[Closed] Road hydraulic discs

You do realise 'that is one brake system', hope brakes used to be and maybe still are awful for brake draggers hence the snooker ball pistons to help, they do boil fluid compared to other systems.

Shimano and avid sorted boiling brakes years ago with two very different braking fluid. Magura to have it sorted from word go.

jonba - Member

Having had a quick skim through that I would say it is a significant flaw that the brakes faded because (by his own admission) he was dragging them.

There will be many people who do this, not everyone is a riding god worthy of a pro tour team place like people on this forum.

But most riders won't be fitting ridiculous weightweenie brakes either- it was a selection of bits designed for another purpose that he chose and fitted. Someone who's making that sort of decision should take responsibility for his mistakes.

You do realise 'that is one brake system', hope brakes used to be and maybe still are awful for brake draggers hence the snooker ball pistons to help, they do boil fluid compared to other systems.

Shimano and avid sorted boiling brakes years ago with two very different braking fluid. Magura to have it sorted from word go.

If you look closely at any Shimano piston from the last 8 years or so, it's got a phenolic insert which holds the pad away from the metal piston.. The only brake I ever managed to boil was an old Deore which was pre this design.

C2 pistons used to have fins on the inside to dump heat from the pads and piston into the fluid!

I read that article before.. The guy has some good points to make. It's not as if he was using anything too unusual or doing anything that out of the ordinary. He won't be the last person so build something up that's got no mass in the rotors to dump heat into, and then drag his brakes so that they overheat. There'll be a lawsuit or two thrown about and then some new warning labels on new bikes before it becomes common knowledge amongst roadies about how to brake properly.

But most riders won't be fitting ridiculous weightweenie brakes either- it was a selection of bits designed for another purpose that[s] he [/s] the manufacturer chose and fitted.

It was a demo bike, so you'd like to think there was some thought in the choice of components. Most people will ride what their bike comes with. I totally agree with jonba, as I said on the previous page. Easy as it is to dismiss this as 'terrible journalism' it's a potentially massive issue.

I can imagine though that even these can be made quite a bot lighter with discs as the resin wont soften with brake temperature build up, so you don't need extra meat there to support the tyre when warm.

I'd not bet on that. They all have reasonably low pressure limits (Bontrager ones are 115psi, Lightweight slightly less IIRC) because the sidewalls of the rim aren't strong enough to withstand the force the tyre exerts. That doesn't change.

There may be slight improvements, naive to think otherwise, but I don't think we're suddenly going to see the weight tumbling on wheelsets - you can do 1000g tubs easily, and sub-700g is being done. That will not happen with disc wheelsets.

Shimano and avid sorted boiling brakes years ago with two very different braking fluid. Magura to have it sorted from word go.

Ahem. You could boil HS33s.

It was a demo bike, so you'd like to think there was some thought in the choice of components.

It was his (poor) choice.

You don't put moped brakes onto a sportsbike - that's effectively what he did.

If you want thinner depth rotors you need to increase the diameter (see Buell). Small diameter rotors are wrong for lots of reasons such as frame loading, torque required to provide a given decelleration, heat dissipation.

mechanical disks might be better

They won't cook.

Irrespective of who made the choice no one said "that's a bad idea". People [i]will [/i]want the lightest, are all bike shops going to be equipped to know that a brake which functions perfectly on a CX/MTB is not appropriate for the road?

How much of an issue would pad/rotor contamination be? I'm thinking more for the pros. Like in a pile up, plus they must pick some crap up on long wet days? I imagine a wet day on strada bianchi might eat some pad.

wouldn't mind seeign a road version of the [url= http://www.ashima.com.tw/products_01_06.html ]Ashima PCB[/url]...

Did I say carbon already? Can't wait for Messier-Bugatti-Dowty to get involved...

