In this post, I lay out the reasons why and provide you guidance on when you should buy a disc brake equipped road bike, rather than one with rim brakes.
While the debates about road bikes equipped with disc brakes are far from over, I believe it’s now clear that these bikes will soon become the predominant type sold to road cycling enthusiasts. What’s left for each of us enthusiasts considering a new road bike are the decisions about when to get one and what road disc brake bike or combination of frame, components and wheelset to get.
I’ve reached this conclusion from following the back and forth about road disc products over the last couple of seasons with both interest and skepticism and weighing the merits and looking into the future from the perspective of a road cycling enthusiast. My conclusion did not come after one or more meetings or rides with persuasive company representatives (of which there have been a total of none).
This shouldn’t be a shocker. Actually your reaction may be more like “Uh, what long ride have you been on that kept you out of touch for so long?” Disc brake versions of popular road wheels have been made for cyclocross bikes for several years, disc brakes for road bikes were introduced in 2013, and the major bike companies had a road disc bike or two in their line-up last year and are adding many more this year.
But now, the momentum is very strong and near the proverbial ‘tipping point’ from which I don’t think we’re going back. The technology development and product line changes for the coming season along with the compelling performance benefits and improvements over rim brake bikes and progress to overcome remaining objections makes clear that there is no turning back.
In this post, I’ll describe the why, when and what of the new ‘road disc’ world – why a road bike designed for and equipped with disc brakes and wheels is better than one fitted out with rim brakes, and when you should feel comfortable buying a road disc bike. In other posts, I have offered you my evaluations of the design, product and performance characteristics of current disc brake bikes, components and wheelsets that lead me to specific product recommendations.
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WHY YOUR NEXT BIKE SHOULD BE A ROAD DISC BIKE
Let me first tell you why I think road disc bikes and components are the present and the future of road cycling. In short, I see three reasons – better braking, faster riding, and greater versatility.
Better braking is perhaps the most tangible and immediate benefit of a road disc bike. With discs, you can brake with more consistency, control and feel (or ‘modulation’) than with rim brakes on carbon or alloy rims. A road disc bike rides equally well on both dry and wet roads and without concern for brake fade or over-heating on carbon wheels.
You may be thinking: “I already brake just fine with rim brakes.” Or, “I go fast and try not to brake very much so why does it matter.” I don’t doubt you brake fine, go fast and brake as little as possible. But, it’s actually those who know how to brake best, who ride the fastest, and cycle in the most demanding situations that know the limitations of rim brakes and are attracted to the benefits of disc brakes.
Disc brakes will make you safer on the roads than rim brakes will but it’s not the only or even the primary reason I think we road cycling enthusiasts will switch to them the next time we buy a new bike. If you can brake more confidently, consistently, and reliability, you can ride more aggressively on a downhill, into corners, and closer in a group, all key to faster riding.
Conventional wheels need to be designed to handle the loads of braking at the rim. They are strengthened and shaped at the rim’s brake track to optimize braking performance. Being free of these considerations, wheels designed for disc brakes hold out the potential for having lighter and more aerodynamic rims, leading to better acceleration and higher overall speeds.
While most (though not all) road disc brake wheels currently are slightly heavier than rim brake ones after adding the weight of the rotors, stronger hubs and a few more spokes needed in the front wheel, the weight of the rims – where rotational mass is most important – can be reduced and enable better acceleration.
As an example, a 40mm deep, 19mm wide (internal width) carbon clincher rim designed specifically for use with disc brakes currently being tested by a company that sources wheels to large brands is 10% lighter as reported in this article from CyclingTips. The entire wheelset, together with hubs, 24 spokes in front and back, rotors and rim tape totals 1552 grams, certainly in range of rim brake carbon clinchers of similar depth and width.
Rims designed for disc brakes can also maintain a rounded or toroid shape all the way through to their edges where they engage the tires, not having to stop short to allow for the parallel brake track found on most shallow and mid-depth wheelsets and many deep ones now. This will improve both acceleration and overall speed.
Hybrid toroid rim profile broken for parallel brake track
Last, having a road disc bike adds greater versatility to what and when you ride. Beyond your typical dry, good pavement, rolling terrain rides, you can take one set of all-carbon, all-around disc brake wheels on wet roads, in the mountains, and on an off-road section or two without concerns. With rim brakes, you’ll really want a set of alloy or carbon-alloy clinchers in addition to your carbon wheels to cover all those situations. A road disc bike will allow you to ride more consistently during the season, earlier and later in the year, and without the need to buy or maintain an extra set or two of alloy wheels to cover the range of riding you might do.
