Originally Posted by
mossi
I keep hearing debates for both types.
Today we have an amazing range for rear cassettes of up to 11-28. Common are the 11-25, 12-27.
Let's say I installed RACE 53/39 with 12-27 and COMPACT 50/34 with 11-25. Consider the following 2 extreme cases:
1. Maximum speed: 53-12 compare to 50-11
2. Maximum power: 39-27 compare to 34-25
Seems like to 2 are similar. Am I missing something? Is there anything bad with the 12-28?
First, there's nothing "bad" about the 12-28...or the 11-23. They serve different uses.
It's true that you can mix and match cranksets and cassettes to achieve similar gearing. Assuming you have similar gearing, one is no better than another, with the possible exception of the fact that the difference in number of teeth in the standard (what you call "race") crankset is smaller (53-39=14) than the compact (50-34=16), and therefore the shifting on the standard crankset can be smoother.
Compact cranksets are used by folks who aren't super fit, and by those who want some help getting up hills - I'm one of them. Standard cranksets are called that because they're what's usually standard equipment on race-oriented bikes.
The 12-28 cassette you mentioned is the large end of road cassettes, with the exception of the new SRAM Apex drivetrain with its 11-32 cassette. It's useful for riders who need help climbing. The other end of the spectrum is the 11-23. That's for fit, strong riders on relatively flat roads.
You can mix and match cranksets and cassettes, and you can further play with the cranksets by replacing chainrings. For basic, standard riders, we usually pick one combination and stay with it. Racers may change either or both around based on the course they're racing on.
Me? Compact crankset, 12-27 cassette. I'm considering changing the big ring to a 48 to get some more use out of the smaller cogs on the cassette, just as an example how you can modify stuff to fit yourself better.