The Obtainable Brembo GP4-MS, GP4-RR, GP4-PR, GP4-RS, GP4-RX and Unobtainable Brembo new GP4 caliper

BMW Alpina

FOUNDING Member & Administrator
Staff member
First the UNOBTAINABLE GP4 Caliper (yes the model code is just GP4 without any alphabet behind it):
I actually contacted Brembo USA about this caliper because I love the cooling fins design and they told me:

Brembo works very closely with MotoGP to constantly improve the brakes. We see the technology trickle down into racing (WSBK, MotoAmerica) and High Performance over the years.
MotoGP R&D and technical evolution is on an accelerated time frame. MotoGP teams have a budget with Brembo and are not sponsored.
Brembo does not sponsor anyone or team and working with MotoGP is a big part of their business. It also help Brembo because they strive to be at the forefront of technology.
There is also differences in cost to manufacture a MotoGP caliper and a street or lower level racing calipers. The MotoGP calipers are billet monobloc and machined to a fine detail.
The cost of this is significant and not something the street market can support the sales of.
As with any industry and business Brembo must reflect on the needs of a market and the performance that is capable vs the price.


Below are the Press Release/News when Brembo launch this GP4 Caliper:

ALL BREMBO BRAKES TRENDS FOR THE 2020 MOTOGP WORLD CHAMPIONSHIP

The new GP4 caliper

The 2020 MotoGP Championship will feature important innovations related to the braking system: after the Valencia test in 2019 and those in February in Sepang,
will be the official introduction of the GP4, the new monobloc aluminium caliper machined from a solid, with radial attachment to 4 pistons.
This caliper is distinguished from that used until last season thanks to an extreme design that incorporates some of the stylistic features
recently used also on motorcycle calipers for road application and that introduces an innovative technical solution: the new fins on the external body of the caliper.
A solution that ensures better and faster cooling of the caliper itself and, consequently, of the entire braking system.
At the same time, the amount of fluid inside the brake system has been reduced, this will allow greater constancy and a decrease in the sponginess of the lever.

Brembo new caliper for 2020 MotoGP_new.jpg

Brembo-GP4-MotoGP-Caliper-First-Look-2020-Jerez.jpg

Brembo-GP4-MotoGP-Caliper-First-Look-2020-Jerez-2.jpg

Brembo-GP4-MotoGP-Caliper-First-Look-2020-Jerez-3.jpg

Brembo-GP4-MotoGP-Caliper-First-Look-2020-Jerez-4.jpg

Brembo-GP4-MotoGP-Caliper-First-Look-2020-Jerez-5.jpg

I will continue with the Obtainable Brembo GP4 family caliper soon 😁
 

BMW Alpina

FOUNDING Member & Administrator
Staff member
Brembo GP4-MS:
100 mm 'GP4-MS' Radial Billet Caliper Kit

The GP4-MS has 100mm bolt spacing and 30mm diameter pistons (4 pistons). This means they are DROP IN replacement to the stock Panigale V4 Brembo Stylema Caliper.
Their banjo and bleeder ports position is also the same as the stock Stylema caliper which means you don't have to change your brake lines or your stock master cylinder (unless you want to).
The GP4-MS is CNC billet from a solid block of aluminum while the Stylema is cast.
Although they are both monoblock in design, however machining from solid allows the use of materials with better mechanical characteristics, greater resistance to high temperatures and, consequently, improvements to the performance of the entire braking system.

Of course due machining also allow for a better finish quality with NICKEL Plating for maximum cosmetic improvement (and of course stricter manufacturing tolerance).
The GP4-MS came with 2 seals per piston allowing it for road use just like the Stylema Caliper.
It will also come with sintered pads for street/track mixed use and can be upgradable to the Brembo Racing Z04 pads for full track use.

Please note that if you decide to upgrade your master cylinder, then you will need a master cylinder with 17mm diameter (NOT 19mm) like the RCS17 Corsa Corta from Brembo.

