Disc brakes to be allowed for pro teams - test period

[Yellow Saddle]

Melting point of aluminium is 660°C. My initial thought was: "No way are people achieving that kind of temperature on bike brakes!" But then I looked into it some more...

Current F1 cars use rotors made of something called "carbon-carbon", which apparently performs poorly below 400ºC and only reaches optimum performance above 650ºC. It says here that brake temperatures can reach 1200ºC in an F1 race:
http://www.racecar-engineering.com/technology-explained/f1-2014-explained-brake-systems/

I'm no scientist but it sounds plausible to me that you could achieve a high enough temperature on a long alpine descent on a tandem to at least soften an aluminium rotor.

The adoption of disc brakes by the pros will no doubt drive technology forward much quicker and we'll soon start to see rotors made of all sorts of exotic materials designed for higher performance expectations. In the same way that F1 technology trickles down to the consumer market eventually, pros using disc brakes will in the long run be a good thing for the average cyclist.

Aluminium is extruded at between 350 and 500 Degrees C under pressure of about 100 000 PSI. I would imagine that a tandem's rear brakes could well melt or at least extrude the aluminium but anyone who goes down an Alpine descent on a tandem with aluminium discs need to be taken out of the gene pool. A large 205mm stainless disc is fine though.

Sintered metal pads used on MTBs work better at higher temperatures than resin pads and easily burns the stainless steel disc so that it settles with a blue colour, This happens (depending on the steel composition) at about 350 degrees C. Any hotter and it turns brownish, which we don't see much. However, this colour gives us a reasonable indicator how hot the hottest brakes become.

Thus, to extrude (push alu out of the stainless-alu-stainless) Shimano disc sandwich you have to have heat higher than 350 and pressure extremely high. Unfortunately I don't know what the pressure is but I think it would be reasonably to assume that the molten disc scenario is only likely under the most unlikely scenarios, such as the Darwinian tandem riders.

 

[HF2300]

Tests on Velotech see rotor temperatures into the low 400 degrees C, so probably not far out. You'd have to go some to get clamping forces in the 100,000 PSI range given likely line pressures of around 2000 PSI though, so perhaps a test situation with higher non-real world disc temperatures?

 

[Andrew Br]

I'm a big fan of disc brakes in road bikes so I welcome this as a step forward. What I can't understand is why the UCI are letting the teams choose which events to run discs on.
Surely it'll lead to a mix of rim and disc-braked bikes on the same event ? That will cause a lot of hassle for the neutral service and, should it rain, there will be a vast difference in braking performance in the peleton.

 

[172traindriver]

I'm a big fan of disc brakes in road bikes so I welcome this as a step forward. What I can't understand is why the UCI are letting the teams choose which events to run discs on.
Surely it'll lead to a mix of rim and disc-braked bikes on the same event ? That will cause a lot of hassle for the neutral service and, should it rain, there will be a vast difference in braking performance in the peleton.

That is a point, but don't forget Campag havent yet released disc brakes, so unless they do any teams running them wont be able to use them anyway.

 

[zizou]

I can see the advantages for discs on the road for commuters, tourers and winter training, and obviously for mountain biking too (i not only remember what mini v brakes were like compared to discs i still have an old mtb with them alongside a mtb with discs). But for road racing rim brakes already work well and the advantage that discs bring to the table is marginal at best and not worth the downsides - whether it be weight, aero, problems with neutral service etc. If pro riders have a free choice in the matter then most of them will not pick disc brakes IMO. And its not because they are resistant to change, if they thought there was a performance advantage they would jump on the bandwagon pretty damn quick.

Apparently this is the biggest difference, braking method. Disks are better for short heavy periods of braking while rims are often dragged on descents. Those racing disks are going to have to change how they think about braking to get the most out of them. Fortunately they don't descend the long alpine type hills in a bunch.

Pros (actually make that experienced amateur riders too) dont drag their brakes on descents, that is bad practice whether it is rim or disc brakes.

Possibly, but it's never going to happen - it's more likely to be a driver for brake pad manufacturers to improve their compounds to work better on carbon rims.

Decent pad compounds and carbon rims have pretty good braking these days.

 

[StuAff]

That is a point, but don't forget Campag havent yet released disc brakes, so unless they do any teams running them wont be able to use them anyway.

Actually, they could, assuming Campagnolo didn't object to their teams using third-party products...either cable discs, or TRP Hy/Rd would work.

