Road bikes with discs
Comments
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Headhuunter wrote:
Yes but the extra weight comes in the wheels too... If you use discs, the wheels have to be considerably beefed up to take the strain of braking near the centre... Whichever way you slice it 7.2kg is pretty damn heavy for a top flight race machine costing £10kmeanredspider wrote:Headhuunter wrote:
It's more than a few hundred grammes! The colnago weighs 7.2, for a 10000 quid bike that's at least a kilo overweightWrath Rob wrote:If you're that fussed about weight then lose a kilo or 2 of body fat. Most of us could benefit more from that than by shaving a few 100's grams off our bike
Some interesting insight into where SRAM is going here
BTW, Bianchi as joined the party too. As have Enigma
Article on Road.cc about aero benefits, or lack of, for disc brakes.
The frameset weighs only 150g more for the disc version than the regular version. If it's overweight, that's only fractionally due to the brakes
I'm looking at building a disc brake single speed at the moment and so I've been looking at 29er rims. I'm surprised to find they are actually much lighter than 700c rims.Mud - Genesis Vapour CCX
Race - Fuji Norcom Straight
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Is that really the case? Aside from the fact you can't use radial spoking in the front wheel, is there really much of a difference? A standard 2x or 3x construction is already very well suited to transferring torque between hub and rim, which is all it's actually being asked to do.Headhuunter wrote:Yes but the extra weight comes in the wheels too... If you use discs, the wheels have to be considerably beefed up to take the strain of braking near the centre... Whichever way you slice it 7.2kg is pretty damn heavy for a top flight race machine costing £10k
Real-world example: I'm about to build a ~1400g disc wheelset for CX. The spec is actually very conservative, using aluminium clincher rims specifically designed for CX and a 28/32 spoke count; I could go even lighter with a carbon rim and/or tubs. I'm expecting this to be pretty robust, and if it's good enough for CX it'll easily be good enough for anything on the road.Pannier, 120rpm.0 -
Well I'm not an expert but the impression I have been given is that disc brakes add weight to the frame, forks and wheels. The wheels need to be significantly beefier because the spokes have to take a lot more strain than in standard wheels...TGOTB wrote:
Is that really the case? Aside from the fact you can't use radial spoking in the front wheel, is there really much of a difference? A standard 2x or 3x construction is already very well suited to transferring torque between hub and rim, which is all it's actually being asked to do.Headhuunter wrote:Yes but the extra weight comes in the wheels too... If you use discs, the wheels have to be considerably beefed up to take the strain of braking near the centre... Whichever way you slice it 7.2kg is pretty damn heavy for a top flight race machine costing £10k
Real-world example: I'm about to build a ~1400g disc wheelset for CX. The spec is actually very conservative, using aluminium clincher rims specifically designed for CX and a 28/32 spoke count; I could go even lighter with a carbon rim and/or tubs. I'm expecting this to be pretty robust, and if it's good enough for CX it'll easily be good enough for anything on the road.Do not write below this line. Office use only.0 -
Headhuunter wrote:Yes but the extra weight comes in the wheels too... If you use discs, the wheels have to be considerably beefed up to take the strain of braking near the centre...
Really? My Volagi aluminium wheels are 50g heavier than Fulcrum Racing 3s and broadly similar cost. Whilst the hubs are heavier, the rims can be lighter as there's no need for a brake track or the wear allowance on the brake track. Weight is obviously far better near the centre of the wheel to reduce the polar moment of inertia.
Yes - that Colnago is heavy but I don't think you can put that all down to the discs. With Volagi's carbon wheels, I can get my bike down to 7.3kg. I'm sure Colnago haven't spent another £6-7000 taking out 100gROAD < Scott Foil HMX Di2, Volagi Liscio Di2, Jamis Renegade Elite Di2, Cube Reaction Race > ROUGH0 -
meanredspider wrote:Roadies are unbelievably conservative so it will be slow.0
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Headhuunter wrote:Well I'm not an expert but the impression I have been given is that disc brakes add weight to the frame, forks and wheels. The wheels need to be significantly beefier because the spokes have to take a lot more strain than in standard wheels...
