My background is 250GP bike racing, BSB, MotoGP spannering, 3.5 owner for 5 or so years. I spent a lot of time on the calipers and became quite OCD about preparation. Having been lucky to work with factory only calipers I appreciate the engineering and the wildly differing requirements of riders/drivers. We had data channels specifically for brake pressure, temps, etc, factory stuff. The first time I looked at the AP's, I thought that they looked a bit basic. I have AP CP5575 (old school 6 pot) on a 1 series with two piece 356mm rotors, my old Atom would outbrake that easily, the 4, I am not sure it would....but might with some leg gymnastics.
Picking up the 4 the brakes were not much short of awful. Long pedal, no bite. I was assured that they needed bedding in time so I followed my usual procedure of heat cycles. The dull drive back on the motorway it's easy to bed them in with a bit of left foot and loads of straight roads. They never came to me. Were they less crap, maybe a little.
I put up with it TBH, but then Ian drove mine and it just reaffirmed how rubbish they are. Now. At this point I am slightly pissed off as the only reason I opted for the 'race' setup was that the 3.5 was just epic on the brakes, so I figured this is the AP 'fit and forget' solution. It turns out not so much.
Enter Chris and Paul, who gave me access to their work, and invaluable feedback. They are amongst a niche of owners who really push and modify the AA4 platform. I came away after passenger rides and generally annoying them for a day at Cadwell with many questions.
Today, Ian and myself had a little look at the AA4 and his AA3.5 setup, both factory. To say a lightbulb has gone on is somewhat of an understatement. The 3.5 uses an Alcon CRH304, application rally, single seater, hill climb, saloon car. The 4 uses AP 7600, application: factory BBK, fast road. I think that's the crux of it, but let's continue.
Q. What are the actual issues with the 4?
1. Pedal travel, totally unacceptable. There is approx 20mm of nothing, then when it does start to bite it's soft.
2. Feel. The pads feel wooden, horrible.
3. Disc colour. There is very little evidence of bite. They have some colour but they don't clean the disc.
Q. What has been the feedback from the factory?
1. Obviously I raised the issue and the brakes will be bled, pads changed as a start.
2. I am told there is a 'new bleeding process'.
3. I have been told there is a chance air is getting into the system.
Q. And what do you think of that?
No comment.
Q. Does the 4 stop?
Yes it stops, but you need to apply significantly higher pressure to the pedal. The initial bite doesn't give you any confidence.
Q. That'll be shitty pads?
I am going to ask the factory to bleed and change pads. If that sorts everything out, happy days. But, the 3.5 used 1144/2500, nothing exotic at all, and it shouldn't need it due to it's weight. I have the option of a Pagid RS14 and Pagid 19/29...and they were epic on an M3 but ate the discs and are really made for big lardy saloon cars.
Q. If not?
I am prepared to be surprised, but having looked more and more at it I think I won't be. So. In the case of these AP 'race' things still being poor I am going to change the calipers. It is my opinion now that the 7600's are primarily made for servo systems, and do not match the OE Tilton master cylinder. We know the Alcon setup was just about the nicest thing, so there is no point flogging a dead AP horse. Caterham, Radical have nothing trick, and pull up like the older Alcon setup.
My advice to anyone reading this and putting a spec together (and until I am proved wrong, which I will be delighted about) is fit standard brakes and buy an Alcon setup yourself. One thing that is really playing on my mind is why did the factory change an established partnership with Alcon? AP to Alcon, there is no change needed, we have measured everything and it's a like for like swap. The Alcon caliper is slightly wider but hole pitch, centerline, offset is the same. Was it a commercial decision or something else? If anyone from the factory can comment on this I would be very keen to know.
We will have brakes. And just like they used to be
If anyone is interested I have a load of pictures on the above.....
Miss-matched brakes?! 