Grabbed_Crow_Mobe

For those of you running AP Racing front calipers, which pad height are you running? I would think that the taller D50s would be a no brainer choice since I would assume that more pad material is better. However, I talked with one forum vendor that said they experienced some fairly bad taper with the tall ones and have since successfully ran the shorter ones. It makes sense since the pistons are offset from the center of the pad on the tall ones. I was surprised to learn that there isn't a price difference between the two heights either (at least for Hawk pads).

What height is everyone running? Any issues?

RedLS1GTO

I ran both on my 02Z. Of course it varies drastically between drivers with different styles but here is what I saw. For reference, I push the car pretty hard in braking zones with some occasional trail braking. I had spindle ducts on the car with Continental GT-I slicks.

With the Ferodo 1.11 D50, I chunked the hell out of them. They lasted very well in terms of actual pad depth but it looked like I threw them on the ground a few times and hit them with a hammer on the edges for good measure. I might actually still have them. If so, I'll put up a pic or 2. Despite the pretty severe chunking on the edges, there was very little to no taper in them. On this I will also add that it was a very cold day. I think a lot of the problem came from not getting them up to temp. When I taped up the ducts I saw a big improvement in consistency and feel. This could also have led to the chunking.

With Ferodo 1.11 D41 I had a lot less chunking but oddly enough, more noticable taper. Feel was good throughout but when I pulled the pads the taper was pretty clear.

My favorite pad was the Hawk DTC70 D41. The feel was amazing. I liked them a LOT better than the Ferodo in that regard. The wear... meh... not so great in comparison. I'd say about 3/4 of the life span of the Ferodo as a best guess (I never measured the Hawks). If you can do it without getting the taper, the D50 might just be the answer.

From an actual stopping and performance perspective, I noticed no difference other than perhaps jusssssssst a smidge more initial bite from the D50 with the same compound (Ferodo 1.11).

Not much of a sample size but it's what I have.

argonaut

I've used several sets of Ferrodo DS1.11 - one set in D41 and two sets in D50 size. I've also gone thru two sets of Willwood H in D41 size. I wouldn't say I noticed any more tapering with the wider pad. Heck - compared to stock any tapering with this system is minor so personally I wouldn't worry about it.

As far as performance goes - I don't think the D50 size is worth any additional cost however. The D41 does the job just fine and lasts a good, long time.

Regarding the DS1.11 - I have not experienced the chunking problem Brian describes. The edges chip off a bit but nothing bad. However - I personally don't care much for this compound. It stops the car, it doesn't fade and it lasts a long time but it doesn't have a lot of initial bite...so you kind of have to get use to the pedal feel.

Rob Willis

You guys tried Carbotechs?

I haven't ever used the taller D50 in my AP t1 kit, but have wondered about it...

I used to love Hawk70s, but trying to clean the brake dust up from those is TERRIBLE.
Carbotechs are sooooooo much easier to live with for ~95% of the performance.

(XP8, XP10, XP12s)

RedLS1GTO

After 2 seasons with Wilwood pads in my C4 w/SL6 calipers (same pad shape as the AP T1 but with a thinner pad material) I decided to try a set of Carbotech pads... The result was destroying a brand new set of rotor rings and pads almost to the backing plate in less than 1 day. Was told something was wrong with my calipers. Oddly enough in 3 more seasons of running both Wilwood and Hawk pads in those same calipers, I never had even a slight problem.

Of course some people here swear they're the best thing out there so who knows.

Z06trackman

I have run the DS11.1, the AP C300, and two sets of the Carbotech XP10s on my AP T-1 kit with DRM ducts and spindle ducts custom fitted to make sure all of the air goes to the center of the rotor. All of these pads were the 50mm height. My C5Z is stock save for cooling on everything and Koni Yellows. I am running R888s. Prior to use I methodically burnished all these pads by the book. Here are my results:

All of the pads tapered both radially and tangentially - just like with the worn stock calipers, only not quite as bad tangentially. The tangential taper does not produce the soft pedal from the fixed caliper that is experienced by the floating calipers.

The only pad which had enough temperature capability was the XP10s. There are very easy on the rotors, and they don't fade.

Both the DS11.1 and the C300 pads where harder on the rotors, with the C300 endurance pad being the most aggressive. Both chunked and smeared due to exceeding their temp capability, and I experienced pad fade with both.

While I have not proven this, I believe the radial taper is due to the 50mm pad being seriously off center from the pistons and the fact that these calipers are designed for 12" max rotors. I believe the tangential taper is due to the flexing of the caliper mounting ears on the uprights. GM fixed this with the ZR1 and those uprights supposedly are now used on all C6s after that.

In spite of the unexpected pad tapering, I have found these brakes to be awesome with the XP10s. I didn't have to replace the rings until I fitted the fourth set of pads. At this point the rotors still had some life, but the cracking was really ugly.

Grabbed_Crow_Mobe

Great to hear! I currently have a set of half used DTC70s in the D41 size so that will be my first experience with this caliper setup. I already have DTC60s in the rear (I previously ran DTC60s in the front too with stock Z51 calipers). I'm anxious to try the popular DTC70/DTC60 configuration.

