Brakes: modulation vs. sponge for stopping power

[Pastashop]

"Modulation" of braking force can often come at the expense of stopping power, if there's excessive flex in the brakeline. Here's a video of the front cable hangar flexing when applying brakes:

https://youtu.be/jZQxRy_7MEw

Assuming that the pure geometric (lever) ratio is identical the different configurations, I can now see how conventional caliper brakes and V brakes could/should perform better in terms of stopping power than canti or centerpulls. It eliminates the hangar – a point of flexure.

Just thought I'd share. I'm still running canti on my main bike! :-)

[icepick_trotsky]

Also a good reason to invest in a sturdier hanger than that flimsy number.

[MikeD]

Hangers can also be a friction point. Not the one above because the cable goes straight in, but the kind that have a noodle with a sharp right angle.

[benb]

There are tons of similar issue across all kinds of different brakes.

e.x. calipers flexing in multiple directions under cable force and/or wheel force.

Fork legs and/or seat stays flexing under brake tension causing reduced clamping.

Mounts for disc brakes flexing (see newer systems with radial mount calipers, etc..)

[cachagua]

I'm not sure flex like that, or anywhere else in the system (seatstays, canti bosses, what have you) would reduce the force applied to the rim... would it?

Squeeze a hypothetical "perfect" system (zero flex) with X force at the lever, and through whatever ratio the brake mechanism introduces, you get Y force squeezing the rim.

Then imagine a system that absorbs, say, 5% by flexing. Squeeze until you get Y force at the rim, and won't you be applying X force just the same? You'll have moved the lever farther, and that added lever travel is what the flex absorbs, but I don't think you have to squeeze harder to get the same stopping power, --unless I'm looking at this all wrong?

Seems like the mechanical advantage in the system would have to change for you to get a different output from the same input?

Not, mind you, that I'm advocating floppy, sloppy brakes. I like mine to feel snappy, same as anyone. But I'm not sure it really affects stopping power.

Bueller? Anyone?

[marciero]

Originally Posted by cachagua

I'm not sure flex like that, or anywhere else in the system (seatstays, canti bosses, what have you) would reduce the force applied to the rim... would it?

Squeeze a hypothetical "perfect" system (zero flex) with X force at the lever, and through whatever ratio the brake mechanism introduces, you get Y force squeezing the rim.

Then imagine a system that absorbs, say, 5% by flexing. Squeeze until you get Y force at the rim, and won't you be applying X force just the same? You'll have moved the lever farther, and that added lever travel is what the flex absorbs, but I don't think you have to squeeze harder to get the same stopping power, --unless I'm looking at this all wrong?

Seems like the mechanical advantage in the system would have to change for you to get a different output from the same input?

Not, mind you, that I'm advocating floppy, sloppy brakes. I like mine to feel snappy, same as anyone. But I'm not sure it really affects stopping power.

Bueller? Anyone?

It seems this way but one issue is that not all of the force flexing the system on the lever side is returned to the system on the brake side, due to friction in the system


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[marciero]

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[froze]

Regular vintage road bikes with side pull brakes don't use hangers, those were found only on cantilevers.

The better designed hangers moved just a hair back and forth not up and down like yours which would cause no noticeable mushy feeling with either except your design probably put some friction into the system. Cantilever brakes, especially low end ones, felt mushy due to the long straddle wire, also known as a transverse wire, and not the hanger. This wire being made of thin cable, see this site: http://www.parktool.com/assets/img/r...cantiT_008.jpg That long wire that goes from one side of the cantilever brake arm up to a triangular shaped piece called a straddle wire carrier, also known as the cable yoke, then back down to the other side of the cantilever brake arm is the transverse wire. When you pull the brake lever the cable has to now not only stretch, as all brake cables do, but it has to pull on that transverse cable which then stretches upward very noticeably, much more than that hanger.

But these brakes were built for a reason, to be put on bikes that had wide tires that other brakes could not clear, and for clearance for fenders. I have two bikes with Cantilevers, one I use for touring, and once I had the cables replaced with modern slicker housing/wire, and altered the straddle wire with a slightly shorter one which resulted in faster response to the pull of the lever, adjusted the cantilever angle (which had to be done due to the slightly shorter straddle wire), lubed all pivot points, and replace the pads with Kool Stop Salmon pads. Doing that stuff made a world of a difference of how the brakes felt.

[MikeD]

I hate spongey brakes. V brakes have 1/4 of the cable tension that cantilever brakes have, and that alone takes a lot of the sponge out of the system. Best upgrade I've made to my touring bike was to go to V brakes.

[froze]

Originally Posted by MikeD

I hate spongey brakes. V brakes have 1/4 of the cable tension that cantilever brakes have, and that alone takes a lot of the sponge out of the system. Best upgrade I've made to my touring bike was to go to V brakes.

I think maybe people ought to read this: http://www.rodbikes.com/articles/brakes.html

[MikeD]

Originally Posted by froze

I think maybe people ought to read this: http://www.rodbikes.com/articles/brakes.html

Interesting, and yet another tandem maker, Santana, recommends V brakes.


