Performance Difference Between Compact and Standard Cranks
 

I have 2 bikes, an Allez with a 50/34, and a Tarmac with a 53/39. The Allez had an R600/105 FD
setup, the Tarmac came with Ultegra.

The Tarmac alwas shifted smoother and quicker. I could adjust both the same way, and the 50/34
was noticably slower and noisier.

I have always been under the assumption that performance was more or less the same in that
range, it was just a weight/durablity difference.

So I had the LBS change the 50/34 to a 105-SL 53/39 Crankset (for reasons unrelated to this
question). At my request they did not adjust the FD, since I always go back and do that myself
anyway. All they did was replace the BB, Crankset, and Chain. BTW, both bikes are using CN-6600
chains.

After my adjustment the Allez now shifts just like the Tarmac. Just as smooth, just as quick.

I realize that I am now changing 14 teeth instead of 16 teeth, and that used to be an issue, but now
all modern FD's claim to work in that range. Has anyone else experienced this? Is it misleading to
tell someone that a 105 FD on a compact set will work just as well as anything else, or is the difference
between R600 and 105 that significant?

Another factor is that even if the chainrings are similar quality, the 53 tooth is going to be stiffer than the 50 tooth because the 53 tooth has a larger BCD (130mm instead of 110mm). Stiffer chainrings up-shift better.