1557398874676GP4-MS.jpg1.jpg
2.jpg3.jpg4.jpg5.jpgGP4-MS with Gold ProTi.jpgMotoCorse1.jpgMotoCorse2.jpg
 

BMW Alpina

FOUNDING Member & Administrator
Staff member
What determines the diameter of the master cylinder if we want to up-spec our V4? Why RCS17?
Hi Pete T,

First the GP4-MS is a street caliper, direct upgrade for our front stock brembo stylema caliper.
But there are higher spec caliper than the GP4-MS like the GP4-RR.

Second,
So a master cylinder is a tube and the piston or in our caliper case (4 pistons per caliper) meaning 8 total pistons from the 2 front caliper are also a tubes.
A tube volume is calculated based on the height of the tube x the area of the base of the tube.

The larger the diameter of the piston which mean the larger the area of the piston surface the more volume will be needed to move the tube at certain stroke.

So the the larger the total pistons surface area (due to the larger diameter of each piston or the amount of total pistons in the front calipers), the larger the master cylinder needed.

Let's make it in real world example.
The RCS 17 master cylinder is the ideal size for the Brembo Stylema Pistons with 8 piston x 30mm diameter/piston

However, the Brembo GP4-RR caliper with 4 piston x 32mm/piston and 4 pistons x 36mm diameter/piston will need more brake fluid to move it a certain stroke because it simply have more surface area.
If you use RCS17 master cylinder on the GP4-RR caliper, you need to pull the lever RCS17 more before the piston of the GP4-RR move at a certain stroke length

hmmm let's make it even more simple...
let's pretend with assumption that when you use the RCS17 on the stock Brembo Stylema, you only need to pull the lever a quarter and it will already push the brake pads touching against the rotor (IDEAL)
but if you use the RCS17 on the Brembo GP4-RR with larger piston area, you will need to pull the lever more than halfway before the brake pads toughing against the rotor (like there is air in the brake line)

On the other hand if you use RCS 19 Master Cylinder with the stock Brembo Stylema, you pull the lever 1/8 and it will already push the brake pads touching against the rotor
but if you use RCS 19 Master cylinder with the Brembo GP-RR, you will need to pull the lever a quarter and it will push the brake pads touching against the rotor (IDEAL)

Then you will ask, what is wrong with pull the lever 1/8 and it already push the brake pads to touch the rotor, well, first the larger the master cylinder the HARDER the force needed to press it so it will make your finger tired.
Second, the too large master cylinder will reduce the FEEL of the brake when you modulate it.

This is in concept similar to front sprocket and rear sprocket.
When you increase the size of the rear sprocket (representing brake caliper), the bike will accelerate faster but your RPM will be higher (thus your lever need to be pulled more)
When you increase the size of the front sprocket (representing master cylinder), the bike will accelerate slower because your engine had to work harder but your rpm will be lower (thus your lever need shorter travel but it will be harder to pull)

Note: the GP4-RR has 108mm bolt spacing so it won't fit our stock Ohlins fork, however I had been told that the GP4-RR might come in 100mm bolt spacing by Brembo USA.
Although the Brembo distributor in Europe did not know about this so ... I am not sure who is right.
But the GP4-RR as track focus caliper does not have 2 seals per piston like the GP4-MS because it is more for track use and came with Titanium Piston. but since GP4-RR only have 1 seals per piston, you will need to clean them (overhaul) much much more often.

Yes, I need to update this thread with the rest of the GP4 caliper range 😁
 

Pete T

Moderator
Staff member
Thanks, Howard, for such a great detailed response. So bigger is not better. It really is a case of matching components. I did wonder because as I watched various Youtubes and Facebook posts I noticed some people have used the RCS 19 and I remembered you chose very carefully when deciding to use RCS 17 on your Anniversario. 👍
 

BMW Alpina

FOUNDING Member & Administrator
Staff member
Brembo GP4-RR:

BREMBO’S CLASSIC GP4-rr CALIPER RETURNS COMPLETELY UPDATED

The Brembo GP4-RR model had been around for many years and last year, Brembo introduce the NEW UPDATED version of Brembo GP4-RR.

