As the title says, I've learned through first-hand experience that upgrading the stock brakes of the Cannondale Synapse to a 'better' component such as the Shimano 105 BR-5600 or the BR-5700 is not a happy marriage. As it turned out, these 105s have a shorter reach than the optimal one required by the Synapse.
Background of my story: Decided to join the "Upgrade Bandwagon" by replacing the stock Cannondale C4 calipers with the Shimano 105s. What others have praised about these brakes are true: They are way better than the C4s in terms of brake handling, modulation and sheer stopping power. Just speculating, but maybe it's the material to which these different products were forged from. But that's the good part. When I installed these 105s I already noticed that the top 1mm portion of the brake pads were higher than the rim, but upon closer inspection, it's not touching the tire's sidewall. Or so I thought. This is the lowest setting the brake arms would allow the pads to go. Didn't give it much attention back then, and during my solo ride last Saturday (July 13th) I began noticing a distinct on-off scratching sound on my brakes, not a screeching/squeaking sound. This is during my fast descents in which I reach speeds of above 30mph. I thought then that maybe my wheels were not true that's why there's some rubbing going on. Being a lazy rider, I just checked the wheels' trueness when I got back home, but not the brakes. Then at the start of our weekly group ride yesterday, noticed to my horror that there were black tars at the top of the brake pads (more on the front than the rear). Looked at it closely, and there I saw that those 1mm portion of the pads have eaten slightly my tire's sidewall. This is when I was forced to admit the lesson that not adequately researching whether the part that's being considered to be put on the bike is a good fit or not.
As I've measured it the 105s have a reach of only 37mm-47mm whereas the Synapse needs 47mm-57mm of reach (as measured using the stock C4). The 39mm-49mm brakes would be just fine I think.
Just putting my experience out there for those who are thinking of doing the same thing to their Synapse. Someone posted that bikes that have relaxed geometry or classified as sport/endurance types require long-reach brakes. I know now that it's true at least for my Synapse, and too late for me when I read that.
