Brembo Big Brake retrofit kits for E28/E23/E24

E28 technical advice asked and given! Troubleshooting, modifications and more.
BenGerman
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Re: Brembo Big Brake retrofit kits for E28/E23/E24

Post by BenGerman »

Sorry I'm just getting back to everybody. Real life has caught up and I spend most of the nights this week at my real job. ;)

I purchased a 6 piston caliper of ebay but got the wrong part delivered. :roll:
Already bought another one which should arrive some time next week.
I still need to confirm the physical differences between the 330 and 350mm setup. The pads are different, the bolt locations are different, but potentially the housing might be the same.

I'm still aiming to have the M7 equipped with Cayenne calipers, E34 MC, 348/345mm rotors and the vacuum booster setup at the Vintage.
I would also like to bring some of the other sets as showcases.

q20v wrote:If you want to sell me a set before your website is up and running I'd love to help out in that respect. You've invested a ton already, I don't mind investing in your brackets if it helps confirm another platform. I've been eyeing 986 rear calipers on eBay lately and there's definitely no shortage!
Agreed, they are easily available.
There is also a nice set of Turbo calipers all around for about $400 OBO! Still a very good deal. The last set of used E31 calipers sold for double that.

It will be a while before I have those brackets ready for serious testing.
I really want to take the first set out myself and give them some good testing. Again, we are not talking about some fancy add on.
This is brakes. Failure of this product can cause serious harm to people on the road.
scarey013 wrote:I’m glad this thread came up. I’ve had a set of 996 calipers for a few years and have been planning on putting them on my e28. A good friend of mine pointed out that the bias would likely be way off, so I started making spreadsheets. Oh joy.
Thanks for sharing all your infos, it's great to see that I'm not the only one out there with those thoughts.
I hope at some point this can be the go-to thread for big brake upgrades on our platform.
My spreadsheet by now has about 15 worksheets with different calculations.

Good information in the M3 rear rotors. At this point, I don't see a good use for them but I'll add them to the list for sure!
skeeter_nohustle wrote:Im in Cincinnati and im the proud owner of beautiful 1985 BMW 735i E23 if you need a donor car for test fitment let me know i can make the drive to you sir. Besides i would love to upgrade my brake system lol
Sounds good, I'll keep you in mind. I have an E23 myself. At this point I would hate to tear a strut out of the car, but I have a good lead to a spare set of struts to take my measurements outside the car.
Philo wrote:Great work and really happy that someone picked up on this project. Looks familiar :D - http://phil.infostreet.com/M5_Images/99 ... lipers.JPG

I'm running the Porsche 996 fronts with E34 M5 rears on a 528e vacuum booster. Visually I like the look of the big calipers and rotors but to be honest I had better stopping power with the original M5 brakes on hydro-boost. I think my issue is not enough vacuum, currently using a 528e booster. Any ideas on how to up the vacuum let me know.

Thanks Ben, keep it up !

P.
Thanks again for all your inspiration. I went through your thread a couple of times to get everything that you already collected.
Too bad your project died after your car!

Vacuum is something I would consider switching over too as well. How did you make it fit in your M5, do you have detailed pictures?
From my measurements it would be extremly tight.
One option could be the E34 booster?

Edit: I believe the ITB setup might be the culprit. It is known to cause lower vacuum pressure than the single TB setup if I'm not mistaken.
Where do you get your vaccuum?

I will try to call you next week.
BenGerman
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Re: Brembo Big Brake retrofit kits for E28/E23/E24

Post by BenGerman »

328x20 in the rear with Turbo calipers will be awfully tight in 16" wheels. The dust shield will need the edges trimmed all around.
Once the brackets are completed, I will test again.
But it might stay a 17" only option and I will have to investigate more towards the 315mm M3 E36 rears with 996 calipers.

Time will tell.

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BenGerman
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Re: Brembo Big Brake retrofit kits for E28/E23/E24

Post by BenGerman »

Added the last missing piece to the caliper collection today. Cayenne aka the anchor. Almost scary how huge that thing is.
And still lighter than most of the factory options (basically every option besides the E31 Brembos).

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As seen in the pictures, I'm not happy with the pad and rotor surface area combination.
It is insane how much surface those 334mm rotors have compared to modern rotors.
For example E46 M3 CSL rotors in 345mm are fully covered by the same caliper / pad combo.

Therefore: the 334mm rotors have been dropped from the equation at this point.

But: I'm already working on another possible solution to maximize rotor surface area just a little more. It would also drop the weight below most of the factory options. That's what I'm leaving it at right now. More details later on.