Here is how the old model looks like:
BREMBO_XA933A0_GP4_RR_Racing_Radial_Calipers_Pinze_Radiali.jpgBrembo_XA93310_GP4RR_Racing_Radial_Calipers_Pinze_Radiali.jpg

and here is how the NEW UPDATED version of the GP4-RR looks like:
Brembo_GP4-rr_pinza_caliper (2).jpgbrembo-eicma-2019-51-2.jpgbrembo-eicma-2019-62-2.jpgbrembo-eicma-2019-66-2.jpg

At this moment, officially it is available in 108mm bolt spacing meaning the Ducati Panigale V4 stock forks would not fit this caliper, however, someone from Brembo USA told me there will be a 100mm version !!! 😌
However, I won't hold my breath since Brembo is really behind due to Covid19 situation. FYI, at this moment, even the 108mm bolt spacing GP4-RR still not available for purchase exactly 1 year after it's launch at 2019 EICMA !!!

The titanium pistons is still the 32-36mm diameter like the previous GP4-RR however, it can accommodate brake pads with an increased surface area compared to the previous version, further increasing braking performance, meaning (from my personal interpretation),
while the previous GP4-RR needs the narrow band rotors, this new GP4-RR should work fine with our stock rotors (or a T-Drive rotors for our stock Stylema calipers).

Of course you will need a larger Master Cylinder than our stock MC...

By the way, what the differences against the stock Stylema? well the GP4-RR is fully machined (billet) and not CAST like the Stylema, plus it came standard with Titanium Piston vs. Aluminum Piston in the Stylema, and of course, the finish/color.
Not to mention the larger piston will give more clamping power and it have differentiated size between the pistons.

I love the gold anodized color, looks classic, so hopefully I can purchase this GP4-RR caliper to replace my Stylema Calipers that I already sold to our good forum member @Styler (y)
The only questions is, should I stick with 100mm bolt spacing (when it is available) or change the forks and go 108mm spacing... 😅
 

BMW Alpina

FOUNDING Member & Administrator
Staff member
Great picture of the latest Brembo GP4-RR with Ohlins FGR300 (or maybe FGR301) posted on Instagram by @Superbike Unlimited :

I also noticed the FGR300/301 came in 2 different lower mounting color, this one is the bright aluminum silver and I think the current version is darker grey aluminum color.


GP4-RR with Ohlins FGR300.jpg
 

Apuca

Member
First the UNOBTAINABLE GP4 Caliper (yes the model code is just GP4 without any alphabet behind it):
I actually contacted Brembo USA about this caliper because I love the cooling fins design and they told me:

Brembo works very closely with MotoGP to constantly improve the brakes. We see the technology trickle down into racing (WSBK, MotoAmerica) and High Performance over the years.
MotoGP R&D and technical evolution is on an accelerated time frame. MotoGP teams have a budget with Brembo and are not sponsored.
Brembo does not sponsor anyone or team and working with MotoGP is a big part of their business. It also help Brembo because they strive to be at the forefront of technology.
There is also differences in cost to manufacture a MotoGP caliper and a street or lower level racing calipers. The MotoGP calipers are billet monobloc and machined to a fine detail.
The cost of this is significant and not something the street market can support the sales of.
As with any industry and business Brembo must reflect on the needs of a market and the performance that is capable vs the price.


Below are the Press Release/News when Brembo launch this GP4 Caliper:

ALL BREMBO BRAKES TRENDS FOR THE 2020 MOTOGP WORLD CHAMPIONSHIP

The new GP4 caliper

The 2020 MotoGP Championship will feature important innovations related to the braking system: after the Valencia test in 2019 and those in February in Sepang,
will be the official introduction of the GP4, the new monobloc aluminium caliper machined from a solid, with radial attachment to 4 pistons.
This caliper is distinguished from that used until last season thanks to an extreme design that incorporates some of the stylistic features
recently used also on motorcycle calipers for road application and that introduces an innovative technical solution: the new fins on the external body of the caliper.
A solution that ensures better and faster cooling of the caliper itself and, consequently, of the entire braking system.
At the same time, the amount of fluid inside the brake system has been reduced, this will allow greater constancy and a decrease in the sponginess of the lever.

