AP Racing BBK on E92 335i
Itís been a while since I bought these and it's about time I posted a review now that I have been through a couple of different brake pads. There isnít a whole lot of information available for this kit and while it shares the same pads as the E46 M3 kit, the rear pads for this kit is a bit unique. So sharing my experiences may help others find the right pads.
Depending on what you do with your car, a time may come when you realize that the standard brakes are not up to the job. I have over the last couple of years done quite a few laps around the Ring and other race tracks and the brakes have always been a limiting factor in how many consecutive laps you could do before having to come in to let things cool down. Braking repeatedly from high speeds would cause the brakes to go a bit soft and after a number of hard laps enough pad material would have been deposited to the discs to make you believe that the discs were warped. This is not something that gives you great confidence and I always felt it was limiting the fun. Changing the brake pads to a more appropriate track pad and upgrading the discs to grooved aftermarket discs would improve this a bit, but not to the degree I was looking for. I wanted brakes that would stand up to repeated punishment on track days and give me more surface area and choice in race pads.
The standard caliper on the 335i is fairly powerful and strong enough to lock up the wheel without any problems, but when pushed hard repeatedly at higher speeds you suddenly realize that the pads are not biting as much as you would like. Having experienced a few hard braking situations on the autobahn and wanting to do more track days, I decided I wanted to upgrade my brakes when the front discs needed replacement. I could have gone down the route of after-market discs and pads, but I didnít want to spend somewhere between 25%- 50% of the price of the BBK only to find that it still wasnít what I was looking for, so I took the decision to go straight for the BBK.
Having experienced the AP Racing brakes on E92Fanís car around the Ring braking late repeatedly from high speeds using Pagid RS29 pads I knew that the APís would stand up to the punishment and the AP Racing BBK offer incredible performance for reasonable money. Pricewise they are not the cheapest and somewhere in the middle with more expensive kits like Brembo, PFC and Alcon. However running more expensive kits are not a guarantee that you wonít have any problems and my other choice would have been PFC, but the price on those are just silly. Generally very few people are running these kits and having real life feedback was important to me. Hearing horror stories from people buying a cheaper BBK and not having anything but trouble, made me decide on a tried and tested solution.
Another important fact in my decision process was that I needed to have a functioning hand-brake as itís an instant MOT failure here if itís missing (Annual vehicle check required by law after 3 years). As this is my daily driver, not having a hand brake would be a big no-no, so the fact that the AP Racing rear caliper uses the rear OE brake discs was a plus. This would retain the OE hand-brake and new rear discs are a lot cheaper than after-market BBK ones.
In UK there are quite a few distributors of AP Racing brakes and they offer fairly competitive prices, so I had a rough idea of what the brakes would cost. The front kit is about £2200 incl. VAT and the rear kit would set you back around £1000. The rear kit is cheaper as it doesnít come with a disc, so you may need to add ~ £160 incl. VAT for a new set of discs.
I bought my AP Racing brakes from Demon-Tweeks as a friend of mine was able to set me up with an account and a good discount, but I found that the other distributors were still fairly competitive on the price, so I could easily have bought it from any of them.
AP Racing produces the calipers to order, so donít expect many shops to have a set on the shelf. As a general rule I was told it would be between 6-10 weeks. In my case the delivery time for the front calipers took around 9 weeks as it was over the summer holidays, and the rears took 5 weeks as they were ordered later.
The part numbers for the kit are:
Black Caliper Kit Number: CP5575-1009.G8
Red Caliper Kit Number: CP5575-1009R2.G8
- RH = CP5575-802S4
- LH = CP5575-803S4
Brake Discs: Groved
ō356 x 32mm / 48 Vane
- RH = CP3581-536G8
- LH = CP3581-537G8
Requires 18Ē aftermarket wheels or spacers
Black Caliper Kit Number: CP6625-1000BK
Red Caliper Kit Number: CP6625-1000R2
- RH = CP6625-8S0
- LH = CP6625-9S0
Brake Discs: Standard BMW
Remember to buy longer wheel bolts as well, as the standard ones are not long enough. The rotor hat is about 3mm thicker than the standard brake rotor.
When the kit arrived, it came packaged in two big brown cardboard boxes and lots of care had been taken to ensure that nothing was damaged. The boxes contained two AP Racing boxes. One for the calipers, brake hoses and fluid and a box with the brake discs already pre-assembled.
Pre-installation picture of contents: (6138)
- Two calipers (In boxes under the top layer)
- Mounting brackets and bolt, washers etc
- Goodridge braided brake lines, with nylon protectors
- 2x bottles of AP Racing Formula Dot 5.1 fluid (500ml each)
- Set of APF404 Brake pads (Ferodo DS2500)
Close-up of brake pads: (6162)
Close-up of mounting bracket: (6143)
Pictures of the front caliper: (6174, 6173, 6176)
Picture of brake disc box and disc: (6228, 6215, 6213)
The discs we very nicely packed in paper, bobble wrapped and then separated by more protective layers in a nice cardboard box to protect them from any transport damage.
