# the calls for a Venge with disc brakes...



## thumper8888 (Apr 7, 2009)

lots of comments to this effect over on Bike Rumor, under their post about the new Tarmac....

I just don't get it...Disc brakes cause SERIOUS drag, something that can just be designed away. It's probably on a par with the drag you save by going with mid-deep wheels. It also adds weight. 
And to put that on the Venge, of all bikes? The idea is just silly.
"Oh, I want an aero bike and am willing to accept the minor compromises like ride quality and slightly less torsional stiffness to get lower drag. But please, give me discs so I can jack the drag back up to what it would be on a Tarmac."
For anyone not riding mountains, and doing it on carbon clinchers, it's a solution in search of a problem, and an expensive solution at that.

Then there is the safety issue. This isn't just UCI being like UÇI was before it's new leadership. Massive wrecks aren't unusual in my races and are already dangerous enough without havibg to fly into a whole nest of what essentially are deli meat slicers.


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## SundayNiagara (Apr 17, 2014)

But they look cool.


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## aclinjury (Sep 12, 2011)

SundayNiagara said:


> But they look cool.


and the bigger the disc, the cooler you look. 140 mm - 160 mm disc rotors are for girls. Men start at 180 mm - 210 mm rotors.


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## dcorn (Sep 1, 2011)

Since I'm not a pro racer, I couldn't care less what the UCI approves. And my Cosmic Carbone SLR wheels already have super sharp, bladed, carbon fiber spokes, so I'd imagine someone getting their finger caught in there during a wreck could be pretty painful. 

Disc brakes, like electronic shifting, are just another evolution in technology. I want my bike to have the best tech I can afford because it makes me feel faster if nothing else haha. 

If you are comparing the Tarmac to the Venge, think of it this way. The Venge has more aero benefit, which should make it faster than the Tarmac. Put discs on the Venge and maybe the drag brings you back to Tarmac levels of performance. Even though the overall aero of a disc Venge is the same as my rim brake Tarmac, I now have two tech advantages over the Tarmac: more aero and better brakes. I'm still coming out ahead. 



PS: I'm one of the people that really wants a disc Venge. I'd LOVE to get the Bianchi Oltre XR2 disc, but damn, $12k+ is just out of my league.


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## tom_h (May 6, 2008)

It would be interesting to see a quantitative analysis of alleged time savings from discs, on a stage with twisty descent.

My guess is timed saved = not much ... not enough to decide a stage.

yeah, you could go deeper into a curve before braking ... but the big time is gained on the climbs, not the descents.

I suspect marginal gains on the descent won't make up for the added weight during a climb or worse aero on the flats. 

And on a flat-ish stage, even amateurs will scarcely apply brakes.


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## Dunbar (Aug 8, 2010)

I remember seeing a wind tunnel test of road bike disc brakes. I think around 10+ watts of additional drag which erases about half the aero savings of the Venge frame. There are also hydraulic rim brakes which would allow you to brake later on tight corners when descending (assuming that even saves time in the first place.)


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## dcorn (Sep 1, 2011)

The weight you add with discs (how much more over rim brakes?) could also be equalized by the wheel rim design. Without rim brakes, wheel designs can go back to being structural and areo. You don't have to design in a brake track, nor create special resins for the carbon to withstand crazy heat. The wheel can be a wheel, and the brake rotor takes over the braking. 

Cmon, you guys really think there won't be aero disc calipers out there in a year or two once the trend catches on? Carbon brake rotors already exist and why wouldn't they since road cars have them? Anyone worried about getting cut during a crash? Make the manufacturers chamfer the edges of the rotors so they aren't sharp. There are ways to engineer out every problem you guys have with road discs.