Grabbed_Crow_Mobe

I haven't tried the Carbotechs. And with this particular caliper, the carbotech pad is significantly more expensive than the hawks so I'll probably stick with the DTC60s or DTC70s.

Funny on the dust from the hawks. It sticks to my stock wheels like glue. But for whatever reason, my CCWs don't get any dust stuck to them, even from heavy track use. They seems to have some super dust repellent built in

0SpeedFreaksUSA

This is really interesting - Would you mind letting us know the Carbotech compound you chose to use and the type of tire and size you were running. Additionally, did you swap out the pads and bed them in? Run them at the next event without bedding them in? Was the Carbotech run on the same rotor/ring with a transfer layer on it from the previous pad you were running? If so, what was the pad? Finally- were the Carbotech's you received pre-scorched/heat treated? (They refer to this as a pre-bed process).

What you describe isn't unique, but there are specific factors that should have lead to what you experienced. Very much looking forward to your response -

0SpeedFreaksUSA

Great write up - Would you mind advising to the total radial and axial float available from the 2Pc rotor assembly being used in the AP Kit?

Please correct me if I am wrong here, dimensionally the C5/C6 uprights are the same. The only difference is that they added some thickness to knuckle deal with the deflection that occurred at operating temperature with the uprights - this was derived by GM during testing at the Nurburgring as their pads exhibited tapering wear.. some of which is being touched here as a pattern.

I'll be happy to reach out to my GM group and check if they are still willing to feed me some info, some of my old FSAE team from many years ago still work with GM.

0SpeedFreaksUSA

Get in touch via PM - I'll try to see what I can do to ease that cost burden for you and make them equivalent, or even less if possible. The whole point being an enthusiast supported by vendors is to find something that works using their help, and I think we can give pricing breaks to help that discovery along

(In regards to the dust, it's usually related to surface finish of the wheel)

RedLS1GTO

XP12/XP10 as per the recommendation I got on the phone. I usually ran either Wilwood A/B or DTC70/60 on that car.

Tires were either Hoosier R6 or Goodyear RS-R (I don't remember which I had on it), 315-35-17. Here is the rest of the setup:



Rings were out of the box brand new slotted Wilwood, same as in the picture. I have bedded hundreds of pads in my life, including at least a couple dozen on this exact car so I can't imagine that being the problem.

Last time I spoke my feelings on the idea of charging extra so that you can actually bed the pads, it didn't end to well so I'll just leave it at no... they were not "pre-bedded".


Long story short, over a span of 5 years with dozens of sets of pads with that setup, mainly Wilwood and Hawk with 1 set of Raybestos thrown in, the only time I had even the slightest problem was the 1 time I had Carbotechs on it. Something about that combo just didn't mesh. Rather than tossing money at it and spending even more money on the "pre-bed" to cross my fingers that it didn't happen again, I just stuck with the others that I knew worked going forward.

Here is what a pad looked like after 1 day at VIR. It's hard to see, but the grooves in it are big enough that the rotors were hopeless. Both fronts, all 4 pads were identical.

Z06trackman

I don't know, but I don't believe the problem is with the 2-piece rotors. I should also mention that I am running the big SKF hubs.

Yes the C5 and C6 uprights are the same. They are also the same front to rear, by switching the sides on which they are used. As I understand it, after GM found the tangential pad taper on the ZR1, they redesigned them with thicker ears, and then at some point they simply used this part on all the cars.

RedLS1GTO

Did you actually measure temps on them?

Given what you say, I think your problem might actually be the exact opposite in that as opposed to overheating them, you are never actually getting them up to the temps they need. I could be wrong, but in a stock power C5Z on R888 with spindle ducts I can't imagine you are actually overheating a D50 1.11 and a C300.

Even driving pretty hard with Continental slicks on my C5Z, I had to tape up 3/4 of my ducts to get enough heat into the 1.11.

Z06trackman

Negative. I have always relied on the look of the rotor and the pads, and of course the presence or lack thereof of pad fade. Both the DS11.1 and C300 faded when I really leaned on them. I have yet to fade the XP10 with my setup.

You offer an interesting premise, and I am a fan of data, but I want to resist because it goes against 20 years of experience; who knows?

I could buy some temp paint for the rotors, or just keep using the Carbotech XP10s I have favored over the last 4 years. I have used a lot of pads prior to finding these. I went with the DS11.1s when I bought the AP T-1 kit because Gary raved about them, then went to the C300 per his advice, then finally got Carbotech to build me some custom 50mm XP10s (they are regular order now) and now I'm happy again.

RedLS1GTO

I trust my butt dyno as much as any data out there so I know exactly what you are saying, but it is another possibility to take a look at. I know that every person is different in brakes so what is true for 1 is not necessarily true for another so despite my experience with them, you could very well be getting them too hot. The C300 and 1.11 both have claimed max operating temps of 1400F vs. 1600F for the DTC70 and 1650F on the Carbotech so your butt dyno could be right. On a track without a lot of time between braking zones to cool them down, I suppose it just might be possible. I would love to see some numbers.