tyrion

True in a sense. Rim brakes comparatively lose leverage due to the fact that the caliper must move a greater distance, but gain leverage due to the very large diameter "disc".

wolfchild

Rim brakes have better mechanical advantage than cable mechanical cable disc brakes simply because a rim has a bigger diameter than a disc rotor....The larger the disc rotor the better the stopping power...A 185 mm or 203 mm rotor will stop better than a 140mm or 160 mm rotor.

phughes

Not really. The bigger rotor he was talking about has more surface area for the pad compared to the smaller rotor, and consequently lager pads. The rim brake still has a small braking surface area. I like rim brakes, but that is not a plus for rim brakes, nor is the correct term, mechanical advantage, that implies force, such as is had by using a lever, the larger rotor simply gives more braking surface area, and better heat dissipation generally speaking.

rosefarts

A disc is a thin piece of metal that would need hundreds of thousands of pounds of compression force to deform. Disc brake manufacturers are free to build those calipers with all the compression they feel is necessary for a good feeling brake.

An aluminum rim is hollow and also serves the purpose of keeping the tire mounted and wheels rolling smoothly. In theory a system could be built that would destroy the rim. Or frame I suppose. I’ve heard anecdotal reports of Magura rim brakes denting rims but they certainly could be built crushier if we weren’t worried about keeping the bike rideable.

Carbon rims and mullet bikes are another huge advantage of discs. Keeping the brakes as brakes and rims as rims is smart.

In the early aughts, I was in a race where we caught the group ahead of us. On a descent. The peloton smelled like burning brakes. So many people, including me, wrecked out of that race due to hot rims popping tires. That’s not a concern for discs. Something to think about.

wolfchild

You're talking about the durability of steel disc rotor vs an aluminum rim, that is a different topic, and of course a steel disc will be more durable than an aluminum rim....The the further the brake caliper is located from the center of a disc the greater the leverage and stopping power.

Maelochs

I don't want to get into a pointless debate .... but anyone who has tested manual rim brakes vs manual (cable discs) vs. Hydro discs .... assuming all three systems were set up properly .... needs read no further.

rosefarts

Durability isn’t the word I’d use. That makes me think about how long before it wears out.

Think of it as material properties and structural integrity.

In order to truly use a rim as a disc, you would need compression enough that the rim would be damaged. This is a non issue on a disc. So the calipers can be specifically designed to clamp harder.

So the whole thought experiment falls apart.

The question should be “how hard does a rim brake need to compress on a (insert rim size) to equal the stopping force of a disc on a (insert rotor size)”.

The follow up question should be “how hard can a hydraulic caliper squeeze the rotor compared with a mechanical caliper? In ft/lbs or newton meters or something.”

The Chemist

Personally, I think cable-actuated hydraulics are the best of both worlds. Super easy to install / set-up since they're just cable actuated with no need for bleeding of the lines, and with the self-adjustment and dual/quad piston design of hydraulics. They're basically set and forget, with no further maintenance required after set up until the pads require replacement.

VegasJen

Now this is just my silly opinion, but unless there's prize money on the line, no way is hydraulic worth the expense. Cable brakes have been around for how many decades? Minimal maintenance, proven reliability, low cost. There's simply no comparison. If you just have money to burn (I never have, probably never will) and you want the latest and greatest tech, or you need that last 0.01 second to beat the next guy, then knock yourself out.

But that's just me.

wolfchild

In my case I've had both hydraulic and cable discs and I prefer cable discs or rim brakes strictly because of simplicity, ease of servicing. and extreme long term reliability....Speaking of prize money, hydraulic brakes are not a guarantee for winning a race, there are still many pro cyclists who use rim brakes.

elcruxio

Modern hydraulics (shimano) are easier to maintain than cables. At least if you follow any reasonable maintenance regimen. You need to swap brake cables and housings every two years or so. Hoses last triple that.

With every housing swap you need new bar tapes.

Every time you swap your cable you need to do the whole adjustable ferrule, brake arm tensioning song and dance. If we compare that to bleeding you put on a funnel, put a piece of hose on the caliper. Let oil flow down through the system. Close both ends and that's it for two years.

When you swap mechanic pads, pull back inner pad all the way, pull back outer pad all the way. Take out wheel (because that's mechanic brakes for you), swap pads, put back wheel, adjust both pads until you have that rub free non spongy spot. That usually takes a while. Oh and adjust cable tension and hope you have enough adjusting space in the ferrule ends.

Compare to hydraulics. Take out pads. Push pistons in. Put in new pads. Pump levers and go ride.

One thing that also doesn't happen with hydraulics is cable freeze. When you go from wet to sub freezing it sometimes happens that the cable freezes inside the housing. That essentially means you'll have no brakes until you defrost your bike. Hate it when that happens. Granted hydraulics used to have issues in the cold back in the day but it seems those have largely been solved.

the expense thing is silly to begin with. We should all be riding walmart bikes because if you're not racing what difference does it make? We all value different things. Personally I value really good brakes. You might value other things. Like your bike being more capable than a walmart one size fits no one.

wolfchild

I hope this is a joke.

phughes

Oh man, I guess I better go swap the housings and cables on my Surly... they are 11 years old. I might die despite the fact they are in very good shape despite multiple cross country tours and commuting. They are clean and shiny, with no fraying, and work very well and smoothly. Thanks for the warning on possible self-destruction.

