This is the Felt DA of Mirinda “Rinny” Carfrae. She rode the bike at the 2012 Ironman World Championship in Kona, Hawaii. While professionals’ bikes certainly get a lot of attention, there are a few important details that went relatively unnoticed at the time. We had the chance to inspect the bike closely at a Zipp, Quarq, and SRAM press event in Tucson, AZ.

The most immediate thing you’ll notice about the bike is that it uses 650c wheels. You may recall that Rinny rode on Cannondale bikes before Felt, and spent most of those years on 700c wheels. Put simply, the bike was too tall in the front, and after consulting with several industry fit experts, Rinny made the switch to 650c.

These specific wheels on her bike are prototype 650c Zipp Firecrest carbon clinchers. Zipp announced the release of the production version of this wheel today, with retail store availability in March 2013.

The thing we mortal consumers do not get at this time, however, is the special hub and 10-tooth small cassette cog on Rinny's bike. 650c size wheels reduce the effective gear range compared to 700c. Assuming the same cassette size, a 650c bike requires 57/42 chainrings to (roughly) equal 53/39 on 700c. In the past, we've seen Rinny riding on a Specialties TA 58 tooth large ring, as it is one of the few available in such a massive size. The bike in this gallery has standard 53/39 Red rings, and uses a custom freehub and 10-tooth cassette cog to increase the top-end gear range. SRAM representatives were tight-lipped on this new development, and simply said that they are "looking at the possibility of bringing this to market".




All images © Greg Kopecky / slowtwitch.com

That's one fast-looking bike.

These prototype 650c Firecrest carbon clinchers do not have dimples yet.

Rinny was one of the first athletes to use the Profile Aeria bar.

That is some very clean front brake cable routing.

The shift and rear brake cables have a heat-shrink tube to pull everything together.

A simple Garmin quarter turn mount.

An ISM Breakaway saddle for Rinny.

The bike features a full SRAM drivetrain...

With a very special rear hub and 10-tooth small cog.

Rinny has custom decals on her 404 650c carbon clinchers.

SRAM does not make pedals, so Rinny relies on Dura Ace.

The Felt DA has a hidden rear brake.

Those don't look like standard SRAM shifters to us...

While the bike is in good condition overall, we can tell it gets ridden... a lot.

Rinny wisely chooses to accept the slight weight penalty of a chain catcher.

Nice bike.