Nitpick: cables don't "stretch", per se (try to stretch a brake cable outside of the housing)...but, more accurately, the housings (and interfaces) distort and/or compress. One can go a LONG way towards minimizing this by using compressionless housings (I've had good luck lately with Jagwire Link housings) and careful routing.

Other than that, the graphic is pretty good IMO.

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http://bikeblather.blogspot.com/

Serious question - how comfortable do you feel in wet conditions and carbon brake surface? I like the P5's hydraulic brakes but still feel iffy when I get to ride in hills (I live in FL). I know alot of it is experie and practice, which is hard for me to get but curious how I'd ultimately feel if I lived in a place where braking was needed.

"Carbon brake surface"...yeah, don't do that. That's one of the equipment decisions I mentioned that should be reconsidered if you don't have good braking. Seriously.

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http://bikeblather.blogspot.com/

It doesn't take very much to overheat many brakes' fluid. Just ride the brake a little longer than normal. Nothing that would kill an aluminum rim or destroy a set of pads. You might overheat your aluminum rim to the point that your tire blows, or glaze your pads, or melt a lower quality carbon rim with the same effort, but you are not going to burn through an aluminum rim just like that. I didn't say that rim brakes were immune to heat related issues, just that with discs you are trading one set of potential (note: "potential") problems with another set of potential problems...

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"I'm thinking of a number between 1 and 10, and I don't know why!"

While I'm not a brake engineer, I have tested literally hundreds of different brakes (mostly mtb, still relatively few road discs out there). The amount of "modulation" on discs runs a wider gamut than on rim brakes. I have a set of sample mtb disc brakes that have about as close to zero modulation as possible. And these are mechanical, not hydraulic, so even with a bit of housing compression they're still more solid feeling than any hydraulic I've tried. They feel rock solid at the lever, and lock up almost instantly. I can easily skid with just my pinky. I've never come across a hydraulic brake that grabbed as hard as these do. But these also have pads about the size of dime, and would fade almost instantly. Hard to keep from locking them up at the start of a descent, and no brakes at all halfway down...

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"I'm thinking of a number between 1 and 10, and I don't know why!"

That diagram simply shows mechanical advantage ratio and has nothing to do with modulation.
Modulation is the feedback at the lever and lack of friction in the system allowing very fine adjustments to power applied to the pads unhindered by stiction.

This is totally separate from amount of lever movement to move the pads.

So is modulation measurable? In modern disc setups, is modulation improved (over various rim disk systems) by the disc pad and rotor itself or by the hydraulic controls? Do you agree that modulation varies from one disc brake setup to another? Why or how?

Having worked in a bike shop that does exclusively high end road, road discs are definitely not being asked for from the customers. We usually bring in a few road disc bike because we have to, and we may sell one throughout the season. The rest we have to put on clearout and sell at our cost just to move them. I maybe get 2-3 customers a year ask about discs, thats it. Customers aren't asking for them. Companies are pushing them.

Discs also create huge problems for bike manufacturers as they have many hurdles to go through to design an effective clamping mechanism. Want thru-axles? To get proper chainline you need longer chainstays, which will make slower handling. Use QR's? The disc may not be properly aligned. That is why many companies are forced into making their own standards, that simply create headaches for the consumers.


As far as safety goes, I've seen a few nasty cuts from people on mountain bikes hitting rotors. The two most recent crashes I can recall had 30+ stitches each. But for however many crashes I've seen/experienced on mountain bikes, it certainly is exceptionally rare for the rotor to cause any kind of cut.

I did a charity ride today and maybe it was my heightened awareness but I saw waayy more disc road bikes than 1. Ive seen in the past and 2. I'd expect to see (especially being in FL). Guessing 2% of the bikes. Still not a lot but more than one a season, which is what I sensed was the rate. Noticed demographic was generally slightly older riders who weren't fast but weren't slow either.

+1,
As i hear the same from my shop (both from a younger and an older mechanic).
To say the industry is not aggressively marketing road discs to consumers, is like admitting to not understanding business.

I ride both, and prefer the calipers on my race bikes.
I really hate to deal with a heavy stiff fork that still flexes and shortens it's trail under disc brake action...necessitating steering adjustments between entering and executing high speed turns.

Biggest drawback of disk brakes, IMO.

One shop that deals exclusively in high end road.....yep, that is clearly indicative of the entire market.