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## thumper8888 (Apr 7, 2009)

dcorn said:


> The weight you add with discs (how much more over rim brakes?) could also be equalized by the wheel rim design. Without rim brakes, wheel designs can go back to being structural and areo. You don't have to design in a brake track, nor create special resins for the carbon to withstand crazy heat. The wheel can be a wheel, and the brake rotor takes over the braking.
> 
> Cmon, you guys really think there won't be aero disc calipers out there in a year or two once the trend catches on? Carbon brake rotors already exist and why wouldn't they since road cars have them? Anyone worried about getting cut during a crash? Make the manufacturers chamfer the edges of the rotors so they aren't sharp. There are ways to engineer out every problem you guys have with road discs.


No there are not ways to engineer out every problem. Weight is the only one. Drag and safety are the real engineering bears here.

And the weight difference is nearly unimportant. Most high-end bikes with high-end wheels are now under UCI weight (though it would not surprise me to see the "new UCI" drop the minimum a bit now that they are moving into the 21st century under new leadership.
Weight isn't the point Drag is, and it's not mainly the caliper, it's the disc. 
This is an aero bike we are talking about. the discs simply cannot be made aero.
A disc is a disc. They have to be so thin to function that really almost nothing can be done to their shape. In the real world, the wind is almost always going to hit them at an angle of 5-20 degrees. Just no hiding that high-drag flat shape.
Chamfering actually would make the disc MORE dangerous. MORE like a blade.
Carbon rotors would solve what? they are just as sharp, just as draggy.
OK, save a few grams.
Back to my first point, we are talking about an aero bike here, one that in my case is already below UCI legal minimum weight.


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## thumper8888 (Apr 7, 2009)

Dunbar said:


> I remember seeing a wind tunnel test of road bike disc brakes. I think around 10+ watts of additional drag which erases about half the aero savings of the Venge frame. There are also hydraulic rim brakes which would allow you to brake later on tight corners when descending (assuming that even saves time in the first place.)


Yes, and 10 watts is about what I gained by switching to Zipp 404s...if the wind is blowing right.


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## dcorn (Sep 1, 2011)

Ugh, arguments for everything eh? 

I'll just reiterate. I don't care what the UCI does, I don't race. Based on the last time I rode my bike down a switchback mountain road, in the pouring rain, and surrounded by hundreds of other people ('13 NY Gran Fondo), I want disc brakes on my bike regardless of the minimal drag penalty. I have Mavic Exalith brakes now, which are supposed to be even better than plain aluminum, and they are. But it was scary going down those hills and barely being able to stop at each turn, while trying not to crash into all the other people around me.


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## thumper8888 (Apr 7, 2009)

dcorn said:


> Ugh, arguments for everything eh?
> 
> I'll just reiterate. I don't care what the UCI does, I don't race. Based on the last time I rode my bike down a switchback mountain road, in the pouring rain, and surrounded by hundreds of other people ('13 NY Gran Fondo), I want disc brakes on my bike regardless of the minimal drag penalty. I have Mavic Exalith brakes now, which are supposed to be even better than plain aluminum, and they are. But it was scary going down those hills and barely being able to stop at each turn, while trying not to crash into all the other people around me.


No, not arguments for everything, logical discussion. That's kind of dismissive of you, insinuating that those who disagree with you are argumentative rather than perhaps offering some reasonable points.
I won't do the same to you. Let me say flatly that I'm glad there are folks like you on the cutting edge, weighing the plusses and minuses and then buying this stuff so that the companies will continue pursuing and refining the concepts. And some of the reasons you offer are certainly reasonable, partic if, as you say, you dont race.
And disc brakes certainly will improve... for example, you can kind of see the day coming when they have antilock systems, which would be a great boon (at least, to those using them if not the people directly behind them in a group ride who dont have them yet).
And I'm glad that they would make you safer going downhill, though I don't think they are a massive safety boost to anyone not using last-generation carbon wheels on mountains or in the rain, something I would venture fewer than 5 percent of recreational cyclists do.
But I do not want anyone using them in a race pack I'm involved in. I do not want to fall at high speed into a pile of bikes with these deli meat slicers. Simple as that.
I would also venture that those around you on a ride like that fondo or group ride should be worried about the same safety issue.
Lastly, you can't say the drag penalty is "minimal." Drag that exceeds the gains from $2,500 Zipp 404s or an entire aero frame would have to be described as "maximal."
But again, if they work for you, hope you enjoy 'em.


