Disc brakes?

redddraggon

Would disc brakes offer far superior braking performance over well set up dual pivots with decent pads on the road?

I'm interested because some people believe that discs are the be all and end all to stopping bikes.

meagain

Well, they ARE, obviously. Why else do you think 180 mph m'cycles use 'em? Never tried cable discs but hydraulics are just better than any Vs, themselves better than any other rim brakes. I assume that as only single-opposed cables not AS good.

andrewgturnbull

Hi Red.

Yes, it's pretty obvious that discs would offer better braking on road bikes, but is it necessary?

I've never found standard calipers on alloy rims to be lacking - even on wet alpine descents.

Having said that, maybe we should look at it another way. Braking on wet carbon rims can be a problem.

What if we downscaled disc brakes so that they were tiny wee things, wee discs the size of a 50p piece? That way we'd get the same braking performance as a caliper, but lighter weight. Maybe we could mount the things _inside_ aero wheels with hydraulic cables snaking through the inside of your frame, then entering through a hollow axle? Or maybe electicallly actuated?

Aerodynamic and weight advantages, weatherproofing and usability gains? Maybe... I'm off down the patent office now!

Cheers, Andy

Ken Night

redddraggon wrote:

I'm interested because some people believe that discs are the be all and end all to stopping bikes.

Why are you interested? What is it about other people's beliefs that interests you?

From previous threads, you'll know I've set up a disc braked crosser on a Ti frame. Love it

I have to say, while convinced, I'm not as wildly impressed with cable operated discs, as I thought I would be (Avid BB7-heavy, liable to the odd bit of rub, front squeals sometimes, and while the stopping, esp in the wet, is pretty damn good, not that much better than well set up cantis) I can imagine the discs getting really fouled up in mud, where the cantis had more clearance



Have a look at Leonard Zinns articles in Velonews-the next big things on road bikes, shock forks, and discs.

Why not hub gears (and brakes) too?


Not quite answering your q up til now, Red-so I would suggest discs are much better than dps-but the weight, cost of pads, is a big put off. I have one road bike with discs, and 3 with DPs

redddraggon

meagain wrote:

Well, they ARE, obviously. Why else do you think 180 mph m'cycles use 'em?

Well as I'm unlikely to get to 180mph that isn't an issue. I seem to be able to be sprinting on the flat at 30mph, and seem to be able to stop within 20 or 30feet, if I try stopping any faster I'll go over the bars.

To me the limitations of braking on a road bike seem to be tyres rather than the brakes themselves, so what good are better stoppers going to do?

ddraver

You have a point there red but I'd add that to lock up wheels even on beautifully set up calipers i have to haul on the levers wheras on my MTB i can lock up the rear wheel with one finger...and even then with no effort at all

The better power, Incresed modulation, lack of problems with wheel truing or dirty cables and ease of use whilst on the bike mean they are a better option than calipers

trashcanman

Hydraulic discs are great on a mountain bike, what worries me about good quality discs on a road bike is the consequences when some riders in a group are capable of slowing down or stopping a lot quicker than others, resulting in a nasty pile up.

ddraver

tbh I'm not sure that would be any more or less of a problem than it is already - plus roadies would come with smaller disks so one would imagine the actual stopping distance may not differ much - as red said the tyre/road conditions would effect how quickly one stopped rather than weather or not the back wheel locked up

Ken Night

I confess to being inspired by this


How can you resist?

giant_man

I don't see the need on a bicycle personally.

redddraggon

giant mancp wrote:

I don't see the need on a bicycle personally.

I can understand the need for them on MTBs maybe, but not road bikes.

meagain

The original question was whether or not offered superior stopping power (YES) not whether or not necessary/a good thing (debateable)! That would be a different Poll!

That 'crosser with discs is one of the best looking bikes I've ever seen.

John C.

Like the look of the cross bike and as I wrecked a pair of 150 pound wheels in a season (rims wore out) it seams a good idea IF they can keep the weight down and there is no drag.

meanwhile

redddraggon wrote:

Well as I'm unlikely to get to 180mph that isn't an issue. I seem to be able to be sprinting on the flat at 30mph, and seem to be able to stop within 20 or 30metres, if I try stopping any faster I'll go over the bars.

To me the limitations of braking on a road bike seem to be tyres rather than the brakes themselves, so what good are better stoppers going to do?

According to rec road bikes faq, you should be able to get 0.6g out of your brakes. Your speed above 12m/s, so s = (v*v)/2a => (12*12)/(2*0.6*10) => 12 - ie you should be stopping half to a third of the distance you are doing, assuming that 30m doesn't include reaction distance - that it's just distance to stop from brakes on.

