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PostPosted: Sat Jan 18, 2014 4:24 pm 
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Joined: Thu Aug 08, 2013 5:52 pm
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Location: Vejle, Denmark
Cheers,

Just wondering: What is the general opinion on disc's? Personally i don't like them for a road bike.

But my main question is will UCI ever legalize disc brakes for road races, and would pro's even wan't to use them?

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Posted: Sat Jan 18, 2014 4:24 pm 


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PostPosted: Sat Jan 18, 2014 4:27 pm 
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Location: Ann Arbor, Michigan
I hope not. I wouldn't use them, but if everyone else is, it makes it too dangerous not to have them


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PostPosted: Sat Jan 18, 2014 4:44 pm 
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The simple answer is yes. We will look back in 5-10 years time in disbelief that we even had the debate. Pandora's box is open. Discs are out there. They aren't going to go away. They will develop further and become the norm. There have been a few early hiccups, but minor in the grand scheme of things.

From a performance perspective, discs have so many advantages. Why wouldn't anybody (including the pros) want consistent, reliable braking which allows for lighter rotating weight in the shape of lighter rims? Look at every other form of motor sport. Braking as late and as hard into a corner as possible is seen as a distinct advantage. This advantage will also be attractive in the professional peleton once everybody has access to it and you don't risk the guy behind you on inferior rim brakes crashing into you.

From a political perspective, Shimano are a big sponsor of the UCI and pressure will mount.

From a manufacturing perspective, once the big 3 all have hydraulic disc brakes (which will happen by 2016 as Campagnolo join the party), the playing field will be level and everybody will be able to stop at the same rate.

From a technical perspective, the problems of weight, aerodynamics of the calliper, heat and wheel swaps will be overcome.

From a 'pro' perspective, bikes already need weight adding to meet the UCI weight limit. The addition of discs, which will also lead to lighter rims anyway (and rotating mass is more important than static mass), will not tip bikes over this weight limit. Even if the UCI revise the weight limit (as seems likely now that it is under review), you will still be able to get a disc equipped bike significantly under the current limit.

I have recently switched over my bikes to both electronic shifting and discs, I won't be going back to either mechanical shifting or rim brakes. The performance advantage is just too great.

I liken this debate (bear with me!) to saddles. Despite the weight penalty, most pros ride what performs well, not what is light. The same will be true for discs.


Last edited by solarider on Sun Jan 19, 2014 5:25 am, edited 3 times in total.

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PostPosted: Sat Jan 18, 2014 4:59 pm 
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Joined: Thu Aug 08, 2013 5:52 pm
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Location: Vejle, Denmark
So,

I guess when it becomes legal, it will also become mandatory?

But when will it become legal/mandatory?

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PostPosted: Sat Jan 18, 2014 11:05 pm 
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Joined: Fri Mar 23, 2012 11:36 am
Posts: 20
Haha, I was expecting a massive debate on why discs, but Solarider just saved us about 20 pages of debating.
2014 is stained with the Sram recall so I'm going with a conservative 2017 for mandatory disc racing, but would love it to be 2016.
Frankly a Magic 8 Ball is more accurate than my guess, just my logic.
I am looking forward to a nice carbon road disc bike in my future, but I'll wait a few more years for all the bugs to be worked out and prices to trickle down.


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PostPosted: Sat Jan 18, 2014 11:29 pm 
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Location: United Kingdom of Great Britain and Northern Ireland
It depends how much 'financial weight' the Far East manufacturers can bear down on the UCI to encourage them to change the rules. Note that I have not used the word 'bribe'.


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PostPosted: Sun Jan 19, 2014 12:07 am 
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Joined: Fri Jul 18, 2008 8:25 pm
Posts: 224
Location: UK
Discs are not all great (even when the earlier problems are fixed):
1) Less aero
2) Could be more dangerous in a crash situation
3) More weight (who is to say the UCI won't now lower the weight limit).

OK all the above may be marginal, but I'm not buying into discs are safer (great more speed to the corner on a wet course, nice). I'd like rim brakes to stay.

solarider wrote:
The simple answer is yes. We will look back in 5-10 years time in disbelief that we even had the debate. Pandora's box is open.


^I have to agree!


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PostPosted: Sun Jan 19, 2014 1:42 am 
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solarider wrote:
T Look at every other form of motor sport. Braking as late and as hard into a corner as possible is seen as a distinct advantage. This advantage will also be attractive in the professional peleton once everybody has access to it and you don't risk the guy behind you on inferior rims brakes crashing into you.



In professional road racing beyond basic function, brakes make no performance difference AT ALL. Cylcists don;t put brake each other into corners, and the only time a disc brake may offer an advantage is going downhill in the rain. Not to mention the obvious difficulty in having neutral support wheels

Bike races are won by the rider with the best intersection of fitness and strategy.


