Brembo BM-4 caliper
 

I first noticed these on CSG’s website as an upgrade to their spec Brembo BBK. I’ve searched all over the internet and I can’t find much info about them. They seem very minimalist and racey but I’m curious if anyone knows more about them or used them.

How much lighter are they than the normal Brembo calipers?

They appear to be a one piece design and it looks like pads may not be able to be loaded from the top without moving the caliper.

I’d appreciate any info anyone has. Pros and cons.

they look like a mutated banana.

i think the only answer here is that they must be ordered in yellow/green.

I have these, ordered through CSG. Recently installed. The BM4 is a mid-point between the basic GT and the GT-R calipers. The basic GT caliper is a two-piece design made by pinning/bolting two separately CNCed from castings pieces, the GT-R is CNCed monoblock caliper made from billet. The BM4 is CNCed from a casting, creating a monoblock caliper, but it is not from billet. I'm not sure the code, but Brembo also has two-pieces which are CNCed from billet and then pinned.

In any case, typically a monoblock caliper has less flex in the caliper body resulting in reduced pedal travel to reach a particular braking pressure and more consistent braking feel and they are more durable under hard use. Forged monoblock is the top end, but it's very pricey, the BM4 seemed to me a nice entry-point since my previous BBK was two-piece forged. Why forged vs cast matters, is essentially the same as with wheels (as both are unsprung mass), is that forged billet is lower weight for equal strength vs CNC or flow-formed castings. So the BM4 weighs more than the GT-R caliper of the same size, and the GT-R caliper is also theoretically stronger, but in both cases it is a monoblock caliper and should perform better than a two-piece design.

Yes, you can still install the pad from the back of the caliper by removing two pins and the spring clip, just as you can on any other Brembo caliper. A standard Brembo caliper pin tool/punch works fine on the BM4.

Picture so you can see that the normal pins are in place... installing pads is easy.

https://i.imgur.com/B2SAKVI.jpg

with a 17x9 wheel

https://i.imgur.com/DizfEN4.jpg

I just installed these on my car. Switched from the ST40 Stoptech kit for supposedly much better pad life and thermal capacity. I was also looking at the higher end Brembo Clubsport kits but was wanting to stay on 17X9 inch wheel. I doubt they would've fit even with the smaller 332mm rotor. I would say I only have abut 4mm of clearance from the caliper with my 949 6UL's.

I'm sure these weigh slightly more than the ST40 kit and wish I would've of weighed them. At first I thought these were a downgrade to the the Stoptech's and was looking at their C43 kit because I always thought 2 piece rotor was better. After a little research looks like 1 piece has better thermal capacity in some applications.

On the other hand, I've heard the bolted 2-piece calipers are stiffer because of all the steel from the bolts vs having the same thing made out of a single piece.


Also, while a 1-piece rotor is heavier, all that extra weight is in the hat and not especially useful as "thermal mass' as far as I know. Additionally, the thermal expansion of a 1-piece rotor tends to bow the whole thing out because of the hat, being solidly connected and not as hot. A floating rotor ring gets to expand freely, plus can move back and forth a bit and reduce knock-back. I don't think I would ever consider a 1-piece rotor as better for a performance application just because it's heavier.


Anyway, the calipers definitely look neat and I'm sure the kit works just fine compared to similar setups. I really like the C43 kit because the replacement pads and rotor rings are so cheap. I think that Brembo kit uses a stock STI/PP 326mm rotor? So that is definitely a benefit there.

The CSG Spec kit uses the 326mm rotor, but I believe the normal Brembo kit has a different rotor. I agree on your comments regarding 1pc vs 2pc, although I will say that the actual task of replacing a 1 pc rotor is much simpler than replacing rings on a 2pc, I do like the advantages of lesser rotating/unsprung mass with a 2pc design and I don't think the hats add much thermal mass due to their location. I previously had an AP Racing Sprint kit, and had I had an Endurance kit I probably would have stuck with it, but the Sprint didn't have enough thermal mass with its smaller 299mm rotors.