You're probably under-using the front brake - 0.5 or the total 0.6g of stopping power is there. A typical road bike can take 0.68g of stopping before flipping, on the level.

http://draco.acs.uci.edu/rbfaq/FAQ/9.17.html
http://www.sheldonbrown.com/brakturn.html

Using the front brake more aggressively while pushing with your arms should stop you much faster. From the second link: "Jobst Brandt has a quite plausible theory that the typical "over-the-bars" crash is caused, not so much by braking too hard, but by braking hard without using the rider's arms to brace against the deceleration: The bike stops, the rider keeps going until the rider's thighs bump into the handlebars, and the bike, which is no longer supporting the weight of the rider, flips."

Anyway, you won't stop faster with disk brakes in the circumstances above. They will cut in faster in the wet, to some extent.

Shimnolo

Never read so much flannel from the rim brake apologists. Why won't you just accept what everyone else knows ...... disc brakes are the future as they work soooo much better.

I'm betting that in ten years time half the Tour de France teams are running very, very lightweight discs and easily outbraking the others into each bend.

And while we're on the subject, cable discs are pretty good too. The new Tektro IOX is a prime example of a superb, affordable system that is simple to maintain.

Come on folks, embrace progress.

redddraggon

meanwhile wrote:

redddraggon wrote:

Well as I'm unlikely to get to 180mph that isn't an issue. I seem to be able to be sprinting on the flat at 30mph, and seem to be able to stop within 20 or 30metres, if I try stopping any faster I'll go over the bars.

To me the limitations of braking on a road bike seem to be tyres rather than the brakes themselves, so what good are better stoppers going to do?

According to rec road bikes faq, you should be able to get 0.6g out of your brakes. Your speed above 12m/s, so s = (v*v)/2a => (12*12)/(2*0.6*10) => 12 - ie you should be stopping half to a third of the distance you are doing, assuming that 30m doesn't include reaction distance - that it's just distance to stop from brakes on.

You're probably under-using the front brake - 0.5 or the total 0.6g of stopping power is there. A typical road bike can take 0.68g of stopping before flipping, on the level.

http://draco.acs.uci.edu/rbfaq/FAQ/9.17.html
http://www.sheldonbrown.com/brakturn.html

Using the front brake more aggressively while pushing with your arms should stop you much faster. From the second link: "Jobst Brandt has a quite plausible theory that the typical "over-the-bars" crash is caused, not so much by braking too hard, but by braking hard without using the rider's arms to brace against the deceleration: The bike stops, the rider keeps going until the rider's thighs bump into the handlebars, and the bike, which is no longer supporting the weight of the rider, flips."

Anyway, you won't stop faster with disk brakes in the circumstances above. They will cut in faster in the wet, to some extent.

I don't know why you've gone into the mechanics, I was only giving rough estimations so you can't really draw anything out of the values I gave in the quotation.

Ken Night

meanwhile wrote:

Anyway, you won't stop faster with disk brakes in the circumstances above. They will cut in faster in the wet, to some extent.

I took the bike out today to have a play with the brakes-you're right. When dry the limitation is the road surface and the amount of rubber on it. Modulation is so much better though.

Braking into a corner is better with discs.

When wet, the disc braking is so much better than DP/rim brakes

Shimnolo wrote:

...... disc brakes are the future as they work soooo much better.

I'm betting that in ten years time half the Tour de France teams are running very, very lightweight discs and easily outbraking the others into each bend.

And while we're on the subject, cable discs are pretty good too. The new Tektro IOX is a prime example of a superb, affordable system that is simple to maintain.

Come on folks, embrace progress.

You're probably right-back to the original question-braking is better with discs


Dave (meagain)-you're right about that Everti bike-it's spot on. I can't resist a crow-my Carpe Diem is the bike I reach for when I want a lot of fun-sublime ride made better by discs and the satisfaction of my Shimergo combo

JohnC-I'm using Open Pros on XT hubs-without any trick stuff on the bike, it's about 19lbs with knobbly tyres fitted

Smokin Joe

I'd love disc brakes. The mere fact that the life of my rims would be indefinate swings it for me, speaking as the owner of a pair of two year old Ventos on my winter hack that look like they have been scored with a chisel.

ddraver

I reckon It ll take one of the groupset manufatures to combine with a big bike firm to put one top of the range disk model out and the conversion (at pro level) will take maybe two years

The major factor halting roadie disk production is that as yet there are no specificdisk forks/hubs or brakes for the road market - they are allretro fitted MTB

I'd be really interested to see a dura ace disk brake for example maybe 140 front 120 rear witha small lightweight, aerodynamic caliper...but it will require someone to make a frame and fork set with disk mounts!!

meagain

Has not the UCI (dumbo stiflers of innovation as thay have alway been) "banned" discs for road racing?

ddraver

Dunno - would nt surprise me!!

