Disc Brake Road Bikes

[TopFuel]

But, would you want to be able to lock up your brakes more easily? Do you want to be able to easily drag your rear wheel or go over your front? Ill say that they would have to increase the performance of road tires a lot before it is really needed to get disk brakes.

 

My point is not the locking up of the wheels, but rather the ease of effort to get there. Basically that my new brakes allow for 1-finger braking, whilst absolute braking power may not be all that much greater. In essence, the disc system is providing more mechanical advantage allowing less input to translate to "greater power".

 

EDIT: And this is what I think most people mean when they say disc brakes brake "harder/better"

Edited July 9, 2013 by TopFuel

[Tumbleweed]

The locking up argument is for those who don't know how to ride a bike. What brake does a Tour rider use more on a descent? The front or the rear? The front. How many of them do you see going OTB unless they hit something?

 

The force it requires to lock up the wheel is irrelevant, and saying that rim brakes and discs require the same amount of force is just as irrelevant. Braking systems are not just about force and not just about power, but a combination of the two. A hydraulic system is far superior at converting the force input into the power in the system into output force.

Edited July 9, 2013 by Tumbleweed

[TopFuel]

Which is why I would advocate their use. Less input means that riders can have more control of the bike, for obvious reasons.

[NickD]

In a nutshell:

1.0 Rim brakes have significant pure mechanical advantage over discs. Try and stop a spinning wheel by the tyre as opposed to the hub.

2.0 The mechanical advantage of hydraulic brakes is gained by the size of the piston at relative to the piston/s at the caliper. The pressure in the system is the same when the lever is depressed, therefore the gain is directly in proportion to the relative sizes of the pistons.

3.0 The biggest advantage of disc brakes would likely be that the rims are not heated up by prolonged braking. Remember Joseba Beloki's fall when the rim overheated and the tubby rolled off the rim.

4.0 Disc brakes would require cross lacing on both the front and the brear wheels.

[Johan Bornman]

JB, won't it help with power and modulation? Point being, yes I could lock up my V-brakes before, but it required much more user input than with my current disc brakes (XT), which only require a finger. So they may not increase power, but improve modulation throughout the lever's stroke?

 

Depends what you mean by modulation. I see modulation as two issues:

 

1)The smoothness of the mechanism and therefore the predictability of X-amount of finger force.

2) The way the freeplay is taken up (preferably quickly) and thereafter how the increased finger pressure translates to increased stopping force.

 

You may want to include effort (finger pull) in the modulation equation.

 

On a new cable brake, modulation is excellent. On worn cables, it is poor.

 

The amount of effort required to stop the bike can be increased or reduced at the designer's will. By simply modifying the lever, you could exert more or less force and indeed, some fancy V-brakes have a variable lever that takes up freeplay quickly but then reduces leverage to improve modulation.

[Johan Bornman]

But, would you want to be able to lock up your brakes more easily? Do you want to be able to easily drag your rear wheel or go over your front? Ill say that they would have to increase the performance of road tires a lot before it is really needed to get disk brakes.

 

I'll say this again: we already have the maximum traction (in other words, tyre performance in braking) that the bike design can handle. It is no use making tyres better in the front since they already cannot skid. It is no use making them better at the back since at maximum deceleration only the front wheel makes contact. Tyre design is already even better than what we can utilise,

[Tumbleweed]

Modulating a brake has got nothing to do with smoothness or play; it has to do with the system's ability to be regulated and tweaked in an instant (or many micro-instants - think cadence-style braking) to utilise a system to its fullest efficiency. This is where, I believe, disc brakes win. Due to the hydraulics, the force at the output side requires littler effort, is more responsive, and is more manageable from shorter, sharper force inputs from the lever.

 

My other issue is with shudder. We've all experienced it with discs for one reason or another, but decent servicing - much like if you've had a pair of Avids, and loved 'em - and they'll serve you well. Shudder is part and parcel of running rim brakes. Got given a lovely set of XTR V-brakes, which I put on an SS thingie I did to a 'Dale. Simple bike, but the flex in the arms of the callipers could be disconcerting.

