This disc brake thing.

[bianchi1]

Or, rather than being a fact, it could be a subjective opinion....

No.... it's definitely a fact they are ugly.

( I await the Campagnolo version which undoubtedly will be beautiful but not work quite as well...and need a £100 tool to adjust)

 

[jowwy]

Defo opinion only...........discs are no uglier than calipers and do a better job - thats fact

 

[HF2300]

Modulation is a buzz-word that's easily overused but it does merit some explanation. I would define it as fine and predictable control of the brakes...

Futher, modulation is good when the movement is smooth. Gritty cables don't offer good modulation but delivers increasing and decreasing stopping force in jerky curves. Drum brakes, be it on a car or bicycle, don't modulate well. They have a self-servo action that catches you with surprise lock-up.

... disc and rim brakes will provide exactly the same stopping force ... In the dry, the two are exactly the same and can't cause a peloton pile-up.

On modulation, isn't the fact that some older V-brake and non-Vbrake systems weren't linear a bit of a red herring unless the peloton are still using them?

Isn't the reason car drum brakes have that action because they are designed so that in operation, the shoe tends to wrap to the drum? Rim brakes don't have that action.

Surely braking force is dependent on friction material, surface area, leverage, actuation etc. etc. and thus will be very variable from design to design and between rim brakes and discs? Or are you thinking of other limiting factors (tyre's grip on the road, rotational moment around the front hub, how heavy the guy who might be thrown over the bars is, etc.)?

 

[Yellow Saddle]

On modulation, isn't the fact that some older V-brake and non-Vbrake systems weren't linear a bit of a red herring unless the peloton are still using them?

Yes, but I had to define modulation first so that I don't get bitten on the arse by the but...but...but crowd. Hence the mention. They are exactly what modulation is NOT.

Isn't the reason car drum brakes have that action because they are designed so that in operation, the shoe tends to wrap to the drum? Rim brakes don't have that action.

It isn't the design, it is a by-product of the design and an undesirable one. All brakes nowadays are power-assisted and don't require self-actuation.

Surely braking force is dependent on friction material YES, surface area, NO leverage, actuation NO, but leverage yes etc. etc. and thus will be very variable from design to design and between rim brakes and discs? Or are you thinking of other limiting factors (tyre's grip on the road, rotational moment around the front hub, how heavy the guy who might be thrown over the bars is, etc.)?

Rotational movement at end-over limits is around the road contact point, not hub. But I'm not sure what you want me to be thinking of?

 

[Dogtrousers]

Looks aren't everything. Otherwise we'd all be riding with those lovely looking Campagnolo Delta brakes which look absolutely beautiful but which reportedly were not terribly good brakes ... or at least were very hard to set up.

 

[PhilDawson8270]

Rotational movement at end-over limits is around the road contact point, not hub. But I'm not sure what you want me to be thinking of?

Surface area can affect braking performance (Don't know how to quote the post you quoted).

Though probably not in the way @HF2300 is getting at. But if you're heating the material beyond optimum performance limits, an increase in surface area to dissipate heat under braking will improve performance. Similarly, if you're not getting enough heat in to get them to optimum temperatures, a reduction in surface area will improve the effective of the system.

 

[Yellow Saddle]

Surface area can affect braking performance (Don't know how to quote the post you quoted).

Though probably not in the way @HF2300 is getting at. But if you're heating the material beyond optimum performance limits, an increase in surface area to dissipate heat under braking will improve performance. Similarly, if you're not getting enough heat in to get them to optimum temperatures, a reduction in surface area will improve the effective of the system.

Yes, but I wanted to keep it simple and just stick with COF. But now that we're on it.
Surface area also helps if the wheel is nearing the slip angle and encounters a small area with reduced adhesion - a few grains of sand, a drop of oil, whatever - then the larger footprint will see this as a smaller portion of its overall surface area and be more forgiving. Also, at the rubber's sheer limit but under the adhesion limit, a larger surface area will be subject to less shear and then either grip better or last longer.

Most of us dont' ride that way though.

 

[oldroadman]

Looks aren't everything. Otherwise we'd all be riding with those lovely looking Campagnolo Delta brakes which look absolutely beautiful but which reportedly were not terribly good brakes ... or at least were very hard to set up.

Not quite, they were completely useless...the only reason for using them was if you got paid to do it, and there is a point at which the money/danger of injury equation tends towards looking after the injury risk.- or you spent the money on medical bills!

 

[Yellow Saddle]

Surface area can affect braking performance (Don't know how to quote the post you quoted).

Though probably not in the way @HF2300 is getting at. But if you're heating the material beyond optimum performance limits, an increase in surface area to dissipate heat under braking will improve performance. Similarly, if you're not getting enough heat in to get them to optimum temperatures, a reduction in surface area will improve the effective of the system.

Sorry, I just read your post again. I assumed you were talking about larger surface area on tyres and answered that non-question.

Yes, bigger surface area in braking is better if the friction material doesn't need higher temperatures to operate at. For instance, sintered pads work primarily with adherent friction and require high heat for the COF to increase enough to make them operate with less force and over shorter stopping distances. If you have a brake disc of 140m and increase it to 201mm, then you usually have to change the friction material to a resin pad that works primarily with abrasive friction.

 

[T.M.H.N.E.T]

Oh look disc brakes in a group and no helicopters fell from the sky, no kittens drowned and no movistar riders in sight.


View: https://youtu.be/4z4LbKEXtck

 

[albion]

I do wonder if a mixed rake apparatus peleton might lead to more accidents.

 

[HF2300]

Yes, but I had to define modulation first so that I don't get bitten on the arse by the but...but...but crowd. Hence the mention. They are exactly what modulation is NOT.

Ah. So your thrust was really

A good feel could still provide poor modulation, I'd say..

? OK, with you.

It isn't the design, it is a by-product of the design and an undesirable one. All brakes nowadays are power-assisted and don't require self-actuation.

I'm not sure that's correct. Though self-energising results inevitably from the forces acting on the leading shoe, it's taken advantage of in brake design, rather than being designed out as not desirable (your second sentence even implies the necessity in pre-vacuum servo brake systems). Anyway, it's really irrelevant and perhaps a nitpick on my part, since in context we're talking rim vs disc brakes.

Rotational movement at end-over limits is around the road contact point, not hub

Yes, true, and I wasn't thinking - though it's even more complex, as the road contact point / tyre contact patch in an endo continually moves forwards rather than being fixed.

But I'm not sure what you want me to be thinking of?

I'm not sure what you're asking?! You commented that rim and disc stopping force was exactly the same in clean dry conditions. If you were considering just the brake system, that can't be the case; so I assumed you meant that the limit of stopping was (not doing) an endo, and so was trying to clarify whether you were discussing the complete system (bike, rider, road, grip, etc.) rather than just the brakes.

Surface area can affect braking performance. Though probably not in the way @HF2300 is getting at.

What way did you think I was getting at?

 

[ufkacbln]

Having seen the injuries supposedly inflicted by disc brakes (a bit like being gouged by a blunt serrated edge knife) I think they should be banned until a form of shrouding is fitted to the disc/caliper.

This has been disallowed in similar circumstances.

A protective chain guard for the chain rings has been excluded as a "non structural fairing" that redues drag

I suspect that for the same reason a disc guard would not be allowed

 

[T.M.H.N.E.T]

Having seen the injuries supposedly inflicted by disc brakes (a bit like being gouged by a blunt serrated edge knife) I think they should be banned until a form of shrouding is fitted to the disc/caliper.

 

[PhilDawson8270]

What way did you think I was getting at?

Bigger brakes = more friction = more stopping power Is where I assume your thinking was.