Carbotech 1521 issue
 

This weekend I installed the Essex AP Sprint kit with Carbotech 1521 pads (in addition to 1521 pads on the OEM rear calipers) and I'm pretty disappointed. I'm sure it has nothing to do with the AP kit and it's certainly possible that I'm expecting too much from street pads.

I put the new brakes on and bled them thoroughly and went out to bed in the 1521s with ~7 hard braking events from 60-10. The rotors turned a nice shade of blue and I started to get pad fade. However the pedal never felt all that confidence inspiring and I really had to mash on it to threshold brake.

I bled the brakes again and got a couple tiny bubbles from one of the AP calipers. Ok, problem solved, right? Not really... The pedal is now a bit higher and firmer but the main problem still exists.

The initial bite and pedal application feels fantastic. Firm and responsive as I'd expect. I press harder and harder and don't get a linear response though. I can barely engage ABS and I can feel a hard spot in pedal application that I assume is the master cylinder bottoming out.

Keep in mind that I have pretty sticky RE-71R tires, so even coming from OEM pads on OEM calipers and I could barely lock up my brakes... Essentially the 1521 pads seem to have the same ultimate performance as the OEM pads but better initial bite.

The issue seems exactly like what this guy experienced (hurray google search): http://www.camaro5.com/forums/showthread.php?t=371995

So am I simply expecting too much from the pads or do I still have more air that needs to be bled out?

Sounds the same as mine. 1521 is a soft street pad. If you're rolling on RE71R's I'm not surprised you can barely lock them up.

That's pretty much what CSG Mike implied too.

A buddy of mine had them on his tow rig truck and couldn't lock them up either... Put good parts store pads on and could fade them a bit easier but at least they'd lock up.

Bah. I guess my expectations were just too high. At least I won't be over braking at autocross? :iono:

Given the Sprint is not really changing brake bias, it's not adding stopping power either. You'll probably prefer an AutoX pad, AX-6 if you want Carbotech. I like mine but I can't get them to stop making horrid noises.

I've used the AX6 on my GTI (actually they were in use in my avatar as a track pad cause slow and light weight, lol) and they dust horribly and make terrible noise until you get them really hot... Which isn't going to happen on my drive to work so I really wanted to avoid that.

The AX6s also have a pretty bizarre cold behavior, they feel a LOT like my 1521s feel but with one good stop off the highway as they warm up the friction ramps up quickly and you end up putting your face in the steering wheel and stopping 50 feet short if you kept the same pedal pressure. I imagine you've noticed this already :)

Same BBK, same street pads, they work as expected on the street with low dust. They last forever and they fade if you push them too hard. AX6 comes alive much quicker and much harder from cold but will also fade on persistent abuse.

These are not an aggressive pad. I have used them in stock sizes on non-ABS Solo/RallyCross cars on purpose to tame front inner lockup.

Thanks guys. I guess I was just expecting too much from them. I guess I'll look for something a step up if I ever wear these out.

I have used the XP10s for autocross and they have been great. Much more aggressive than the 1521.

Using XP10s on the front of my GTI (too lazy to put street pads on it again) and it simply locks up the fronts way before the rears. Kinda unpleasant to drive at autocross because you have to be super gentle on the pedal.

In my experience, 1521 compound is useless for AX, AX6 is most appropriate for AX and XP compounds usually won't get up to temp at AX and are harder to modulate than AX, but would work...

Interesting to hear. Well if your GTI brakes are anything like my R brakes, then i believe the XP10 pad would be too much for that setup. My R has touchy brakes stock, i love it, but the wife finds it irritating.

I have used XP10s for AX with no worries, but our AX course is a bit different than most. I see speeds as high as 90mph quite often. And I am too lazy as well to change out the pads. They work great on the track and AX for me. I understand your concern, since the GTI locked up to easy. But on my BRZ I run an AP kit with XP10s and I currently have RE71s (i miss my RS3s) installed and my car doesnt lock up to early. In fact brake modulation is pretty good. Just my experience so far.

Chatted with Mike a bit, sounds like there's either something seriously wrong with my pads or I still have air. I can barely activate ABS with the pedal bottomed out... I'll try bleeding them again tonight, I've got ~100 miles on them now and abused them yesterday so any air should have worked its way to the top of the calipers.

My GTI has pathetic brakes, mushy and plenty of slop in the top of the pedal travel, etc. Things were different on the Mk2's :)

The XP pads dust and squeal and generally annoy me... No experience with the XP10s on the BRZ at an autocross though, but I'd likely find them too touchy for my tastes.

Well my guess is, you know what you like and have the experience to make a good decision. I hope you figure out what is going on, and Mike should be able to help.