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Originally Posted by echappist
out of all the new disc-brake equipped aero bikes, only the Cannondale seems to be worth the trouble.
Otherwise, manufacturers are contorting to get people to buy the disc-brake bikes. The 2016-2018 Trek Madone was a fine rim-brake bike, but that bike would have been faster than the 2019 disc version. So Trek made the 2019 rim-brake bike slower as well, just so they can say that their disc-brake equipped bike is faster than the corresponding, same-year, rim-brake bike.
Irony here is that a rim-brake Cannondale would likely be faster than the disc-brake C'dale, but I don't think C'dale would be debuting that bike any time soon.
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This seems to be borne out by a recent Tour Magazine test of the latest aero bikes. A link to the test and a discussion of it can be found here:
https://weightweenies.starbike.com/f...p?f=3&t=154692
Here's a summary of the results:
Quote:
All tested at 45kph:
2019 Cannondale SystemSix Disc - 203w
2016 Trek Madone - 204w
2016 Specialized Venge ViAS - 204w
2016 Cervelo S5 - 205w
2016 Felt AR FRD - 205w
2019 Cervelo S5 Disc - 206w
2016 Canyon Aeroad - 208w
2019 Specialized Venge Disc - 208w
2016 Giant Propel Advanced SL - 210w
2016 Scott Foil Premium - 211w
2016 BMC Time Machine - 211w
2016 Look 795 - 212w
2019 Trek Madone Disc - 212w
2019 Ridley Noah Fast Disc - 213w
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The aero road bikes from every manufacturer in the test got slower when they redesigned it for disc brakes, except for Cannondale. But even for the Cannondale, they redesigned and re-optimized the entire bike, so who knows whether redesigning and re-optimizing around rim brakes wouldn't be faster still?
I've read the Cervelo white paper on the S5 Disc, which claims that the S5 Disc is faster than the previous S5 (no surprise there - every manufacturer claims their new bike is better than their old bike). But if you look closer, you'll see that they changed many aspects of the design (such as routing all the cables internally through the special stem, headset and fork). They mention how much power each change saved, and it adds up to more than the power saved by the whole bike - which implies that switching from rim to disc resulted in a power loss, for which they had to redesign other parts to make up for.