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PostPosted: Wed Mar 14, 2012 9:52 am 
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I do not think that is valid or fair to say or compare road bikes to mountain bikes. Mtb's will most of the time be over built, because they are more likely to be drop and abused. I have not ridden mtb that much, but how fast can mountain bike descent; it's it faster or slower than a road bike. Better technology is not the solution to lack of skill. People that ride holding the brake levers will continue to do so, now they will not get tires rolling off, but might get spokes that have pulled trough the rim which presents another hazard. I am all for improvements, but we have to face the facts they are not going to improve safety that much.
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Posted: Wed Mar 14, 2012 9:52 am 


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PostPosted: Wed Mar 14, 2012 10:18 am 
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Per the above question: I think you asked this before and I answered!
Link to the thread post.

Requote:

prendrefeu wrote:
roca rule wrote:
Would you say that you can descent faster on a mountain bike than on a road bike?


Typically and technically speaking, a mountain bike will descend as fast as a road bike under the same rider.
What are the differences?

-A mountain bike on a dirt road will see massive and abrupt changes in speed. Dirt roads in the mountains are typically ridiculously steep (ever wonder why they aren't paved?). In a typical descent in the Santa Monica Mountains a rider can go from 10mph to 45mph in a matter of seconds, then needing to go back down to 15mph about 30 seconds later. Disc brakes are remarkable for the needs here, as terrain can change very rapidly. Dirt road descents are typically not very long, and not very straight - although those do exist, they are rare. Often after a few seconds of descending the terrain will change rapidly, necessitating a dramatic reduction in speed and/or trajectory.

-A road bike is often able to descend at a fast speed for a longer period of time as the roads are comparatively more gradual and descents are significantly longer, allowing the rider to accelerate with gravity or pedal strokes until a terminal velocity is achieved.

-A good comparison would be a mountain bike and road bike descending a very steep, very technical road with off-camber turns, changing radii, and other hazards. If you put both on slick tires, my money is on the telemetry of speed being relatively close in top speed, delta values, and slowest speed. Local examples include Tuna Canyon (down) and Las Flores (down). Of note: RedBull staged a downhill TT/race on Tuna many years ago.

-A road bike with slick tires on a dirt road will not be as fast as a mountain bike with dirt tires on that same road, and vice versa. "Horses for courses" as the idiom goes.

Continue talking amongst yourselves. :mrgreen:

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PostPosted: Wed Mar 14, 2012 1:29 pm 
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RollingGoat wrote:
But by adding in the front of the bike you're only adding in things that are the same for both. Same rider, same pedaling force, etc. Therefore adding in the front triangle you aren't changing anything, and so can be removed from the model as it becomes irrelevant. Therefore my conclusion is still correct.

As an aside, we're both ignoring the fact that mountain bikes have had disk brakes for over ten years now and the problem of increased loading at the dropouts has been solved by now many times over, whether it's an actual problem or not.


I'm not adding the front end of the bike but if you calculate the moments acting on the rear end in the dropout you have also to consider internal (cohesive) forces because you are "cutting" the bike to write the equilibrium. We don't agree, I will try to write the equations properly someday to know who's right

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PostPosted: Wed Mar 14, 2012 5:11 pm 
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Epic-o wrote:
I'm not adding the front end of the bike but if you calculate the moments acting on the rear end in the dropout you have also to consider internal (cohesive) forces because you are "cutting" the bike to write the equilibrium. We don't agree, I will try to write the equations properly someday to know who's right


Yes but the internal forces that are included when you include the front triangle are as a result of factors that are present in both cases. Therefore a simplified model is allowable because the inclusion of the front triangle wouldn't create a difference between cases.

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PostPosted: Wed Mar 14, 2012 8:15 pm 
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bones wrote:
Well excuuuuuuuuuuuse me. Your bad though. Instead of saying, ""I think the challenge will be convincing the competitive cyclist that a disc brake system is worth the trade-off for increased weight, and poor aerodynamics."......................... You should have said "I think the challenge will be convincing competitive cyclists that...." So, somebody needs to learn some English grammar, not me.


not taking any sides, but just sayin'... :roll: :smartass:


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PostPosted: Wed Mar 14, 2012 9:13 pm 
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luckysix wrote:
bones wrote:
Well excuuuuuuuuuuuse me. Your bad though. Instead of saying, ""I think the challenge will be convincing the competitive cyclist that a disc brake system is worth the trade-off for increased weight, and poor aerodynamics."......................... You should have said "I think the challenge will be convincing competitive cyclists that...." So, somebody needs to learn some English grammar, not me.


Not taking any sides, but just sayin'... :roll: :smartass:


I can play the grammar game too!

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PostPosted: Wed Mar 14, 2012 9:20 pm 
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:popcorn:

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PostPosted: Wed Mar 14, 2012 9:48 pm 
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I'll get in on the grammar chat!

I think "Your bad though" was correct in that context. He was insinuating it was his bad, or his mistake in the phrasing. But I think bones was incorrectly attributing it to someone in the forum rather than Paul Lew (the Reynolds rep who actually said it in this piece).

I also don't see any problem with the phrasing "the competitive cyclist," as "the" in this case indicated that it was referring to competitive cyclists in general, not the company (which would be a proper noun, and "the" probably would have been left off).


Back to brake chat though...