Ken Night

ddraver wrote:

I reckon It ll take one of the groupset manufatures to combine with a big bike firm to put one top of the range disk model out and the conversion (at pro level) will take maybe two years

http://www.trekbikes.com/us/en/bikes/20 ... /portland/
http://www.retrobike.co.uk/forum/viewtopic.php?t=20658

ddraver wrote:

The major factor halting roadie disk production is that as yet there are no specificdisk forks/hubs or brakes for the road market - they are allretro fitted MTB

I'd be really interested to see a dura ace disk brake for example maybe 140 front 120 rear witha small lightweight, aerodynamic caliper...but it will require someone to make a frame and fork set with disk mounts!!

Forks-available in the US
Carbon
Winwood-Dualist
Bontager Satellite
and a couple of others

Steel
Salsa and a few others

Forks-available in the UK
Carbon
I spoke to Bontrager-a very awkward highly opinionated and unhelpful national sales manager it must be said, no intention to import for a couple of years

Kinesis are about to launch two sets-one of the prototypes can be seen on my bike. The other one looks like the Bonty ones on the American bikes above

Steel
Kinesis have done one for years, as have a couple of others, who I can't remember


Brakes-road specific -for use with ergos/STIs
Tektro
Avid
http://www.sram.com/en/avid/mechanicald ... es/bb7.php
Shimano do one (BR550?) Difficult to find on their website

Hubs
I used XT as my bike has 132.5 dropouts, you can get DT Swiss in 130 disc tabbed (Campag freehub too)but at around £280, my budget wouldn't stretch to those. If it had, I'd have been able to have Campag 10 on all my bikes

Frame
I bought my cross frame 4 years ago-with disc tabs and disc specific forks (the latter weren't good) Plenty of crossers have disc tabs.
It can't be long before you'll see a pure road bike with them too-anticipating the future


HTH

ddraver

None of them are full on road bikes though - I'm talking about Alberto Contador riding a top of the range Trek madone (is that the one?) with disks next year not someone riding one to the shops and back or a CX bike or even a sportive bike (which I think i said clearly enough really)

(disclamer - any other pro is included alongside Alberto - he was just on the front of the home page and so was kinda in my head at the time)

Ken Night

ddraver wrote:

None of them are full on road bikes though - I'm talking about Alberto Contador riding a top of the range Trek madone (is that the one?) with disks next year not someone riding one to the shops and back or a CX bike or even a sportive bike (which I think i said clearly enough really)

You're right-my BB7s are too heavy to build onto a road bike.

I was illustrating the small amount of disc orientated stuff that is available-and that it's on the increase, hence a pointer for the future

I should also point out the Kinesis forks weigh in at 550g which is another disincentive to fit them to a road bike

I feel the advances in materials making fantastically light bikes a reality, tends towards an obsession blinding one to the possibilities of other ways of including advantageous technology-such as hub gears and disc brakes

FWIW I have a 1990s steel Colnago fitted with Record, which weighs more than the disc braked crosser.

As I've mentioned before, my disc braked crosser is an indulgence-I've done it because I can and I enjoy it.

One of the three caliper fitted bikes has a single pivot rear, which is plenty

Of the remaining two, the 1990s Record dual pivot rear isn't half as good as the 2004 Centaur DP on the last bike

in sport..........

simbil1

I'd only want a disc on the front - completely pointless on the rear. The thing that I like about a disc is the modulation that can make the difference between locking or not when braking heavily.

I reckon a very road specific system is in order that matches an optimised wheel - there must be a few gains they can make to the rim once the braking surface doesn't need to be there.
The disc could be maybe be very small and light - like 60mm and integrating the cables into the fork to a minimal caliper on a single point mount might make the weight penalty neglible.
I suspect that an optimised road specific system might loose some of the modulation though and if it is UCI banned, the manufacturers ain't going to make a new system anyway.

Monty Dog

Surprisingly, the majority of the ones convinced are the ones that have actually tried it and typically the majority of naysayer haven't! I've had a disc'd up crosser for a few years - the big difference is the power, the modulation and the fact that you can brake later and mid-corner which would upset a rim brake no end. With it being very easy to get under the UCI limit for road bikes, I expect it won't be too soon before we start seeing discs in the road - particularly on some steep alpine descents in the wet. Interestingly Shimano have had a road disc hub available for the last few years. I believe the UCI ban on disc brakes was only for sanctioned 'cross events.

3leggeddog

My ideal winter trainer for here in the lakes would have a front disc brake. Careering dwn newlands in dirty wet conditons would be that bit more secure. Also in the summer months I have suffered high temp blow outs descending wrynose.

Funnily, the descents around here are faster in the winter when there are no leaves on the heges and the visibility so much better.