What I'm trying to do in this thread is add facts to the debate. I think there are lots of impressions but I'm not sure these line up with the real-world facts.
And even then, the real world differences are tiny for the vast majority of riders. Racing snakes and weight-weenies might find they can shave a few g off the total weight but, even then, I'm not sure the weight is being used where it can be most effective.ROAD < Scott Foil HMX Di2, Volagi Liscio Di2, Jamis Renegade Elite Di2, Cube Reaction Race > ROUGH0 -
Probably 2 reasons for this, firstly UCI regulations re disc brakes, although most people don't race and this doesn't affect them, manufacturers know/believe that road riders want their bikes to look like pros bikes, so if the pros aren't riding discs then keen amateurs won't want them either. Secondly, it would take expensive reconfiguration of factories and redesign of frames, forks and wheels to to bring disc brake road bikes to the mass market, this is probably an expense that manufacturers are unwilling to pay. Why redesign sub £1k bikes to take discs when they can keep churning out the existing designs and still sell?Veronese68 wrote:meanredspider wrote:Roadies are unbelievably conservative so it will be slow.Do not write below this line. Office use only.0 -
What's your justification for that statement?Headhuunter wrote:The wheels need to be significantly beefier because the spokes have to take a lot more strain than in standard wheels...
Quick back-of-envelope calculation suggests that in the most extreme braking situation (almost locking the front wheel with fat rider behind the saddle) the tension on an individual spoke due to braking will increase by something in the order of 300N, or 25-30% of the steady-state tension. Intuitively, I'd imagine the peak loading due to hitting a pothole, on the most highly-loaded spoke, would be much more, maybe an order of magnitude higher.Pannier, 120rpm.0 -
Agree completely. Were it not for the UCI being so conservative I suspect bike design would have moved on significantly more than it has.Headhuunter wrote:
Probably 2 reasons for this, firstly UCI regulations re disc brakes, although most people don't race and this doesn't affect them, manufacturers know/believe that road riders want their bikes to look like pros bikes, so if the pros aren't riding discs then keen amateurs won't want them either. Secondly, it would take expensive reconfiguration of factories and redesign of frames, forks and wheels to to bring disc brake road bikes to the mass market, this is probably an expense that manufacturers are unwilling to pay. Why redesign sub £1k bikes to take discs when they can keep churning out the existing designs and still sell?Veronese68 wrote:meanredspider wrote:Roadies are unbelievably conservative so it will be slow.
I was just pulling your leg.0 -
The article I mentioned in C+... I really can't defend it with calculations!TGOTB wrote:
What's your justification for that statement?Headhuunter wrote:The wheels need to be significantly beefier because the spokes have to take a lot more strain than in standard wheels...
Quick back-of-envelope calculation suggests that in the most extreme braking situation (almost locking the front wheel with fat rider behind the saddle) the tension on an individual spoke due to braking will increase by something in the order of 300N, or 25-30% of the steady-state tension. Intuitively, I'd imagine the peak loading due to hitting a pothole, on the most highly-loaded spoke, would be much more, maybe an order of magnitude higher.Do not write below this line. Office use only.0 -
Ah, I see.Headhuunter wrote:
The article I mentioned in C+... I really can't defend it with calculations!TGOTB wrote:
What's your justification for that statement?Headhuunter wrote:The wheels need to be significantly beefier because the spokes have to take a lot more strain than in standard wheels...
Quick back-of-envelope calculation suggests that in the most extreme braking situation (almost locking the front wheel with fat rider behind the saddle) the tension on an individual spoke due to braking will increase by something in the order of 300N, or 25-30% of the steady-state tension. Intuitively, I'd imagine the peak loading due to hitting a pothole, on the most highly-loaded spoke, would be much more, maybe an order of magnitude higher.