Having asked around a couple of shops for some prices to get this fitted and been quoted anywhere between 4-6 hours, I decided to tackle the installation myself with the help of a friend who had done this before. I quite enjoy doing a bit of DIY and having read the very thorough installation manual that came with the kit, I knew exactly what we needed to do and that we wouldnít have any unexpected surprises during the installation.
The car was driven up on a set of Race Rams to get enough clearance to place the jack under the centre jacking point and then placed on axle stands on the normal front side lifting points. So during the install the car was supported by 2 axle stands and the jack. Nice and secure.
Old disc and caliper before install: (6237)
In the end we probably ended up spending around 5 hours fitting the kit. We could have done it quicker, but we took our time and double checked everything to get the least run out on discs and bled the brakes a couple of times to get the last bubbles out.
AP Racing caliper fitted to drivers side (RHD): (6265)
In order to reset the service light we had to fit a new brake sensor, however this kit doesnít use the sensor, so the sensor was fitted and then poked through to the engine bay where it was zip tied securely. After this we could reset the brake service indicator. Since fitting the BBK the value in iDrive has dropped even thou the sensor is not in contact with anything, so should it drop to 0 or give me a warning then I can easily reset it again as the sensor is fresh. Just donít rely on the sensor and inspect the pad thickness after hard use.
All done and back on the ground: (6283)
Pre-installation picture of contents: (8906)
Pictures of rear caliper (8912 & 8915)
Caliper bracket (8932)
Bolts and adapters (8937)
Ferodo DS2500 pads (8940)
Comparison between rear BMW Stock pad and AP Racing pad (8945)
Done (Sorry, didnít have time to clean the wheels) (9027)
ē Bedding in
The bedding in procedure for the AP discs is a bit special as the discs are not heat treated, so itís important that the bedding in procedure is carefully followed and when done let the brakes cool down so they are stone cold before they are used again. This is best achieved by bedding them in at night on an empty stretch of road where you can bring the temperature up gradually doing 6 blocks of 5 stops from 50-20mph and then have a cooling down period between each block. I find that a nice stretch of road with a roundabout at each end or short motorway section with on-ramps help keep the car moving at all time. When done, try not to use the brakes when driving home and park up and leave it to cool off over night.
When driving the car normally you feel the stronger response from the brakes and the braided lines gives you a much nicer pedal feel. It feels easier to modulate your braking and it has a very reassuring feel to it. Under light braking you may hear a slight increase in the braking noise because of the grooved discs, but this is quite normal and disappears if more force is applied.
I have done quite a few track days since fitting the front brakes and the difference is amazing. Where I previously would only be able to do relative short sessions and almost immediately feel the brakes starting to fade after a couple of hot laps. The APs allowed me to stay out for 20-25mins and have consistent strong brake feel throughout the session. The Ferrodo DS2500/APF404 pads hold up very well on track for a fast road pad and you have to push them very hard to get a hint of pad fade. This would quickly disappear if you eased off a little. Over 160 laps of Brands Hatch Indy circuit I only felt this happen once after pushing very hard into the corners and braking late. The much larger pad and thicker disc really helps with the heat dissipation and to keep temperatures down.
If better braking performance is needed on track then there are several pads with track or race compounds available for the AP Racing calipers. These pads may not be suitable for your normal daily driver as they tend to have less bite when cold and may squeal until they are up to temperature. However once warm you wonít believe the bite they have. Changing pads on the AP Calipers is very easy and doesnít take long per side. You just have to remove the retaining clip, undo two pins at the back of the caliper and you can yank the old pads out. The pads have a hooking eye that you can use to pull them out with, so this can be done even when they are hot.
If you have more time when you change the pads you should really push out the pistons a bit more after the pads have been removed. This allows you to clean the pistons properly and avoid dirt and grit damaging the seal.
New pads for this kit comes with 17mm pad material and should last a fair bit. My DS2500 pads only lost 2-3mm after two track days (160 laps of Brands Hatch) and 4000 road miles later. From past experience a standard BMW pad would only last around 25-30 laps around the Ring if pushed hard and would send the CBS counter into panic mode dropping on average a 1000 miles per lap (13 miles).
There are a couple of brake pads available for this kit and depending on your use you may not need a race pad for track. Certain compounds may also not be compatible with each other so the discs may need to be scrubbed down and pads re-bedded if changing between different manufacturers, but this really depends on the compound. If this is not done, you may actually end up with less performance or brakes that squeal.
