Rims Vs. Discs

Since I started this blog, I've written about the disc brake vs. rim brake arguments a bunch of times, but it's been awhile, and think of how much has changed on the subject just in the last couple of years. In 2013, disc brakes were rapidly taking over on mountain bikes, but on road bikes, discs were still in their infancy. Today, it's beginning to look more and more like the days for rim brakes are numbered, including for road bikes. Even Campagnolo recently launched their own disc brake system. The professional teams are still debating whether or not to make the switch, but they're still doing "trials," enduring some protests, and going through a few growing pains. But on road bikes for the non-professionals, we're starting to see discs gain the upper hand, and I figure it's only a matter of time before discs supplant rim brakes on road and racing bikes entirely. I'm still not convinced that's a good thing, but I believe it's inevitable.

I saw a post on the Velo-Orange Blog a couple of months ago about The Great Brake Debate. I'm a fan of V-O as being a good source for practical and proven components and gear for non-racers - and I'll bet a lot of Retrogouch readers are probably in the same camp. Well, V-O now offers a couple of their very practical frames with accommodations for disc brakes. The "Debate" post was a brief look at some advantages of the two systems and didn't really pick sides - but there are a few dozen comments on the post where people weigh in on the systems. Opinions seemed pretty divided.

Okay - now here's a shocker. I've recently been trying out a decidedly non-retrogrouchy bike equipped with disc brakes -- kind of a long-term trial (long story - don't ask for details, 'cause it really doesn't matter). I'm trying to decide if it's going to become a permanent part of the fleet. I had rented bikes with disc brakes a couple of times in the past and been underwhelmed, but now I've had a chance to get some more meaningful experience with them. For the record, I currently have bikes in my stable with vintage (70s - 80s era) single-pivot sidepulls, modern dual-pivot sidepulls, vintage centerpulls, traditional wide-profile cantilevers, low-profile cantilevers, U-brakes (basically a type of brazed-on centerpull -- as mounted on my tandem) and V-brakes (aka direct-pull cantilevers). That means I get to use and compare pretty much every type of brake that's been used on bikes over the past 50 years or more right out of my own garage. I should note that any vintage brakes I use have been updated with modern brake pads, which is something I highly recommend.

I still don't have a final verdict on discs - but so far I haven't found anything to really change my mind. Here are some observations:

Wide profile cantis.

Wet weather: Without a doubt, the main advantage of discs comes with wet road conditions. That's not really a surprise. With rim brakes in the rain, there can sometimes be a brief sense of panic when you pull the brake lever and there's a moment where it seems like nothing is happening. I'm sure we've all been there. It lasts roughly the distance it takes for the wheels to make a full revolution - or about the circumference of the wheel, but it can feel like forever. The brake pads essentially have to "squeegee" the rim before they can really get a grip. The phenomenon is much improved with good aluminum rims compared to old chrome-plated steel rims of the past - but it can still be a little scary sometimes. Discs obviously aren't affected by rain as much since the disc brake surface isn't sloshing through the puddles, and the pads can clear water off the disc much more quickly than with rim brakes. Score one for discs.

Dry weather: I honestly don't really sense a big difference in braking when it's dry. It's really hard for a lone person to measure things like stopping distances precisely and do side-by-side comparisons, but it really feels to me like any difference in stopping distance is small enough to make no appreciable difference at all. If you never ride in the rain (or at least, never intentionally) then it still seems to me that disc brakes don't really have an advantage here.

Stopping power: That's something that gets thrown around A LOT by disc brake cheerleaders -- that disc brakes have "so much more" stopping power. "Superior stopping power." "Incredible power." "It's an indisputable fact," they say. People make the claim and repeat the claim so much that it seems to be accepted without any proof (or perhaps even despite proof). It's a "begging the question" fallacy. The fact is, today's rim brakes - whether we're talking about side-pulls, center-pulls, cantilevers, or V-brakes - all have the power to lock up a wheel easily. The braking is probably affected more by the type of rim and the brake pad than by the particular brake design. That is, chrome-steel rims are pretty lousy brake surfaces (but then again, they're also really rare nowadays) and every report I've seen on carbon fiber rims says that they're not a whole lot better. But with aluminum rims and decent brake pads, even inexpensive brakes can lock up a wheel. It's a basic fact that once a brake locks up, it has met and exceeded the maximum braking power possible. You can't exceed "locked up."

So what the hell are all these disc cheerleaders talking about? I think what a lot of people describe as "superior braking power" is a misinterpretation of the sensation between the input or force they apply to the brake lever, and the perceived stopping action they get from the brakes. Disc brakes seem to be able to apply a lot of stopping power with little effort or force on the brake lever. It's not really that there's more stopping power (there can't be), but rather, that one can get that power with less effort. I suppose this would be a good advantage for someone who has smaller hands, or whose hands aren't as strong.

These old Campy brakes will lock up
the wheel, but it takes some effort to do it.

The thing is, however, that this isn't just a "rim vs. discs" phenomenon. One can experience the same kind of difference between different types of rim brakes. For example, the old single-pivot sidepulls I have on some of my vintage bikes can still stop the bike perfectly well and in a hurry if necessary. But most of them tend to require more force on the levers than the modern dual-pivots. The modern dual-pivot sidepull brakes can stop the bike with a lot less effort - even with hands on the tops of the levers. V-brakes have so much mechanical advantage that most of them require special brake levers (they have to match the amount of cable pull, or else the lever can bottom out against the bar before the brake pads hit the rim!). If I had to rank the brakes in my stable from "hardest" to "easiest" in terms of effort, I'd say that the old Campagnolo side pulls take the most effort, while the V-brakes and the disc brakes are the easiest. I've seen where Rivendell's Grant Petersen even puts V-brakes ahead of discs in that regard, but to me (at least with the examples I've tried) it's kind of a toss-up. The modern dual-pivot side pulls are close behind those, and the various cantilevers are somewhere in the middle.