Consumers are absolutely looking for road discs. They may not be shopping in the store where you worked, but they are looking for them.

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Chicago Cubs - 2016 WORLD SERIES Champions!!!!

"If ever the time should come, when vain and aspiring men shall possess the highest seats in government, our country will stand in need of its experienced patriots to prevent its ruin." - Samuel Adams

A fair demand for mid and lower range road bikes with discs in the UK.

It rains here. People ride on less than perfect surfaces. This promotes the use of larger tyres and mudguards. Rims can wear quickly too in these conditions. This makes discs attractive.

My next winter/commuter bike will have discs.

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Developing aero, fit and other fun stuff at Red is Faster

Modulation gains in disc systems over conventional rim brakes come from multiple reasons.

Obviously the big one is hydraulics lack of cable friction and housing flex. So the same can be had from hydraulic rim brakes in this regard.

Another major one is the very much higher clamping forces of discs so that pads are made from very solid material, so more hand pressure means more braking, unlike rubber rim pads that compress and loose a lot of the hand force to merely squishing. This is why even cable discs can be very good compared to same level rim brake.

Rim brakes have long levers to reach around the tyre to the rim, flexy no matter what you do. Disc brakes have a very compact setup with no tyre to reach around, so very little flex.

Disc pads can be run extremely close compared to a rim brake, so designers are free to make use of what would have been wasted lever movement on a rim brake which must run with reasonable rim clearance.
This is not a modulation thing, but it is the reason that disc brakes can be made very powerful as the full lever movement can be used for braking and not waste the first third or half to rim clearance.

Because the disc setup does not squish pads and flex long arms, there is no loss of power in the extreme high power end of travel, so that more of the lever movement can be devoted to more common partial braking inputs, whereas a rim brake needs to keep a fair portion of the lever travel available to allow for flex under full power braking.

Differing disc brake feel can come from many sources also.
Shimano XT trail brakes can feel a bit on/off to those that are not used to them, they actually modulate very well, but the short lever movement made possible by the varying pivot point of the lever (servo wave) brings the pads in contact very quickly and then the lever enters into a very high power mode that catches some users moving from lesser powerful brakes to these brakes.
Organic pads also tend to have very high initial bite compared to metallic or semi metallic pads, so pads can play a large role in the feel of the brake, just like rim brakes.
Some pads have high initial bite but don't gain power linearly at high forces, so different lever feel, but the modulation is still there.

Many people (most) mix and match the meaning of modulation with lever ratios, so the conversation gets very confusing when you have no idea if the reviewer is talking lever ratios or actual modulation.
Poor modulation is just a shit brake to use at the limit, no matter the lever pull.
Good modulation is a great brake to use at the limit, no matter the lever pull.
It's just some great modulating brakes with short lever pull take a while for you to reset your brain to the extreme power available.
But a poor modulating brake is never good near the limit as fine control is masked by flex and friction losses.

Notice that this conversation has nothing whatsoever to do with being able to lock the wheel, just simply the ability for fine control at the limit where it is required most.
You know the times, over cooked it coming into the corner (or simply out braked your mates to get position or that dickhead dived right into your line forcing you to change to a slower line.) and need to keep braking at the limit whilst negotiating the corner on the limit, this is where modulation shines.

The shortening of the wheelbase due to rearward fork flex under braking actually increases trail as the wheel contact point is moved further behind the steering axis.
Disc braked and rim braked applies the same reward force to the fork during braking.
It's due to the wheel trying to drag the fork backwards along with it.
Nothing whatsoever to do with the braking system involved.

Back to unknowledgable keyboard trolling for you.

Interesting, thanks.

Whether or not they're asking for them, I do see people being forced to discs as they go to buy their next relaxed geometry bike. If you want a 105 level or better Synapse, you'll likely find it's only available in a disc. The same applies to the Roubaix (non Di2) bikes.

I've actually worked for 3 different shops over the last 6 years. But this one the last 3. Same thing applies. Selling a road disc bike is exceptionally rare. We do have a few lower end road bikes (starting around 1200), and people seem fine on calipers. Often times its a matter of cost vs. benefit. Disc bikes usually seem to add a few hundred dollars to the end price tag, with little benefit (we don't have mountains here).

To the poster above me, the roubaix has a non disc version. We carried both, and the disc version did not sell until we put it on sale at cost. The owner only brought in one Roubaix with disc this year, just as a show piece.

