Road hydraulic discs

Good point, I do think a simple effort to chamfer the pads and shape calipers to guide the disc in would sort it though.

Kinetic energy in an 80kg rider on a 7kg road bike doing 40mph (a fairly conservative speed on a road) = 14,000J.

Kinetic energy in an 80kg rider on a 12kg MTB doing 30mph (pretty brisk off-road) = 8,400J.

Or to put it another way, in energy terms bringing the road bike from 40 to 30mph is about the same as bringing the MTB from 30mph to a standstill.

Tiny rotors on road bikes? I think not 🙂

anotherdeadhero – Member

I don’t drag brakes riding on the road on my own (I reserve this for mincing like a scaredy cat on the MTB) but in groups its often unavoidable. My recollection of the etape is that until you work into clear air, the first couple of descents are mostly slowly dragging your brakes waiting for euro numpties to clear out of the way, and I’ve spent plenty of time dragging my brakes behind useless car drivers dribbling down a hill, where my only other optiosn would have been a) stop completely, or b) life-risking mentalist overtake.

There are other options – alternate brakes or brake in bursts – both prevent the heat build up

40mph = “fairly conservative” LOL!

On an Alpine descent maybe, in the UK probably reached on relatively few rides, and hardly ever braked from to a standstill.

As I’ve said above, it’s more complex than simple examples, and you’re not even choosing relevant ones.

So my point is even more valid if roadies are going that much faster than MTBers. 140 road hydro discs are too small

EDIT: too slow! (pardon the pun)

40mph is a very conservative top speed for descending on a road bike. I live in South London and can hit 50 no probs on a few roads near here and have to slow to zero for junction etc at the bottom. These speeds can be reached on local road race circuits too so the example given by mike d is relevant.

Since when can 180s not cope on proper MTB descents?

And do you mean steep ones where you’re doing a few mph all the way down? i.e. unlike anything you’d ever do on a road bike?

Tiny rotors on road bikes? I think not

Big hot rotors in a crash… the smell of burning flesh.

Wasn’t crashing one of the reason Spinergy wheels got banned?

Since when can 180s not cope on proper MTB descents?

you’re just being silly now. I’ve been talking about the alps and I’ve seen plenty of cooked 180s when MTBing out there. The C59 shown in the OP is aimed at people who will ride proper races and Grand Fondos, Etapes etc so will need brakes that don’t boil.

Spinergies got banned because they could chop bits of you off, you’d have to be pretty unfortunate to stick any part of you in a rotor during a high speed off.

On an Alpine descent maybe, in the UK probably reached on relatively few rides, and hardly ever braked from to a standstill.

I’ll except the second point, but 40mph isn’t that fast, most rides in the Cotswolds will see me doing 40+ at some point, and i wouldn’t say the Cotswolds are alpine.

Well like I say my 160s coped fine – what brand were those brakes anyway?

And as I say the energy dissapation on a road ride is likely very different.

Thosrn cycles dis some research and discussion on disc brakes with tandems concerned about heat build up
some figures and stuff about how ad why the heat builds up. I disagree with the conclusion but some of the geekery might be interesting

http://www.thorncycles.co.uk/tandembraking.html

Hayes, hope and avid. A quick google shows that cooked brakes aren’t something I’ve made up!

Out of interest which bit of the conclusion do you disagree with TJ – I thought it seemed fairly sensible and logical.

Ah sorry leggy, I use shimanos, I keep forgetting that other folk also buy sub-standard brakes.

Fair enough, I’ve just bought some m810 Saints for my big bike for this summer as they’re meant to be amazing. I’ll still use 200/180 discs though.
And the discs on that C59 aren’t shimano!

clubber – Member

Out of interest which bit of the conclusion do you disagree with TJ – I thought it seemed fairly sensible and logical.

That disc brakes on tandems are dangerous. thorn will not allow discs on any of their tandems

Tiny rotors on road bikes? I think not

I already run idscs on my commuter/trainer. They are 160mm rotors though. They handle 50mph descents no problem. Loads better than rim brakes. Rim brakes are history.

I already run idscs on my commuter/trainer. They are 160mm rotors though. They handle 50mph descents no problem. Loads better than rim brakes. Rim brakes are history.

Are they hydro discs?

I like the idea of discs for road bikes, carbon rims in the wet and even the dry sometimes are horrible for braking, I just don’t see 140s as realistic.

On an Alpine descent maybe, in the UK probably reached on relatively few rides, and hardly ever braked from to a standstill.

I’ll give you the latter point, hence my other example:

Or to put it another way, in energy terms bringing the road bike from 40 to 30mph is about the same as bringing the MTB from 30mph to a standstill.

All I’m getting at is that brakes potentially have to work harder on road bikes because they typically go faster and because kinetic energy is proportional to the square of velocity which makes relative weights pretty much irrelevant.

I agree they may have to work harder, but the main issue is heat build-up, which mtbs are IMO more prone to, given the difference in they way they are ridden.

We can’t compare, but given how much better even 160mm discs are at stopping than v-brakes, they are bound to be better than road caliper brakes.

Haha!

