Brembo GT kit 405/380

[pzz67]

I just had a brembo gt kit installed on my car.

However the brake pedal feels a lot worse than stock.
It feels very spongy the top 50% of the brake feels like it doesn’t even bite at all.
The mechanic has assured me there is no air in the lines.
They said it’s to do with brake booster going from 4/2 to 6/4.
Would this be the case?

Also with ignition off, I step on the brakes 3 times and it firms up but I can push it right to the bottom with a little force.
I tried it on my daily Audi a1 and once it firms up I cannot push it any further.

This brake kit is turning to be a headache for me.

Thanks

[bracer]

While it can be true that more pistons can make for longer pedal travel that's not a given. It has to do with volume of pistons. If the 6/4 has more total volume the pedal will travel further, but will have better modulation and higher ultimate force capability. You could make a single piston caliper that was huge and it would have longer pedal travel.

Most brake companies try and match volume as close as possible, and changing it can mess with ABS, balance, etc... I can't image Brembo got that wrong, but who knows.

I strongly suspect they have air trapped in the system (ABS can be tough) and they haven't got it out of the system.

[NickyC]

I've purchased several BBKs over the years for my BMWs (Stoptech/Brembo) and each time the initial bite has felt spongy compared to the stock setups. You will adjust to it, just don't have the mindset going in that because you have an upgraded kit that all of a sudden the moment you touch the brakes the car will just dig into the pavement.

The F8x ///M cars already have some pretty good brakes stock, keep that in mind too.

[aBMWfan]

Originally Posted by blackey

While it can be true that more pistons can make for longer pedal travel that's not a given. It has to do with volume of pistons. If the 6/4 has more total volume the pedal will travel further, but will have better modulation and higher ultimate force capability. You could make a single piston caliper that was huge and it would have longer pedal travel.

Most brake companies try and match volume as close as possible, and changing it can mess with ABS, balance, etc... I can't image Brembo got that wrong, but who knows.

I strongly suspect they have air trapped in the system (ABS can be tough) and they haven't got it out of the system.

I have the Brembo kit and it’s perfect. It’s needs to be properly bled. The 6/4 Piston argument not sure what that means

[aBMWfan]

Originally Posted by NickyC

I've purchased several BBKs over the years for my BMWs (Stoptech/Brembo) and each time the initial bite has felt spongy compared to the stock setups. You will adjust to it, just don't have the mindset going in that because you have an upgraded kit that all of a sudden the moment you touch the brakes the car will just dig into the pavement.

The F8x ///M cars already have some pretty good brakes stock, keep that in mind too.

Opposite for me. Stock brakes very spongy, Brembo GT Type 3 kit has really smooth and firm bite. I recommend BBK for the F8x

[pzz67]

Originally Posted by NickyC

I've purchased several BBKs over the years for my BMWs (Stoptech/Brembo) and each time the initial bite has felt spongy compared to the stock setups. You will adjust to it, just don't have the mindset going in that because you have an upgraded kit that all of a sudden the moment you touch the brakes the car will just dig into the pavement.

The F8x ///M cars already have some pretty good brakes stock, keep that in mind too.

I don’t doubt the stopping power of it.
It just feels like I have to push the pedal down further to stop compared to previously.

Luckily the dct only moves when you give it gas, otherwise I’d imagine I would have to put the pedal to the ground just to hold it at a stop

May bleed again and see how it goes

Thanks though

[FlyingLow78]

Definitely bleed it again. My StopTech BBKs were bitey as hell and I miss having brakes that felt like boat anchors were being thrown overboard. The stock brakes, by comparison, feel quite spongey.

It may also be worth noting that I tried three different methods for bleeding the brakes on my car, and the best results were always achieved with a device called a MiteyVac. It connects to an air compressor and has a reservoir to collect the used fluid. It literally sucks all of the air out, leaving only the fluid.

TIS calls for the use of a device like a Motive Power Bleeder, and it works by pressurising the car’s brake reservoir. It worked ok, but not as well as the MiteyVac.

The last way to bleed the brakes is by pressing on the brake pedal with a bleed screw open, and re-closing it at the bottom of the pedal stroke. You continue to evacuate air with pedal strokes, doing each corner separately, until the air is out. This method takes forever and does not work well. You’re better off getting one of the tools listed above.

[Encanto]

Originally Posted by aBMWfan

I have the Brembo kit and it’s perfect. It’s needs to be properly bled. The 6/4 Piston argument not sure what that means

This.

[IK6SPEED]

Originally Posted by pzz67

I just had a brembo gt kit installed on my car.

However the brake pedal feels a lot worse than stock.
It feels very spongy the top 50% of the brake feels like it doesn’t even bite at all.
The mechanic has assured me there is no air in the lines.
They said it’s to do with brake booster going from 4/2 to 6/4.
Would this be the case?

Also with ignition off, I step on the brakes 3 times and it firms up but I can push it right to the bottom with a little force.
I tried it on my daily Audi a1 and once it firms up I cannot push it any further.

This brake kit is turning to be a headache for me.

Thanks

Hmmmm.....finally someone with same feeling as me.

Had countless correspondence with Danni and 3 different aftermarket shops bleed it.

To me, once warmed up they have more bite. However running without using for several miles scares the hellout of me that I’m not going to stop in time.