Bike manufacturers are pushing it.

A little tangent topic , but I thought I heard or read someplace that hanging a hydraulic brake bike upside down by the wheels is a bad idea. Something about the fluid getting pooled wrong and causing the need to bleed the brakes.

Is that true ?

Can be, any air in the system can over time make it's way up to the caliper.
Shouldn't be air in the system though.

So 3 different shops over 6 years....so the majority of time before discs became readily available.

Gotcha.

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Chicago Cubs - 2016 WORLD SERIES Champions!!!!

"If ever the time should come, when vain and aspiring men shall possess the highest seats in government, our country will stand in need of its experienced patriots to prevent its ruin." - Samuel Adams

It's fine on any new (last 5-8yr old) disc brake system. There shouldn't be any air in the system, but even if it is, as soon as you flip right side up and pump the brakes it'll be back to normal.

Actually, if you suspect air has made its way into the caliper, the best thing you can do is pop offf the wheels and push the pistons back into the housing to ensure none gets trapped there where it can do the most harm.
Then leave the bike sit right way up forca little while before pulling the levers.

I think a big part of the modulation advantage for disk brakes is the human part of the system. I find on my (crappy) cantilever brakes on a very cheap cross bike I still get enough power to lock up the wheels, it just takes a LOT of hand & forearm muscle to do so. With the disk brakes on my MTB or my new cross bike I find I get all the power I need with 2 fingers. People have much better fine motor control when pulling relatively gently with two fingers than when "grabbing a handful" of brakes.

Back in the day I had an MTB with regular brakes, and some long descents my forearms would be completely pumped and my hands would be cramping up.

I think a bit part of the disc brake advantage is the finesse you can have when you only need one or two fingers to brake. That being said, while I love my discs off road I don't feel a need for them on road.

Yes. This can be a key factor, and as you point out isn't limited to separate disc braking systems. However, even cable actuated systems can be significantly improved in this regard with prudent cable and housing selection and setup.


This is where you go off the rails...just because the pads are an elastomeric compound, it doesn't mean they are easy to compress.


Not necessarily. There are plenty of integrated braking disc calipers that don't have "long levers reaching around the tire". TriRig Omega is one. The new centerpull brakes on the Madone are another. The Magura hydraulic rim brakes too.


Here is where you go off the rails again...the disc pads HAVE to be run with close clearance because they have to be set up with large "leverage" (i.e. high force/low travel) between the master cylinder and the pads. This is necessary because the clamping forces HAVE to be high due to the small (relative to a rim brakes 622mm diameter "disc") diameter of the braking surface and the proportionally lower braking torque generated for a given clamp force and friction coefficient.


Again, not true...in fact, certain brake types can be designed with a progressive actuation, with large travel during the first part of the lever application and lower travel/higher leverage in the latter portions. That's something that's difficult to do with hydraulic separate braking disc systems


Yep, and it's that "bite" that is one of the things I dislike about separate braking disc systems...then tend to be "grabby" at times...especially under very low wheel speed conditions (like when negotiating a tight switchback on a MTB). The pads also don't last very long in sloppy conditions...and beware if you're out riding on the road as it first starts raining. It's fairly easy to contaminate the pads with road oils and drastically reduce the braking power...be careful when washing your bike as well, for that matter, for the same reason.


The problem I see here is that you have your mind made up about what each braking system can and can't do...and aren't interested in exploring why or why not that is. Oh well.

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http://bikeblather.blogspot.com/

Interestingly enough, I've been using a 2-finger rear, 1-finger front braking technique on both road and MTB since...oh...about 1986 :-/

One thing I noticed when first switching my MTB to discs was that the "free" lever travel (i.e. the travel prior to pads hitting) was a lot lighter on the disc systems than on the V-brakes on there previously. That REALLY cut down on the "forearm pump" and "hand cramping" on long descents...and is why I mentioned above that I have the opinion that this is a big part of what most folks describe as "modulation" ability. The good news is, it's possible to get the same type of lever feel with rim brake systems.

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http://bikeblather.blogspot.com/

I bet Jonny Hoogerland wishes the UCI would ban barbed wire fences.

I'm glad no-one has every been hurt by a bike equipped with rim brakes.

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TriDork

"Happiness is a myth. All you can hope for is to get laid once in a while, drunk once in a while and to eat chocolate every day"