Shimano Di2 hydraulic road disc brakes spotted

[__PG__]

I am too far past it to worry about being elite speed, but I would love a fairly light road bike with discs just for the stopping improvement; particularly coming down places like MT Coottha and mt Nebo.

I wouldn't try 1st-generation road hydraulic brakes down a huge mountain descent just yet. Braking in cyclocross (low speeds on gravel/mud) is a bit different to braking at 70 km/h on tarmac.

[kunalraiker]

I am too far past it to worry about being elite speed, but I would love a fairly light road bike with discs just for the stopping improvement; particularly coming down places like MT Coottha and mt Nebo.

I wouldn't try 1st-generation road hydraulic brakes down a huge mountain descent just yet. Braking in cyclocross (low speeds on gravel/mud) is a bit different to braking at 70 km/h on tarmac.

I completely agree, remember the MTB Demo by GIANT I had been to, was too scared to brake as it would just lock the bike.
I once had to jump of the bike at high speed to avoid a fall.

Imagine the same braking efficiency on Road Bike.I don't want to Slide or Dive into something, please spare me

[Mulger bill]

I am too far past it to worry about being elite speed, but I would love a fairly light road bike with discs just for the stopping improvement; particularly coming down places like MT Coottha and mt Nebo.

I wouldn't try 1st-generation road hydraulic brakes down a huge mountain descent just yet. Braking in cyclocross (low speeds on gravel/mud) is a bit different to braking at 70 km/h on tarmac.

There's been years of dev work done on them, the only salient difference is the lever.
I've made those sort of silly speeds on 1" slicks on my old Giant XTC on road using 1st gen Avid Juicy7s. They howled like wolves at a full moon and the pads were smoking at the bottom of the descent but I never felt (too) worried.

[barefoot]

They will be heavier, much heavier really as compared to my cable brakes.

Weight is overrated in the real world. Aero is more of a problem but I doubt any of us could ride a bike fast enough on the flat to notice the difference (all other thing being equal)

But but but...

At the moment, rims are compromised by the requirement to provide a braking surface.

Take that requirement away, and they can be significantly lighter and more aero.

It won't happen immediately, but I'd expect to start seeing some very tasty disc-specific carbon rims hitting the market not long after hydraulic brifters make their presence felt.

tim

[Mulger bill]

Weight is overrated in the real world. Aero is more of a problem but I doubt any of us could ride a bike fast enough on the flat to notice the difference (all other thing being equal)

OY!
Why are you trying to start another round of where's when there's still a game in progress?

[clackers]

What's the point, given the cable brakes are excellent at stopping.

Yep, I've got some BB7s, just about the best cable discs around, but my hydros are even better, Kunalraiker - power, graduated control, and self-adjusting for pad wear.

[MichaelB]

2. Points made

First- Weight
Second- Cosmetic-Looks
None of these have anything to do with trying a road bike with Disc.

Counter point

Weight : You have no idea of the weight, so how can you comment ?
Looks : Beauty is in tyhe eye of the beholder. Personally, i favour safety and being able to stop over a minor cosmetic issue.
Actually trying : Before you make disparaging comments, you need to try. Then you will realise the added weight (4/5ths of stuff all) when compared to the added weight of a rider, lights, spares etc is really a furphy, and so is the aero.

[MichaelB]

I am too far past it to worry about being elite speed, but I would love a fairly light road bike with discs just for the stopping improvement; particularly coming down places like MT Coottha and mt Nebo.

I wouldn't try 1st-generation road hydraulic brakes down a huge mountain descent just yet. Braking in cyclocross (low speeds on gravel/mud) is a bit different to braking at 70 km/h on tarmac.

Yes it's different. So you brake different. What does the 'method' of braking have to do with it.

I've been running the pre-production TRP Parabox from before the local Aussie distributors had them.

I have done many high speed descents with 15 - 25km/hr hairpins in succession, and at 95kg, had no issue whatsoever.

They key is the correct rotor for the road.

[Xplora]

Yeah, the Road.cc (?) reviewer put himself into the meatwagon using the lightest CX rotor available and then blamed the discs for his failure to descend safely. It could very well be that a huge 200mm rotor could be ideal for big descents. Or not.