They are efficient and offer high performance: ... maintaining a constant level of efficiency whether hot or cold, at both low and high speeds. Its absorption capacity [b]is between two and three times greater than that of steel[/b], making for substantial savings in material and representing gains in weight.
...
they are lighter (around four times lighter)

...Carbon/carbon beats all records for endurance, increasing the longevity of the brake discs and lengthening the intervals between replacements.

My emphasis

How much would carbon/carbon discs cost on a bike? And would they work, assuming they'd need to be <2mm thick, in order to work within the space available.

Brakes that go on fire? AWESOME!

I'm waiting for a Ultegra level hydro brake, cable gear Sti's myself. Available in both 2x10 and 3x10 systems like they are now.

Wait on, I doubt they'd go to the effort of pleasing luddites who dont want Di2 but for some reason do want hydro disks?

But most riders won't be fitting ridiculous weightweenie brakes either- it was a selection of bits designed for another purpose that he chose and fitted. Someone who's making that sort of
decision should take responsibility for his mistakes.

I use aligator rotros on all my bikes, 160/140 windcutters on the old singlespeed, 180/180 aries on the Swift and 203/180 aries on the Pitch, never had a problem with them, once boiled the rear 140 but that was in a fast group ride arround Tunnel Hill so a quick pace, lots of short sharp hills (both up and down) and lots of braking (as it's in a group).

But most riders won't be fitting ridiculous weightweenie brakes either-

Er, what planet are you on? most riders are looking to save weight not add it. If lightweight rotors save weight, and if you look at mtb rotor prices, are cheaper they will get used.

Carbon rotors/discs need to get HOT before they work. They work fine in F1 or on planes where the speeds are very high and the braking forces very powerful but the reason that carbon wheels have a reputation for being a bit "snatchy" under braking is because it takes a while for the heat to build up then suddenly WHAM, the power comes in.

140mm discs on a road bike will be brilliant. Build the hydraulics into the STI, combine with electric shifting and you've got a bike with no cables, full internal cable routing, nice clean lines on the frame and virtually maintenance free in that respect!

One report from a guy who can't use his brakes properly is hardly conclusive...

Prob some room for a bit of weight seeing as lots of pro bikes have to have weight added.

Prob some room for a bit of weight seeing as lots of pro bikes have to have weight added.

Yes, but the UCI is talking about removing the weight limit altogether and replacing it with a list of approved/tested components, a bit like a more stringent version of CEN. Which would mean no more prototype parts, but would allow marketers to sell lighter bikes, as the current 15lb weight could probably be built for arround £2k if you shopped arround (PX frame/fork, ebay hubs, stans rims, SRAM Red and you'd be under 7kg easily I reckon).

I was running Avid BB7s in Mallorca last year with 160mm Shimano centre lock XTR Discs. Consistently solid braking on even the longest of road descents with no hint of fade whatsoever. Sometimes simpler might just be better! 😀

I've been hankering for hydro discs for quite some time but given previously poor experiences with Hope M4s in the past, I'm waiting to see who can design a decent hydro brake that is reliable for cross and road use. I have to admit that I would be hesitant to run anything less than a 160mm disc and would even prefer a 180 mm up front though no one appears to be making after market compatible forks yet of a carbon persuasion. Now if I can just get a 180 mm bolt thru style carbon fork for my cross bike, I'll be happy! It might seem like overkill but I'm not looking for a race bred superbike but something that is reliable and which won't have me wondering whether my brakes will work or not.

I said this about a year ago

The UCI are pants

Have run road BB7s on touring/commuting bike for 8 years now, and performance has been fine (including Alpine descents with full 4 pannier camping kit load).

People have been using MTB hydraulic brakes for long, steep descents for a long time, so I can't see why properly designed hydraulics should not work successfully on road bikes.

Dragging your brakes is not a "road thing" in my experience. The recommended technique (on or off road) was always to pump your brakes, even back in the days when rim brakes were all that was available.

I was always taught the rear is for feathering and the front will stop you.