Also clearly visible:
There is no way to make a 348mm rotor fit a 17" (Style 42 17x8 pictured) wheel at this point.
skeeter_nohustle
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Re: Brembo Big Brake retrofit kits for E28/E23/E24

Post by skeeter_nohustle »

Thank you for your commited R&D im excited to see the out come with a modern brake ,rotor and pad set up for my beloved E23
q20v
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Re: Brembo Big Brake retrofit kits for E28/E23/E24

Post by q20v »

Hey, how are things going?
BenGerman
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Re: Brembo Big Brake retrofit kits for E28/E23/E24

Post by BenGerman »

Not a lot of progress in the last couple days, real life kept me busy.
But, I now a have spare E28 strut and we are working on the front adapters.
Still aiming for driving a car with the big brake setup (Cayenne) to the vintage.
1st 5er
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Re: Brembo Big Brake retrofit kits for E28/E23/E24

Post by 1st 5er »

BenGerman wrote:... real life kept me busy.


:rofl:
skeeter_nohustle
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Re: Brembo Big Brake retrofit kits for E28/E23/E24

Post by skeeter_nohustle »

Any new updates ?
BenGerman
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Re: Brembo Big Brake retrofit kits for E28/E23/E24

Post by BenGerman »

It will be at least another week before any more updates will be posted.
The front adapters are in the works.
skeeter_nohustle
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Re: Brembo Big Brake retrofit kits for E28/E23/E24

Post by skeeter_nohustle »

Sounds ..thanks !
BenGerman
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Re: Brembo Big Brake retrofit kits for E28/E23/E24 - Poll ti

Post by BenGerman »

Finally got around working a little more on potential pricing and summarizing all the options.
The question is now, what would you guys be interested in?
Curious to see what everybody thinks!
If at some point there is high interest in one particular version, I am willing to negotiate with Suppliers for rotors, pads and rebuild kits to get a lower price. Maybe even have a whole batch of calipers powder coated.

Image

Assumptions:
Prices include calipers, caliper rebuild (new seals & powdercoating) for used ones, rotors, pads and adapter where necessary. No SS brake lines included yet which might be necessary for the connection.
Costs for V, VII & VIII are for the complete BBK from Turner / ECS.
Estimated caliper costs:
- Cayenne $200 per set of fronts
- 996 Front $200 per set of fronts
- 996 Rear $200 per set of rears
- 986 Rear $150 per set of rears
- ATS Front $250 per set of new fronts, no rebuild costs (for customer powdercoating) applied
- E31 Brembo Fronts $500 per set of fronts
Rebuild costs for Porsche calipers about 300 for a set of 4. (45 for seals per caliper, 30 for powdercoating per caliper)
Rotors are priced off ECS for Zimmermann, Meyle or Brembo, whatever was the cheapest.
Pads are priced off ECS for Pagid, Jurid or Textar (factory replacement options).
E23s require different rotors in the rear (Different Offset), E32 750i or F10 528i seem to be potential options.
T_C_D
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Re: Brembo Big Brake retrofit kits for E28/E23/E24

Post by T_C_D »

I am interested in buying ATS front adapters only. Is that an option?
cek
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Re: Brembo Big Brake retrofit kits for E28/E23/E24 - Poll ti

Post by cek »

BenGerman wrote:But it might stay a 17" only option and I will have to investigate more towards the 315mm M3 E36 rears with 996 calipers.

Time will tell.
What's the word on 16" wheel fitment here? Your latest didn't make the answer clear (to me anyway). Great work on this, regardless!
BenGerman
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Re: Brembo Big Brake retrofit kits for E28/E23/E24

Post by BenGerman »

T_C_D wrote:I am interested in buying ATS front adapters only. Is that an option?
It for sure will be!
I'm not looking into offering the whole kits all the time. So the adapters will most likely be the only thing I will offer for sale.
This is more of an overview how much the total costs for an upgrade would be to evaluate what kits that make sense.
cek wrote:
BenGerman wrote:But it might stay a 17" only option and I will have to investigate more towards the 315mm M3 E36 rears with 996 calipers.

Time will tell.
What's the word on 16" wheel fitment here? Your latest didn't make the answer clear (to me anyway). Great work on this, regardless!
From what I found out, there is huge differences in the fitment of different wheels.
For example: Style 42 17x8 has about the same room as a Style 5 16x8.
At this point I'm very confident that all the options with 324mm front rotors and 328mm rear rotors (close call there) will clear the Style 5 16x8 wheels. I should be able to confirm for sure in the next 2 weeks.
Individual fitments will have to be discussed.
adam_poll
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Re: Brembo Big Brake retrofit kits for E28/E23/E24

Post by adam_poll »

I'm still most interested in the VIII.3 with ATS calipers front and 986 rear. I would likely just buy the adapters from you and slowly build/rebuild the rest of the kit to spread out the cost and use up my track pads in my current 540i setup.

Thanks for the continued effort.