View attachment 973

View attachment 974

View attachment 975

View attachment 976

View attachment 977

View attachment 978

I will continue with the Obtainable Brembo GP4 family caliper soon 😁
These are special! I’m trying to understand which “practical” direction to go with the braking system. I’ve started with the T-drive rotors. I really like what you did with yours here
 

BMW Alpina

FOUNDING Member & Administrator
Staff member
These are special! I’m trying to understand which “practical” direction to go with the braking system. I’ve started with the T-drive rotors. I really like what you did with yours here
Hi Apuca,
if you are keeping your stock front Ohlins fork, then the best choice for Brembo caliper is the GP4-MS because it have the 100mm mounting bolt spacing exactly like your current stock Brembo Stylema Caliper.
Or a more economical choice would be the Brembo Stylema R Caliper which is an upgraded version and fitted standard on the V4 Superleggera
This 2 calipers above also allow you to use stock Master Cylinder

If you plan to change your fork, for me at least, the choice will be the latest version of GP4-RR (make sure you get the latest updated version because there are still older version for sale). But this will need a fork with 108mm caliper mounting bolt and larger Master Cylinder. Brembo USA told me last year that they are planning to issue a GP4-RR in 100mm bolt spacing, but that plan is now unclear after the covid-19...
 

Keith97

New member
The T-drive rotors are heavier than the stock rotors. I have the t-drives on my back up wheels but run brake tech irons primarily, they offer much more stopping power. I am also running the gp4-ms calipers but replaced the pistons with Ti vented ones and pulled out the dust seals since this is a track only bike.
 

HKMP7

First 9 & Moderator
Staff member
The T-drive rotors are heavier than the stock rotors. I have the t-drives on my back up wheels but run brake tech irons primarily, they offer much more stopping power. I am also running the gp4-ms calipers but replaced the pistons with Ti vented ones and pulled out the dust seals since this is a track only bike.
Are you running the Ferodo Xrac pads on the Irons?
 

Tsaico

FOUNDING Member
Brembo GP4-RR:

BREMBO’S CLASSIC GP4-rr CALIPER RETURNS COMPLETELY UPDATED

The Brembo GP4-RR model had been around for many years and last year, Brembo introduce the NEW UPDATED version of Brembo GP4-RR.

Here is how the old model looks like:
View attachment 1925View attachment 1926

and here is how the NEW UPDATED version of the GP4-RR looks like:
View attachment 1927View attachment 1928View attachment 1929View attachment 1930

At this moment, officially it is available in 108mm bolt spacing meaning the Ducati Panigale V4 stock forks would not fit this caliper, however, someone from Brembo USA told me there will be a 100mm version !!! 😌
However, I won't hold my breath since Brembo is really behind due to Covid19 situation. FYI, at this moment, even the 108mm bolt spacing GP4-RR still not available for purchase exactly 1 year after it's launch at 2019 EICMA !!!

The titanium pistons is still the 32-36mm diameter like the previous GP4-RR however, it can accommodate brake pads with an increased surface area compared to the previous version, further increasing braking performance, meaning (from my personal interpretation),
while the previous GP4-RR needs the narrow band rotors, this new GP4-RR should work fine with our stock rotors (or a T-Drive rotors for our stock Stylema calipers).

Of course you will need a larger Master Cylinder than our stock MC...

By the way, what the differences against the stock Stylema? well the GP4-RR is fully machined (billet) and not CAST like the Stylema, plus it came standard with Titanium Piston vs. Aluminum Piston in the Stylema, and of course, the finish/color.
Not to mention the larger piston will give more clamping power and it have differentiated size between the pistons.

I love the gold anodized color, looks classic, so hopefully I can purchase this GP4-RR caliper to replace my Stylema Calipers that I already sold to our good forum member @Styler (y)
The only questions is, should I stick with 100mm bolt spacing (when it is available) or change the forks and go 108mm spacing... 😅
lovely pictures , and makes me want to spend money again.....damn you! 😂

I mean why Japanese bike went with 108 in their fork? Any incentive to go 108? better leverage on radial mount? I can’t figure out the science behind that....

one thing to point out, mono block is great presentation of rigidity. Which transferred into rider’s feedback, the combo of brake pressure is all base on rider’s feedback and how it inspires confidence.

I have learned and admittedly the science and art behind brakes is very addictive. Because now, I want to set myself to get a GP4 now! o_O
 
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