An Afternoon With Zipp

This week I got a visit from Zipp’s head of marketing and media relations. He stopped by with examples of their new designs, in particular, the new Firecrest 808s and the carbon clincher 404s, which also benefit from Zipp’s new Firecrest rim shape.

You’ll find below this post my belated review of the previous iteration of the 404 in tubular form. It is unequivocally the fastest wheel I had ever ridden. Well, it used to be. I’ve ridden the 808 and it, well, I’ll get to that.

Deep-section carbon fiber wheels all have a “V” shape in cross section, that is, except for Zipps. The 404s I’ve been riding employ a hybrid-toroidal shape that makes them both faster and easier to handle. The new Firecrest shape doesn’t really look fast when viewed in cross-section. It looks rather fat and not exactly fast. Looks are often deceiving.

Not only is the Firecrest shape faster, it adds stability in a cross wind and increases rim strength for impact over rough road (or pavé). The most surprising aspect of the Firecrest shape is how Zipp engineers were able to tune the shape in the 404 and 808 so that the center of pressure, that is, the focal point of a cross-wind’s pressure on the rim was not only near the steering axis, but slightly behind it. The thrust here is that a cross wind from the rider’s left didn’t push the rider to the right, but rather ever-so-slightly steered the rider left and into the wind, making these wheels stunningly stable in a cross wind. To ride the 808’s stability in a cross wind is to know the meaning of unlikely.

Total claimed weight on the 808s is 1519g. That said, there’s a fair amount of carbon that constitutes rotating mass. Even though the wheel is reasonably light, I wondered just how easy it would be to accelerate. What surprised me was they were as easy to accelerate as any of my lightweight clinchers.

The wide rim bed (25.94mm front and 26.24mm rear) gave the tires an ideal platform to retain their true tubular shape. Cornering on a twisting descent on the 808s was Cirque du Soleil-nimble. Brake response was decidedly even and smooth, but one small word of warning: This rim shape is very wide. Brake set up and brake shoe position are such that you won’t be able to swap other wheels in or out for the 808s without taking some time to adjust both the brake and the brake shoes.

This was but one ride and Zipp has more patented and trademarked technologies that I’ll go into later when I’ve had a chance to ride these wheels in greater depth. My initial sense is that the new 808s are the fastest wheels I’ve ever ridden by a couple of country miles.

 

, ,

4 comments

  1. Souleur

    tell us more Padraig:-)

    nothing graces our bikes like a pair of zipps
    i would especially be interested in your thoughts on tubies vs clinchers?

    thanks in advance


    1. Author
      Padraig

      There’s not much I can add so far, though as I understand it, the rim bed is pretty wide on the clinchers, so it’s possible to change flats without a tire lever. Of course, nothing rides like a tubular, but life in SoCal means debris and I need to change flats quickly. I really want to put some more miles on those 808s. A wheel with a rim that deep shouldn’t handle that well, but it does.

  2. one60

    I was surprised at how wide those rims are as compared to most clinchers. Have you measured the width of a tubular mounted at the proper pressure with a caliper?

    Many people refuse to run anything smaller that 20-23mm clinchers on 19mm wide rims, for fear of ‘losing speed’. I wonder if the wider contact is in part responsible for the quickness you describe.


    1. Author
      Padraig

      One60: Specialized has been doing a bunch of research on tire width, contact patch and rolling resistance. Wider tires are proving faster. While it’s heavy as hell, the new Roubaix with a 23mm tread on a 25mm casing has, according to the test results I’ve seen, the lowest rolling resistance of any Specialized tire.

      For my part, I never ride a tire narrower than 23mm. Never.

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>