When disc forks become readily available/affordable, I'll start using them

JamesB

Superior stopping power YES

MTBs off road definitely unless you 1. wish to have trouble stopping with wet rims (all to common on MTBs) and 2 wish to grind thro` rims; after a year MTB I converted to discs and have`nt regretted it.

As for road bikes, I was shocked by lack of stopping power on my road bike with calipers, but have got use to it. However I also ride a hybrid Ti MTB conversion with 1.23" skicks and use discs (initially Avid BB5 now Hope Minis, similar ON road braking performance) and find that they have huge advantages in that they work reliably no matter what the conditions (eg this is my winter bike / poor conditions bike) AND I get about 1000miles out of a set of pads; on LEJOG last year the discs were a definite plus point as on wet lanes / wet conditions no worries about having to dry out brake contact areas first --- and you also don`t get such mucky rims from the discs!

meanwhile

redddraggon wrote:

meanwhile wrote:

redddraggon wrote:

Well as I'm unlikely to get to 180mph that isn't an issue. I seem to be able to be sprinting on the flat at 30mph, and seem to be able to stop within 20 or 30metres, if I try stopping any faster I'll go over the bars.

To me the limitations of braking on a road bike seem to be tyres rather than the brakes themselves, so what good are better stoppers going to do?

According to rec road bikes faq, you should be able to get 0.6g out of your brakes. Your speed above 12m/s, so s = (v*v)/2a => (12*12)/(2*0.6*10) => 12 - ie you should be stopping half to a third of the distance you are doing, assuming that 30m doesn't include reaction distance - that it's just distance to stop from brakes on.

.

I don't know why you've gone into the mechanics, I was only giving rough estimations so you can't really draw anything out of the values I gave in the quotation.

Actually, I can. Unless "20 or 30 metres" means "really 12" then your braking technique isn't getting the most out of the bike. The same is probably true of most people who haven't raced off road or done messenger work. It's nothing to be embarrassed about and can probably be fixed with minimal effort if you read the Sheldon Brown link and doodle about it in a quiet spot. Skilled aggressive use of the front brake is one of the techniques most likely to save a rider's life, and probably the easiest to learn.

If it makes you feel better, you're probably VASTLY faster than me at everything but braking right now. And, ok, probably turning, because deliberate countersteer is a rarely learned skill too, and someone was nice enough to teach me. But my cardiovascular fitness is way down from what was, and is going to months to return when I get the new bike, so you'd utterly cream me in any kind of race right now.

meanwhile

Ken Night wrote:

meanwhile wrote:

Anyway, you won't stop faster with disk brakes in the circumstances above. They will cut in faster in the wet, to some extent.

I took the bike out today to have a play with the brakes-you're right. When dry the limitation is the road surface and the amount of rubber on it. Modulation is so much better though

Braking into a corner is better with discs.

That's really interesting. Possibly the rim is distorting under the cornering load, reducing rim brake efficiency? Which wouldn't be a factor with discs.

When wet, the disc braking is so much better than DP/rim brakes

I have heard that if the discs themselves get wet - eg by immersion - then you're totally screwed. Rare circumstance, but something to watch for if your bike ends up in a deep puddle.

Another gotcha that I've heard is that disc wheels should have strong spokes and lots of them; I can't say how true this is. The point was made in some forum discussion about the Portland Trek, which has discs and quite light weight wheels.

As someone said, people with discs seem happy with them, and the objectors to be disc-less. Users of Avids seem especially happy, I've noticed.

While I'm agreeing with people, the comment about getting most of the possible benefit from putting a disc on the front makes obvious sense too. Assuming the rider has proper braking technique, and that he's on the road (rear brakes are more useful when the ground is slippery). Front disc is what I'm planning for my new bike.

I agree that discs will be big on road bikes in the future. The other tech I think we'll see a lot of are internal gear hubs - the Rolhoff is as efficient as a freshly cleaned derailer, lasts forever, and doesn't need cleaning every week on a commuter bike. All that has to come down is the price.

meesterbond

meanwhile wrote:

I have heard that if the discs themselves get wet - eg by immersion - then you're totally screwed. Rare circumstance, but something to watch for if your bike ends up in a deep puddle.

I can only really comment about MTB brakes (Hope and Hayes mainly), but they do still work, even when really, really wet... there may be a slight degradation in stopping power if the pads are soaked, but I definitely still have wet disks than wet rims on a mountain bike..

Unfortunately they (particularly the Hopes in my experience) wail like a banshee if any moisture gets close which is really annoying.

There was an article in one of the mags last month (actually may have been this month's Pro Cycling) on where the future of road bikes would be... they got opinions from the techie guys at Trek, Ibis and others and other than further integration (bars, stems, headsets, BBs etc designed into the frame) disc brakes and suspension were the future...

Off road though, the excessive power of discs has meant a lot of trails get really torn up by people braking too late and hard into a corner... very annoying..