Oval chainrings may not be a new invention, but coupled with the enhanced chain retention of a narrow-wide tooth profile, oval chainrings are more popular than ever.
What is the dead spot?
Imagine your chainring is a clock face, with your pedals in the 12 o’clock and six o’clock positions. This position is known as the dead spot, where it’s difficult to create much pedal power or leverage. By effectively lowering the gear ratio at this point in the pedal stroke allows your legs to get past this point and into the more efficient part of the pedal stroke toward the 3 o'clock and 9 o'clock positions.
Oval chainrings have the equivalent of 2 less teeth on the chainring where your pedal stroke is weakest, and the equivalent of 2 more teeth on the chainring where you have the most power. The radius of the chainring is constantly changing so the torque needed to turn the cranks is constantly changing to better match your power output. The design of oval chainrings enables you to apply more power throughout the more efficient part of the pedal stroke, effectively increasing the gearing by two teeth and hence producing more power on each pedal revolution.
Oval chainrings increase the peddling efficiency and maximize the output of our naturally very un-round pedal stroke. With oval chainrings, you’re effectively pushing a bigger gear where you’re strongest and a lower gear where you are weakest, so the rhythm of the pedal stroke is evened out dramatically.
Other benefits include the enhanced traction oval chainrings offer, particularly on mountain bikes. When the going gets steep, a small front chainring paired with a range extending 40-46 biggest cog can be a recipe for rear tire slippage. That’s only exacerbated by the uneven application of power on the pedals produced with round chainrings. One effect of an oval chainring is that you’re keeping a more consistent rotation speed throughout the entire pedal stroke, which helps keep the tires planted on the ground.
The Rapidé OVL Ring maximizes the part of the pedal stroke where power is produced, and minimizes resistance where it isn’t, allowing you to get on top of a gear.
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