Onto the rear brakes. I got a little smarter this time and disconnected the soft line from the hard line at the chassis first and put the rubber cap on the hard line to stop the brake fluid leak.
And then I went to remove the rear caliper. It’s not a T55 torx which is too small. Okay, I make another run to Home Depot but they don’t have anything bigger. Next, I went to Autozone and bought a T60 and T70 torx as surely, one of those should work. Nope! After a bit of searching online, I found the answer on a Saab or Skoda forum of all places that it’s a M14 spline. I put in the order on Amazon and I’m back in business in a couple days.
Before doing the brakes, I watched a YouTube video from Tommy L Garage where he did the brake swap on a 991.2 Carrera. The 991.2 used T55 torx front and rear for the calipers. I watched another video from Jet Fuel Only on doing the brakes on a 718 GT4. The GT4 used T55 torx front, 10mm hex on the rear, and T30 torx for the rotor screws. I don’t see any reason for the difference in fasteners at all, so it seems to me Porsche just uses what they can get their hands on at the time. The fastener industry can catch you out as I know from experience. The lead time for a fastener can be 20 weeks, or more, if you run out of the size you need. I recommend checking what particular fasteners Porsche used on your car before tackling this job. Or just order all of the tool options.
The rear pads use more of the available surface are compared to the front pads, but there is still some undercutting.
Here you can see how much leaner the AP Racing Radi-CAL caliper is compared to the stock Brembo. On the stock setup, you can see the brake pad wear sensor wire and where I cut off the connector. Doing a pad install on the Radi-CAL is easy with just the removal of the bolt and the pads slide out the top, similar to my old StopTechs on the S2000. The stock Porsche Brembo setup, you have to take the whole caliper off which involves other steps like removing the brake line bracket to the spindle.
New versus old rear rotors.
20 comments
I’m an Essex/AP Racing customer as well. The amount of pad thickness and those DS2500’s are amazing. I did get some howl in certain conditions that I could never remediate, and eventually swapped to a lesser pad; which I do semi regret. But that’s another story. The weight savings were impressive too.
Tech support has been superb as well. Make sure to join their FB group, they post sales, and answer many tech questions.
Can you please drop the McMaster Carr P/N for those interested in getting that same check valve as well??
-Dan
I got this one:
https://www.mcmaster.com/6079T56/
1/4″ barb on both ends, nylon body, 316SS ball, 302SS spring, buna n seals, 1 psi cracking pressure. I think all the materials should be compatible with brake fluid.
Great article – the AP calipers are pretty cool, but it’s strange that a bleeder valve ends up facing the ground.
Your tip about using a check valve for bleeding brakes is brilliant, and a huge thanks for sharing the McMaster part you used. That will be a huge timesaver!
FYI, for anyone else reading this, the stock rear calipers don’t need to be removed from the upright to change the pads. The rear calipers use the same general design as the 996 calipers I have on my car. There is a small cotter pin on the inboard edge of the top pad retaining pin (visible in the 4th photo on Page 5) that is right next to the pad sensor wire. When the cotter pin has been removed, the pad retaining pin can be driven from the inside of the caliper towards the outside. This releases tension on the spring clips, and finally the pads can be lifted straight out of the caliper. The hardware kit for the 996 calipers is 996-351-959-01-OEM for a photo that may help to show the parts I’m describing.
Way way back in the day, I used Speedbleeders on my Nissan which were the bleed valves with built-in check valve. I didn’t particularly like the quality of them and a buddy had one break off in his caliper. But I just took the concept from them and Motion Pro and applied it. I think the Motion Pro just had like a flapper valve as I recall the fluid could flow right through it with nothing but gravity pressure. I like this McMaster part because it actually requires some pressure to crack the valve open.
On the rear caliper, yes, good info! I gave the brake pads to a friend and I learned about that cotter pin and retaining pin remove the rear pads from the caliper. I’m not a fan of that cotter pin!
Would cutting out a wedge out of the heat/dust shield make more sense than removing it entirely? Thinking about heat and the wheel sensor and adjacent ball joints.
I thought about it for a few minutes. If you watch the Tommy L Garage video of the brake install on the 991.2, that front dust shield actually has a hole in it to get more air to the rotor on the Carrera. Why the design difference? I’d guess different engineers and they didn’t talk to each other. I do have prior history of running without dust shields on the front brakes. My old Nissan didn’t have the shields for about 100k miles. And the S2k had them gone for most of it’s life in my possession. My thoughts are: the BBK runs cooler and I also do a thorough cool-down coming off track. So the brakes won’t get as hot in the first place and then I allow them to cool down significantly coming off the track. When the car is stationary is where I see heat from the brakes being the greatest risk as there’s no airflow to act like a thermal shield. But I really only see this as a potential issue with heavy track use and that’s mitigated by a thorough cool-down.
Do not remove the shields… they are heatshields for the ball joints. Especially if you track the car !
Also, the air does not need to hit the friction area straight on, it is pumped from the inside of the rotor by the vanes, that’s what does the cooling and that’s why the steering arm on the knuckle has this weird shape.
And I hope you did not just shove the struts all the way in without getting a proper alignement ?
Brakes looks cool though !
Correct, you want as much air to the central part of the rotor as possible to get maximum cooling. Air flowing through the central vented section of the rotor cools both inner and outer rotor surfaces along with having a lot more heat transfer surface area due to the vanes between the rotor surfaces. Getting rid of the stock shield opens up a lot more airflow path area to get to the center of the rotor; especially with the AP rotors that have a larger inner diameter of the rotor surface. As for heating of the ball joints, it was a consideration in my decision. I see the largest risk being heat transfer by radiation, so I may add on some heat radiation reflective tape as a mitigation. That said, as I noted in a previous comment, I’ve run without the dust shields on my two prior fun cars without issue. Again, part of it is mitigation through procedure also which is doing a super thorough cool-down after a track session. For the alignment, I just did a DIY toe adjustment in my garage as noted in the article. I have plans for a full suspension overhaul, so the car will getting a full alignment then to track specs.
