New Specialized SHIV Disc

Discuss light weight issues concerning road bikes & parts.
Hexsense
Posts: 513
Joined: Wed Dec 30, 2015 12:41 am

by Hexsense

We need some tests, between very slim cross section profile but porous Sram Centerline X disc rotor, and deeply filled but with fat carbon spokes and fan-like rotating fins of Shimano Dura-ace, Ultegra rotors. Which one is more aero. One side is slim and low cross section, another side is like deep dish, except that it is has much wider "four spokes" carbon arm and rotating fan in the center.

Life would be a lot easier if FSA, Rotor or other company make a deep aero disc rotor without fan blade.

by Weenie


prebsy
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Location: PHL

by prebsy

Tri tech is always gonna look a bit quirky but I love the front end

Bordcla
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by Bordcla

Calnago wrote:
Tue Oct 09, 2018 3:00 pm
Roel W wrote:
Tue Oct 09, 2018 2:53 pm
Disc brakes don't influence the steering of the bike that much, even with crosswinds. That's because they are rather close to the hub. If that would be the case, large sprockets should also not be used on tri bikes.
Not even talking about the steering effects, simply the negative effect on aero, and it is negative. So what, you ask... well, here they are claiming to be attempting to squeeze every last bit of aeroness from this frame, and then they go put disc brakes on it. Also pretty hard to claim that discs will make them faster on the downhills in this case. How much do you think the brakes are even being used at Kona, or most tri courses for that matter. I've ridden the big island on a regular bike, and while we did a lot of the Kona course, what I don't recall is having to use the brakes a whole lot.
And don't get me started on massive cassettes on road bikes, I've joked in the past that the only reason I can see for those is to hide the ugliness of the huge rotor on the other side. But that's another topic entirely.
How many PH.Ds in aero engineering do you hold and how many reliable quantitative studies have you realized in the subject of aero or non-aeroness of disc bikes to speak in such definitive terms?

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Calnago
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by Calnago

None. Some stuff is just common sense.
I do have a business degree however and a fair bit of experience with understanding how marketing and business decisions play into all of this.
Colnago C64 - The Naked Build; Colnago C60 - PR99; Trek Koppenberg - Where Emonda and Domane Meet;
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Monkeyfudger
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by Monkeyfudger

dcorn wrote:Without relying on the wheel rim for braking, wheel designers can use different carbon layups, different resins, and different rim shapes to make the wheels lighter and more aero.
How’s that going for MTB rims? Are they using new/different resins/layups? MTB’s have been on discs for the entire life of carbon rims and they basically look exactly the same as alu rims, granted we don’t have aero on the MTB, but they’re really not that different. At all.

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Calnago
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by Calnago

Really, before this turns into another disc vs rim fight... just stop. It's not. Discs have their place for sure. I'm just pointing out that for this particular discipline, and this particular bike, where the designers go all out to point out that "aero is truly everything", and then they add disc brakes to the mix..., the marketing spin quite frankly is out of control and the rationale for putting disc brakes on this bike has nothing to do with increasing it's "aero performance".

Like was already said, it's amusing when even the most infitessimaly small gain in aero, be it from a hidden piece of 4mm cable housing or whatever can be achieved, then that gain is marketed as, well... a marginal gain and not to be discounted in any way. Yet, when anything takes away from the aeroness, even much more than marginally, the difference is downplayed as "negligible". Just look at this bike. How hidden from the wind could rim brakes be here. Almost completely hidden I would think. Look at the width of those forks... just have a couple pads being pushed out to the rim when braking, and otherwise they're completely hidden. And for the rear, just slap on a set of under the chainstay direct mount brakes (after all, that's what they were initially designed for), and voila, again... almost completely hidden from the wind. But instead... they slap on a 140mm pie plate of a rotor to each wheel and some calipers along with it. If they can claim a 4mm cable is unaero enough to warrant hiding from the wind, then a 140mm plate against a cross wind is something they might want to consider avoiding as well. Just sayin...
Last edited by Calnago on Tue Oct 09, 2018 8:21 pm, edited 1 time in total.
Colnago C64 - The Naked Build; Colnago C60 - PR99; Trek Koppenberg - Where Emonda and Domane Meet;
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dcorn
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by dcorn

Monkeyfudger wrote:
Tue Oct 09, 2018 7:40 pm
dcorn wrote:Without relying on the wheel rim for braking, wheel designers can use different carbon layups, different resins, and different rim shapes to make the wheels lighter and more aero.
How’s that going for MTB rims? Are they using new/different resins/layups? MTB’s have been on discs for the entire life of carbon rims and they basically look exactly the same as alu rims, granted we don’t have aero on the MTB, but they’re really not that different. At all.
Why don't you fill me in on how many rim-brake carbon mtn bike rims were made before the switch to disc? Just doing quick research, it looks like even the carbon spinergy rims had an aluminum brake track. So I'd say since mtn bikes have disc brakes, wheel designers can focus on ride quality, tubeless tire retention, and impact strength of carbon rims without having to compromise the design with a brake track that will see a ton of friction and heat. Go check out some of the modern mtn bike rims from Enve and see how the bead hook has changed, how the strength has increased dramatically, and now they are making wheels that are pinch flat resistant even with tubeless tires.