You do know you can't believe everything you read in the press, don't you? Normal newspapers are bad enough, but when most of the content of a magazine is about products/events that are advertised in the same magazine (and probably based on press releases from the manufacturers/organisers) there's a massive conflict of interest. You'll probably get a better quality of information on this forum; at least some of the contributors will have a background in relevant areas such as engineering. All you have to do is apply your own critical analysis to figure out who actually knows what they're talking about...Pannier, 120rpm.0 -
I'll admit that I was trolling a little. Simple fact is that I just don't really like the look of discs and have never been in a scenario where I felt like I needed them - and I've done plenty of descending in the wet, even with a carbon braking surface. I'll have a look see when the tech is good enough, but ATM it's all a bit of a bodge isn't it? Also I worry about my Zipps overheating on long descents, so the idea of a smaller braking SA scares me a little. Imagine discs get very hot, imagine crashing on a long descent and getting burned by your discs... insult to injury.
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Yes, yes! I know you can't believe everything you read in the paper! But it seemed a well reasoned article... I haven't got it in front of me, I'm probably misquoting it. I was just throwing what I had heard out there....TGOTB wrote:
Ah, I see.Headhuunter wrote:
The article I mentioned in C+... I really can't defend it with calculations!TGOTB wrote:
What's your justification for that statement?Headhuunter wrote:The wheels need to be significantly beefier because the spokes have to take a lot more strain than in standard wheels...
Quick back-of-envelope calculation suggests that in the most extreme braking situation (almost locking the front wheel with fat rider behind the saddle) the tension on an individual spoke due to braking will increase by something in the order of 300N, or 25-30% of the steady-state tension. Intuitively, I'd imagine the peak loading due to hitting a pothole, on the most highly-loaded spoke, would be much more, maybe an order of magnitude higher.
You do know you can't believe everything you read in the press, don't you? Normal newspapers are bad enough, but when most of the content of a magazine is about products/events that are advertised in the same magazine (and probably based on press releases from the manufacturers/organisers) there's a massive conflict of interest. You'll probably get a better quality of information on this forum; at least some of the contributors will have a background in relevant areas such as engineering. All you have to do is apply your own critical analysis to figure out who actually knows what they're talking about...Do not write below this line. Office use only.0 -
Yeah I have to say I've never had a problem with standard road bike brakes but then I've never tried disc brakes, may be they would be a complete revelation....Il Principe wrote:I'll admit that I was trolling a little. Simple fact is that I just don't really like the look of discs and have never been in a scenario where I felt like I needed them - and I've done plenty of descending in the wet, even with a carbon braking surface. I'll have a look see when the tech is good enough, but ATM it's all a bit of a bodge isn't it? Also I worry about my Zipps overheating on long descents, so the idea of a smaller braking SA scares me a little. Imagine discs get very hot, imagine crashing on a long descent and getting burned by your discs... insult to injury.Do not write below this line. Office use only.0 -
The image of that thing in the first post broke my soul.Food Chain number = 4
A true scalp is not only overtaking someone but leaving them stopped at a set of lights. As you, who have clearly beaten the lights, pummels nothing but the open air ahead. ~ 'DondaddyD'. Player of the Unspoken Game0 -
I really can't see the point in discs for road racing; calipers are actually a very elegant solution; the brake "disc" is already there and provides plenty of thermal mass, the calipers can be very lightweight, and the mechanism is simple and robust. If not requiring a braking surface allowed you to build the rim significantly lighter there might be a case, but I'm not convinced you'd be able to get rid of enough material to make a difference.Il Principe wrote:I'll admit that I was trolling a little. Simple fact is that I just don't really like the look of discs and have never been in a scenario where I felt like I needed them - and I've done plenty of descending in the wet, even with a carbon braking surface. I'll have a look see when the tech is good enough, but ATM it's all a bit of a bodge isn't it? Also I worry about my Zipps overheating on long descents, so the idea of a smaller braking SA scares me a little. Imagine discs get very hot, imagine crashing on a long descent and getting burned by your discs... insult to injury.