The AP brakes with the DS2500 pads really are fantastic. Great feel, so easy to modulate. I like the level of initial bite of the DS2500 pads, which is to say, not aggressive. Very stock-like. They seem more linear with temp too compared to the stock pads; the stock pads friction mu seemed to jump dramatically once they passed some temp threshold. That took 3 hard brakes going from about 100mph to 60mph. So far with the AP kit and DS2500s, I haven’t run into that issue.
Having been involved with tons of record braking race cars, keeping balljoints cool was never a design consideration nor has any damage to the ball joints or outboard bearings ever been observed.
“A simple DIY solution used by competitive vehicles like those of J’s Racing in Japan, for example, is to wire heat-reflective fabric (Kevlar weave or similar) onto the outside of tie rods and ball joint boots. This simple modification can help extend the life of your suspension components for less than a few bucks, and allow you to remove those restrictive brake heat shields for better cooling.”
https://www.motortrend.com/how-to/impp-1103-protecting-your-suspension-tricks-of-the-trade/
A few S2k guys did this. Again, the issue really arises if you come off track hot and sit stationary. Lots of S2k guys also liked to run the stock brakes and crack rotors every two days because they ran super hot… Going bigger brakes reduces peak temps, more airflow reduces peak temps, and doing a good cool-down mitigates the heating while parked issue.
After I read this article I went and looked at a 718 GT4 and guess what, they do not have front dust shields. They do have little plates that cover the tie rod ends from the radiant heat. I know these points have already been covered above but just wanted to add another data point. Now to see if the GT4 part can be used on my 718 GTS or if I can simply trim my dust shields in a what that would retain that portion to shield the tie rod end.
Funny that you mentioned 911 base Carrera brakes possibly under powered, I agree with your assumption. I have a 2020 Carrera C4 and when I’m driving the canyons around LA, the stock pads are not happy (start dusting hard once over a certain temp), and have a lack of initial bite. I can’t imagine using the stock pads on a track day. I’m used to my 2005 lotus Elise with oversized stock brake setup (upgraded to DBA two piece and ferodo ds2500 ). The base Carrera brakes are 330mm front and rear with 6 pot front and 4 pot rear. For why brakes are sized differently from front engine to rear engine cars, see https://www.theautopian.com/an-engineer-describes-the-ideal-brake-curve-and-why-cars-have-such-vastly-different-brake-sizes/. The Carrera S has an 350mm rotor and larger pad areas. Girodisc also provides an upgraded rotor at 350mm with shims to use the base Carrera calipers. I am waiting for my stock pads to wear out and have ferodo ds2500 in the garage ready to swap out. The Essex package is nice, but quite an investment. I’m trying upgraded pads first, then upsized rotors. My use case is mostly daily, with about once a month canyon, and once a year track (button willow). Really enjoying the articles so far on the Cayman, looking forward to what ever else you’ll be adjusting.
In your case, I would go ahead and do the 350mm Girodisc upgrade when you go to swap pads in order to gain the thermal capacity which in turn will improve life. I do see a downside being the brake bias will change, but I think that’s a worthwhile tradeoff. Splurging a bit more would be going with just the front AP Racing setup. I’m planning on keeping this car until I can’t drive stick anymore, so a very long time, and that’s why I splurged.
Thanks for this build series. It is well written and very useful. I too have a Cayman T.
Given the odd, small effective size of the factory front pads, is upgrading to a full size pad a possibility to gain some braking capability?
I measured the stock camber using my iphone and got .6 degrees. I am going to look into moving the tops in and redoing the toe. Seems like a great no/low cost improvement!
Thanks for the good work and I am looking forward to seeing how your tune goes.
ps. Have you considered selling your tailpipes -they look to be much better than what is currently on the market.
After you adjust the camber, definitely make sure to zero out the toe or you’ll shred the tires! For my x-pipe, if there’s interest, I could sell the design to an existing company and they could sell it.
Oh yeah, to answer your question on using a pad that’s full surface area, it should gain capacity and life just by having more mass to start with. Just be aware it may tweak the brake bias a bit.
Quick update, today I did remove my heat shields on my 718 GTS. I used the trick Bob mentioned and I safety wired heat shield material around the lower ball joints and tie rod as a precaution. Recently I have been getting a strange noise when braking sometimes, often right after I come off the track and the first braking application as I enter the paddock but sometimes the first stop sign when leaving my house. When I removed the rotor to take off the heat shields today I see that the heat shields are all scratched up from where presumably little rocks were rubbing between the rotor and heat shield. The heat shield has these pressings that could possible hold little debris. I have heard other GTS models make the same noise. Not sure how the T model heat shields compare or if this is more prone to the GTS front brakes. The rear brakes heat shield is very small and looks similar to what was posted in this article.
Nice! If you look at picture at the bottom of page 2, you can see a scrape mark where something got between the rotor and dust shield. It wouldn’t surprise me if gravel and pebbles are getting flung between the dust shield and rotor via the brake duct and the airflow hole. If it were me, the dust shield part number would be the same between all the 718s. Considering the GTS rotors are only 20mm diameter larger than the base Cayman, assuming they are the 350mm size, I can’t imagine Porsche would make a unique dust shield for the GTS.