Join Date: Jul 2007
Location: Los Angeles, Ca
Bikes: Litespeed Archon, Ultimate, Palmares, Blade. BMC Pro Machine. Trek 7.3 FX Commuter
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I don't have the q rings, but all of my bikes have the rotor crank system that basically accelerates the ascending crank to elimitate the top dead center of the pedal stroke when one cannot apply any power to the cranks because of the crank orientation.
They are heavy: about an extra pound over top of the line carbon crank sets, and have more and smaller bearings which require more atention and probably have more friction than the larger 'outboard' bearing type of cranks. They are also probably not as stiff as the best cranks out there.
However, studies done in Spain show an increase of up to 18% in power output, and the amount of increase was proportional to the incline grade and inversely proportional to cadence, meaning they likely will help proportionally more for grinders than spinners.
The differences between the q rings and the Rotor RSX4 cranks set are mainly weight ( q rings are lighter) and cost ( cranks cost 700-1000). But also realize that whereas the crank set actually eliminates the dead spot, the rings only improve it ( that is the effective crank length during top and bottom dead center are smaller than at other times during the pedal stroke.