So this thread is becoming fairly interesting evolving from poor braking to comparisons of non-ABS to ABS. I mentioned earlier in this thread about doing a caliper upgrade from a 2 piston caliper to a 6 piston caliper. I still think this would be a great upgrade but I wanted to follow up on the 2 piston to 4 piston upgrade that I am in the middle of on my CB750.
So don't disregard this until you have complete reading it because I think it is 100% applicable to the poor braking that originally started this thread. As part of my upgrade I was originally going with 4 piston calipers and bigger rotors, but elected to use my existing rotors to begin with. This is still in the prototype stage so disregard the ugly mounting bracket.
After mounting the new calipers I wanted to test drive and to make sure I had maximum pad to rotor surface coverage. This would verify that my calipers were mounted properly. So once I had a high confidence level the brakes were function as I anticipated I want to go for a ride and test what I just discussed. On each rotor face inside and out I drew lines out with a marker from where the mounting bolts for the rotors are to the outside edge along the braking surface. The thought here was to see if the pads gave me full coverage on the rotors and that the mounting brackets were correctly position. Keep in mind that the rotors are from a 1983 bike, they are not warped and the thickness is well within spec and the overall braking surface is in good condition and there are brand new brake pads in the calipers.
So I went out for a breakfast ride to test many aspects of the new calipers, do they stop, can I now use two fingers, do the rotors get hot, etc. almost a 100 miles later I get home very pleased with the braking but still not thrilled as I was expecting more. But I did achieve two finger braking at 80 mph which before required one full hand and then some, rotors were warm but not hot, and everything else was good. Then I started to look at my rotors and what I discovered was surprising.
My rotors although not warped they are not flat across their surface. Meaning from inside to outside on each face I have high/low spots. See Picture. So if you look at the marker line that I put on the rotor faces you will see that parts of the lines are still there and some parts are gone. So this has done two things for me one it tells me looking at the lines that I more or less have full coverage of the pads against the braking surface. But more importantly it tells me that I do not have full contact of brake pad to rotor surface leading me to believe that this is also part of the poor braking issue. Remember I used new pads.
So is it reasonable to assume that on used rotors there is a good possibility that poor braking can be attributed to insufficient contact of pad to rotor leading to poor braking or wooden brakes. This is a simple test anyone can do but New pads are required as the are flat and not worn. I guess one could do it with used pads but I am unsure if it would tell much. The assumption here is that overtime the pads will conform to the surface of the rotors.