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Discussion Starter #1 (Edited)
I am starting this thread as a few of us are looking at options to modify the OEM brakes, specifically to improve the long term track worthiness of the whole system. So to start with, I will try and document the existing system characteristics.

OEM Specifications:
Front:
Manufacture: Brembo
Part Number @ Left (Driver): 20895801
Part Number @ Right (Passenger): 20895802
Piston Number: 4
Piston Size: 38mm (Aluminum)
Axel Leading/Trailing: Trailing
Axial Pin Separation: 130 mm
Axial Pin Offset from Rotor Center: 50mm (approximate)
Rotor Diameter: 305 mm
Rotor Thickness: 28 mm

Rear:
Manufacture: TRW
Part Number @ Left (Driver): ???
Part Number @ Right (Passenger): ???
Piston Number: 1
Piston Size: 41mm (Steel)
Axel Leading/Trailing: Leading
Center to Center Mount Distance: 110.0 mm
Rotor Diameter: 292 mm
Rotor Thickness: 21 mm

Rebuild Kits:
Front:
Manufacture: Brembo
Dust Boot Part Number: 20.4872.45
Seal Part Number: 05.5955.57

Alternatives: Centric P/N: 14337016
Raybestos PN: WK463
AC Delco 18H463
Rear:
Manufacture: ???
Rebuild Kit Part Number: ???

Alternatives: Centric P/N: 14362056
Raybestos PN: WK910
AC Delco 18H1160

Brake Bias:
I am using information I found on the M3 forum, which jives with other internet searches. You can find the info here: http://www.m3forum.net/m3forum/showt...p?p=1065614092

For Piston Diameters, Rotor Diameters and other parameters, please see above.
Pad Width:
Front: 52.1mm
Rear: 47.6 mm

Pad Type: Ferodo DS2500 @ 300 degC (Friction Factor 0.425)

I am also assumed that the brake fluid pressure front and rear are the same. I have no idea if this is actually the case, but from my understanding it typically is.

Math time.....

Overall Equation
Brake torque generated at the wheel, individually Tf and Tr, is given by Equation 5:
Equation 5: T{f,r} = P · Atotal · Reffective · cF
T{f,r} = Torque at wheel
P = Pressure
Atotal = Combined area of all pistons within a caliper
Reffective = Effective radius of pad placement to rotor
cF = Coefficient of friction of pad material

Front Brakes Area
For a Floating: 2-piston and Fixed: 4-piston caliper:
Equation 7: Atotal = 2 · pi · (rpiston_12 + rpiston_22)
Atotal = Total combined effective area
rpiston_1 = radius of piston 1 *
rpiston_2 = radius of piston 2 *
* - refer to Equation 4 to obtain radius from diameter)

Rear Brakes Area
For a Floating: single piston caliper:
Equation 6: Atotal = 2 · pi · rpiston2
Atotal = Total combined effective area
rpiston = radius of piston *
* - refer to Equation 4 to obtain radius from diameter)

Using this information... I get an overall Brake Bias of 64% front, 36% rear or a ratio of 1.78
 

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Discussion Starter #2 (Edited)
Upgrade Options

Rotor Options:
On the track, the stock rotors just don’t survive long. Some owners have reported warping on tracks that are hard on brakes. When I measured temperatures between stock rotors and Sector111/Inokinetic (Girodisc) on track, we noted a couple of hundred degree Fahrenheit difference in temperature. Granted this comparison is between two different drivers (and skills), but when I finally switched to the Girodiscs, I have seen a drop in temperature.

To my knowledge, there are two aftermarket “race inspired” rotor options available in the aftermarket. Tarox and Sector111/Inokinetic (Girodisc). Both of these designs keep the OEM size, but use better cooling vane designs, a fixed two piece design, and offer a slightly lower weight vs OEM.
Tarox @ Alfa9Supply
Girodisc @ Inokinetic

Currently there are no true “race” rotors available from AP Racing or others. We should be able to fit up to 330 mm rotors without much difficulty, but no one has (yet).


Caliper Options:
As several us have noted, the OEM calipers have a few fundamental design issues that cause issues for track use. This includes dust boots that can easily melt after one session, to aluminum pistons. There are a few options that may be available for the industrious users that we have on the forum. Perhaps some of you will try a few of these ideas

1) High Temperature Dust Boots: There appears to be a “High Temperature” version that StopTech advertises. The StopTech part number is 750.99004. The part is made from Silicon appears to be made from Silicon which typically has a maximum operating temperature of 300 °C. If the OEM version is the standard EPDM rubber, it would have a maximum temperature of 150 °C. The issue with Silcon is that it will degrade if it comes in contact with Brake fluid!!!! It could be a good option for some, if care is taken with the brake fluid.