Be aware that you can only take the off-road versatility of road disc brakes so far. While some ‘alternative’ category disc bikes are being made for on-road and off-road cycling, most gravel grinder and cyclocross bikes are built sturdier than road disc bikes, the later designed to have more clearance between the bottom bracket and the ground to allow for the bumps, stumps and jumps you might come across during your adventure. The front forks, seat and chain stays on off-road bikes are also designed to allow for wheels and tires that are often far wider than you would want to run on the road and are therefore less aerodynamic. But, there’s nothing preventing you from using a road disc bike for an occasional ride combining some pavement and modest amounts of mud-free or dirt surface riding on paths that don’t have lots of pot holes or require a lot of clearance.
Much less clearance on road disc (left) than cyclocross disc bike
While the three major benefits I’ve just described convince me to recommend that your next new bike should be a road disc one, there are any number of reasons why some believe road disc bikes will not take root or do so slowly including:
- Performance – Heavier bike and components, less aerodynamic
- Quality – More service required (e.g., bleeding discs), noisy, more complex to maintain
- Change – UCI has not approved road disc bikes for racing, there’s a lack of standards on key components, it will take years for disc components to be designed or optimized for road use, discs ruin the bike’s aesthetics, etc.
Some of these are correct (e.g. UCI has not fully approved road disc bikes for racing though they are allowing teams to test them in races starting after the 2015 Tour de France, brakes can be noisy but only during bedding in), others are either wrong (e.g. more service required), insignificant or indiscernible (e.g. aerodynamic and weight differences) or are little different from today (lack of common standards, years to optimize). I go into further detail on most of these and other questions and issues in the specific posts on road disc brakes, bikes and wheels linked to above and also at the bottom of this post.
Weight is an oft mentioned concern working against disc bikes in some enthusiasts minds so let me try to address that one here. Together the brakes, wheels and frames used on a road disc bike add about 450g, or roughly a pound over the same model of road bike frame equipped with rim brakes and wheels.
Before you go all weight weenie on me against that extra pound for a disc bike, answer a couple of questions. Do you know to the gram or even pound how much your current bike or bikes weigh? How much more weight do you add with the tools, tubes, snacks, gels, water bottles you pack for a ride? How much weight did you add-on your body with the meal or drink you had the night before a big ride?
Count me down as ignorant on all three of those questions.
I know some of us obsess and are willing to pay large sums to avoid adding a half (227g) or quarter pound (about 113g) of weight in our components and wheelsets (guilty again), but adding an extra pound of weight for all the benefits that a road disc bike brings is, for me an easy trade-off to make.
Unless you are a fit racer, a pound or two really doesn’t matter. And if you can ride faster in and out of the turns and down descents with the confidence of your disc brakes underneath you, would you be willing to add a pound of weight to your bike? You should be.
Bottom line, if some combination of better braking, faster riding and greater versatility is more important to you than a few extra grams or watts or trips to the shop or the governing body or industry finding common ground around technology and standards, then I think it’s less a question of whether and more a question of when. So let’s look next at when is the right time to get a road disc bike.
WHEN YOU SHOULD BUY A ROAD DISC BIKE
When should you feel comfortable buying a new disc brake equipped road bike? With any relatively new product category like this one, there are always some product aspects that will change and improve more or less frequently and significantly. Still other changes and improvements won’t matter beyond a certain level to certain riders.
For example, I expect road disc wheels will change and improve a good amount each year over the next few years with more aerodynamic and lighter wheels, having been freed of the constraints of designing around a brake track and with more purpose-built road disc hubs. We’re really at the earliest stages of development for road disc wheels and while cyclocross disc versions of popular road rim wheels have been around for a while, that product segment has been too small to put dedicated design resources against to optimize the wheels. The speed at which new rim and wheel designs can be created, tested and brought to market, and the number of companies in the wheelset market able and willing to invest in the much larger road wheel market to get a leg up are both great. Wider, more aerodynamic and lighter rims will make for quicker accelerating, faster overall, and better handling disc wheels.