I'm pretty ambivalent about them, but I am curious to know a bit more about brake fade and all that jazz. Can anyone who has ridden hydraulic discs on the road (or on mountain bikes in the same sort of descending you'd find on the road) comment about what sort of effort would be needed to get brake fade through boiling fluid? The Bikerumor article showed issues with minimal 160mm rotors, but were the actual calipers or pads the wrong choice?

It sounds like there are three potential areas were heat management is needed, the rotor, the pads, and the fluid as well? Does one usually fail before the others, or do they fail as a complete system?


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PostPosted: Wed Mar 14, 2012 10:00 pm 
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BeeSeeBee wrote:

Back to brake chat though...

I'm pretty ambivalent about them, but I am curious to know a bit more about brake fade and all that jazz. Can anyone who has ridden hydraulic discs on the road (or on mountain bikes in the same sort of descending you'd find on the road) comment about what sort of effort would be needed to get brake fade through boiling fluid? The Bikerumor article showed issues with minimal 160mm rotors, but were the actual calipers or pads the wrong choice?

It sounds like there are three potential areas were heat management is needed, the rotor, the pads, and the fluid as well? Does one usually fail before the others, or do they fail as a complete system?


I'm thinking about disks for my next road bike so I called TRP and Volagi to get their side of the story:

a) Tyler (the bikerumor guy in the article) was running a minimalist Ashima rotor that operates at unusually high temperatures. This is because some of the design features of the disk itself (like the windows in the brake track) cause it to heat up unusually fast, which contributed to the problem.

b) The TRP Parabox system he was running was a prototype that TRP and Volagi both say was having issues with keeping air out. According to Volagi, when they had the pre-production Parabox systems at Interbike last year they had to be bled 3 or 4 times throughout the show. That's how bad the problem on the pre-production ones was. However this has been fixed for the production models.

c) Volagi and TRP both think that Tyler may have set them up wrong. Whether that's true or not I don't know but I heard it from both sides so I thought it was worth mentioning.

d) The TRP Parabox has a small rear pad, which is being changed to avoid glazing and overheating.

Volagi has been testing down to a 140mm rotor and apparently for a 150lb rider, you only really get fade if you try to get it.

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PostPosted: Wed Mar 14, 2012 11:09 pm 
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BeeSeeBee wrote:
........ Can anyone who has ridden hydraulic discs on the road (or on mountain bikes in the same sort of descending you'd find on the road) comment about what sort of effort would be needed to get brake fade through boiling fluid? .......


Rolling Goat has nailed it pretty well, and also in the Bike Rumour article, it mentioned that the rider had shortened the lines to suit the bike, so there may have been issues with the bleed/connections as well.

I'm 90kg on a 12kg bike, and even on a steep (but short descent with avg 10% over 3.0km but several sharp hairpins) and having to ride the brakes more than usual due to traffic, the rotors were hot, but the rotor spider was cool and the caliper was only slightly warmer.

The braking level was the same at the end as it was at the satrt, as was the controlability. :thumbup:

With a sensible rotor and reasonable braking technique, I don't think it will be an issue (10,000km + of disc road riding)

Cheers

Michael B


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PostPosted: Thu Mar 15, 2012 12:15 am 
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Firefly...


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PostPosted: Thu Mar 15, 2012 12:22 am 
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Wingnut wrote:
Firefly...


If that bike were a chick, I'd hit that.

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PostPosted: Fri Mar 16, 2012 5:12 am 
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MichaelB wrote:
RollingGoat wrote:
....

So basically, I don't think any of us really have a handle on just how powerful road disks are going to be because none of us have ridden them and the guys who have aren't saying much other than stuff along the lines of "more powerful than you'd expect"


I'll chime in here. I have ridden a convereted 2007 Argon18 Platinum that was fitted with an alloy CX fork and 160mm G2 rotor/BB7 combo for 6,500km. No issue in any of the mentioned hassles.

I now own a 2011 Kona Honky inc fitted with the TRP Parabox and 180/160mm Ice-Tec rotors (3,500km and going). Again no issues re locking, fading, aero (don't go fast enough) and excess weight 9I'm no lightweight).

Tyres on both bikes were either 25C Hutchinson intensives, 24C Conti GrandPrix or 28C Schwalbe marathon Supreme.

They work well in the dry (as good as rim brakes, if not a smidgen better), but in the wet, there is no comparison. QED.

I have also ridden a Volago Liscio at a recent World Tour event, and that was just as good (braking wise) and a sweet ride.

many of the naysayers have NEVER ridden a ROAD bike with discs, so it's all unfounded hysteria.

I know it works, and am converted.




Does the Volago come with a road fork or a cyclocross fork? It is hard to find a good carbon road fork with disc tabs on them, but there are more and more carbon cyclocross forks out now.


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PostPosted: Fri Mar 16, 2012 5:43 am 
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bones wrote:
Does the Volago come with a road fork or a cyclocross fork? It is hard to find a good carbon road fork with disc tabs on them, but there are more and more carbon cyclocross forks out now.


Yep, it's one that is specific to that bike.

SJS Cycles have one - from Evo in Taiwan. Max tyre size is 28C.

Website shows it in stock.

It is not the same as the 2011 Kona Honky Inc as the disc mount is different.

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Posted: Fri Mar 16, 2012 5:43 am 


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PostPosted: Fri Mar 16, 2012 1:48 pm 
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bones wrote:
Does the Volago come with a road fork or a cyclocross fork? It is hard to find a good carbon road fork with disc tabs on them, but there are more and more carbon cyclocross forks out now.


Right now you can get a fork from Wound Up, and Enve has confirmed that they have a road disk fork in the works.

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