Adam
q20v
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Re: Brembo Big Brake retrofit kits for E28/E23/E24

Post by q20v »

I would just be interested in 986 rear adaptors. I would source my own disks and calipers.
BenGerman
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Re: Brembo Big Brake retrofit kits for E28/E23/E24

Post by BenGerman »

It’s been a rough day in the shop.

Good news first: the ATS calipers seem to work good, no big adapter required.

The bad news: there is no way to make the 1st Gen Cayenne rotors work. :( the mounting holes are in the way, no matter which way we tried to move the caliper. It would require at least a 14” rotor. And that requires 18” wheels.
So it won’t happen. I was really confused first, as the calipers are being used on E30s, but the E30 strut (mounting position for the factory calipers) is a lot smaller, giving enough room for an adapter.

But: I hate giving up and just ordered a set of 2012 Panamera 6-piston calipers.
They are top mount and I still see a chance to make those work. Plus they are lighter and take up less space in the wheel.
Thradya
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Re: Brembo Big Brake retrofit kits for E28/E23/E24 - Poll ti

Post by Thradya »

BenGerman wrote: Image
Am I reading this incorrectly? It seems like 745i's brakes are rather decent and upgrades don't make much sense from price/performance perspective? Or the upgrades fade way less or something?
BenGerman
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Re: Brembo Big Brake retrofit kits for E28/E23/E24 - Poll ti

Post by BenGerman »

Thradya wrote:
BenGerman wrote: Image
Am I reading this incorrectly? It seems like 745i's brakes are rather decent and upgrades don't make much sense from price/performance perspective? Or the upgrades fade way less or something?
You are reading it correctly in regards of the brake torque.
There is a couple of factors influencing the brake torque.
The explanation for the high torques for the E23 system are based on the small diameter of the master cylinder.
The E23 only runs a 22.2mm Mc, while E28s have 23.8 and E34s have 25.4mm.
The smaller the surface Area of the MC piston, the higher the pressure in the brake like, the higher the pressure on the caliper pistons, the higher the brake torque.

The question is now: why not just run the 22.2mm MC in every setup?
Ultimately the stopping of your car is defined by a couple of things. If you just reduce the diameter of your Mc, your pedal travel will increase significantly. The feeling you get when braking is basically the amount of brake fluid that you move through the lines at the same time, trying to displace the volume of the caliper piston(s).

That’s why a lot of people like to do the upgrade to the 25.4mm Mc on the E28. The ultimate brake torque is decreased, but the brakes can be modulated way better by the driver.
The same thing is being done by a lot of Porsche Track Guys that upgrade the factory MC with 25.4mm ( for 911 Turbo, Cayman, Boxster and so in) to the MC of the 911 GT3 which is 27mm in diameter.

The more piston area you have, the more you will have to compensate the increased fluid flow with a bigger MC.

In regards of the E23 brakes you are right. The rotors are only 284mm in diameter, the pads have a very small surface area. Both of these factors are mayor contributors to brake fading.
Also the available pad choice is very limited.

Which brings me to the last point: friction coefficient of pads.
This is one of the main contributors to increase brake torque.
All my calculations are based on a friction coefficient of 0.4, which according to my research is an average number for factory brake pads.
If you choose to go with a full blown race pad (let’s take the Hawk DTC-70) your friction coefficient at temperature can be as high as 0.85. With that being said, the friction coefficient under normal operating temperatures (street driving) is even lower than 0.4, which is reached at around 370 F pad temperature.

Now if I take the friction coefficient of 0.85 and combine it with the cayenne calipers and 324mm rotors I can increase the brake torque from 638kNmm (yes, I just realized the error with my list, using the wrong units, i didn’t convert mm to m, therefore we will go with Nmm for now) to 1,355kNmm. That would be almost triple the original torque of a 535i front brake. Imagine what that feels like, given everything else stays constant.

The Brake torque number is mainly there to compare the front to rear Bias, as it is based on the assumption of a 1000N input force on the MC, which is defined by the operator and pedal leverage. This can also be affected by the MC size, which defines the position your pedal stiffens up and therefore the position of the pedal where you are appliying the pressure.

Hope that helps to clarify the technical background a little bit.
Thradya
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Re: Brembo Big Brake retrofit kits for E28/E23/E24 - Poll ti

Post by Thradya »

BenGerman wrote:You are reading it correctly in regards of the brake torque.
There is a couple of factors influencing the brake torque.
The explanation for the high torques for the E23 system are based on the small diameter of the master cylinder.
The E23 only runs a 22.2mm Mc, while E28s have 23.8 and E34s have 25.4mm.
The smaller the surface Area of the MC piston, the higher the pressure in the brake like, the higher the pressure on the caliper pistons, the higher the brake torque.