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PostPosted: Sun Jan 19, 2014 2:16 am 
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+1

Also to make these amazing features avaible to the road cyclist other things will have to change first..
If you want the extra power and all those things that disk could bring then your going to need much better/softer tires.. ( expensive and won't last long ) and maybe suspension to help keep the tires firmly planted on the road and giving all the grip you can.. Basically with the changes in wheel spacing and all that jazz we'll be riding around on MTBs..
It's a long way from good, it's totally half baked marketing rubbish right now aimed squarely at selling new bikes to Hubbards.. Braking doesn't make you fast.. It's not braking that does that :roll:

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PostPosted: Sun Jan 19, 2014 2:37 am 
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bobqzzi - Races have absolutely been won/lost on wet downhills where disc braking would have provided an advantage (Milan St Remo 2013, World Road Race 2013 to name but 2 recent examples).

bobqzzi - Time can absolutely be saved by braking later into a corner. It's a fact of physics that if 2 objects are travelling at the same velocity, but one decelerates before the other, leaving the other to travel at the higher velocity for longer, then it will arrive later. To say that braking later into a corner won't offer an advantage if like my grandfather seeing a faster driver whizzing past the car window as he tootles along in the inside lane of the motorway and saying 'he won't get there any faster'. He definitely will you know!

sugarcane - I am not debating that certain things will need to be addressed before discs become the norm. But be addressed they will. Disc brakes on road bikes are coming, and will become the norm. The UCI will legalise them (the OP's question), regardless of online forum experts like us!


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PostPosted: Sun Jan 19, 2014 3:25 am 
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I think any time gained in decreased braking distance on any but the hilliest course would be negated by the aerodynamic loss, and particularly, the time lost in a wheel change. In these days of "marginal gains" where people are moving small rim brakes out of the wind to gain +/- .005% of a gram of drag advantage I find it strange that the other camp is moving towards adding a large amount of exposed surface area to the fork/front wheel (probably the most important area of the bike for drag).

In addition, the weight of the rim will decrease, which is certainly rotating mass, and is more peripheral, but the hub mass and the mass of the disc, all rotating, as well as the extra spokes required (all rotating) may actually increase the total rotating mass of the wheel, even taking into account the increased moment of inertia of the rim due to its increase distance from the axle.

No one will dispute the advantage of consistency in braking in the wet, but raw power of braking is down to tyre technology/width. A skilled braker on rim brakes would likely see little difference compared to discs in regards to braking distance in the dry.

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PostPosted: Sun Jan 19, 2014 3:35 am 
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Has anybody yet done an aerodynamic test of rim vs disc?

I can't help thinking that the cleanliness in the turbulent area around fork crown vs rim brakes might offset some of the disadvantage of the disc brake equipment near the fork tips. Look at the front and rear profile of this bike (and it's a CX bike, not even a road bike). It looks more aerodynamic than anything with rim brakes to me, but I am not talking from the informed perspective of a wind tunnel test. Hence I would be intrigued to see some test results.

http://brimages.bikeboardmedia.netdna-cdn.com/wp-content/uploads/2014/01/Chickens-Morvelo-CityCross-16.jpg

And let's not forget in all of the debates about aerodynamics, that the presence of a tiny calliper or 140mm rotating sliver of steel with a frontal profile of 2mm is nothing compared to the lump of flesh and bone sat on the thing! Very small amounts of drag are pretty inconsequential vs the benefits.


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PostPosted: Sun Jan 19, 2014 5:59 am 
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Location: Santa Cruz, California, USA
I doubt they'll ever be mandatory but they'll most likely be allowed by the UCI in the next few years.
The braking difference between riders of equal skill on rim brakes vs discs will be less than the difference due to differences in skill alone. Even at the very top level. So the fantasy of riders crashing because someone on a disc brake bike slows so much faster is just that,a fantasy.

Even if riders could stop remarkably faster with discs, they'd just brake later for turns. If you have ever passed a rider on a descent by out braking them (or by cornering faster) you know how easy it is to execute a safe pass.

They're not illegal in USAC (USA amateur) races and so far I've not seen one.


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PostPosted: Sun Jan 19, 2014 5:28 pm 
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Location: Winterpeg
Main benefit from disc brakes on road bikes will be increased revenue on SRAM, Shimano and Campagnolo P&L reports.

Few year old road rim brakes are strong enough for me to lift my rear wheel off the ground when braking hard in dry conditions. In wet you wouldn't have enough traction to do this. I do get that disc brakes are appealing, but I don't think the MTB disc brakes would be that awesome when slapped on a road bike and paired with road levers. I started riding when brakes actually were not strong enough, but they were loud a f***. Modern rim brakes are quiet and very powerful and having disc brakes on few of my off road bikes doesn't make me a believer of this technology somehow being superior on the road.

And in downhills the rider who goes around the corners fastest is often the fastest descender. On a bike your aim is to carry as much speed around the corner as possible and in motorsports you try to get back on WOT as soon as possible....different beasts...

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PostPosted: Sun Jan 19, 2014 5:34 pm 
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solarider wrote:
Has anybody yet done an aerodynamic test of rim vs disc?

I can't remember exactly who reported it but I believe it was in Velonews where one of the aero "gurus" was asked this very question. His response on some preliminary testing of disc brakes versus rim brakes in the wind tunnel was that it wasn't good. Doesn't surprise me in the least with that disc churning up and creating all kinds of dirty air right out in front. So don't be holding your breath for any claims of aero benefits from disc manufacturers because not only are there none, the negative aero effects are significant. Just as more rotating spokes create more dirty air than than fewer rotating spokes, a rotating disc with it's associated hardware creates dirty air as well. Time will tell I suppose if they really are the panacea that some make them out to be. For now, I'm sticking to rim brakes for my highest performing road bikes, although discs would be awesome on a dedicated grunge weather bike.

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Posted: Sun Jan 19, 2014 5:34 pm 


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