The biggest problem I can see with that specific bike is that it has Shimano and not Campag on it, which is illegal 😉

The aftermarket manufacturers are hot on the case with this!
http://road.cc/content/news/54247-trp-launch-di2-compatible-hydraulic-road-brake-levers

140 hydraulic discs on road bikes don't make sense unless the rider is just doing flat crits or similar. You wouldn't dream of running baby discs on an alpine MTB bike, so why would a road bike be any different when the kinetic energy that needs to be dissipated through heat is going to be about the same? The same goes for "general UK" riding, 180ish is sensible both on and off road.

You wouldn't dream of running baby discs on an alpine MTB bike, so why would a road bike be any different when the kinetic energy that needs to be dissipated through heat is going to be about the same?

IS it the same though? I doubt it.

160 road and off here, works fine.

IS it the same though? I doubt it.

yes.

70km/h down to 30 for a corner in the same amount of time requires the same amount of energy to be dissipated regardless of the bike.

and where is "here" for your 160s, the Alps?

I would wager that the kinetic energy dissipated when slowing down an Alpine MTB with fully kitted rider would be greater than a road bike with rider purely becuase the total mass of the MTB is greater than that of the skinny wheeler. Or am I confused?

70km/h down to 30 for a corner in the same amount of time requires the same amount of energy to be dissipated regardless of the bike.

If both are the same weight, yes, but how often are you doing that?

My point was brakes are used in very different ways on an mtb and road bike, so it's not as simple as you think. On a road ride, even in a group/race, I'm not using the brakes nearly as much as mtb, and the use is less draggy. This is even on Alps types rides which don't really exist in the UK.

I have used 160s in the Alps fine BTW.

I would wager that the kinetic energy dissipated when slowing down an Alpine MTB with fully kitted rider would be greater than a road bike with rider purely becuase the total mass of the MTB is greater than that of the skinny wheeler. Or am I confused?

Averarge speeds differ hugely. 30mph off road is scary, and most tracks hve minimal straight bits to make them interesting, so your speed is limited by how rast you want to go and/or cornering speed. Road bikes hit 70mph in the Alps and energy = mv^2 so proportional to mass, but proportional to the square of speed, and the faster you go the more power needs removing to maintain that speed down a constant slope.

MTB's are slowed a lot by wind resistance, tyre drag, and the ground itself (roll into a rocky section completely rigid any you'll stop, this doesnt happen on the road, you'll just keep on getting faster and faster).

Also, remember road bikers [b]HAVE[/b] to drag their brakes in the peleton downhill so as not to hit/overtake the guy in front, imagine the carnage if they had to grab/release all the time to stop them building up heat.

Surely one reason to not go big on rotor size is tyre size? You can have the strongest brake in the world but what use is it if the tyre can only cope with 1% of the force? I know the other side of this is hand/arm effort required to operate the brake but I suspect that certainly at the rear there is little need for anything bigger than 140mm. On an unladen racing bike anyway.

The original statement was for the same speeds.

[i]70km/h down to 30 for a corner in the same amount of time requires the same amount of energy to be dissipated regardless of the bike.[/i]

But no, I don't fancy 70kph off road thanks.

the current 15lb weight could probably be built for arround £2k if you shopped arround

Not at all interested in road discs for a race bike though - I see the "advantages", but the thing is there's actually nothing wrong with the braking on my road bike, plenty enough power, modulation is fine, not too much effort required. I'm sure plenty of people will want the bling, but real world advantages for normal people?

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.

That said, overworn rims can blow and tubs can melt, neither of which is pretty. My limited experience of cooked discs on the MTB is that its a comparatively benign fail mode.

I guess this dosn't bother the big hitters much, becuase they're always off the front ... and only ever apply the brakes to collect their trophies.

don't think it's been mentioned but pros probably don't need it as they weigh about the same as an average bidon; some sportive riders are built more like the team car.

curious to see how they are going to design the brakes to get a fast wheel change.

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?

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.