Detailed product description
- Perfect tooting due to a correct teeth orientation and full-profile teeth.
- Each chainring tooth is perpendicular oriented to the pitch-curve. This is a requirement for optimal mechanical efficiency
The PowerCurve tooth profiles are not “adjusted”. They have been correctly machined over the entire circumference. Full-profile teeth reduce chances of the chain jumping off.
- Sufficient stiffness by using 3 mm aluminum
- Smooth shifting aided by 6 stainless steel chainlifters,
Inner chamfer and shift gates in the teeth on the outer chainring.
Anti-wear and anti-oxidation treatment by anodizing and Nituff® processing.
Nituff® is a surface treatment that dramatically enhances the properties of a hard anodized metal surface:
- Higher oxidation resistance
- Self-lubricating surface with low friction
superior to ordinary hard anodizing.
- Chain stability on outer ring is 100%: no chain drop off.
This was tested by 26 test riders on nearly 20 000 km, in competition and in other challenging bike road conditions.
- Aero chainrings
- Sufficiently large ovality (25% for outer and inner rings )
The ovality is the ratio of the major axis to the minor axis length of the oval. If the ratio is e.g. 1.25 then the ovality is 25%.
According to research and testing chainring performance increase with increasing ovality. For practical reasons ovality is restricted to 25% to avoid mounting problems and to prevent the chain drop off the outer ring when shifting towards the smaller cogs. Chain stability was thoroughly and comprehensively tested. See above.
- Geometry of the shape
The PowerCurve consists of 4 shape sectors: a circle arc, a transition to flat, a flat section and a spiral of Archimedes as transition from flat to round. Justification of the PowerCurve shape, see “Science”
Rotor Q-Ring is a quasi mathematical ellipse. Ogival has one single shape sector (circular segment). Polchlopek (1970) consists of two shape sectors (circular segment and flat teeth-segment). Doval shows three shape segments (two different elliptical arcs and a flat section). Osymetric is composed of five different sections (circle arc, a flat teeth-segment, three arcs with different curvature as a transition from flat to round).
The shape sectors of the PowerCurve which are similar to the shape sectors of other manufactures are substantially different in size (number of teeth or number of degrees).
- Crank positioning or crank offset.
The crank of the PowerCurve chainring is oriented in the optimal position yielding a maximal kinetic crankpower gain combined with a minimal peak-power load in the extensor joint muscles of knee and hip.
This “optimal crank orientation angle” is confirmed in studies and by tests. See “Science”.
However the optimal crank offset is also a function of the bike geometry and the seating position of the cyclist. PowerCurve provides 3 mounting possibilities: a crank orientation angle of 68°, measured clockwise from major axis of the chainring (Road Bike), a crank angle of 76° (Time Trial Bike) and of 84° (provides an additional correction possibility for an extreme forward seating position).
Other manufacturers of oval chainrings position the crank mostly at 105° to 110°. Having the major diameter vertical and the crank arm at e.g. 110° (clockwise), the vector of the pedal force is almost maximal in this position.
But the direction of the pedal force vector is far from being optimal. In this position the tangential pedal force component is small and only generates a “modest” crank moment that contributes relatively little to the crank power output. That crank position with greatest force vector is certainly no guarantee of crank power maximization. Moreover, in that mounting position the above mentioned non-circulars have their largest gears close to the less effective pedalling sectors. At increasing and higher pedalling rates these ineffective positions become more distinctive.
Only the Polchlopek oval positions the crank arm relatively good to get crankpower gain, namely at 78°, measured clockwise from major diameter.
All the other manufacturers of ovals copy the “erroneous” crank arm orientation from each other.
- Aesthetic attractive finish
Black anodized with Italian design logo.
Stylish lettering with technical info on PowerCurve outer and inner ring.
Logo and lettering by laser engraving.
- Equivalent maximum and minimum round chainrings
Depends on ovality.
|Equivalent round chainrings|
|54 teeth||25%||60.8 teeth||47.3 teeth|
|52 teeth||25%||58.5 teeth||46.2 teeth|
|44 teeth||25%||49.5 teeth||38.5 teeth|
|42 teeth||20%||46.2 teeth||38.2 teeth|
|38 teeth||25%||42.8 teeth||33.3 teeth|
A PowerCurve 42 teeth chainring with 20% ovality feels like a 46.2 teeth ring during the power stroke and like a 38.2 teeth ring at the dead spots. In between, all other teeth sizes.