Im sure They could make this happen with Potts being a sponsored athlete.

Maybe, it it'll cost you. Most aero wheels have a low spoke count for aero and weight savings. Disc wheels need more spokes because the stress from braking at the hub (disc) gets transmitted to the rim through the spokes.

AFAIK, you can't replace the hub of full disc wheel. That is the solid rear disc wheel, not a disc brake. Even if you could, the disc is likely not going to do well with that kind of stress that it was not designed for. Most of those cost $1000 or more.

One potential advantage of a wheel with a disc brake is that wheel manufacturers may be able to redesign the rim to be more aero, light, etc if you no longer have to worry about building in a brake track for rim brakes. So you'd be losing that potential advantage.

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Don't drown. Don't crash. Don't walk.

I don't think I'd exactly call the bike he rode in the race as "optimized" for rim brakes...

Like I mentioned above, so far the best "apples to apples" comparison we've seen on this has been the Culprit test, as outlined here: http://road.cc/...-which-are-more-aero

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http://bikeblather.blogspot.com/

 
It is difficult to test "apples to apples" because as its been pointed out each version (rim and disc) will be optimized for that standard. Disc equipped bikes can test faster than rim brake equivalent models due to the design freedom in the aero critical areas of the system (headtube, fork) which outweigh any negative affects of placing a disc caliper on the fork and rotor on the hub. You gain more than you lose if done correctly which we discovered with the S3 disc.

The other huge benefit, though not as exciting as aerodynamics, is that stiffness and handling greatly improve with through axles so overall the complete bike "system" is improved and we always want to push the performance of our bikes.

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Jakub

You will never get a test that has two optimized bikes. Companies will not devote the time and money to develop their best rim brake version and their best disc brake version and put them in the tunnel.

This is about as best as we can do. Their seems to be advantages to going with disc brakes so that is what they will chase next.

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Just want to clarify that there is no reason to tie thru axles to disc brakes, the same approach could be applied to rim brakes if the industry was so inclined. Though if I recall, there were some QR loosening failures that were attributed to the different stresses that resulted from the use of disc brakes in their early days.

Wrong. Follow the link to the Culprit test I posted above. That's far better than taking a bike with a head tube with a nice parabolic leading edge and then literally hot-melt gluing a smooth "blob" on the front... and then wondering why it's not very aero :-/

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Prove it. So far you have not. "Hand waving" and saying "it's difficult", doesn't cut it. The burden of proof is yours.


Then we should be seeing a rush to add them to rim brakes bikes too then, huh?...I mean, if it's SO much a difference, right? :-/

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I find it disheartening that Damon is involved with that "story" on the front page. I guess it did mention that there are things to consider, but then why publish such things? If you want to prove disc brakes are faster show the 2 independent versions that show it accounting for all items. how is a rotorless disc hub a good comparison in and of itself? I am not going to use that type of wheel on my rim brake bike in an event where I am trying to minimize time

You are correct that disc brake models can use QR's, as you noted there are some issues with that, namely slipping wheels and inconsistent alignment of the rotor and pads.
If you are reinforcing the fork leg to include threads for a through axle it makes sense to use that extra material to mount a disc caliper and optimize the fork crown structurally and aerodynamically. Another benefit is the option for extra tire clearance which is typically limited by the rim caliper.

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Jakub

I completely agree. It seems like Damon was hyping up some amazing test results we'd all be shocked with, but it was all quite disappointing in the end.

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Both of which can be solved by merely changing the dropout to be forward opening, rather than the traditional front fork dropout being downward opening. I have a Salsa Vaya fork that does exactly that and I have zero issues with alignment or slipping on a disc-braked bike.


Besides...I believe Pooks was pointing out that through-axles could be used on rim brake setups. In other words, if it truly is a better system, then it can be implemented without switching braking systems. It's not tied to either.




Isn't that succumbing to the false assumption that a rim brake needs to be a typical add-on caliper? How about using some of the "what if?" brain power being wasted on trying to work around the structural and aerodynamic challenges of adding a separate braking disc to re-imagining how the rim brake system should be incorporated?

Does one really need more tire clearance than THIS on a road racing or TT/Tri bike?

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http://bikeblather.blogspot.com/

That's true. The burden of proof is on anybody who makes a claim either way. Nobody has the requisite information to make the claim as to which types of brakes are "faster".

Sure...but we have logic, physics, and tests that have done the best job at "apples to apples" comparisons (like the Culprit test linked above) which suggest fairly convincingly that one version has a much higher burden of proof.

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Please remember when posting about my data that I was using an ashima mtb post mount caliper since sram wouldn't give me a caliper to use after they first released. These numbers were from San Diego wind tunnel in 2013..... Way before anyone else jumped into the road, tri disc development. New flat mount will result in lower drag.

But yes, same rim profile 20/24 rim, 24/24 6 bolt hub disc. And disc front wheel was slightly out of true.

Bingo.

Tom is only diligent about details that support his argument.

Did I say the test was perfect? No. I merely pointed out that so far it's the best example we've seen of not unfairly hampering either system and allowing for important properties (such as spoke count) to be varied.

Sure the drag could be less with a different disc caliper...but, 100g of drag at 30mph less? Doubtful.

edit: Besides, the pics I've seen of those Ashima calipers show them to be quite svelte, even in post mount. Definitely nothing like the monsters on the P5X builds.

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Also there is the fact that almost all the bikes being shown right now have the TRP/HyRd brake on there. That think is a monstrosity. Likely a moot point going forward given that shimano has a lever in the pipeline and I'm guessing sram does as well.

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Heath Dotson
HD Coaching:Website |Twitter: 140 Characters or Less|Facebook:Follow us on Facebook

I'm sure this has been asked before, but are forks with more clearance better aerodynamically?
I don't know the terminology, but I assume there is an interaction between the air coming off the spinning wheel/spokes and the fork.
I know it's not as aesthetically please as nice tight clearance.

There are really two schools of thought on that. One is with tight clearance you reduce front area and the wind "sees" the wheel fork as one unit (see Wiggins hour record bike). The second is that spacing the forks wider allows the air through cleaner and also reduces pressure build up by the spinning wheel. Both can work, but it is all in the execution.

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Heath Dotson
HD Coaching:Website |Twitter: 140 Characters or Less|Facebook:Follow us on Facebook

I've often hear this said about braking force transfer. But a rim brake has to transfer the braking force from the rim to the hub to stop the rider/bike. Why is this less force than transferring in the opposite direction? Why can rim front wheels be radially spoked but not disc? Either way, the force is transferred along the spokes, requiring a minor amount of flex so that the force is not exactly tangent to the rim in a radial wheel.

This point is one of the reasons why disc brake equipped bikes are so exciting for engineers at Cervélo. Rim brake designs have been around a long time on road bikes and have been designed and re designed to squeeze out better and better performance. Disc brakes have been around a very short time for road and Tri - flat mount is very new. The fact we are able to better the aero performance and improve the bike as a whole this early into the development of disc for road / Tri speaks to the large possibilities ahead.

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Jakub

I dont know, my physics is not good enough to answer that. I'm just repeating what more experienced wheelbuilders have told me... but if you're sceptic, then I'd say why dont you try radial lacing and report back ;)

Umm, you did more than that. You used it as your prime example of a test which is "fairly convincing" that one type of brake requires a higher burden of proof than the other. You did not merely point out that it's the best example of a test, you made a subjective claim about the quality and strength of that test.