Tom A. wrote:
DarkSpeedWorks wrote:
Hi Josh,
Any idea of what some of the fastest (lowest measured rolling resistance) 25mm (as printed on sidewall, not necessarily actual measured size) tires are? Say, the top 3 to 5 tires?
Of the ones I've rolled, the top 5 are:
1. Continental GP TT (states 23, but measures 24.6mm on a narrow rim)
1. Specialized Turbo Cotton (pick either 24 or 26)
2. Continental Force (states is a 24, but actually measures 25mm on a narrow rim)
3. Zipp Tangente Speed 25C
4. Continental GP4KS2 25C
As you can see, even with this list, asking for "printed on sidewall" sizes isn't very helpful...
I would add to Tom's list:
1. Vittoria CorsaSpeed TLR 23 (measures 24.6mm on 17c rim and is fastest tire we've ever tested..)
2. Michelin Power Competition 23mm which also measures 25mm on 17c Rim.
Also Tom asked:
Quote:
And really, in the sense of a wheel being "fast" in regards to the "rule of 105", you're really talking about at higher yaw angles, right?
And I'd say that this gets really dependent on rim design. For a really well designed rim, the Rule of 105 is mostly about the stall angle..which will be out at the higher yaw angles..but for many non-excellent rim shapes, the Rule of 105 can be the difference between air separating at 2 degrees yaw or 10 degrees yaw. The rule was actually formulated in 2001-2002 when we were doing a bunch of general-science type of tunnel work to figure out the next generation of aero and is what put us on the path to bringing Full Toroidal rims to market. Good example of the genesis of the rule would be my Original Campagnolo Shamals with silver aluminum rims circa 1994. With an 18 mm tire they behave almost like a modern aero rim as we see the drag drop with increasing yaw out to about 5-6 degrees yaw, but with a 21mm tire, the drag climbs from zero.. so you are talking 2-5 watts difference out 2.5 and 10 degrees. The tire narrower than rim isn't making the simple V shape work like a modern rim, but it is at least giving you decent flow over the windward rim faces and helping close up the void off the trailing edge of the tire that much faster.
http://www.SILCA.cc Check out my podcast, inside stories from more than 20 years of product and tech innovation from inside the Pro Peloton and Pro Triathlon worlds!
http://www.marginalgainspodcast.cc