The question that everyone is asking or will eventually ask sooner or later. Should I buy a disc brake equipped bike or a rim brake equipped bike?
One of the main reasons to adopt the newest technology is obviously to future-proof your equipment. The general assumption is that new tech = future-proofed. Is that true though? Yes and no. Caliper mounting standards and thru axles are much more volatile to change with disc brake bikes.
The change in thru axle standards have been ever-progressing in the world of MTB already and it makes sense that road bikes will eventually follow suit. Frame builders like to utilise different thru axle/spacing standards to facilitate certain frame attributes. In search of stiffer frames that are lighter and offer wider tyre clearance, different thru axle spacing methods may be required. This may mean that your set of wheels suddenly is no longer compatible, or if you are quite lucky to have a well-supported hub-set, an adapter plug could be used to accommodate.
Recently a new flat mount standard was adopted, which required different hardware. Once again, this may change in the future as frame builders come to refine road disc applications.
On the rim brake side, 9mm QR and brake mounting standards are relatively stale in terms of development. You either have a frame utilising a standard road caliper mount or a direct mount. The 9mm/135mm QR standard has been around for a long while and should be supported for the foreseeable future.
So in this case, whilst you think that disc brakes might just be future proofing your setup, you may be surprised that it is actually the other way around. (At least for a while until the industry settles down).
There is no denying that Disc brakes are more powerful than rim brakes. In the wet, the gap opens up even more. So if you plan to ride in the wet or live in a part of the world that has unpredictable weather, the choice is already made for you. For the rest of us, you will often hear from the strongest supporters of rim brakes that the performance is simply enough.
Whilst we also ride road bikes with rim brakes, we do wonder with an open mind whether having "enough" braking performance is a good thing. Surely there aren't any detriments to having more than just enough braking performance, as long as it is modulated properly? After all, it is versatile and handy to have in situations where emergencies require every ounce of braking power?
There is no doubt at the current moment, disc brake setups on road bikes are less aero versus their rim brake counterpart. However, frame builders are allowed to optimise disc frames more, to even out the disadvantages.
The newest Trek Madone 9 is probably the best case of this. Trek has completed testing to show that their new Madone 9 is pretty much similar in terms of "aero-ness" between the rim and disc versions. The disc-framed Madone 9 can maximise UCI rules in ways to actually make a faster frame, because it is not bound by the limitations of a rim brake design.
Ultimately, the new Madone 9 disc is a faster frame vs the Madone 9 rim frame but the braking setup is slower for the disc. And when all things are considered, they even out. We predict that in the near future, disc setups will become more aero versus a rim setup, especially if groupset manufacturers look into aero brake calipers too.
On average, a disc brake setup adds approximately 0.5kg of weight onto your bike, given similar level components. This is definitely a detriment if only performance is considered and something that isn't easily changed. Even if you spent more money in getting a disc setup "tuned", you could argue that putting the same amount of money into a rim brake bike setup would also lower it more comparatively.
The only thing we can hope for is that as technology matures, disc groupsets will come down in weight and further options are available. One upside argument to disc brakes in terms of weight is the possibility of a lightweight wheelset. The most important aspect of weight on a wheelset is rotational weight. The rim plays the biggest part in rotational weight on a wheelset - and when you consider that disc-specific rims do not need reinforcement around the brake track, the possibility is higher for lighter wheelsets (when optimised for a disc brake setup).
Since manufacturers do not need to manage temperature and stress loading on rim surfaces in traditional ways, we hope to see some really lightweight wheels that will fully take advantage of brake discs.
A further consideration is the "feel" of the brakes along with the brake rub. Some find that disc brakes lack the feeling of being "connected" in a way that mechanical cables offer. Since the cable always has a bit of tension connected to a spring, the feeling of this is often lost with a hydro disc brake setup. As a result, this can make it harder for riders to judge their braking modulation (at least initially).
Overall, the subject of brake disc rub is a harder issue to delve into but certainly an issue that at least requires some more effort to correct, versus its rim brake counterpart.
Final Thoughts
Our belief is that disc brakes are becoming more viable day by day. Whilst there is the superior technology, there is still certainly room for improvement. This advantage will increase more in the future until it is the dominant method of braking on road frames. This said, it doesn't mean that rim brakes will be phased out. There will always be fans of a tactile brake setup and certainly lovers of having a bike that is exceedingly light.
Reading this article, you would think that CCACHE is pro disc brake. Truthfully, we were exactly the opposite not long ago. We were actually fans of rim brake setups and still are, but after doing the maths and weighing up all the pros and cons unbiasedly, it is hard to ignore the advantages of disc brake setups.