Was about to try something else after a year of this (replace master cylinder)....but your post leads me to believe that might not be issue.

Yes, big headache here.

[aBMWfan]

Originally Posted by IK6SPEED

Hmmmm.....finally someone with same feeling as me.

Had countless correspondence with Danni and 3 different aftermarket shops bleed it.

To me, once warmed up they have more bite. However running without using for several miles scares the hellout of me that I’m not going to stop in time.

Was about to try something else after a year of this (replace master cylinder)....but your post leads me to believe that might not be issue.

Yes, big headache here.

Huh? No headaches for me. Not sure what you’re doin wrong

[pzz67]

Originally Posted by IK6SPEED

Hmmmm.....finally someone with same feeling as me.

Had countless correspondence with Danni and 3 different aftermarket shops bleed it.

To me, once warmed up they have more bite. However running without using for several miles scares the hellout of me that I’m not going to stop in time.

Was about to try something else after a year of this (replace master cylinder)....but your post leads me to believe that might not be issue.

Yes, big headache here.

Yes they have bite! However mine feels really soft
Like no resistance/pressure at all. It just sinks if I rest my foot on it unlike before it’ll only go down a little bit until it gets harder.

Doesn’t get hard at all.... soft all the way through.
Pretty much the top 40% of the brake does nothing, it’s useless.
Brake likes come on but doesn’t do any speed reduction.

[pzz67]

Originally Posted by aBMWfan

Huh? No headaches for me. Not sure what you’re doin wrong

Does yours feel exact same as oem brakes?

Mines got longer brake pedal travel before the it actually feels like the calipers start grabbing the rotors.

But all in all the soft as fk brake pedal is what’s killing me.
Feels like I’m stepping in quicksand, just sinks in with no resistance/pressure.

[aBMWfan]

Originally Posted by pzz67

Does yours feel exact same as oem brakes?

Mines got longer brake pedal travel before the it actually feels like the calipers start grabbing the rotors.

But all in all the soft as fk brake pedal is what’s killing me.
Feels like I’m stepping in quicksand, just sinks in with no resistance/pressure.

No they feel more on point than the stock brakes.

The symptoms your describing were the issues I had with the stock brakes.

Did you buy new? What condition are your pads/ rotors? Dust Boots/ seals ok?

Any leaks?

[pzz67]

Originally Posted by aBMWfan

No they feel more on point than the stock brakes.

The symptoms your describing were the issues I had with the stock brakes.

Did you buy new? What condition are your pads/ rotors? Dust Boots/ seals ok?

Any leaks?

They were secondhand, I had them repainted and reconditioned.

Pads and rotors are brand new.
No leaks.

I wish it was something wrong so I could pin point what is the causes of this is.

[aBMWfan]

Originally Posted by pzz67

They were secondhand, I had them repainted and reconditioned.

Pads and rotors are brand new.
No leaks.

I wish it was something wrong so I could pin point what is the causes of this is.

Damn I understand that frustration.

Are you in California?

[pzz67]

Originally Posted by aBMWfan

Damn I understand that frustration.

Are you in California?

Not anymore, back in New Zealand now.
Im like the only one here with modified f80 m3.

and mechanics here i would say aren't too experienced with f80 m3 let alone modifications for this car.

[IK6SPEED]

Originally Posted by aBMWfan

Huh? No headaches for me. Not sure what you're doin wrong

I'm not doing anything wrong as confirmed by 3 different shops including one Brembo (Danni) sent me to.

Mine were brand new.

[aBMWfan]

Originally Posted by IK6SPEED

I'm not doing anything wrong as confirmed by 3 different shops including one Brembo (Danni) sent me to.

Mine were brand new.

That’s strange. Brembo shouldn’t be giving headaches especially if it’s new

[Shortyy]

Bleed again with a power bleeder and cycle the ABS pump while you’re doing it (you’ll need a snap on scanner, laptop to cycle the pump)

I bleed this way and it’s spot on, one time I got a tonne of air into my system and it was a bitch to bleed and get all the air out, but with a power bleeder and cycling the pump it eventually came good. You could have loads of air in your system after the brake swap.

[pzz67]

Originally Posted by Shortyy

Bleed again with a power bleeder and cycle the ABS pump while you’re doing it (you’ll need a snap on scanner, laptop to cycle the pump)

I bleed this way and it’s spot on, one time I got a tonne of air into my system and it was a bitch to bleed and get all the air out, but with a power bleeder and cycling the pump it eventually came good. You could have loads of air in your system after the brake swap.

Just had it bled again with 2 man pedal pumping method.
Thinking of just buying fluid and go to the dealer to do it.
Do they cycle the abs/dsc unit when bleeding?

[clutchdj]

I have the gt kit on the f80 and pedal is more progressive compared to stock (mostly due to pads I think) and definitely not spongy. You should not be noticing a significant difference in pedal travel between stock and the BBK. Like others have said probably air in the system. Take it to the dealer and request to speak/diagnose with a master tech. Keep us updated thanks.

[aBMWfan]

Originally Posted by clutchdj

I have the gt kit on the f80 and pedal is more progressive compared to stock (mostly due to pads I think) and definitely not spongy. You should not be noticing a significant difference in pedal travel between stock and the BBK. Like others have said probably air in the system. Take it to the dealer and request to speak/diagnose with a master tech. Keep us updated thanks.

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