2) Stainless steel Pistons: The advantage of SS pistons is significantly lower heat transfer to the brake fluid and better durability. Racingbrake.com does sell a replacement SS piston for a reasonable price. I will contact them to see about a specific part for the Alfa.

Obviously, the best option would be to replace the rotors and calipers with something like AP Racing or Brembo Racing systems. This option would cost the most, but give you the best long term track performance.
 

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Brembo Brakes: OEM & Upgrade Information

Great stuff @DrPyro2k.
I noticed a huge improvement since I switched to the Gyrodisc rotors.
They have all those improvements yet the cost of those rotors is the same as OEM.
I may look at replacing my caliber pistons with the stainless steel ones you mentioned. I’m quite happy with the stock brake set up once you change the rotors, pads, brake fluid and change the brake lines to stainless steel ones. But any others improvement is just all the better. And you have some good suggestions.

I rebuild my calipers every 2 years so I don’t really care about the melted dust boot I think it’s mostly just cosmetic. If I notice the pads tapering quite a bit or wearing unevenly I would rebuild the calibers earlier.

Superior braking ability is one of the 4C’s greatest strengths. I think I have exploited that strength a bit too far a few times. Few things I’ve learned:
1. If you track a lot change your brake fluid to the highest temperature in DOT4 you can get and do it a couple times during the year if you track more than say 15 times or if you really overcook your brakes. I was in Fontana California very hot weather and there was a red flag track situation in which I had to stop with really hot brakes. I kept creeping forward a little bit like I’m supposed to do but my brakes were literally smoking. Fortunately the track exit was right there and the track officials saw my situation and let me leave the track. I then drove very slowly in circles in the parking lot to cool the brakes down. I really think it only takes one event like that for you to change your brake fluid. I didn’t change my brake fluid but I should have as later I saw that it boiled over and probably lost a lot of it’s efficiency. I did notice after that my brakes overheated easier.
2. Get great brake brake pads. I REALLY like the new PFC 13 front brake pads. Same material as the PFC 11’s but they’re a bit thicker so they last longer and fit right in there. I think I got like seven extremely hard tracking days out of them which I thought it was amazing.
3. Front brake cooling ducts. I have a separate post on it that explains what I did. it also lists some options if you don’t want to cut into the front grill as I did. But my powder coated black textured front grills are almost indestructible so it’s a one time deal with no maintenance or upkeep to keep it looking perfect. And that is a part of the car and that really gets a lot of road rash.
I really notice the brake cooling difference. You can drive harder and longer in sessions and the pads and rotors run cooler so they last longer. So it’s one of the few mods that actually pays for itself!
 

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Great information, and excellent of you to put it all in one place for us.
I’ve linked this thread in the DIY index.

Here’s a post from Gale from this morning, which is exactly along the same lines...
https://www.4c-forums.com/7-new-member-introductions/44042-2017-alfa-romeo-4c-coupe-36.html#post995282

Here is the static brake balance calculator if anyone wants to play with it. http://www.tceperformanceproducts.com/bias-calculator/

You can see exactly what happens if you use different front / rear pads or if you increase only front disc diameter, etc. That's what we're currently working on before we go into a performance brakes upgrade. And we have opted for a high end, AP Racing kit, both front and rear. No budget upgrades on 4C, like we promised.

All the data in this print screen are accurate, I have measured them all. 4C front / rear brake bias is 64% / 36%.

My feeling was right. 4C is a very front biased like I was already telling, but it feels good to have a calculation to proove that. Trail braking is pretty much impossible with that spec. What most of user experience in 4C is that when you take the leg from the accelerator pedal off, the car starts to oversteeer (throttle steer), but when you step on the brakes it neutralizes again. That's not trail braking it's throttle steer. If you don't believe you can give it a try. Drive a long corner with steady throttle (no acc., no decc.) Than release the throttle abuptly. Car will oversteer. Now drive the same corner with steady throttle (no acc., no decc.), but have your left foot on the brake. Keep the throttle steady and suddenly step on the brakes lightly. Car will stay pretty much neutral and if you'll step on the brakes harder it will understeer. So trail braking is not there. I think there is a common sense among us, that I don't have to tell that you should only test this in a proper place. :D

Because of that car has really really good straight line stopping distance, so you can outbrake pretty much anyone, but corner entry speed is low. With a bit more rear biased brake balance, you could actually trail brake into the corner, carry more speed into it and still not loose much on the straight line braking. Just a few interesting cars to support this theory:


  • Alfa Romeo 4C (40/60 weight distribution) and (64/36 brake balance)
  • 991 GT3 RS (42/58 weight distribution) and (50/55 brake balance)
  • Cayman GT4 (45/55 weight distribution) and (55/45 brake balance)
It is nothing wrong with that. The 4C is built to be user friendly, the alignment, the rubber bushings, brake bias, everything. Car is set up to fit majority. Every car is set-up to be user friendly, but 4C is quite a beast underneat honestly, so if the car would come out of the factory with a track focused spec, most of the cars would be wrecked on the streets in no time. Short wheelbase, wide track, wieght distribution and turbo engine. It's a perfect combo for a beginner to let his ambitions superseed his talent. And in the point of normal people's view, when the car oversteers into the wall it's usually the car's fault, and when the car understeers into the wall it's usually a user's fault.

