12/16/14 1:15 AM

Saw this:

http://velonews.competitor.com/2014/12/bikes-and-tech/discs-drag-wind-tunnel-testing-disc-brake-road-bikes_355621

12/16/14 4:42 AM

It was a given that the disk brake bike would not be as aerodynamic. The disk itself is has a lot of surface area to create drag at high yaw angles.

A real world test on a mountain course is in order. Let the pros race the disk set up during the high mountain stages where defending is as much a part of the race as the climbing. If the brakes are SO much better than the racers on disks should show a definitive advantage.

Just like lighter wheels may not seem like that much, then you slap those babies on and go, "Oh Wow!" these are faster. I am curious to see if that holds true for disk brakes.

On a rainy TdF mountain stage they would be an advantage. On a dry day, I foresee nothing to be gained by the disk wheel set up.

I have said it before and will reiterate it again. We have always had disk brakes on our bikes, rim brakes are a HUGE disk. As long as the rim surface is clean and the pads fresh rim brakes work wonderfully. Of course, getting them wet is a major concern and always will be. Disk brakes have the advantage there.

12/16/14 11:20 AM

It seems perhaps a few things should not be ignored:

No braking heat to soften sewup glue on the rim.

Superior modulation certainly then Carbon Rims and cork dejour pads.

Even lighter carbon rims. better acceleration with less rotational mass at the tire, better climbing performance as a result.

Now Pros may not experience this as I do with carbon due to mass of ars. Carbon Rims just do not give me enough and confident braking performance, not even close to what I get with Al rims and superior PADs. And I have never got into a high heat situation with carbon rims either where performance gets exponentially worse than AL rims.


But, on the weight, maybe there won't really be any advantage?? The spoke beds may need to be stronger and make up for any lack of material at the non existent brake track on a disk wheel.

12/16/14 4:58 PM

I still say, let them race them and see how it plays out.

I don't think brake modulation will make up for the drag they add. Plus to really get the most out of the better brakes the rider has to be fearless.

They say if you brake you lose. Even on the the decent in to Pau that is evident. The leaders on that drop from the clouds just let it run most of the way down.

I have not seen a rolled tubie in a major race in MANY years. I don't think soft glue at the pro level is very much of an issue.

12/16/14 5:03 PM

Rolled tubies not an issue. Blown clinchers from heat is an issue, but moreso in grand fondo type events.

12/16/14 5:07 PM

Do carbon rims have enough heat buildup during descending to melt tubular glue? I know aluminum rims get deadly hot.

12/16/14 6:07 PM

As far as side drag, in groups not sure it is really going to be significant. Although a few extra watts off the front alone or a group of 3-4 when the chasing Pelolon can rotate back on the opposite side the wind is coming from, as that already do... Bigger groups may wind up loosing a few less watts to disc drag. And considering the coin spent for less than a watt at the pro level.

True enough though, not seen a rolled tubie since Belloki...

And Aluminum should shed heat better than carbon. Which is why the coatings tech on the brake surface has got where it is, and would not be required with discs.

12/31/14 10:24 AM

The thing about carbon is that it doesn't conduct heat well, so for a given number of watts of stopping power there is a much higher surface temperature at the brake track. This higher temperature means a more severe temperature gradient with the air stream, so there is much greater localized heat dissipation and thus less heat flow going into the central portion of the rim where the glue is.

There is also less heat conduction available in carbon to pull heat out of the sidewalls, so clincher rim sidewall failure has been a problem when earlier resin matrices could not handle "heavy braking" temperatures.
But temperatures can climb with only slow but steady inputs of heat, where slow conduction also means a slow net out-flow of heat, so temperatures at a tubular rim's glue layer seemingly might get dangerously high at some level of continuous braking.

I suspect though that carbon rims are actually better than aluminum in this regard, though certain glues can show heat-related softening early on as I have experienced in the past.
Likely at the pro level where tire/glue experts do both lab and field testing, known-adequate glues will be available in all cases for the particular rims being used.

1/1/15 7:23 AM

Who actually lives in an area where hills are that long and steep? I suspect our Aussies may but I am not positive.

I have no issue with heat build up in my rims. In fact I have reached down after the only hard stop on my lunch route just to see if I could detect ANY warmth beyond the 40C temps I was riding in. Nada, no heat at all. That is with carbon or Al rims.