Early stage R&D is hardly the time to bag the tech, that's for sure.

[Nobody]

Yeah, the Road.cc (?) reviewer put himself into the meatwagon using the lightest CX rotor available and then blamed the discs for his failure to descend safely. It could very well be that a huge 200mm rotor could be ideal for big descents. Or not.

Early stage R&D is hardly the time to bag the tech, that's for sure.

It was BikeRumor.com.
http://www.bikerumor.com/2012/02/14/roa ... they-work/

[Xplora]

Yeah, that's the one. Garbage article... I can't believe the website editor allowed it onto the site, because it showed the writer to be a prize twit

[MichaelB]

Yeah, that's the one. Garbage article... I can't believe the website editor allowed it onto the site, because it showed the writer to be a prize twit

There was also the unanswered question of the quality of the bleed, as he had shortened the lines as well.

[barefoot]

Yeah, the Road.cc (?) reviewer put himself into the meatwagon using the lightest CX rotor available and then blamed the discs for his failure to descend safely. It could very well be that a huge 200mm rotor could be ideal for big descents. Or not.

Early stage R&D is hardly the time to bag the tech, that's for sure.

Two things for certain:

1) Energy in (kinetic / potential energy) = energy out (heat).
Can't be created or destroyed, and all that.
If the rotor can't dissipate the heat generated by the brakes, it will get hotter. Hotter things are better at dissipating heat, so whatever the disc (be it 140, 200 or 700mm), it will reach an equilibrium temperature. The less effective the rotor is at rejecting heat to atmosphere, the hotter that equilibrium temperature will be.

2) Disc brakes can operate at much higher temperatures than rim brakes.
I work in automotive braking. We have brakes in the lab working just fine with the rotors glowing, well over 600°C. That's with resin-based pads, on hydraulic brake systems, which is what 100% of cars use.
I don't know much about sintered metal, but I know they go there for motorcycles, trains and industrial applications where the brakes get really hot.
I also don't know anything about the friction materials currently used in bicycle disc brake pads, but I really find it hard to believe we're pushing hard against the temperature limits of the best friction material technologies in existence. As a very crude indication... I've never seen a bicycle disc brake glowing red like I regularly see car disc brakes.
By comparison, rim brakes. Alloy rims, filled polymer pads. Alloy melts at <700°C... loses plenty of strength before that. And it's a very good thermal conductor, so whatever temperature your braking surface is getting to, your tyre bead and tube will be in contact with almost the same temperature. Rubber isn't good with temperature... especially when it's trying to contain 100psi air.


So, combining - a disc brake system WILL get hotter than a rim brake system, because it isn't as good at rejecting heat. But a disc brake system is MUCH better at coping with high temperatures than a rim brake system - and IMO has the potential to be significantly better than the current implementation.

As above, I'm not convinced the friction materials currently in use are all that good. And that's aside from all the work that could be done to improve brake cooling. Why can we cool the processor of a laptop computer, but can't cool a (significantly hotter) bike brake? Calipers don't even have cooling fins yet...

tim

[Daccordi Rider]

I reckon if Shimano really challenged themselves they could make those shifters look even bulkier and uglier, if they really tried.

That being said I'd be happy to give it a go.

[barefoot]

Yeah, that's the one. Garbage article... I can't believe the website editor allowed it onto the site, because it showed the writer to be a prize twit

Hehe.

This bit says it all, really:

The brake fade that led to my accident is something I’ve experienced on my mountain bike on several occasions with multiple brands of brakes.

Numerous cases of severe brake fade on his MTB, and never pondered whether he might be doing something wrong? I don't remember ever fading MTB discs. Started running out of grab on cantis and Vs a few times, but discs tend to hold up a bit better IMO. But most people don't do a long continuous drag on both brakes at the same time - rim or disc; road, mountain, or car - and expect the brakes to still be there when you need them.