Edited July 9, 2013 by Tumbleweed

[Tumbleweed]

 

Snip, snip...

 

It is no use making tyres better in the front since they already cannot skid.

 

Snip, snip...

 

 

Why would you want or design a tyre that could skid?

[Starvin' Marvin]

Hmmmm. Last time I looked all heavy trucks still have drum brakes.

 

You still haven't explained efficiency.

 

Remember, cables don't stretch and there is no significant loss of force applied.

 

No cables snapping - is that really an issue?

 

Adjustment - is that an issue?

 

I really think we're looking at disc brakes for all the wrong reasons. I have already acknowledged conditions where they do makes sense but I just see the same old fallacious arguments over and over again.

 

Hi JB Mercedes Benz Actros trucks have been using disc brakes since 1999/2000.

Edited July 21, 2013 by Starvin' Marvin

[Dustbug]

As I understood it - stand open for correction is UCI will not approve discs on road races for a couple of years as most modern frames cannot take the stresses of discs and also the tests have shown the disc brake bikes have a distinct advantage in that they can brake later faster and harder into the corners etc enabling a faster pull off resulting in a average speed gain advantage which is fairly large. But UCI are more concerned with safety as the combination of the two types of brakes breaking at different speeds in a large group cornering could and will result in some serious accidents.

[Johan Bornman]

As I understood it - stand open for correction is UCI will not approve discs on road races for a couple of years as most modern frames cannot take the stresses of discs and also the tests have shown the disc brake bikes have a distinct advantage in that they can brake later faster and harder into the corners etc enabling a faster pull off resulting in a average speed gain advantage which is fairly large. But UCI are more concerned with safety as the combination of the two types of brakes breaking at different speeds in a large group cornering could and will result in some serious accidents.

 

Where are these tests? I don't believe that any test that shows that disc brakes on a roadbike can give the advantages stated above, exists. Such a test would defy physics. I say it again: the limiting factor in stopping faster is not the force applied at the brake, but the high centre of gravity that causes a fast-braking cyclist to go over the handlebars. We have to improve that before we can brake faster.

[chris_w_65]

Where are these tests? I don't believe that any test that shows that disc brakes on a roadbike can give the advantages stated above, exists. Such a test would defy physics. I say it again: the limiting factor in stopping faster is not the force applied at the brake, but the high centre of gravity that causes a fast-braking cyclist to go over the handlebars. We have to improve that before we can brake faster.

 

Or in the case of rear brakes the lack of tyre grip that causes the wheel to lock which can already be achieved by grabbing a handful of the rear brake lever

[SwissVan]

Unless you spend all day descending mount Everest or riding in wet muddy conditions ALL of the time like the euro cyclo cross riders this is a *** idea....

 

Are the road bike manufacturers running out of ideas to market their products?

 

What's next, Thru axle instead of Quick release?

[Red Zone]

I see the main advantage on full carbon rims as there will be less brake induced (heat) failure. Second benefit is better performance in the wet. I don't really see any other tangible benefit. You all know how you need to hang your weight back when slamming on your rim brakes to stop your back end sliding out and doing an endo, disks are not going to change this so there is not point from a stopping point of view.

 

Disks may be less aero than rim brakes, weigh more, more finicky, probably more weight on the fork and make a road bike look silly, give me rim brakes for sure

[SwissVan]

 

 

Disks may be less aero than rim brakes, weigh more, more finicky, probably more weight on the fork and make a road bike look silly, give me rim brakes for sure

 

 

Ditto that

[gummibear]

Unless you spend all day descending mount Everest or riding in wet muddy conditions ALL of the time like the euro cyclo cross riders this is a *** idea....

 

Are the road bike manufacturers running out of ideas to market their products?

 

What's next, Thru axle instead of Quick release?

 

I saw a road bike yesterday on the net with a thru axle.Will see if i can find it again.