Originally Posted by
cobra_kai
Have you tested the crr of the compass tires vs continentals or just going by feel? Based on the roller testing data from Tom Anheult (
Blather 'bout Bikes) you are probably giving up around 15 watts to a pair of GP4000. I'm wondering if there is any data to support the 'fast rolling' claims of the compass or whether people are simply biased and regurgitating the company's claims.
Where's the 15 watt difference? I looked over the google doc as well as read through Tom's comments in the thread at slowtwitch and he notes that:
It might not be clear, but I tested BOTH the regular and EL versions of the Snoqualmie Pass tire. They "bracket" the Strada Bianca Pro in the list. It appears that for that model, the EL version is worth only ~1-1.5W per tire between 20-30 kph.
Per this comment it appears the chart is showing that it's possible to go from a 23mm racing tire to 44mm tire and only give up 2-3 watts. That's amazing, I'd say that qualifies as "fast rolling" as much as anything else. Looking at the watt values for other tires in the google doc is also eye opening. The smooth tread Compass tires are very fast for their size and appear to roll as well as the good/average 22/23/25 racing tires. It's also interesting to note the spread of different GP4000s tires tested did not all test consistently as well as the performance of tubulars wrt the Compass tires.
Slowtwitch Thread.
Google Doc
However, IMO this comment from Tom makes the tests worthless. Small, smooth diameter roller tests are the worst tire tests to try to apply to the real world.
- It's important to remember that the smooth rollers are of relatively small diameter, which results in a more "curved" contact patch deflection than for the same wheel load on flat ground. Erring towards the side of higher pressures in the testing will help prevent undue influence of "side knobs" coming into play in the drag measurements. In other words, I don't want side knobs affecting things when they may not be getting deflected out on the road.