 

[jifdave]

campag have been working on them for years apparently.
http://road.cc/content/news/96330-c...-are-working-hydraulic-disc-brakes-road-bikes (14oct 2013)

 

[oldroadman]

Someone commented that on long mountain descents the race is not bunched. No, it's a long line with close spacing, and if the bloke in front goes down, you have to act fast to avoid hitting him.
That's that, now the business about dragging brakes is spheroids. Braking is done firmly, on the straights, just before the bends. On carbon rims with alloy facings on the braking surface. This works fine. Back in the day all rims were alloy, brakes were not quite so good as today, but still descending speeds were above 80km/hr. I'm amazed we all survived!
Personally I'm not concerned about profis using disc brakes, what worries me is when they are allowed at local level and the numpties panic brake, then the next thing is a big heap of people on the ground. So although pro peloton will likely be 2017, let's hope it takes at least a couple of years to get down to local level. Then it's all or nothing, it's simply mad to have some on rim and some on disc, accident waiting to happen.
Now that wouldn't mean lots of new bikes being sold, by any chance, would it. there's a thought. Bet no-one in the trade ever thought of that....!

 

[Citius]

I don't see the issue with mixing disc and caliper brakes in amateur races - nobody ever brakes anyway.

 

[oldroadman]

I don't see the issue with mixing disc and caliper brakes in amateur races - nobody ever brakes anyway.

They don't go fast enough, don't know how to, can't corner anyway, are you referring to lower category (2/3/4 level) races by the word "amateur" - a classification which does not exist? In fact it seems to be just the opposite, there's far too much braking because of lousy skill levels in a certain percentage, and unwillingness to learn or be told anything. So seriously, it would be mad to mix systems. All or nothing. Still, the manufacturers will do all right, so that's OK then.

 

[Citius]

Brakes get dabbed in the bunch all the time, but that type of braking is agnostic to either disc or caliper. Short of riding down an alpine col, you rarely slam the anchors on good n proper in any kind of bunch racing (pro or amateur) and most of the braking you do is designed to scrub speed off, not bring yourself to a dead stop.

Skill levels are irrelevant too. Skill is the application of a technique - unskilled riders will still fvck things up, regardless of whether they are on disc or caliper.

So no, I don't think it matters, and I don't think mixing brake types will be anything like the carnage that some people think it will be. In any case, at amateur race level, the two types will have to sit together - because there is no other practical and cost-effective way to introduce them to the membership in a way that they will accept without rioting in the streets of Manchester.

 

[andrew_s]

Where?

Ventoux (end of post), during a magazine brake test, and again, on a real hill
The last link, on the real hill, is a solo, ballasted to fat bastard territory
just put "ice tech rotor melt" into google for more

 

[Yellow Saddle]

Ventoux (end of post), during a magazine brake test, and again, on a real hill
The last link, on the real hill, is a solo, ballasted to fat bastard territory
just put "ice tech rotor melt" into google for more

Mein Gott!!!

 

[Yellow Saddle]

They don't go fast enough, don't know how to, can't corner anyway, are you referring to lower category (2/3/4 level) races by the word "amateur" - a classification which does not exist? In fact it seems to be just the opposite, there's far too much braking because of lousy skill levels in a certain percentage, and unwillingness to learn or be told anything. So seriously, it would be mad to mix systems. All or nothing. Still, the manufacturers will do all right, so that's OK then.

This issue is moot. The minimum stopping distance from a given speed is exactly the same for disc and rim brakes. It is a fallacy that disc brakes allow you to stop quicker.

 

[oldroadman]

Brakes get dabbed in the bunch all the time, but that type of braking is agnostic to either disc or caliper. Short of riding down an alpine col, you rarely slam the anchors on good n proper in any kind of bunch racing (pro or amateur) and most of the braking you do is designed to scrub speed off, not bring yourself to a dead stop.

Skill levels are irrelevant too. Skill is the application of a technique - unskilled riders will still fvck things up, regardless of whether they are on disc or caliper.

So no, I don't think it matters, and I don't think mixing brake types will be anything like the carnage that some people think it will be. In any case, at amateur race level, the two types will have to sit together - because there is no other practical and cost-effective way to introduce them to the membership in a way that they will accept without rioting in the streets of Manchester.

I wouldn't be too sure of that, there were plenty of times in the peloton when we came to a dead stop behind crashes (or indeed at the notorious level crossing gates). The limiting factor is as ever grip, and a concern is that over strong application of any brake can cause a slide, which IF the disc is potentially more powerful could be a serious issue. The difference in the wet - already described by users - is possibly a bigger worry, because people WILL start braking faster (and possibly later) on discs and the effect in a big peloton can be easily anticipated!