Front Caliper Dimensions?

[psych0hans]

I just picked my 390 up (I'm in the US) and I would concur that the front brake is the weak link on the bike. I've had several other bikes with much better 'bite'. I'll be upgrading my front brake system piece by piece and will report on what I find each step of the way. Mind you, my feedback will be purely subjective based on what I 'feel' on the bike. It seems the 320mm disc is not available at this time. My dealer said it is noted as discontinued through KTM. So, it may be tough to get a hold of one. I'll start with EBC pad upgrade, then try the wave rotor from KTM, then I'll install a new radial master cylinder with good fluid. I just ordered a 16mm radial unit from Braking. But it was a wild guess on the proper size required. If anyone has a definitive knowledge on the proper size, I'd love to hear from them. Thanks.

16mm should be plenty, make sure you get rid of the ABS and give the bike a proper bleed. THAT is the weakest link in the brakes...

 

[edderz 33]

Sharing from my experience.1) i begun race with standard setup with ABS being disabled. S**t.. the bike dont want to stop! Seems like i dont have initial bite at all. no braking power. this happen just after few laps.2) Standard system with EBC HH sintered brake pad. Improved initial bite but after few laps, brake fade seems too much. still having poor braking power3) Install brembo master pump from RSV4 (same model as KTM 690 i think). Not much improvement. just partly solved brake fade issue. however, less tiring as u dont need to squeeze the lever as hard as before.4) Install 300mm Galfer wavy rotor and sintered Galfer pad. Slightly better initial grip. still facing brake fade issue but taking slightly longer for it to be happened. u can race with this.5) Remove ABS system and reroute the brake line from master cylinder direct to caliper. This is a lot better. better initial bite but still not superb yet. Brake fade still happen..but its okay..pretty normal i think.I think the Brake fade issues is due to std rotor. easily overheated then the heat transferred to caliper.i would like to have better initial bite and braking power, so i think with caliper swap i would have all what i wanted.

 

[Ktmpro]

Here is one option...80mm Caliper kit direct fit for RC390!

 

[D2M]

RC8 fork swap is fairly easy. You can then use a standard 100mm Brembo or other radial caliper. This setup is extremely powerful, I am using original master cyl and its a 1 finger brake.

 

[psych0hans]

RC8 fork swap is fairly easy. You can then use a standard 100mm Brembo or other radial caliper. This setup is extremely powerful, I am using original master cyl and its a 1 finger brake.

I can attest to that. The only issue I had was getting the alignment right. Also have ordered better brake pads, as I was using cheap Chinese ones earlier. Hopefully that will make it even better. Also ordered a vacuum bleeding kit to take care of air in the system.

 

[D2M]

If you are having trouble bleeding the brake. Try removing the front master cylinder top cover and pump the lever several times extremely fast, rapid fire. From my experience tiny air bubbles get trapped inside the cylinder pump. As you are rapidly pumping the lever you should see tiny air bubbles rise up from the 2 small holes in the cylinder. Have rags on standby as some fluid may splash out while doing this. It worked for me well, my brake is extremely firm..