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View Full Version : Angry Ass E34 Brake Upgrade thread (generally applies also to E24, E28, E31, E32)



BleedsBlue
04-26-2021, 05:55 PM
As we are in the midst of development on additional brake upgrades, it was high time for a clean, new thread detailing what we are offering, with a venue for folks to comment, critique, and collaborate.

Available now - Front Axle
Currently available today is our best-selling F30 335i-based 340x30mm, Brembo 4 piston Street brake upgrade. The combination of enhanced performance and budget-friendly parts availability have understandably led to many street-focused customers opting for this kit. Best paired with the E34 540i/M5 rear brake package (300x20mm rotor, single 40mm piston sliding caliper), this kit yields only a 0.1% change in brake bias over the factory E34 M5. While street-focused, these front brakes are completely up to the task for a full-weight E34 540i/M5 on track, which we have tested personally (and our customers have tested themselves).

Advantages:


Cost used (just $69.72 for adapter kit (https://angry-ass.com/product-organizer/p/340x30-4-piston-front-brake-system-street), rotors are under $350/pair new from BMW [cheaper through us], and calipers can often be found for $200-500/pair used)
Cost new - at just over $1500 all-in for all new parts, there is no better OEM+ front axle upgrade option
Minimal weight change from stock E34 M5 front brakes, with greatly increased brake capacity
Parts availability: consumables are easily available from BMW or aftermarket; pad shape is shared with all F80/2 M3/M4 and M2
Some 17" wheel fitment (most with small spacers): BMW M System, Apex race wheels, OZ Futura, Racing Dynamics, etc


Disadvantages:

Fits few OEM 17" wheels without spacers; most wheels hang up via the barrel, making the issue impossible to solve with spacers. This is the primary reason for the development of the smaller AP Racing kit, detailed below
Not a race caliper, if you are speccing brakes for a true track car
Not an unsprung weight-savings advantage over stock E34 M5
The ideal rear-axle complementary kit, E34 540i/M5, is now difficult to source used or new (some components are NLA)


https://live.staticflickr.com/65535/50671904238_b153a9df31_c.jpg

Competition Kit
For track-focused customers, we are soon to release a production version of a caliper and rotor combo that 93FIM5 has been running on his personal M5 for over two years: our AP Racing 355X32 6 Piston front kit (https://angry-ass.com/product-organizer/p/355x32-6-piston-front-brake-system-competition). The production hats are currently being drilled for non-M rotor retention screws, but these kits will soon be ready for order. Specifically designed to accommodate BMW M System wheels, the Competition kit is intended to fully maximize the available brake real estate within track-ready 17" wheels. While 93FIM5 has been running a version of these brakes with the now-unobtanium, late-M5 328x20mm rear brakes, the bias numbers work out nicely with the stock 300x20mm E34 540i/M5 rear kit as well.

Advantages:


Adapts modern race caliper and rotor technology seen on F80 M3, 991 GT3 etc BBKs to our great era of '80s/'90s metal
The most effective braking system you can fit under 17" wheels
Affordable (~$300/ea) rotor replacements (unlike Brembo GT kits et al) with option for burnishing in pad compound of choice; highly available, wide variety of pad compounds
Weight reduction over stock E34 M5 front brakes


Disadvantages:

Cost - at $5,000, this kit costs more than many entire E34s
Widespread 17" wheel fitment unlikely
Both currently-available rear-axle kits, E34 540i/M5 pre-5/'94 and E34 M5 post-5/'94, are rare to find used and have NLA parts if sourcing new (an alternative is coming... see below)


https://live.staticflickr.com/65535/51140975858_cb6fbb84d9_c.jpg

Coming soon - Small AP Front (Street), Big AP Rear (Competition)
First, let's talk about an affordable BBK for those with common OEM 17" wheels (Style 5/19, 32, et al), 16" wheels, and even some 15s. We were disappointed by the packaging of the 340x30mm kit for 17" wheels, and decided to pursue a front axle option to accommodate a variety of smaller wheels. There is a minor small diameter tire resurgence, and many prefer small wheels - they should not have to suffer with stock or limited brake options!

Enter:
https://live.staticflickr.com/65535/51140089282_94d771a50f_c.jpg
(Shown is the available 299x32mm rotor, which is incredibly tidy and light)

The "Small AP" front kit, with the much-loved older-style AP Racing caliper design in a sensible four piston layout. The two AP Racing rotor options (299 and 325mm) we are pursuing will shed weight over stock E34 M5, but the 299mm rotor is particularly light and efficient. Paired with the four piston caliper, we expect the 299 to fit under select 15" wheels and most 16" wheels; the 325mm should sneak under some 16" and all 17" wheels!

Because we can, we are also looking to dovetail this caliper bracket with fitting the one-piece OEM E31 324mmx30mm rotor, which are typically under $200/pair. This option is designed purely for economy's sake, and secondly because E31 Brembo calipers are so hard to find now.

Even with all-AP Racing components (and Angry Ass designed and produced rotor hat and caliper bracket), either of these AP kits will be quite affordable, with each caliper costing a little over $300 and each rotor around $200. The price of our components is volume-dependent as always, so chime in if these kits are of interest!