Now, the reality is, hydraulic brake systems need to have the fluid changed every two years since the fluid is hygroscopic. Maybe you got the two mixed up. Either way, both systems work, it's all a matter of choice.

GhostRider62

I have mechanical disc brakes on a mountain bike for many years, I like them. They stop quickly and modulate well.

I recently got a new bike with SRAM Red Axs and hydraulic brakes. I am not in love. I cannot get them to stop squealing. I did everything I read (proper bedding, cleaning, sandpaper, adjust ad nauseum. They are good out of the driveway and just into my ride.). It turns out that despite the proper 9.5 n-m torques adapter bolts, the caliper moves very quickly into a ride. I also do not care for the modulation of them.

I am sure I will eventually like them once I can figure out how to keep them from moving. I do not see any improvement over my mechanical discs in terms of stopping power although I have never tested that out.

terrymorse 

For real? I have seen only disc brakes in the UCI races for a few years now. Those guys ride what they're told to ride.

Are you talking domestic pros?

elcruxio

My cables simply do not survive multiple years. Perhaps it's the road salt or whatever but after two years they start getting sticky and sucky.

Anyways I'd imagine most hydraulic brakes these days use mineral oil instead of DOT fluid. Since it's hydrophobic you don't have to change it all that often. We have a bike that hasn't been bled in a decade. No ill effects so far. But just because you can leave something for that long doesn't mean you should.

GhostRider62

I believe Pinarello riders have had the option but no other team. Maybe 1-2 riders overall not using disc brakes.

VegasJen

Same here. But I live in a very warm, dry climate. All my bikes are at least 10 years old, although I haven't had any of them since new, but I have yet to replace a brake cable. Maybe a couple shots of dry film lubricant and off I go. Brakes are literally the last thing I think of when I take a bike out for a spin.

terrymorse 

Mostly dry California riding here.

I'm trying to remember when I replaced brake cables on my 2011 Addict, which gets ridden a few thousand miles per year.

Definitely once, but that was because the bike insisted it be driven into the garage while on the top of the car. Lots of things got replaced after that. Stupid Addict.

So call it one brake cable set replacement in 12 years and > 20,000 miles. I also replaced the pads once.

Derailleur cables and housings are another story. I replace them when I need to replace bar tape, about every 3 years. I do not want those cables breaking off inside the shifter.

79pmooney

How am I still alive? I only do housings when they need it or they've been there a while (like years) and I am retaping the bars.

With not very expensive 3rd and 4th hands, none of this is very difficult. If the brake has one of those good cams that can be operated half open, this gets really easy. Basic bike stuff. Fully graspable by 12 year olds.

...

I'll grant you that. But in 3 Ann Arbor winters and every non-college year winter in Boston until I was 26, I never had cables freeze. (Or if they did, it was such a non-event I didn't notice.) I didn't own a car until my 30s. I've ridden in nearly every weather Boston and Ann Arbor have to offer.

I do too. All my bike have good ones. Yes, I ride with considerations for rim brake limitations doing major descents and in the wet. I ride within tire considerations on wet and dirty pavement. Potholes, Leaves. So? I also love that a quick look at cable rim brakes and a hard squeeze on the levers is all I have to do to know these brakes will stop me later. Pad rubbing? Easy fix and just as easy to do a ride-worthy fix with no tools at all; often while riding. (A lot of my levers have releases that can be ridden "off" so a little more reach but all the braking power.)

rosefarts

I think what’s going on here is that we’re arguing over the difference between “good enough” and “better”.

Properly adjusted and maintained cable brakes will definitely stop you. Rim or disc, no matter. The bike will stop. It sure will.

Hydraulic discs are better. Full stop (pun intended).

Does it matter? Probably not.

Some people struggle to learn new things. Others don’t want new tools. Some are more concerned about the mythological roadside repair than anything else. Mechanical brakes are good enough usually.

The advantages of hydraulic brakes have been adequately outlined here. If you can’t get your head around it, honestly it’s fine. Cables will get it done.

A little FWIW, a car has 4 hydraulic brakes. The e-brake which barely works is cable. The car is slightly heavier than a bike though.

tomato coupe

A lot of them are electro-mechanical now.

elcruxio

Things here tend to get dramatically fatalistic real quick. But I suppose that's a way to emphasize things. Maybe it's a regional thing.


Do I want to know what 3rd or 4th arms are?

But compare that to bleeding. These days it's literally pouring oil into a funnel.

I had a frozen cable last week. We have a lot of freezing a thawing with slush and that's pretty hard on cables. Especially with the road salt.


​​​​​​​I don't follow your point with this paragraph.

phughes

It all depends for me. These have lasted a long time. Replacing every two years as a rule is simply ridiculous though, whereas replacing hygroscopic fluid is more important since the moisture in the fluid will cause issues with the brake internals. You are correct, mineral oil is nice, and is not hygroscopic.

SkinGriz

I think the Ebrake on a Volvo actually pushes a plunger pressurizing the normal brake system.