And you are right, disc mtn bike rims look just like rim mtn bike rims precisely because they don't have to worry about aero. No real shaping is necessary, just hold on a tire and hold the spokes.

I'd love to know how many of the 'disc deniers' in here are engineers or scientists since they have such strong opinions on how the technology of disc brakes over rim brakes is just marketing BS. :roll:

Jugi
Posts: 126
Joined: Sun Jun 24, 2018 8:10 am

by Jugi

Monkeyfudger wrote:
Tue Oct 09, 2018 7:40 pm
How’s that going for MTB rims? Are they using new/different resins/layups? MTB’s have been on discs for the entire life of carbon rims and they basically look exactly the same as alu rims, granted we don’t have aero on the MTB, but they’re really not that different. At all.
A cantilever brake would look quite funky around 2.6” tire and a 45mm outer width rim. A fat bike with cantilevers would be an interesting technical exercise. :roll:
Calnago wrote:
Tue Oct 09, 2018 8:00 pm
How hidden from the wind could rim brakes be here. Almost completely hidden I would think. Look at the width of those forks... just have a couple pads being pushed out to the rim when braking, and otherwise they're completely hidden.
Didn’t you pay any attention to the actual construction of this bike’s fork, just saw the word ”disc” at the header and decided to rant? There is no place to put an integrated brake caliper in this fork. This bike has evolved past rim brakes.

spud
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by spud

exactly - the big payoff in aero comes from integration and lack of derailluer/brake lines exposed to wind flow, in conjunction with aero profiles normal to wind flow, and where possible, reducing cross sectional area. Putting on rim brakes would require a TON of resources to figure out routing so that the resulting mechanical action would not be too heavily compromised. And in end, you'd still have compromises, both in operation, and maintenance. Putting discs on the bike makes thing much easier, mechanically more reliable and servicable, and a lot cheaper. Get used to it, discs are here to stay.
And yes, my road bikes have rim brakes.

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Calnago
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by Calnago

spud wrote:
Tue Oct 09, 2018 8:39 pm
...Putting on rim brakes would require a TON of resources to figure out routing so that the resulting mechanical action would not be too heavily compromised. And in end, you'd still have compromises, both in operation, and maintenance. Putting discs on the bike makes thing much easier, mechanically more reliable and servicable, and a lot cheaper. Get used to it, discs are here to stay.
And yes, my road bikes have rim brakes.
I don't think it would be that hard to do at all, if they chose to do so. And remember, this bike is supposed to be ALL about aero, so to incorporate something that is less aero than a pretty simple alternative is ludicrous unless the greater business goal is in mind, and it is. There's often compromises, but on an all out aero tri bike, where aero is absolute king and you might use the brakes, well... just about never, where do you suppose the better place to make a compromise might be... Aero, or Braking? Just think about this for even a second... Specialized is very aware of the debate over the lack of aeroness of disc brakes. Don't you think they would have said that the disc brakes on this bike are more aero than any available alternative, if they could even remotely show that to be true, or somehow spin things to pretend that to be the case at least. Of course they would have. But in this case, silence is golden. The spin cycle keeps spinning.

And of course discs are here to stay, that's not at issue here. But there are places where they work better than others. That's all.
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spdntrxi
Posts: 1888
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by spdntrxi

a few companies have stated their disc bikes to be more "aero" then the rim brake versions.. it's rarely apples to apples but look at the new madone. If trek can....the bigS can too.. bmc, cervelo, you get the ideal. Why the hard headiness Calnago?