For the Competition junkies...
Especially as simple and affordable sliding caliper rear axle kits are becoming rare, it was time to design a commensurate rear axle upgrade to pair with our intense AP Racing RadiCAL 6 piston front kit:

https://live.staticflickr.com/65535/51140089217_1c30c77e08_c.jpg

Offering the same revolutionary race caliper design as the front Competition 6 piston kit, this will be a rear 4 piston RadiCAL kit with a 340x28 J hook rotor. Specified with a racier brake bias than factory (more towards the rear, now upgraded to handle more rear bias), this kit is a perfect complement to the front Competition equipment - and is future-proofed for a likely larger front Competition upgrade intended for big-power cars, with 18" wheel requirements.

The Rear Competition setup will be pricey, but cheaper than the front at least!

A parting note

I'm assembling weight numbers for all of these options (including best estimates for kits not yet built), and will update the thread as I know more
I can't overstate how much customer interest and commitment drives our production numbers, which then lowers customer cost - please share your thoughts and interest
A blabbering dissertation on rear axle "upgrades": We are regularly asked about a rear upgrade to pair with the 340x30mm 4 piston Street upgrade, which likely enjoys a 50-75% take rate purely for aesthetic reasons. We are not in the business of designing chassis upgrades for aesthetics alone, so we may never design a rear axle kit when the stock E34 540i/M5 rear yields such a great bias with the 340x30mm front. It pays to note that even modern M5s, with twice the horsepower and topping two tons, retain single piston sliding calipers... that said, we are currently going through the motions of running bias numbers and adapter studies for the "F30 M Performance" two piston Brembo rear caliper, to determine if this makes sense. I will update the thread on this topic as well

a777fan
04-26-2021, 11:05 PM
Brent,

Thanks for taking the time to summarize for 2021! I love the fact that you guys are still at it for these platforms.

I’ve got to say, a day doesn’t go by without me thinking about the 340 upgrade for the fronts. Someday, I’ll be ready!

123zorn
05-03-2021, 10:36 AM
Once the small front AP setup becomes available, I'd be very interested in knowing the fitment for 15" rims. I usually run 15" in cooler weather, either snows or all seasons on stock basketweave rims or some old ATS rims from my E28 (yes, I have 4 sets of mounted tires and yes I have a problem).

circuit.heart
05-03-2021, 05:52 PM
Just to add to the F30 rear discussion - I've been down this road before and 100% agree with Brent. It's an annoying conversion, and not nearly as cost-effective as the front. Between somewhat large piston sizes and a 324-328mm rear rotor, there's a lot more brake torque from the rear switching to the F30 caliper. I had huge issues locking up the rear brakes first unless a more aggressive pad is used in front, OR the tires are just so slippery that there's not much weight transfer to the front under braking.

There are ways to make the F30 rear caliper work, but the 540i/M5 rear is very good as-is.

690109

690110

BleedsBlue
05-03-2021, 06:49 PM
Brent,

Thanks for taking the time to summarize for 2021! I love the fact that you guys are still at it for these platforms.

I’ve got to say, a day doesn’t go by without me thinking about the 340 upgrade for the fronts. Someday, I’ll be ready!

Absolutely - we get a lot of questions via email and Instagram (and Facebook, which we try and immediately route to email), so it was past time for a reference thread with community participation.

That's great to hear - just let us know! No rush, as in the next 6-12 mo we will have more options, clearly :D


Once the small front AP setup becomes available, I'd be very interested in knowing the fitment for 15" rims. I usually run 15" in cooler weather, either snows or all seasons on stock basketweave rims or some old ATS rims from my E28 (yes, I have 4 sets of mounted tires and yes I have a problem).

We are definitely tracking that, as well! We also have a thread going on MyE28, which should get more small wheel focus I expect.


Just to add to the F30 rear discussion - I've been down this road before and 100% agree with Brent. It's an annoying conversion, and not nearly as cost-effective as the front. Between somewhat large piston sizes and a 324-328mm rear rotor, there's a lot more brake torque from the rear switching to the F30 caliper. I had huge issues locking up the rear brakes first unless a more aggressive pad is used in front, OR the tires are just so slippery that there's not much weight transfer to the front under braking.

There are ways to make the F30 rear caliper work, but the 540i/M5 rear is very good as-is.

690109

690110

Very good points, and the math we are seeing completely backs up your empirical evidence - both are valuable! I think we are close to identifying a safe way to adapt the rear calipers, but the bias change may prove too much on paper to warrant an expenditure. Especially considering the majority of our customers are using the 340mm front.

By their own admission, most folks asking about the rear Brembos are in it for looks, but that's not really enough for us to bring a product to market...as we are quick to point out, the use case for a near 50/50 sedan is so low. If the F90 Competition M5 still rocks a sliding rear caliper...?

Fatandre
05-09-2021, 06:14 PM
I love where this is going. Waiting for the AP set.
Wish you could do more of goodies for the V12 crowd.

https://live.staticflickr.com/65535/51167970087_52dc242023_k.jpg (https://flic.kr/p/2kXxdQP)Untitled (https://flic.kr/p/2kXxdQP) by andres petur (https://www.flickr.com/photos/140377417@N05/), on Flickr
https://live.staticflickr.com/65535/51122993053_d0a3089995_k.jpg (https://flic.kr/p/2kTyGJH)Untitled (https://flic.kr/p/2kTyGJH) by andres petur (https://www.flickr.com/photos/140377417@N05/), on Flickr

bimmerjan
04-27-2023, 01:25 AM
And now there's no upgrade available :( I wish more people chimed in on this. Any updates to producing the big AP kit Front + rear?