It's no surprise that top athletes like Chris McCormack - who has won at Kona on the Zipp Tangente - and the women of Team Exergy TWENTY12 are seeing the benefits of Tangente aero tires. After all, your tires have the highest airspeed of any part of your bike, and the front tire is your machine's leading edge. It took us 14 months and two trips to the wind tunnel to get it right, resulting in the 21 mm version of the Tangente saving up to 9 seconds over 40 km compared with a traditional non-aero shaped tire when each was paired with a Zipp rim. The secret to the aero success of the Tangente line of tires is the shape. The leading edge radius has a slightly more pronounced point than a traditionally round-shaped tire, starting the airflow transition from tire to rim sooner and more efficiently. While also helping the Tangente cut through the wind, we've used our patented ABLC dimples to help the tire better adhere to any road surface more efficiently than a traditional "file" tread pattern, helping to deliver better cornering and braking. The dimples are not connected to one another, resulting in a lower overall stress in the tire casing and a smoother rolling and longer lasting tire. Tangente clincher racing tires come in 21 mm or 23 mm widths. Average weight 245 g, /- 10g (for clincher). Valve stems of 37 to 40 mm in length recommended for use with Zipp valve extenders. Packaging includes tire pressure chart to optimize rolling resistance by rider weight and front/rear use.