(Available in exact pad shape)
Good fast road pad with good cold bite and friction coefficient. The pad is a little on the dusty side and can have a slight tendency to judder when bringing the pad up to temperature on track. This tends only to be for 1-2 corners and then disappears and I have not had any issues with this on the road.
(Available in exact pad shape)
Race pad with very high friction coefficient and supposed to be good, but I would not recommend this pad as it has a reputation for eating brake discs at an alarming rate. Brake discs should last you a couple of pads, but with this pad itís more like a couple of discs per pad.
Good fast road pad with little dust.
Excellent race pad that are Ďkindí to the discs. The pad offers amazing stopping power when up to temperature and a set lasted me two Ring trips (50 laps) and a 3-4 track days before they were completely worn down. They offer very consistent braking, but do squeal a little when using them day-to-day. They are a little expensive at around £250 a set.
Decent track pad comparable to the Pagid RS29 pads and at half the price they are worth a consideration. I have been using these for a while and so far no brakes squeal. At £125 a set they are worth a try. Pad references may say they are 18mm thick, but this is incorrect. They are 17mm and has a rubber shim on the back. Just peel off the rubber shim and they will fit just fine.
Performance Friction offers a great replacement disc for the AP kit. The disc is of better quality than the AP disc and should last longer. It is also heat treated, so this would make bedding in the brakes easier.
PFC replacement discs - Performance Friction CP3581-536/537 - AP Replacement Brake Disc
Installing a set of AP Racing brakes is not exactly going to save you any un-sprung weight. Itís more likely it will be the opposite as the calipers, pads and discs are bigger. For the rears itís only a 260g difference (lighter), where the front will more likely be heavier. Unfortunately I forgot to weigh the fronts before fitting them so I donít have the exact weights for that. I would say it would be at least 1kg heavier if not more as itís both thicker and bigger. If anyone buys this kit then please weigh the fronts and Iíll update the numbers:
AP Racing Front BBK
Caliper (inc. pins) ?g
Carrier bracket ?g
Pads (new) ?g
AP disc (new) ?g
Total weight per side: ?kg
AP Racing Rear BBK
Caliper (inc. pins) 2811g
Carrier bracket 311g
Pads (new) 968g
BMW OE disc (new) 8200g
Total weight per side: 12.29kg
Front BMW 335 brakes:
Caliper (+clip) 3415g
Carrier bracket 1854g
Pads (worn) 787g
Disc (worn) 10700g
Total weight per side: 16.75kg
Rear BMW 335 brakes:
Caliper (+clip) 2792g
Carrier bracket 963g
Pads (new) 602g
BMW OE disc (new) 8200g
Total weight per side: 12.56kg
ē Problems / disadvantages?
Coming from standard BMW brakes that are fairly quiet, then you may feel that there is a little bit more drumming when applying light brake pressure. This seemed more noticeable when the brakes were new and I donít notice it anymore. In general itís fairly standard when you go to grooved discs that there will be a bit more noise, but nothing that would put anyone off. In a way itís quite a reassuring sound.
The only issue I had with the rear brakes were the occasional brake squeal from the DS2500 pads when they were new. AP Racing sent me a set of rubber shims to resolve this and that fixed the issue.
Anti-squeal shim: (9593)
The information from AP Racing did say that the front calipers required aftermarket 18Ē wheels to clear the calipers and I knew it would be tight to get my 193M winter wheels to fit. AP Racing do have card board template that I could use, but I just didnít expect it to be this tight:
Close-up of how tight the space is on a 193M wheel: (6306)
So I knew I needed spacers to avoid collisions with the weights. The 193M wheel slopes in after the weights, so there would be enough space if the wheel was pushed out a bit. The AP Racing rotor hat is 3mm thicker than the standard disc so to keep the same track width all around, I opted to buy a set of 12.5mm Eibach spacers for the front and 15mm for the rears. This gave me enough clearance to avoid the weights and no rubbing.
Front 193M with 12.5mm spacer (2412):
In a way Iím actually quite happy that I went with the fronts first so I got to experience the difference in the brake balance. Running with just the fronts felt fine and it did not upset the brake balance too much. But if you donít want to fit both Front and Rear, then you could just upgrade the rear pads to something better and you would be pretty good. The fronts do most of the braking anyway. However that said, fitting the rears have made a big difference to the overall brake feel and it has given the car a very positive ability to shed speed. Having the front and rears fitted really completes the job and gives me the option to run the same pad material all around. Later I fitted ÷hlins coil-overs and this improved the performance of the rear brakes. The standard Msport suspension is a bit soft and the nose dives quite a bit under hard braking making the rear light.
Overall Iím really happy with the kit and itís given me great experiences on track days driving the car at the limits!