I can't imagine how a monoblock caliper would ever flex more than a pinned caliper... so I believe you've heard that, but I can't fathom how it's possible nor have I seen anything elsewhere saying that. Kind of defeats the purpose, so I doubt that is the case.

Because the monoblock is a block of aluminum, the 2-piece caliper has a bunch of steel going through it.

Steel is about 3x stiffer than aluminum and being made out of a forged monoblock or whatever doesn't make up for that. A caliper without steel bolts going through it is usually lighter though.

On the other hand, I don't have an actual tested example. And this information generally comes from places like stoptech that only make a 2-piece bolted caliper. This also doesn't consider the shape and design of the caliper. But if you took a monobloc, cut it in half, and bolted it back together with steel bolts I'm pretty sure it would be stiffer.

@CSG I was specifically told this kit was an upgrade to the stoptech kit in terms of pad life despite the cheaper price compared to the C43 kit. Maybe they can explain exactly why? I will report back on how long my new CSG C2 pads last compared to the pads that were on my stoptech kit. To be fair I had Gloc pads in that kit so it won’t be an apples to apples comparison. So far I am pleased with the minimal noise from the C2 pads, quietest race pads I have ever driven. I don’t think I’ll need to swap back to street pads anymore between events, that along with the supposed longer life should justify the high cost.

subbed. this is interesting. I have a c43 kit and happy with it. only commenting to learn and hear feedback. I didn't even know these were a thing for our platform.

Thermal capacity is a function of mass. 1pc discs are physically simple compared to a 2pc system (disc, hardware, bell). Because of additional parts, you can expect a cost difference. 2pc Brembo GT kit is about $1500 more than a 1pc Brembo GT kit.

Discs can vary in quality based on the metallurgy and manufacturing processes. While the base materials are the same elements, the quality control of the material is different. As a result, different manufacturers have different characteristics inherent in their discs. Based on the origin of the disc, you can almost spot where the discs are manufactured. Is that a bad quality to have? Not necessarily. If price point is what people are looking for as their number one criteria, then parts need to be manufactured in specific locations to bring the price point down. If quality is what you're looking for, you'll find that the engineering involved and the metallurgical characteristics will be superior.

Consistency is what drives the cost up and what people pay for. You'll find that the factory OEM system is quite capable and people tend to throw in much lower quality products at it hoping it will provide benefit. The friction material is one of the most important aspects in brake performance. Adding that component to a high quality kit will further maximize the potential of the brake system.

We have tested a majority of brake systems and compounds available in the market. If you have any questions on brake systems and goals to improve brake performance, you may contact us via PM or e-mail. :)

I weighed my BM-4 kit and stuff related to it, weights are as follows:

7.3lb - Caliper without pads
22.7lb - Brembo Sport slotted disc (33S60114)
23.8lb - Brembo blank disc
7.1lb - Caliper without pins and spring
2.54lb - included pads
0.19lb - pins and spring

For reference, the older GT caliper is supposed to weigh 7.5lb without pins and spring based on a pic on FT86SF

I've been using this kit for a few years, as well as one of the first CSG C1 pads. I'm still on that SAME SET OF PADS on my car. Here's some shots of them in action.

All action shot credit goes to Motolyric http://www.motolyric.com/

https://i.imgur.com/QkU4EN7.jpg

https://i.imgur.com/aZPbGfg.jpg

https://i.imgur.com/0qMizwm.jpg

https://i.imgur.com/GDHgFsv.jpg

Do you need a spacer to clear your APEX 17x9 wheels with this caliper?

No, it does not require a spacer to clear. I do have a spacer though in those photos in order to have the exact same (to the mm) track width on my car when I change wheels or change camber settings. I run spacers with all of my wheels for this reason, but I can verify that a spacer is not necessary to clear the calipers... the APEX BRZ wheels clear most aftermarket brakes for this platform without any issues as they are.