Another thing I notice is that centerpulls and cantis can offer good power and modulation - but there are some factors in setup that can affect it. Centerpulls, especially long-reach ones that mount with a center bolt above the wheel, can flex quite a bit. U-brakes, or brazed-on centerpulls, will flex less, wasting less energy. But with both of those, as well as with cantilevers, flex can still crop up either through the extra cable used (the yoke and straddle cables, for instance) or even at the cable stop (some cable stops are pretty wimpy, whereas a thick forged one can firm up braking a lot). That flex can make the brakes feel a little bit spongy under hard braking -- but again, they still offer all the stopping power necessary.

Adjustability and Maintenance: This is one area that doesn't get talked about as much - but from a retro-grouchy perspective, I think it's huge. Disc brakes are much more "finicky" about adjustment and maintenance than most rim brakes. In getting rim brakes set up, one needs to get the pads installed so that they line up on the rim properly - which is quite easy to do, and once set, shouldn't really change much through the life of the pads. Second, one needs to set the brake arms so that the pads are the proper distance from the rim. Too close and they'll rub, too far apart and they might not be able to reach the rim before the brake lever runs out of travel. In-between those two extremes of "too close" and "too far" is a "just right" sweet spot, and yet there is a pretty wide tolerable range that will still work fine. As the pads wear down, the distance to the rim increases, and it is necessary to re-adjust them which takes only seconds and usually requires no tools. Just turn the little barrel adjuster a bit every couple of months. But even if a person is terribly lax in that little bit of maintenance, it can still take quite a while before it gets to be a serious problem. In that way, rim brakes can be very forgiving of indifferent maintenance.

Disc brakes are harder to adjust, and less tolerant of neglect. Disc brake pads are by design set much closer to the brake disc, and there's a very small margin for variance. It's not unusual for the brake pads to drag slightly on the disc, even when the brakes are released. I've encountered plenty of people who say that the little bit of drag is just something you get used to with disc brakes. Try to adjust them so they don't drag, and they can be too far apart for secure stopping - and if a person can find the "sweet spot" it doesn't last long because the pads (which are typically a lot thinner than rim brake pads) wear down quickly and need to be re-adjusted or replaced more often. If neglected, it doesn't take long before the brakes can become totally ineffective. This is one point where hydraulic brakes may be better than mechanical ones (the hydraulic system is supposed to self-adjust as the pads wear) - but the pads still wear more quickly than rim brakes and they don't tolerate neglect.

It ain't all that pretty, but it's still very functional -
and easy to keep it that way

For people who keep on top of maintenance, these may not seem like problems - but consider how many people these days are either inept or simply indifferent about maintenance. I don't just mean people who ride rusted second-hand clunkers because they can't afford anything else. There are a lot of people out there riding $10,000 bikes who can't even change a flat tire! Now just try to imagine today's state-of-the-art bike as tomorrow's second-hand clunker. That old rusty mountain bike locked to the parking meter might not be pretty, but its cantilever brakes will work a long time without maintenance. Will the same be true of disc brake equipped bikes in 10 or 20 years? Will the correct parts even still be available?

And that gets me to the next thing. Rim brakes are well established, mature technology. Compatibility for parts is wide ranging. If a bike is equipped for cantilever brakes, then pretty much any brand of cantis and V-brakes will work as well as any other. If a bike is built for caliper brakes, pretty much any brand of sidepull or centerpull will work. Brakes from different brands are overall pretty similar to one another in design and function. In other words, most sidepull brakes all work pretty similarly regardless of brand. Most brands' V-brakes are functionally similar to the other brands. There aren't a lot of proprietary designs and unique standards. There are only a couple of different "standards" for brake pads, so as long as someone knows if they need "threaded" or "smooth" posts, compatibility shouldn't be much of an issue.

There are 25 unique styles of pads in this one picture alone.
Good luck figuring out which one you need. And don't get mad
if the local shop only stocks a few of them.

Like so much of the latest technology for bikes, disc brakes make the idea of "standards" something of a joke. There are several different mounting styles, and numerous adaptors that may or may not make one compatible with the other. There is a plethora of different styles, sizes, and shapes of pads - some being proprietary to a particular brand or even to a particular model of brake. It's not even enough to say "I need pads for Shimano disc brakes" because different models in the Shimano lineup might use completely different pads. Same goes for most of the other brands, too. How many unique types of disc brake pads is a local bike shop likely to keep in stock?

Wrapping this up, it goes without saying that disc brakes are obviously taking over. The time will come when only the cheapest bikes -- maybe some childrens' bikes perhaps - will come with traditional rim brakes. Keep in mind that disc brakes are even being featured on bikes at Walmart selling for barely more than $100. Whatever kind of disc brakes are on bikes like that cannot possibly be an improvement, or worth the hassles they will likely lead to over time.

I have no doubt that the technology will continue to improve. Maybe they will get to where there's some semblance of common standards. For example, maybe they'll get the number of different pad designs down to an even ten. Of course, such changes would automatically make a huge percentage of the disc brakes and some of the complete bikes on the road today obsolete, but until these things happen and the technology matures, I'm still hesitant to give them a big endorsement.

I'm still trying the bike with discs. They may be a benefit this winter when the roads turn wet and slushy. But apart from that, I'm just not that convinced.