Re: Feels like trying to stop a freight train...
Here is the copy of a email from my mechanic-basically I have him do things I'm too scared to do myself including brakes and electrical. Obviously I respect his opinion and though there was some good info here, feel free to add your opinion on what he says:
"Anyway, in regards to the brakes on the R6...
My belief is that the 19x18 brembo is sized too large for the relatively small-diameter pistons found in the R6 calipers. This minimizes the mechanical advantage, which means whatever force you input at the lever will not be magnified very much at the calipers. Conversely, when you either decrease the master cylinder piston size, OR increase the piston diameter / number of pistons, you increase mechanical advantage, which means you magnify the input at the lever more... meaning less pressure to achieve the same braking force. The trade-off is in lever travel.... the more your braking force is magnified, the more lever travel will be required to move the pistons out the same amount.
The R6 / R1s have always had awesome calipers. But their awesomeness comes from their internal stiffness, and part of that stiffness itself comes from the very small piston diameters they use (smaller than any other sportbike I'm aware of). Most people don't take this into account when purchasing aftermarket components. IMO, every time someone slaps an aftermarket brembo on a bike with R6 calipers, they **** it up.
I wanted to pull up that spreadsheet I mentioned - where I have the dimensions of just about every master cylinder / caliper combo imaginable along with their calculated leverage ratios. Unfortunately I had to wipe my ssytem last week due to a virus, & that file is gone. Regardless, I feel you'd be much better off with a smaller master cylinder (smaller as in smaller piston size) in order to magnify your input force. That alone may or may not solve all your braking problems, but I'm sure it would help.
Have you ridden a stock R6? They have pretty nice Brembo MCs stock that are sized appropriately for the calipers. Granted, they're cast MCs, not forged, so they're not the best, but the leverage ratio makes more of a difference than the material stiffness. Even if you'd rather go with an aftermarket MC, getting on a stock R6 would give you an idea of what the brakes will feel like with something sized appropriately. Going off memory, the stock MC is either a 14 or 16mm piston.
BTW - In case you're not familiar with master cylinder sizing, the first number is the piston diameter, and the second number is the distance from the pivot point to point where the lever exerts pressure on the piston rod. Going up in piston diameter will decrease lever travel but increase the amount of pressure required to get X-amount of braking force (you're moving more fluid for each unit of lever travel). Going up on the 2nd number does the same thing. So a 19x18 will have more lever travel than a 19x20, but will require more force at the lever to get the same amount of force at the caliper. Likewise, a 16x18 will have more lever travel than a 19x18, but will require more force at the lever as well."
2009 250r Track
2007 R-6 Track
ASMA#451 Low and Slow