observed any brake fade, temperatures on the rotors and calipers are significantly lower than the PCCB's which in turn I believe is helping to control tire pressure PSI (I am making less adjustment over the day). As you stated the ability to quickly change pads is a must have feature.

Thanks! Mike.

JRitt@essex

I've been thinking more about this situation, and I wanted to say that I sincerely appreciate you sharing your displeasure with not being able to migrate your old parts to your new car. I wish you had sent me a PM or email about it rather than posting in the manner that you did, but regardless, it's good that our organization knows how you feel. I've posted here on the forums in the past about my frustration with our current policy, and I genuinely want to find a solution that is equitable for all our customers. I'm going to circle back on this topic for further internal discussion. I can't promise our policy will change, but we are always open to listening so we can do better by our clients. Thanks.

JRitt@essex

Thanks so much for the kind words Mike, and I'm glad you're enjoying your brakes! You should always feel free to reach out to me directly if you have any further questions. I may be able to provide some additional insights and experience on any topic of concern.