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[Pastashop]

Originally Posted by froze

Regular vintage road bikes with side pull brakes don't use hangers, those were found only on cantilevers.
The better designed hangers moved just a hair back and forth not up and down like yours which would cause no noticeable mushy feeling with either except your design probably put some friction into the system. Cantilever brakes, especially low end ones, felt mushy due to the long straddle wire, also known as a transverse wire, and not the hanger. This wire being made of thin cable,

Careful here... It's true that the straddle cable can introduce parasitic sponge into the system, but that's been recognized and taken care of even in conventional cantilevers – here's a Shimano design:


There were plenty of other designs in the salad days of purple ano CNC parts... and even before with the roller-cam design (in some ways a better version of the centerpull, IMO, but in other ways worse).

But be careful to not misuse the term "friction" – the flex in the straddle cable doesn't add much to the parasitic friction of the system. That's pretty much all in the cable-housing interface. For modern cables & housing, particularly on the front brake, it's basically a non-issue – as you point out below. Different issue than straddle cable.

cables replaced with modern slicker housing/wire, and altered the straddle wire with a slightly shorter one which resulted in faster response to the pull of the lever, adjusted the cantilever angle (which had to be done due to the slightly shorter straddle wire), lubed all pivot points, and replace the pads with Kool Stop Salmon pads. Doing that stuff made a world of a difference of how the brakes felt.

... as is the issue of the cable stop flexing.

BTW, the cable stop in the video is an aluminum Ritchey unit. I'm using non-aero levers and old XT canti arms (+ salmon KoolStop pads). I probably just have a stronger-than average grip. Or the cable stop might be thinner than optimal. :-)

[benb]

Those straddle cables probably never stretched enough to make much difference.

One of the "devil in the details" items with Cantis is that as the brake moves through it's travel the angles of the straddle change and it changes the mechanical advantage of the brake, in a negative direction IIRC. It's one of the things that makes them require careful design and setup. That is a much bigger factor than any of the cables stretching. And it's one of the design items that has been eliminated in most of the other brake types.

Rodriguez has a good point about Cantis being designed to work on road bikes and most of the others not having been designed for them, although that has changed with the recent hydraulic disc setups. V-Brakes, Mini-Vs, and some of the Mechanical Discs are all shoehorned into use with Drop bar levers without having been primarily designed for them and vise versa.

[froze]

Originally Posted by Pastashop

Careful here... It's true that the straddle cable can introduce parasitic sponge into the system, but that's been recognized and taken care of even in conventional cantilevers – here's a Shimano design:

I understand the newer designs got past that which we speak of, however if you look at the bike in the video it's an older bike, and unless they upgraded it, which it doesn't appear to have been then it has the "old fashion" straddle cable.

And nowhere did I say the stretch in the straddle cable was a big deal, all I said was that the cable probably stretches more than the hanger.

I've used the "old fashion" design now for a few years on my touring bike and I've had no issues (after the improvements I made which I mentioned earlier), with stopping, there might be some minor flexing because even after the improvements they still don't feel like my Superbe single pivot road bikes, but the Cantis don't bother me either. And the cantis clear my 27" 1 1/4 tires and fenders.

Disclaimer:
I never worked on Cantilever brakes in my life till I got my 85 Schwinn Le Tour Luxe about 6 or 7 years ago, so after I fiddled around, lubing, adjusting, replacing the pads with them for about a month and reading stuff on the internet I finally decided to take the bike into a shop that was familiar with Cantis, the mechanic there did the straddle wire change and adjusted the Cantilever angle and tension. He also replaced the cables, something I originally didn't think was necessary since the original (yes, original) cables only had 250 or so miles on them, but he quickly convinced me that the newer cables have less friction so I just had him do it even though I could have done that myself. I do know that after he got done with it there was a day and night difference on how they felt, responded, and modulated.

[MikeD]

Originally Posted by benb

Those straddle cables probably never stretched enough to make much difference.

One of the "devil in the details" items with Cantis is that as the brake moves through it's travel the angles of the straddle change and it changes the mechanical advantage of the brake, in a negative direction IIRC. It's one of the things that makes them require careful design and setup. That is a much bigger factor than any of the cables stretching. And it's one of the design items that has been eliminated in most of the other brake types.

Rodriguez has a good point about Cantis being designed to work on road bikes and most of the others not having been designed for them, although that has changed with the recent hydraulic disc setups. V-Brakes, Mini-Vs, and some of the Mechanical Discs are all shoehorned into use with Drop bar levers without having been primarily designed for them and vise versa.

That Rodriguez article is out of date and is wrong today with respect to V brakes. Tektro and Diacompe make V brake compatible brake levers. Current STI brake levers are long pull and work with V's. Thicker V brake pads are now sold, and I'd rather replace a V brake pads than a canti one with the unthreaded brake studs (a huge PITA). And V brakes don't squeal any worse than canti brakes do.

Where canti brakes fail is in cable hangers that flex and bend the brake cables at sharp angles, the straddle wire which has to be set at the proper length or the brake leverage is crap (plus it has the falling rate problem), the straddle cable hanger which crimps the cable with a pinch bolt or set screw causing cable damage, and a failure mode where if the brake cable breaks, the straddle wire falls onto the tire. If you have a knobby tire that's a trip over the handlebars and a face plant. If your cantis have the smooth brake shoe studs, they are a royal pain to adjust. I've had numerous canti brakes on bikes over the years and found V brakes to be a huge improvement over them.

Yes, I admit they may be a problem with clearance for fenders and with older brake levers, which may necessitate the use of cantis over V's. Tektro makes a wide range of V brakes with different length arms.