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## tom_h (May 6, 2008)

thumper8888 said:


> No there are not ways to engineer out every problem. Weight is the only one. Drag and safety are the real engineering bears here. ....
> ... This is an aero bike we are talking about. the discs simply cannot be made aero. ...


It's not just the disc.
Front disc wheel cannot be radially spoked, or they would buckle when braked. So most will have 2x pattern and more spokes.
Another source of drag, although I dont know how much that is relative to the rotor itself.


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## s4gobabygo (Jul 28, 2010)

thumper8888 said:


> I do not want to fall at high speed into a pile of bikes with these deli meat slicers. Simple as that.


there are already sharper, more dangerous things on a bike to land on than a flimsy brake rotor (an exposed 53t chainring comes to mind), and if the addition of brake rotors is the straw that breaks your camel's back, you might just have to make your own decision about the dangers of your chosen sport. i can't speak for the UCI, but whether it be racing, fondo, group ride, coffee run, whatever... pretty soon you're going to be following plenty of wheels with discs attached to them (if you aren't already).


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## TheBaron (Jun 5, 2013)

The thing I love about my S-Works Venge is how streamlined and slick it looks. I can't comment on the watts difference between the two break types are but what I do know if they don't look aero and having them on the frame would change the slick streamlined look of the bike.

I'd never buy a BMC bike but I did enjoy watching Tyler Phinney's solo victory in the Tour of California as I loved the clean-ness of his bike. I want the next Venge to have an integrated front brake and the rear break underneath the frame just like Tyler's. 

Hopefully if/when they release a new Venge they will do the same as the Tarmac and provide two versions, one with each of the break types. If they do I know which I will select.

I doubt we will ever know (unless one type is dropped from the product range) but in regards to the new Tarmac, I'm interested to know the breakdown in sales by break type.


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## dcorn (Sep 1, 2011)

TheBaron said:


> I'd never buy a BMC bike but I did enjoy watching Tyler Phinney's solo victory in the Tour of California as I loved the clean-ness of his bike. I want the next Venge to have an integrated front brake and the rear break underneath the frame just like Tyler's.


If not disc, then at the very least the Venge needs integrated brakes. Don't know how any bike calls itself aero without the front brake behind the front fork or integrated into it. I think the Ridley Noah Fast does it better than anyone else.


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## tom_h (May 6, 2008)

re "aero" brakes:
Calipers under the bottom bracket bracket get splattered with road dirt and water, and usually have accessibilty problems. One mfr's model, IIRC, cannot have the pad holders adjusted unless the small chainring is removed! Stupid ... i would never buy a road frame using under-BB mounting.

re integrated brakes -- the Giant Propel uses mini V-brake, carbon arm calipers, mounted behind the fork. Can't speak to its "aero" effectiveness, but:
- brake feel is softer & "spongy"
- cannot easily adjust pad-to-rim separation, needs spacers. 

These complaints may be peculiar to Giant's design, the Giant_Shimano team uses after-market alloy calipers made by swiss company Fourrier. They are also somewhat easier to setup for different rim widths. But I'd be leery of V-brake or "linear brake" designs modified for road use, even though they're fine for MTB use.

Shimano now markets "direct mount" dual pivot calipers where each pivot bolt screws into fork arm, no center main bolt (but it's not a V-brake). They are more sleek _looking_, dont know about effectiveness , ease of service, or other potential shortcomings.


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## 1Butcher (Mar 15, 2011)

So the discs slice meat up a little. There would be less bloodshed since everyone would be braking and those hot discs would cauterize all the wounds. Couple of Band Aids and they will be off to the race again. 

Tires do the real braking. Discs would help on the descents cause the heat would not be on the rim. Other than that all that extra braking probably would not slow you down much faster cause the tires can already lock up now with rim brakes.


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## carbonLORD (Aug 2, 2004)

I have an idea...


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