Conversely, I expect road disc brakes and shifters will change and improve less remarkably for the next few years. Why? There’s already been great progress and now at least two rounds of integrated shifter and hydraulic brake levers designed and introduced for road disc brakes by both Shimano and SRAM, the two largest road brake component manufacturers who together probably hold at least 75% of the road bike component market share. While the calipers and discs each company offers for road bikes are essentially the same or largely based on each company’s off-road ones, the weight or aerodynamic penalties are not so large as to cause all but the professional and high level amateur racer to hold off at this point. So I think it’s unlikely we’ll see significant change to what the companies are offering now until the 2017 model year after disc brake component designers get further direction from the body governing professional cycling racing.
There are a great number of road disc frames that have been introduced for the 2015 model year based on and carrying the same model name as the already popular and best-selling bikes and frames set up for rim brakes. Most of these are endurance bikes, like those shown in the top row here, but we have already seen some of the most popular race bikes designed for disc brakes too including those in the bottom row.
The road disc bikes available this season offer many tangible performance benefits and improvements over what you can get buying another rim brake equipped bike. Waiting another year or two for further improvements in road disc bikes, wheels or components may be worth it for some and not for others.
Let me try to be specific on this last point about when is right for you, based on the kind of rider you are. Road cycling enthusiasts – the almost daily riders like you and me who each year put a few thousand miles or kilometers on our carbon bikes typically costing at least $2500/£1500/€2250 and up to 2x or even 4x of that amount – have many reasons why we do what we do. Principal amongst these, based on research I’ve seen, is our goal to either
- Race and compete against others,
- Do endurance riding and events, or
- Build and maintain fitness levels
We make purchase decisions, according to this same research, based primarily on one of these criteria
- Pro use
- Aerodynamics
- Weight
- Overall Performance
- Comfort
Cost is of course always a criterion, but for most road cycling enthusiasts it’s more often a tie breaker when choosing between two options within a budget range that you’ve established for the same level of comfort, overall performance or the other criteria I’ve listed. As you go up the list above, we enthusiasts tend to prioritize those criteria more and meeting a budget goal less.
I’ve ordered and aligned the riding goals and purchase criteria listed above into three types of enthusiasts. Those whose primary objective is 1) racing and competing are likely to decide what to buy based on what the pros use, the aero characteristics and weight of a bike, components and wheelset. Those targeting 2) endurance riding and events are more likely to buy on the basis of some combination of weight, overall performance and comfort, and those 3) focused on fitness are likely (or should be) deciding on one product over another for overall performance and comfort reasons.
From my evaluation of the product available this season, there is a wide and competitive enough range of good road disc bikes, components and wheelsets on the market now to provide third type of enthusiast, the ones who ride to build and maintain fitness levels with the braking, speed and versatility benefits they’ll get from a road disc bike.
Yes, there will be more and perhaps better or better suited bikes, frames, disc brakes, hydraulic shifters and wheelsets coming in the future. But, the weight, performance and comfort gains will not likely be so much better on newer road disc equipment over what you can get now based on what I’ve seen to make you want to buy a rim bike now or hold off buying a road disc bike for more than another season. I say more about what is out there in the individual posts on road disc components, bikes and wheelsets I provided links to in this one.
For the endurance and endurance event rider (the second type of enthusiast), it’s a good time to really be considering your disc bike and component options. If one suits you, go for it. If not, know that a good option for you will likely come within a season. The weight penalty going to disc is around 450g across the bike, components and wheelset right now. To many people, that amount is insignificant relative to how much weight they could easily drop in other places on their bike (e.g. saddle bag) or person (e.g. waist line).
Contrary to how technology usually “trickles down” from the gear developed for racers to that used by mere mortal cycling enthusiasts like me and you, disc technology on the pro road cycling circuit is lagging the pace of the road consumer market, which itself has benefited greatly from what’s already been learned and developed for mountain bikers and cyclocross riders. Because of sponsorship agreements, Campagnolo not entering the disc brake market yet, and the conservative nature of the cycling governing body and pro riders, discs will be adopted more slowly by pro and top amateur racers than enthusiast cyclists.
Regulations and standards for professional and amateur racing sanctioned by the international governing body will likely come after the experiences and feedback the pros have in their races later this year and through 2016. With that, the rate of introduction of new road disc endurance bike frames we’ve seen in the last couple of years is likely to come to race and aero bikes in the 2017 season.
In the meantime, road cycling enthusiasts who are amateur racers (type 1) will not be allowed to use road disc bikes in competition. There are already a number of top end road disc race bikes available for those enthusiasts who prefer the more aggressive fit and ride of race bikes, but never intend to ride them in a sanctioned race.
https://intheknowcycling.com/2015/01/08/why-and-when-to-buy-a-road-disc-bike/
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