[Closed] Road hydraulic discs

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).

[img] [/img]<

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.

http://www.bikerumor.com/2012/03/07/leaked-colnago-c59-carbon-formula-disc-brake-equipped-road-bike/

[img] [/img]

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.

[b]IF[/b] 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

[img] [/img]

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.... 😉

As exciting as the new top end bling shown in the OP is, if Shimano/3rd party Hydraulic road discs are only just arriving as a Di2 only option now, I can still see more basic cable discs making the biggest initial running on the road bikes that real people can actually afford to buy, if Shimano don't do a tiagra or 105 level cable operated caliper that can work with their existing STI units (like the BB7/BB5) then they are total mugs, and could easily lose a chunk of the market to SRAM...

I'd expect to see lots of Disc compatible frames, still with canti mounts in the next 18-24 moths to give people future upgrade options...

Out of interest are road bikes now adopting the 135mm spacing, post and/or IS mounts direct from MTBs or will they all decide to re-invent things all over again?

As for sustained alpine descents cooking a set of 140mm discs?
Well it might seem obvious to all of us armchair experts, but I suppose someone had to blaze the trail and write that article first, to be fair I don't think He's trying to de-bunk discs for the road, it is new terratory for many roadies and I don't think all of the technical issues are fully appreciated...
He talked to manufacturers and I think it rounds up the challenges that they face quite well, in short they are going to have to try and make lighter brakes that can accomodate longer periods of heavy use, the point is made that bigger rotors and other cooling features will help, but ultimately there will also be a period of adjustment while road riders, generally not used to discs, need to adjust to their operation...

TandemJeremy - That disc brakes on tandems are dangerous ...

[img] [/img]

Ooops 😉

(TJ - this ain't a dig, I actually agree with you, and the above picture is essentially irrelevant, if superficially funny)

we need a caption competition to go with that pic....

stop eyeing up my arse!

cookeaa - new Shimano mechanical discs:

http://www.bikeradar.com/news/article/shimano-sora-and-tourney-2013-first-look-33204/

oh and yes 135mm spacing for road bike discs.

Reading this thread I do wonder how anyone gets up to 40 or 50 mph but then I remember I live in Suffolk it pretty flat here and long decents are several counties away. So from my perspective where the fastest you are ever going to go is about 35 mph (very breifly) around my way discs are pretty pointless as the short 35mph decent is always followed by a hill afterwards. Rim brakes are not history, I still use an MTB regulalry with canti's and they are fine for Thetford.

For riding in the hilly areas I can sort of see the point but I do think take up will slow by club riders, certainly the clubs I know in Suffolk.

However having said all that, the Colnago in that link is a neat bike and I would have discs on a road bike over d12 which to me is completly pointless as I never get trouble with my cables or shifting and there is no battery to charge which I would forget to do.

As a mechanic that has worked in road racing my concern is wheel swaps in a race situation and the how easy it would be to swap a wheel when you have to negotiate how the caliper is mounted in relation to the new wheel and spacing etc. The whole 10/11 speed situation has already throw a curve ball into spares and speed in wheel swaps.

discs are pretty pointless

d12 which to me is completly pointless

Both already discussed at length...

disc brakes on tandems are dangerous.

That theory is debunked by practical experience.

After sintering some HS33s on our tandem bringing it to a stop from just 40mph and nearly sailing through a Give Way we went out and got discs (big ones) for ours and it's the best thing we ever did for it. Never touch them to see how hot they've got though. ooyah

In the summer I saw some Americans on a tandem with a gargantuan disc on one end (I think it was back but can't remeber, will have to see if I took a pic) and a V brake the other, which seemed like pretty strange decision making on the manufacturers part (or buyers if it was a custom build - either way they were matching F&f so presumably designed/built to go together).

There are braking issues with tandems you don't tend to get with half-bikes, which explain Thorn's stance on this - and having a V brake on the front along with a big disk on the back. The problem is that going down a hill a tandem will accelerate to a much faster speed, and have a lot more energy to dump in the brakes - therefore a lot of tandems actually tend to have 3 brakes, 2 normal ones and a drum brake. The drum brake is used as a drag brake going downhill to keep the speed down without overheating the main brakes. We've only ever had rim brakes on ours as I've always reckoned we don't tend to carry as much load as some, and that I'm skilled enough not to need to drag a brake going down a hill - yet we once had a tyre blow off due to heat on a descent which wasn't that long or steep, but was narrow and twisting and required keeping the speed down.

Discs seemed like an obvious replacement for the rim brakes and the drum drag brake resulting in less complication. The trouble is, even a big 203mm disk doesn't have as much heat capacity as an old-fashioned drum brake. Therefore you are liable to overheat the braking system. It's not rocket science here - you have twice the load on a tandem, yet people who would complain that a 140mm rear disc is too small seem to be happy using something smaller than 280mm on a tandem. This is the issue Thorn have with using disks - the fact they work OK for some people doesn't mean there isn't a potential issue if used by people who might otherwise have a drum.

The front V, rear disc is a Santana thing - you can read some of their argument for that at: http://www.precisiontandems.com/artdiscbk0.htm

Aracer - sorry but I disagree. we have cooked discs on our tandem but only in extreme conditions. Short steep downhills rolling slowly down using only one brake

thorns stance is based on a number of mistakes and only considers old tech. Part of the stance is no tandem rated suspension forks are available or tandem rated disc brakes - both just wrong in fact.

Personally I would never want a rim brake tandem - why not have the best available brakes?

That link you gave - this

Those reasons include the fact that due to the increased weight two riders exert on the rear wheel, it is virtually impossible to lock up the rear wheel under the most extreme braking- this makes it a wonderful location for such a smooth stopper. (After all, the braking power of an unarticulated V-brake-, one without a parallel-push mechanism-is already strong enough to lock up a tandems front wheel.)

The front brake is the most effective one. Its where you should have the best brake

sorry but I disagree. we have cooked discs on our tandem but only in extreme conditions. Short steep downhills rolling slowly down using only one brake

You disagree that it's an issue for you, or that it's an issue for anybody else? I'm not saying that Thorn are right, just that there is some logic behind their stance.

It's also interesting that you disagree with it being an issue, then go on to give an example of where it is 🙄

That link you gave - this... Is nonsense

Not my words - hence how I phrased my intro to the link. You do have to bear in mind that Santana sold that on road bikes, so the situation is somewhat difference to your experiences off road. Or do you still think that everybody has the same requirements as you?

is a Santana thing

If it was my tandem (and I accept I have only ridden on a couple of times) I would want a big disk at the front for stopping power and an exqually big one at the back to avoid heat build up from dragging the brakes.

Not sure why you would want anything else really.