But if you're looking for an ontrack perfection, then there is so much more it can be done to make 4C faster. Brakes are on of the things for those who have already done the bushings and the suspension.

 

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Discussion Starter #5
High Temperature Rebuid Parts/Kits:

I have done some digging around on Racing Brake's website, and finally found most of the parts for our cars

High Temperature Dust Covers
https://www.racingbrake.com/High-Temperature-Dust-Boots-38mm-Qty-4-ea-p/db-38(ht).htm - $36/side

There are two piston lengths available in the 38mm diameter. I'm not sure which one our car uses, and I have completed my rebuild and didn't make this measurement. Perhaps someone will measure and update us when they do.

The SS pistons 30mm Length:
https://www.racingbrake.com/Stainless-Steel-Pistons-p/p38x30.htm

The SS pistons 32mm Length:
https://www.racingbrake.com/Stainless-Steel-Pistons-p/p38x32.htm

Racing Brake pistons have had some very positive feedback from the Porsche community, so I feel comfortable recommending them for our cars. Since I JUST finished the rebuild I won't do the upgrade for another year or so.

An alternative source of piston and High Temperature Rebuild Kits is Ohio Performance Solutions. Their pricing is better on the seals & Boots. I have emailed them to inquire about availability. They are new into the SS piston development, so not sure when those might be available.

https://www.ohioperformancesolutions.com/product-page/38mm-stoptech-brembo-brake-caliper-individual-pressure-seal-high-temp-dust-boots
 

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Discussion Starter #6 (Edited)
Brake Fluids

Great stuff @DrPyro2k.
1. If you track a lot change your brake fluid to the highest temperature in DOT4 you can get and do it a couple times during the year if you track more than say 15 times or if you really overcook your brakes. I was in Fontana California very hot weather and there was a red flag track situation in which I had to stop with really hot brakes. I kept creeping forward a little bit like I’m supposed to do but my brakes were literally smoking. Fortunately the track exit was right there and the track officials saw my situation and let me leave the track. I then drove very slowly in circles in the parking lot to cool the brakes down. I really think it only takes one event like that for you to change your brake fluid. I didn’t change my brake fluid but I should have as later I saw that it boiled over and probably lost a lot of it’s efficiency. I did notice after that my brakes overheated easier.
Brake Fluid: Yes it is CRITICAL that you change your fluid to a High Temperature fluid and do it regularly!!! Depending on where you are in the world, availability and applicability of racing fluids will change. Motul 600 (~$17/500ml) and Motul 660 ($25/500ml) are very popular choices in the US. Castrol SRF is also highly recommended but also quite expensive @ $65/1liter. Personally, I have used Torque RT700 ($33/500ml) and have been reasonably happy with it. The major issue that I have with it is wet boiling point. As I live in a VERY high humidity area, I can NOT go more than 6 months with the Torque or I will see issues with brake fade. The advantage of the Castrol is the higher wet boiling point which is why I am considering changing to it. The issue with the Castrol that my race shop mentioned is that you can't swap back to a cheaper fluid or seals could break down. I'm not sure how true that is, but it is something to consider....
 

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Great stuff! Will try the high temp dust boot next time they need to be replaced

我從使用 Tapatalk 的 SM-G9650 發送
 

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I went with Castrol SRF. I regularly (after a few track days) bleed the calippers until I get clean fluid out. Usually I use around 300 ml --> This way I always have clean an new fluid.
Usually I don't go more than 2 consecutive fast laps as the tires overheat (semislicks) and you loose 0.3 - 0.5s / lap --> I feel the first lap is always the fastest one meaning the tires have more grip (usually at ambient temperatures above 20 grd)

Some say that they need a few laps to put some heat in the tires --> I don't understand this except if it's cold outside combined with "hard compound semislicks)
 

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I am starting this thread as a few of us are looking at options to modify the OEM brakes, specifically to improve the long term track worthiness of the whole system. So to start with, I will try and document the existing system characteristics.