The question is now: why not just run the 22.2mm MC in every setup?
Ultimately the stopping of your car is defined by a couple of things. If you just reduce the diameter of your Mc, your pedal travel will increase significantly. The feeling you get when braking is basically the amount of brake fluid that you move through the lines at the same time, trying to displace the volume of the caliper piston(s).

That’s why a lot of people like to do the upgrade to the 25.4mm Mc on the E28. The ultimate brake torque is decreased, but the brakes can be modulated way better by the driver.
The same thing is being done by a lot of Porsche Track Guys that upgrade the factory MC with 25.4mm ( for 911 Turbo, Cayman, Boxster and so in) to the MC of the 911 GT3 which is 27mm in diameter.

The more piston area you have, the more you will have to compensate the increased fluid flow with a bigger MC.

In regards of the E23 brakes you are right. The rotors are only 284mm in diameter, the pads have a very small surface area. Both of these factors are mayor contributors to brake fading.
Also the available pad choice is very limited.

Which brings me to the last point: friction coefficient of pads.
This is one of the main contributors to increase brake torque.
All my calculations are based on a friction coefficient of 0.4, which according to my research is an average number for factory brake pads.
If you choose to go with a full blown race pad (let’s take the Hawk DTC-70) your friction coefficient at temperature can be as high as 0.85. With that being said, the friction coefficient under normal operating temperatures (street driving) is even lower than 0.4, which is reached at around 370 F pad temperature.

Now if I take the friction coefficient of 0.85 and combine it with the cayenne calipers and 324mm rotors I can increase the brake torque from 638kNmm (yes, I just realized the error with my list, using the wrong units, i didn’t convert mm to m, therefore we will go with Nmm for now) to 1,355kNmm. That would be almost triple the original torque of a 535i front brake. Imagine what that feels like, given everything else stays constant.

The Brake torque number is mainly there to compare the front to rear Bias, as it is based on the assumption of a 1000N input force on the MC, which is defined by the operator and pedal leverage. This can also be affected by the MC size, which defines the position your pedal stiffens up and therefore the position of the pedal where you are appliying the pressure.

Hope that helps to clarify the technical background a little bit.
That was an excellent explanation! Thank you!
BenGerman
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Re: Brembo Big Brake retrofit kits for E28/E23/E24

Post by BenGerman »

After the frustration with the 1st Gen Cayenne calipers, there was only one way: go even bigger.
I ordered another caliper, this time off a 2012 Cayenne (92A). The main difference is the mounting style, while the older Cayenne caliper has a bolts that mount sideways, the newer ones are bolted down from the top, just like the 911 caliper. This will hopefully allow me to design a bracket that works on the E28 struts.

First impression: that thing is huge!
But, it seems like it is shaped less bulky, allowing for easier Fitment in the wheels.
And indeed, the 16” Style 5 fit with 334mm rotors the way it seems.

Now it’s time to sell some of the old cayenne calipers. (I have 10 Porsche, 2 Brembo E31 and 2 Cadillac calipers in my basement :roll: )

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Edit: Fits like a glove!
A couple slight mods to the caliper and it will be a perfect match to the 334mm E38 rotors or the 330mm 2-piece rotor solution.
It's crazy how BIG that caliper is in person.

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Last edited by BenGerman on Mar 25, 2018 2:22 PM, edited 1 time in total.
maxpossu
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Re: Brembo Big Brake retrofit kits for E28/E23/E24

Post by maxpossu »

adam_poll wrote:I'm still most interested in the VIII.3 with ATS calipers front and 986 rear. I would likely just buy the adapters from you and slowly build/rebuild the rest of the kit to spread out the cost and use up my track pads in my current 540i setup.
Also voting for ATS front, 986 rears! :up:
skeeter_nohustle
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Re: Brembo Big Brake retrofit kits for E28/E23/E24

Post by skeeter_nohustle »

Amy updates ?
BenGerman
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Re: Brembo Big Brake retrofit kits for E28/E23/E24

Post by BenGerman »

Still working on it. Sorry there hasn’t been a lot of updates lately.

I’m still confident I will have a car at the vintage showing a set. At this point it is more realistic that I will have a set of Cadillac calipers mounted to my car. Ultimately I will run the Cayenne calipers, but I’d like to show the combination that everybody here is interested in (Cadillac + 986).
BenGerman
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Re: Brembo Big Brake retrofit kits for E28/E23/E24

Post by BenGerman »

I got 2 more rotors in today (324x30 --> E23, E24, E28, E34 Front & 336x22 --> E23, E32 rear).

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The combination above will be mounted to my car at the Vintage with ATS and 996 Turbo Calipers.
Even though it's slightly suboptimal for now, it is only an intermediate step before the Cayenne calipers will be mounted with 2 piece 345x32 rotors.
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