801 320mm brake discs

I changed my rotors to 320mm and there was a difference. The bigger difference was when I swapped on some Brembo calipers I had laying around from a Ducati monster. I’m sure if I did sintered pads it would be even bigger but it’s 2 finger braking with whatever pads were stock on a monster.
 
If I remember correctly, you changed the discs to some stock 1290 KTM/Galfer 320mm discs?
 
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Yeah they are 1290 rotors. I am running stock dual 701 galfer discs on my 701’s mag wheel set up. They work great but do seem to be noisier than normal. They feel a lot different than the 1290s..
 
I am not skilled enough, but ... if I use for example Brembo M4.32, these calipers are same dimensions and same diameter of brake cylinders (pistons) as the original JJ. So they would brake "the same", no? Or? Where should the better braking come from??
If I will fit some M50, it will have bigger diameter of the cylinders, which means, that there will much longer lever movement on the master pump, no? But brake better, this is clear.

I was surprised, that 300=>320 discs will make just 6,7% difference of stopping power ... due to my mathematics :-D
 
animals21 said:
I am not skilled enough, but ... if I use for example Brembo M4.32, these calipers are same dimensions and same diameter of brake cylinders (pistons) as the original JJ. So they would brake "the same", no? Or? Where should the better braking come from??
If I will fit some M50, it will have bigger diameter of the cylinders, which means, that there will much longer lever movement on the master pump, no? But brake better, this is clear.

I was surprised, that 300=>320 discs will make just 6,7% difference of stopping power ... due to my mathematics :-D
Click to expand...

6.7% is the difference between breaking on time ore not, hehehe.

I am not skilled neither but I guess the Brembo M4 will be more rigid therefore loosing less power and you will probably feel it in the initial bite. I guess they will also handle better the heating when breaking hard.

For me the original JJs are good enough for street but I do not like the initial bite, it is too progressive. Perhaps changing the master cylinder will have more direct impact in braking power.
 
I'm not 100% sure about the 801 J.Juan calipers; but my guess is they are like the Duke 790 J.Juan calipers; 2x 30mm and 2x 34mm pistons.
The Brembo M50 calipers are 4x 30mm pistons.
 
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None of this is really about braking power, it is about having more thermal overhead. Unless you are tracking your bike going to other calipers or larger rotors is simply not necessary - the brakes are sufficient to lock up the tire so there is more stopping force available than traction. However there appears to be some issue with the metallurgy of the stock rotors and they way the are prone to warping, so that is a reason to switch. The fact that you can get larger rotors that save 1kg each is another. Looking cool like a racer is a third. If you just don't like the initial bite switch pads and save hundreds of dollars over calipers.
 
@animals21, I do agree with @toast449.
The braking system as a whole is somewhat more complex; it’s the calipers and its piston sizes, the brake master pump and it’s piston size, the volume of the braking fluid that needs to be moved/pumped and also the design of the ABS-system (software), which is precisely matched to the components and the volume.
When replacing brake calipers on braking-systems with ABS, it is strongly recommended to use calipers with piston sizes identical to the stock calipers; otherwise, the ABS-system (software) may fail to function correctly.
From what I know, the advantages of the M50, Stylema, etc. lie primarily in reduced weight, better heat dissipation and greater rigidity; advantages that can be important during racing and intensive use on the track.
 
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For those who might be interested, here the weights of the various Galfer and Brembo brake discs.

Galfer DF801CW; 300mm: 1175gr
Galfer DF787CW; 320mm: 1380gr
Brembo Oro 78B408B0: 320mm: 1620gr
OEM KTM-Galfer; 300mm: 1858gr.

DF801CW.jpg 1788238496579.jpg 1788238639096.jpg
 
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I didn't like the braking performance right from the start either; I replaced the stock pads with ZCOO ones, and it improved significantly. I'm happy with it as it is for now.
Besides, as long as you keep the Pirelli MT60RS tires on, the braking will always be poor.
 
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