V-brakes also have the advantage of not sticking outside the frame. My tektro wide profiles stick a full 3cm outside the fork and frame and they do catch body parts and clothing.

Don't worry... I'm here now - what did I miss? :D

Also not quite true about the fender clearance issue. V's are finicky with fenders, while properly set up cantis allow tonnes of room. A lot of people actually site the clearance of cantis as another reason to use them on touring and cyclocross bikes.

(edit: A hint on how to avoid frustration if installing fenders on a bike with U brakes: don't.)

Of course, all this depends on proper set up, and cantis are a pain in the arse if you don't have a lot of practice.

Vs can't be tweaked to have quite as much power as a carefully set up canti, but they have more than enough power for just about anything and are dead simple to adjust.

Actually, the centre-pull cable design of low profile cantis allows for nearly infinite power (really!!!) if you know what you are doing. The power of a V brake is fixed and less than that of a canti set up for super high power. But Vs are waaaay easier to set up and much less likely to be done wrong or in a way that gives you less than maximum power.

Actually I'm sure you could get even more power out of a v-brake if you used a standard pull lever and NOT a v-brake specific lever. The drawback is that you will have minimal pad to rim clearance to get it to work and NO tolerance for any rim that is even slightly out of true or pads that don't want to centre reliably.

Now I'm sure that what your doing with a low profile cantilever setup is making the cross cable so short that it effectively pulls as sideways as possible, just like a v-brake and since you are using low cable pull levers you have good mechanical advantage but you also have all the issues of close clearances with no tolerance for any out of true wheels or non centering pads.


In the real world v-brakes offer you the best of all worlds with no fussy issues to sort out.

Anthony

You are correct in your description of the setup, but not why it provides stopping power... if you consider a set of low-profile canti brakes with a very short straddle cable - for argument's sake lets say it is so short it goes straight across. To actuate the brake you pull up at the middle of the straddle cable. After the pads hit the rim we can consider the brakes as a static system - all forces balance each other out. the tension in the cable pulling up at the middle of the straddle is a certain amount, lets call it 't', and each side of the straddle cable must hold approx. 1/2 of that, or 't'/2. BUT the centre cable is pulling straight up and the straddle cable is pulling at a very shallow angle with almost no vertical component at all, so the tension in the sides of the straddle cable have to be much much much higher than just 't'/2... 't'/2 is just the vertical component of the force the straddle applies to the brake arm and there is the larger horizontal component (larger because the low straddle cable is much more horizontal than vertical).

The actual amount of tension in the straddle cable is:

t/(2 X Sine A) where A is the angle between the straddle cable and horizontal... As A approaches zero (horizontal), Sine A gets extremely close to zero, and a non zero number, 't' divided by a number approaching zero approaches infinity...

For example, if the straddle cable is at 30 degrees, with cable tension of 10 lbs: 10lbs/(2 X Sine 30) = 10 lbs cable tension in the straddle cable. If A is decreased to 10 degrees 10lbs/(2 X Sine 10) = 28.8 lbs. at 5 degrees the tension is 57.4 lbs, at one degree the tension is 286.5 lbs...

If you pull the brake cable on a V brake with 10 lbs tension, the brake sees 10 lbs tension - no more and no less.

The problem, as you said, is that it gets increasingly hard to set up a brake with a very low straddle cable, including tire or fender clearance and rim run-out clearance. Also, the more you pull the cable the higher the straddle angle gets and the less this trigonometric leverage effect works for you. But it is not difficult at all to set up a low-profile canti with significantly more power than a V brake.

Unless you want fenders, or racks, or tires full of mud, or you just want to get the best possible braking. V's work well all the time, but they never really excel.

OK, I admit. I forgot about the oblong thingy that goes between the slider that moves up & down as you adjust the lever and the cable end point. But as it's free to tilt it doesn't change the leverage.

But that's exactly what you do. The only thing confusing the issue is the intermediate link between the cable anchor point and the adjustable slider in the setup. And since that link is hinged and free to align itself with the pull it doesn't affect the leverage.
As far as the mechanical forces are concerned the cable might just as well run "straight" from the barrel adjuster and to where the slider sits on the stroke adjustment screw.

Attachment 92647

Green, red and yellow are the available effective lever lengths(somewhat exagerrated)
The part circled in turquoise is the link that's free to toggle. When the brake is engaged it'll align itself along the shortest route available between the adjustable slider and where the cable enters the barrel adjuster.
With the adjuster set at its two opposite end points you get a slightly different angle between the cable and the lever but more importantly you do get different effective lever lengths, and with that different strokes.

There's really no way around it. If you're able to change the "feel" of a brake w/o changing the stroke or the leverage - then what is it you're changing? The flexibility of the brake lever?

You are changing the length of the lever arm but not the amount of cable that the arm pulls. The anchor point is free to pivot so all it does is change the angle at which the cable pulls out of the housing. The length of cable pulled out remains the same.

I've played a little with the Speed Dials and, personally, the difference is pretty subtle. More a gimmick than an actual benefit:rolleyes:

Shimano Servo-wave levers do make a difference. If nothing else, the variance in leverage creates a level of modulation you can't get with conventional rim brake levers. That and the fact that at max leverage and properly set up brakes, the brakes will throw you over the bars if you don't mind your manners.

It's funny, there's a section in the Shimano instructions that advise practicing braking with these levers in a controlled situation so that you don't do an unexpected endo later on. This, of course, is only true if you remove the adjusment blocks so that max leverage can be applied.

In all seriousness, they really are good levers-

Well, finally!

Be careful now, you're in violation of a very basic rule here:
If you have two levers of different length but both moving the same number of degrees, then the tip of the longer lever will traverse a greater distance than the tip of the shorter lever.
Changing the length of the lever, and maintaining the degree of arc w/o changing the distance covered is pretty much the same as claiming to be able to draw two circles of different diameters but with the same circumference.

Which doesn't change the fact that the length of the lever changes.

No. I just went out and took a few measurements. With the stroke adjustment set to top the lever will pull 30 mm of cable before bottoming out against the handle bar, but with the stroke adjustment set at the bottom the lever will only move 22 mm of cable before bottoming out againt the handle bar.

Your results may vary if you've engaged the reach adjustment screws, but apart from that my results should be repeatable within a mm or so.

AFAIK, Speed Dial levers DO adjust the amount of cable pull for a given amount of lever movement. It may not be enough to make it work for either V or Cantis, but that is what the dial is for.

The little hinge part that the cable head goes into (circled in blue in the drawing) always stays parallel with the cable and for that reason can be considered part of the cable. The point where this hinge attaches to the speed dial adjusting rod can be considered the cable anchor point, and this point moves. The closer to the lever pivot this attachment point the shorter the radius of the arc the cable end travels, and so the less the cable is pulled.