dcorn
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by dcorn

Calnago wrote:
Tue Oct 09, 2018 9:01 pm
spud wrote:
Tue Oct 09, 2018 8:39 pm
...Putting on rim brakes would require a TON of resources to figure out routing so that the resulting mechanical action would not be too heavily compromised. And in end, you'd still have compromises, both in operation, and maintenance. Putting discs on the bike makes thing much easier, mechanically more reliable and servicable, and a lot cheaper. Get used to it, discs are here to stay.
And yes, my road bikes have rim brakes.
I don't think it would be that hard to do at all, if they chose to do so. And remember, this bike is supposed to be ALL about aero, so to incorporate something that is less aero than a pretty simple alternative is ludicrous unless the greater business goal is in mind, and it is. There's often compromises, but on an all out aero tri bike, where aero is absolute king and you might use the brakes, well... just about never, where do you suppose the better place to make a compromise might be... Aero, or Braking? Just think about this for even a second... Specialized is very aware of the debate over the lack of aeroness of disc brakes. Don't you think they would have said that the disc brakes on this bike are more aero than any available alternative, if they could even remotely show that to be true, or somehow spin things to pretend that to be the case at least. Of course they would have. But in this case, silence is golden. The spin cycle keeps spinning.
How about this: Specialized already went down that rabbit hole of "make a bike as aero as possible with rim brakes, but also have fully integrated cables". They already played that game with the Venge Vias and they lost, big time. Go listen to the CyclingTips podcasts where they talk about specifically that. Now you're telling them to do the same thing again with an even more complicated bike. I'm sure they did the math and decided disc brakes were much, much less of an evil than a bunch of exposed cables and really complicated, proprietary, half-assed rim brakes.

Maybe you're right and they didn't talk about the disc brakes because they don't ADD to the aeroness of the bike. But completely integrated cables certainly do. And thru-axles without a lever definitely do (plus adding stiffness). Plus, having a bike you can actually work on, adjust for fit, and break down for travel is just as important, as they learned on the Vias.

BrianR
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Joined: Thu Jun 21, 2018 4:38 pm

by BrianR

Calnago wrote:
Tue Oct 09, 2018 7:11 pm
None. Some stuff is just common sense.
I do have a business degree however and a fair bit of experience with understanding how marketing and business decisions play into all of this.
I don't think you get to reduce a complex concept (of aerodynamics) down to "it's just common sense" lol. It is key to your argument though, so carry on!

spud
Posts: 669
Joined: Sat Feb 07, 2009 5:52 am

by spud

Calnago wrote:
Tue Oct 09, 2018 9:01 pm

I don't think it would be that hard to do at all, if they chose to do so. And remember, this bike is supposed to be ALL about aero, so to incorporate something that is less aero than a pretty simple alternative is ludicrous unless the greater business goal is in mind, and it is. There's often compromises, but on an all out aero tri bike, where aero is absolute king and you might use the brakes, well... just about never, where do you suppose the better place to make a compromise might be... Aero, or Braking? Just think about this for even a second... Specialized is very aware of the debate over the lack of aeroness of disc brakes. Don't you think they would have said that the disc brakes on this bike are more aero than any available alternative, if they could even remotely show that to be true, or somehow spin things to pretend that to be the case at least. Of course they would have. But in this case, silence is golden. The spin cycle keeps spinning.

And of course discs are here to stay, that's not at issue here. But there are places where they work better than others. That's all.
New Trek Madone has the option of rim brakes. 10 years from now, you want try to find spares for that proprietary brakeset, or just buy another flat mount disc caliper?

I know, who among us keeps a bike for 10 years? I'm still part time riding a 9 year old bike, but she is getting tired and a bit noisy periodically.

by Weenie


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Calnago
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by Calnago

spdntrxi wrote:
Tue Oct 09, 2018 9:31 pm
a few companies have stated their disc bikes to be more "aero" then the rim brake versions.. it's rarely apples to apples but look at the new madone. If trek can....the bigS can too.. bmc, cervelo, you get the ideal. Why the hard headiness Calnago?
Fair question, the hard headedness isnt' directed so much at the disc brakes themselves, as much as it's directed at the marketing spin that gets more out of control by the day. There are places, and I would hazard a guess, that Kona Ironman is one race where discs are just not needed and, with any crosswinds, are less aero (due to the rotors) than say, a well hidden rim brake. Yet, discs are being pushed at every level no matter the appropriateness. So why, in the one event where aero matters above all else, with no UCI Rule constraints, do they put disc rotors on bikes if it isn't for marketing purposes. And yes, the tri world is the perfect place to sell this, cuz they'll buy anything. Hope that answers your question a bit better.

To the poster that supposes that common sense is not worth anything, I submit that if I have a 6 inch disc in my hand and hold it flat side facing a fan, that I will feel more pressure than if I turn the disc on it's side so that only the edge is facing the fan. This, you do not need a degree in aerodynamics to understand. Or even really much intelligence, for it is easy to feel.

Carry on... I'm sure the bike is very aero, and I suspect it could be ever so slightly more aero, if they really chose to make it so.
Colnago C64 - The Naked Build; Colnago C60 - PR99; Trek Koppenberg - Where Emonda and Domane Meet;
Unlinked Builds (searchable): Colnago C59 - 5 Years Later; Trek Emonda SL Campagnolo SR; Special Colnago EPQ

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