There’s Geekery and then there is experience.

We took our tandem with Bob trailer and 2 panniers & all sorts of other bits and bobs from the Himalayas in Nepal down to the Indo-Gangetic plane. Not many bigger descents than that and I wasn’t afraid to pick up the speed.

Magura Louise with 208/180 discs no problems.

That disc brakes on tandems are dangerous. thorn will not allow discs on any of their tandems

Right ok, no issue with that.

just thinking out loud here, mtb lower ultimate speed and a tendancy to scrub speed so there is time for heat to radiate from rotors, road bike, brake hard into corner, harder braking and shorter time period but same amount of kinetic energy to loose, so road disc will get hotter?

It’s all about common sense.

You see some people driving their cars in the mountain with the brakes held on the whole way. Wait at the bottom and you’ll see the same people stop get out and stare at their smoking brakes with disbelief.

We are probably going to see the same thing happening in the next few years as roadies buy disc equipped bikes but don’t understand their limitations and how to manage them.

Disc brakes work just fine on the road in the mountains.. I’ve used them myself. It just depends how you use them.

On an Alpine descent maybe, in the UK probably reached on relatively few rides, and hardly ever braked from to a standstill.

I think that’s a valid point. I have a hill in each direction on my commute (different places) which I can hit 40mph on, both of which have roundabouts at the bottom. So, on my commute from leafy Surrey into the City, most times I ride!

What about the difference in how one rides an MTB on the road? Most (not all) folk on an MTB on the road will be bimbling down, and braking conservatively, the gearing is more limiting to ones top speed anyway. It’s quite plausible that someone on a road bike will be properly hooning on the descents and thus trying to scrub off more speed more regularly.

And virtually all the ‘proto’ road bikes appearing are coming with 140mm rotors, so saying 180mm is plenty is probably a bit late. One assumes the R&D has been done…

just to clarify, I run hydro discs on my commuter/trainer (XTR calipers, 160mm rotors) and it’s fine. 50mph descents. No issues.

Maybe on a massive Alpine descent you’d get them really hot but I’ve not had any fade issues on the local hills.

Personally, I’d run 160 discs rather than 140. Hardly any heavier but better power and heat management.

we’ll, it seems pretty clear that the manufacturers are.intending 2013 to be the year of disc’d road bikes

http://www.bikebiz.com/news/read/brake-makers-want-uci-to-allow-disc-brakes-on-road-bikes/012726

interesting comments on testing alpine descents (though “they would say that, wouldn’t they”)

High-quality QRs are likely to be able to withstand high ejection forces on vertical drop-outs but fitting thru-axles to road bikes is an even safer option

*is depressed*

Why not just have the dropout facing forwards a la Salsa?

Just seen the Colnago, boy do those discs make it look ugly.
Unless it’s just decades of simple lines gone overnight, Sophia Loren with tattoos.

It’s always going to be a matter of taste but I really like how it looks – for me, it replicates the clean lines of track bikes at the fork/head tube and seat stays, while the discs are in a position where for me at least, they don’t really stand out (since the hubs were there already).

More pics of the shift/brake levers – Di2 is opening out the shifter market which is an interesting development. Not a cheap one yet but it’ll filter down I reckon.

Updated! Colnago C59 Carbon: Formula disc brake equipped road bike

So, we’re at 339g for brake/shifter, caliper, rotor, and hardware. Not too shabby considering that the shifter is included and better than some mountain brakes. The photo also shows the cutaway shift paddle(s) and gives a better image of the lever body’s prrofile.

We’ve also been told to expect late-2012 aftermarket availability and model year 2013 OEM spec (on the Colnago C59 if not others). More information as we get it…

So, we’re at 339g for brake/shifter, caliper, rotor, and hardware.

But no battery? Without out that it’s just a brake lever with a bit of wire stuck to it.

IF the weight limit is dropped I reckon it’ll kill off Di2 (and hydro brakes with it) for weight reasons.

how about small twin discs (one each side) on the front like motorbikes and one at the rear?

or/and vented disc?

this is whats needed

does the heat generated from rim brakes on say a TdF alpine descent generate enough heat to increase the “grippyness” of the tyres ?

More to melt the glue holding them on!

I think the Colnago looks good, it looks ‘cleaner’ than a rim brake equipped bike.

I think the Colnago looks good, it looks ‘cleaner’ than a rim brake equipped bike.

Agreed – very neat

I struggle with long sentences, but better brakes = going faster for longer, right?

That disc brakes on tandems are dangerous. thorn will not allow discs on any of their tandems

Shows how little Thorn know – their website annoys me intensely with it’s patronising “we know best” attitude, it’s insistence that “steel is real” and various other cliched rubbish about how carbon and alu frames break. How on earth are discs dangerous on tandems as opposed to any other type of bike?

How on earth are discs dangerous on tandems as opposed to any other type of bike?

Exactly. I suppose all the motorbikes that have been made in the last 20 years are all dangerous too? Just duff thinking.

Discs are better brakes. Only an imbecile would argue that rim brakes are a better design. Well perhaps a weenie might…. 😉