OEM Specifications:
Front:

Manufacture: Brembo
Part Number @ Left (Driver): 20895801
Part Number @ Right (Passenger): 20895802
Piston Number: 4
Piston Size: 38mm (Aluminum)
Axel Leading/Trailing: Trailing
Axial Pin Separation: 130 mm
Axial Pin Offset from Rotor Center: 50mm (approximate)
Rotor Diameter: 305 mm
Rotor Thickness: 28 mm

Rear:
Manufacture: TRW
Part Number @ Left (Driver): ???
Part Number @ Right (Passenger): ???
Piston Number: 1
Piston Size: 41mm (Steel)
Axel Leading/Trailing: Leading
Center to Center Mount Distance: 110.0 mm
Rotor Diameter: 292 mm
Rotor Thickness: 21 mm

Rebuild Kits:
Front:
Manufacture: Brembo
Dust Boot Part Number: 20.4872.45
Seal Part Number: 05.5955.57

Alternatives: Centric P/N: 14337016
Raybestos PN: WK463
AC Delco 18H463
Rear:
Manufacture: ???
Rebuild Kit Part Number: ???

Alternatives: Centric P/N: 14362056
Raybestos PN: WK910
AC Delco 18H1160

Brake Bias:
I am using information I found on the M3 forum, which jives with other internet searches. You can find the info here: http://www.m3forum.net/m3forum/showt...p?p=1065614092

For Piston Diameters, Rotor Diameters and other parameters, please see above.
Pad Width:
Front: 52.1mm
Rear: 47.6 mm

Pad Type: Ferodo DS2500 @ 300 degC (Friction Factor 0.425)

I am also assumed that the brake fluid pressure front and rear are the same. I have no idea if this is actually the case, but from my understanding it typically is.

Math time.....

Overall Equation
Brake torque generated at the wheel, individually Tf and Tr, is given by Equation 5:
Equation 5: T{f,r} = P · Atotal · Reffective · cF
T{f,r} = Torque at wheel
P = Pressure
Atotal = Combined area of all pistons within a caliper
Reffective = Effective radius of pad placement to rotor
cF = Coefficient of friction of pad material

Front Brakes Area
For a Floating: 2-piston and Fixed: 4-piston caliper:
Equation 7: Atotal = 2 · pi · (rpiston_12 + rpiston_22)
Atotal = Total combined effective area
rpiston_1 = radius of piston 1 *
rpiston_2 = radius of piston 2 *
* - refer to Equation 4 to obtain radius from diameter)

Rear Brakes Area
For a Floating: single piston caliper:
Equation 6: Atotal = 2 · pi · rpiston2
Atotal = Total combined effective area
rpiston = radius of piston *
* - refer to Equation 4 to obtain radius from diameter)

Using this information... I get an overall Brake Bias of 64% front, 36% rear or a ratio of 1.78

Have you rebuilt your calipers with new seals?
 

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Discussion Starter #11
@bunta_garage - Yes and No. I rebuilt using the Raybestos kit (WK463) over a year ago and I purchased the high temperature gaskets from Ohio Performance Solutions. The Raybestos have held up quite well on track. But, I have improved my braking technique and installed cooling ducts, so that has definitely improved the longevity of the standard seals. I will replace them with the high temperature version when the current Raybestos die....
 

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Discussion Starter #13
@bunta_garage -

The fronts use 38mm pistons. It looks like they never made a kit for it, so just buy the individual set. You will need 4 sets.


For the rears, don't bother with the High Temperature seals/gaskets. I'm not sure you could actually find a set. For me, it was a waste of $ to even get the rear Raybestos WK910 rebuild kit. The rears gaskets were still in fantastic shape. My thought is that the rears just don't get hot enough to worry about melting gaskets and the piston design seems to limit gasket temperatures (more mass). Just Google "Raybestos WK910" and pick your favorite vendor, its is sub $10.
 

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@bunta_garage -

The fronts use 38mm pistons. It looks like they never made a kit for it, so just buy the individual set. You will need 4 sets.


For the rears, don't bother with the High Temperature seals/gaskets. I'm not sure you could actually find a set. For me, it was a waste of $ to even get the rear Raybestos WK910 rebuild kit. The rears gaskets were still in fantastic shape. My thought is that the rears just don't get hot enough to worry about melting gaskets and the piston design seems to limit gasket temperatures (more mass). Just Google "Raybestos WK910" and pick your favorite vendor, its is sub $10.
Thanks for the info!!
 

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@bunta_garage -

The fronts use 38mm pistons. It looks like they never made a kit for it, so just buy the individual set. You will need 4 sets.


For the rears, don't bother with the High Temperature seals/gaskets. I'm not sure you could actually find a set. For me, it was a waste of $ to even get the rear Raybestos WK910 rebuild kit. The rears gaskets were still in fantastic shape. My thought is that the rears just don't get hot enough to worry about melting gaskets and the piston design seems to limit gasket temperatures (more mass). Just Google "Raybestos WK910" and pick your favorite vendor, its is sub $10.
in europe any supplier ?
 

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Discussion Starter #16
@jeannot - I'm sure there might be, you will just have to google around to find it. Several of the Porsche use 38mm seals, so something comparable should be able to be found.
 
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