If I was building a commuting bike from scratch I'd go for discs, mainly due to rim wear. With the current options available I wouldn't consider anything other than discs for CX. But for performance-oriented road, I just don't see the point.Pannier, 120rpm.0 -
I'm a big fan of discs. I have no plan on ever racing and due to my weight (80kg) and the fact that I already ride a fairly heavy bike adding a few grams doesnt really matter to me.
I am very much looking forward to Hydrolic Road STi for the masses (without the massive pointy hoods).
You cant beat them for commuting."If you always do what you've always done, you'll always get what you've always got."
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I have never been in a situation where I have thought to myself that I needed disc brakes on my bicycle.
Just like being in a car, the first rule of braking is anticpation.Food Chain number = 4
A true scalp is not only overtaking someone but leaving them stopped at a set of lights. As you, who have clearly beaten the lights, pummels nothing but the open air ahead. ~ 'DondaddyD'. Player of the Unspoken Game0 -
Not even descending Balham Hill?Mud - Genesis Vapour CCX
Race - Fuji Norcom Straight
Sun - Cervelo R3
Winter / Commute - Dolan ADX0 -
He'd have to get to the top firstAsprilla wrote:Not even descending Balham Hill? 0 -
I've recently dusted off the old MTB, and on every ride I'm pleasantly surprised at just how good even 10-yr old cable disc brakes are.
I'm looking forward to seeing the new hydraulic road bike brakes evolve. I'd have discs on my commuting bike tomorrow if I could, in fact this thread has prompted me to go shopping for a disc fork for my Pompino.Misguided Idealist0 -
Remember DA hydro DI2 brifters are coming (leaked giant cyclo cross pics are somewhere on t'internet) . As people point out, Rims havn't caught up yet as you will get less rotational mass and am in the market for a set of Carbon Rims but won't as if it rains or I head down some alpine descents everything gets very scary.
I love my BB7's on my fixed road bike, riding it in the wet really makes you think about why we've been wasting our time with rim brakes for so long.If I know you, and I like you, you can borrow my bike box for £30 a week. PM for details.0 -
DonDaddyD wrote:Just like being in a car, the first rule of braking is anticpation.
It is if you're dawdling about in a car taking the kids to their swimming lesson or doing the weekly shop at Fortnum's. But then you don't need power or handling either - a Kia people carrier would be perfect.
If you're driving for fun on a race track, it's about power, modulation (control) and consistency.
The same goes for rim brakes versus discs.
To be honest, I'm always shocked when I take the Focus Cayo out for the occasional spin - I forget just how much more distance I need to allow to stop the thing.ROAD < Scott Foil HMX Di2, Volagi Liscio Di2, Jamis Renegade Elite Di2, Cube Reaction Race > ROUGH0 -
Discs? Bring 'em on!! (at least in time for my next bike...whenever that'll be)
Riding through the winter in wet conditions screws the brake pads and reduces braking efficiency in my experience. I'm speaking very much from a commuting standpoint here but I'd love discs on my bike0 -
Re the weight - the hubs are generally heavier to mount the disc ie the 6 bolt flange, or Centrelock fitting. The lightest disc hubs in the MTB world are circa 120g for the front, though have seen some around 100g. Standard Hope Pro 2 is 185g. Non disc hubs are usually cheaper and lighter.
Disc rims can be made lighter than non disc though as you do not have the braking surface, though on MTB bikes the mass is usually redistributed to form a stiffer, stronger unit.
Spokes, as has been mentioned, cannot be laced radially (at least on one side - some manufacturers do lace radially on the opposite side at the fornt, some say not to at all),: spokes are loaded differently on the brake side ie leading and trailing spokes seeing different loads under braking. From calculations I have seen the overall increase in load per spoke on a disc brake under even heavy braking is only a few pounds. If that is true, then spoke type is going to make little difference.