1/1/15 9:37 AM

"On a rainy TdF mountain stage they would be an advantage. On a dry day, I foresee nothing to be gained by the disk wheel set up. "

this. i dont see any performance benefit to discs from a racing perspective that would regularly and materially affect the outcome of a protour road race, only negatives or neutrals.

i may have mentioned this before, but to erik's point about bikes always having disc brakes anyways...here's a motorcycle OEM (small) that's actually going that way. instead of 2 heavier hub-mounted rotors, they have 1 lighter larger diameter rim-mounted rotor:

1/1/15 12:32 PM

Many parts of the country have mountain descents that easily qualify as problematic for heat buildup. It also doesn't have to be an extremely long grade, as moderate length, steep grades build up heat very rapidly, too.

1/1/15 12:39 PM

The Buell Lightning I had for a few years with the out board single disc was the best MC brake I have used with nothing coming close.

One pinky, two fingers if I was going to get serious.

1/1/15 8:21 PM

I have no quantitative data but I do know that on a long descent (miles) with lots of switchbacks on a loaded touring bike, I stopped about half way down and touched my large aluminum rims (27x 1&1/4 Weinmanns that weighed close to 600 gm. each) and they were VERY hot to the touch. I would say approaching 140 F as I was afraid to hold onto the rim for fear of getting a low-grade burn. Worst case scenario for sure, but not a place I would like to be worried about disc rotors turning red.

1/2/15 9:39 AM

The switchbacks will get to you - it's the constant, repetitive need to scrub speed into the turns that can turn an aluminum rim into a branding iron, or melt brake pads.

1/2/15 5:33 PM

Races don't stop for rain/poor weather. Discs are clearly an advantage in wet conditions...it's not even debatable. And modulation is far superior even in dry.

If it's safer for the riders, why not make the switch. I guarantee that if discs were made available, every Protour team would choose to ride them on wet race days. Most likely they are just waiting for Campagnolo to develop a disc groupset before stamping approval.

1/2/15 11:07 PM

i dont think anyones debating that. it's whether that difference matters to the outcome of the race.

in the case of a pro-tour roadrace, even in the wet, i dont think so.

paris-roubaix in the wet? they're hauling ass on the flat all day long, brakes are almost irrelevant to the outcome of this race. if something bad happens right ahead of you on rain-slicked cobbles in sloppy conditions, you're going down with disc or rim brakes. nobody wins roubaix because their brakes work better in the wet, they win because they're strong as a bull and total f*cking hardmen flahutes. a nice set of FMB tyres will do more for a good result in roubaix than any set of disc brakes.

milan-san remo in the wet? the descent of the poggio is done balls-out. disc may make a slight difference in the gracefulness of the descent in wet conditions, but pros get it done now with rim brakes just fine. nobody is making a gap on the descent and winning on the via roma because their braking is 2% better modulated, they're making it because they're a skilled, fearless descender. as before, a set of supple FMBs would do alot here, as well.

disc brakes may be better for the guys that regularly ride in the back-half of the bunch, but the guys that win ride at the front. disc braking...even with their undisputed better modulation...will not materially affect the outcome of a protour roadrace compared to rim brakes.

this argument is moot anyways...when the protour goes disc, and this will happen as the OEMs stand to make alot of money, it'll be the entire peloton en-mass.

1/3/15 2:09 AM

These drag numbers are irrelevant IMO because the primary reason for going to discs should be rider safety in wet conditions. It is a level playing field if everyone goes disc on wet race days. And I guarantee that 100% of teams and most importantly riders will choose disc on wet days given the option.

1/3/15 10:26 AM

...we'll *never* see a disc-brake TT bike in the protour or at kona! :-)

1/3/15 7:09 PM

Never say never.

Would make no sense for a dry TT. But a wet TT with a climb/descent...

1/3/15 7:30 PM

Having been racing consistently since the early 1970s I can tell you that the brakes are not the limiter in the rain, it is the traction of the front tire and that will not change with a disc.

We are far removed from the days of the old Campy pads. I (and our whole team) use either the yellow carbon Swiss Stop pads or the Equinox carbon pads. No issues with modulation or heat buildup, rain, descents or whatever.

As far as tires go, that is another story. Vitts are good in the rain, Conti's are slick and I wouldn't even dream of pushing any corner in the rain on any type of clincher.

1/3/15 10:26 PM

;-)

sanrensho ... with such single-minded focus on braking I'm afraid you'd never make it to the finish!

1/4/15 12:48 AM

Even pros have to brake sometimes...

3/23/15 12:50 PM

Looks like discs in the pro peloton are a done deal. Coming in 2017.

http://road.cc/content/news/146616-disc-brakes-be-permitted-peloton-2017

3/23/15 3:14 PM

Would Joseba Beloki have crashed in 2003 if he had disc brakes?

3/23/15 5:36 PM

Impossible for us to say. Unless you saw the wheel/tire interface at the time it happened there is no way to know.