The story can pretty much be summarised: "If you're going to ride like a kn0b and crash your bike, it's safer crashing at MTB speeds than road speeds. Hey look, disc brakes on road bikes, howaboutthat?"

tim

[Mulger bill]

This bit says it all, really:

The brake fade that led to my accident is something I’ve experienced on my mountain bike on several occasions with multiple brands of brakes.

Numerous cases of severe brake fade on his MTB, and never pondered whether he might be doing something wrong? I don't remember ever fading MTB discs. Started running out of grab on cantis and Vs a few times, but discs tend to hold up a bit better IMO. But most people don't do a long continuous drag on both brakes at the same time - rim or disc; road, mountain, or car - and expect the brakes to still be there when you need them.

tim

Damn right. A poor workman always blames his tools.

[alex]

when the limiting factor for braking is the common 23mm tyre, i am not sure why we all think we need disc brakes

but ill still buy them... and so will everyone else

campy 11 speed - I DONT NEED THAT! 50 PAGE FORUM THREAD! everyone bought it/wants it
dura ace 7900 - OMGosh SO UGLY! 50 PAGE FORUM THREAD! everyone bought it/wants (wanted) it
di2 - CABLES WORK FINE! 50 PAGE FORUM THREAD! - everyone bought it/wants it

and so on and so on and so on, the same thing happens with every new and different product

[Nobody]

when the limiting factor for braking is the common 23mm tyre, i am not sure why we all think we need disc brakes

I haven't found 23s limiting for braking on good roads. I doubt I could even get the front wheel to lock on a good wet road. But then I only run 85psi in the front.

According to the reviewers of disc brake road bikes, in general, even cable disc brakes offer better modulation than rim brakes.
http://www.bikeradar.com/gear/article/d ... kes-32770/

[Uncle Just]

My 2c. In many ways I like older stuff such steel frames, even DT shifters. But time marches on and developments are happening giving riders far more options. There is so much bang for your buck these days that we would have given our right arm for even today's 105 back in the day. I like disc brakes because they work. In all weathers and are not affected by wheels out of true. They are now and the future and as one poster said when they work out the right configuration for the demands of road biking, wheel technology will advance again. One issue maybe what the take up will be with the pro peleton which to a great extent drives consumer choice. I remember when I first saw disc brakes on a Corratec MTB 20 or more years back I was smitten. Discs just look so purposeful and elegant and if set up right they work better than any brake known. Lastly try coming down Baw Baw in the wet on the best dual caliper brakes as even in the dry you'll have to be very cautious.

[Timeonabike]

I love my disc brakes, the first time I used em I nearly threw myself off the thing.
Was expecting sogginess that I'd come to expect from (albeit really poorly maintained) rim type cable operated brakes.
If these are out in a year, then I've got a year to save for the road bike I've been thinking about getting.ACE.

Cheers,

Time

[Xplora]

Yep I think that's the big sell... modulation is the FEEL of the brake. Road bike standard brakes feel like absolute crap compared to cable discs, and we've all driven cars and know what hydraulic brakes feel like. Mechanics will know how much better fluid assistance feels compared to none on a car! LOL

I don't think it is possible to argue against the superiority of hydraulic for all but the most minor of reasons. We'll have internal routed hydro brakes in time. We'll have aero brakes in time. We'll have less dangerous discs in time (could be a while though). Considering the cost of replacing discs versus rims, I don't know why anyone would even raise the question of "better".

[il padrone]

Lastly try coming down Baw Baw in the wet on the best dual caliper brakes as even in the dry you'll have to be very cautious.

Now that is one very positive advantage for discs I reckon, but not for the reason you are suggesting, rather for descending long steep descents without risk of blowing your tyres off the rim due to brake-induced heating. A really big plus. This was the big problem I had when I rode up, and down, Baw Baw.

[Mugglechops]

I have been running discs on my CX bike for the past 2 years and discs on MTB's since 2003.

Never had an issue with them and I can brake as hard as I want without going over the bars or the world ending

Will probably upgrade to hyd road calipers in the future.

[kunalraiker]

I don't know, Disc Brakes on a Road Bike just feel so wrong to me.

[Mulger bill]

Again. Have you tried them? 'Druther woah over show any day...