I think we will see disc brakes eventually in UCI races. At this end of the scale, if the limit stays the same at 6.8kg, it will not make a difference to them as they will hit that limit regardless. However to you and I, on our £1000 road bikes I can see the weight going up quite significantly, not only because of the increased weight of the system, but the cost of the units meaning lower specced and heavier parts elsewhere.
With good rim brakes I don't struggle on the road. As it gets wetter, the brakes do become less powerful - but then again the wet and often slimy road surface means less effort is needed to lock up anyway.0 -
meanredspider wrote:DonDaddyD wrote:Just like being in a car, the first rule of braking is anticpation.
It is if you're dawdling about in a car taking the kids to their swimming lesson or doing the weekly shop at Fortnum's. But then you don't need power or handling either - a Kia people carrier would be perfect.
If you're driving for fun on a race track, it's about power, modulation (control) and consistency.
The same goes for rim brakes versus discs.
Cars come with an engine and as engine technology has improved - dramatically so, even seen the top gear episode where they race 80s GTI cars against modern day ordinary cars - so must the technology used to slow and stop the motion created by said engine.
Bicycle technology is focused elsewhere: weight, grip, handling, power transfer from rider through the bike to motion. The engine on the bike has not improved dramatically enough for it to justify hydraulic disc brakes in the same way that the engine in a car has. I mean its understandable that you would need disc brakes over drum brakes and ABS on a modern day car and ceramic brakes on a supercar.
Seems excessive on a bicycle tearing through the air at 20mph on a clear stretch of road in a major city.To be honest, I'm always shocked when I take the Focus Cayo out for the occasional spin - I forget just how much more distance I need to allow to stop the thing.
Anticipation in it.Food Chain number = 4
A true scalp is not only overtaking someone but leaving them stopped at a set of lights. As you, who have clearly beaten the lights, pummels nothing but the open air ahead. ~ 'DondaddyD'. Player of the Unspoken Game0 -
Road bike braking is pretty rubbish in the wet, but then that's a combination of caliper brakes and skinny tyres. I'm not sure changing one and not the other solves the issue. In any event, disc brakes are ugly. I don't even use them on my mountain bikes (and I'm even willing to have Shimano on them) so can't see them going anywhere near my road bikes in a hurry.0
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@DDD
But the speed limit hasn't changed. And, TBH, there's sod-all difference between the brakes on my 1960's Alfa and my 2009 Alfa except the latter has ABS (which isn't as effective as threshold braking) and the pads don't contain asbestos. In fact, short of a few material changes, there's nothing fundamentally different with F1 brakes. And even MotoGP bikes don't use carbon brakes in the wet. That's because the disc brake is such an effective design - fully characterised and understood.
And, as for excessive on a bike in a city, what's with 1000g frames, super light wheels, bars, stems, Lycra, etc? If all of that is justifiable, why wouldn't better brakes also be justifiable? After all, I guess all those things are to help you go faster, you need something to help you stop.ROAD < Scott Foil HMX Di2, Volagi Liscio Di2, Jamis Renegade Elite Di2, Cube Reaction Race > ROUGH0 -
If they are better. To me they are not (on the road), and the same will be for others. Also disc brakes vary quite a bit in quality too, it wouldn't surprise me that when they become more common place there will be some pretty ropey units starting to show up.
But if they are better for you, why not?0 -
supersonic wrote:If they are better. To me they are not (on the road), and the same will be for others. Also disc brakes vary quite a bit in quality too, it wouldn't surprise me that when they become more common place there will be some pretty ropey units starting to show up.
But if they are better for you, why not?
Sure, there may be some ropey ones but I think there is actually masses of opportunity for good ones. I love the idea of the TRP HY-RD units for instance. The best we have so far is the very old BB7 and (for me) they are infinitely better than calipers - so much so in the wet. I do find it really difficult to understand why people don't find discs better - for me, there's a clear difference. I would genuinely like to understand why that is.ROAD < Scott Foil HMX Di2, Volagi Liscio Di2, Jamis Renegade Elite Di2, Cube Reaction Race > ROUGH0
