DISC VS. RIM BRAKE OPTIONS

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Choosing A brake-system platform.

In thinking about cycling, Ben Serotta spends much more time thinking about how to go faster or farther, not about how to stop. 

But when you need to slow down or stop, it’s pretty important.  No matter which system you choose, we promise that only top shelf systems will ever make their way to your aModoMio or Duetti. 

Both brake types are produced in a wide range of brands, models, costs, and performance attributes, so it can be misleading to make generalized statements about either type compared to the other.  Based on top-of-the-line comparisons, however, it is fairly clear. Below are the key differences based on a choice of best in class of either system.

DISC BRAKES

Disc brakes are now standard equipment on cars, motorcycles and the majority of mountain bikes. In the last few years, they are also becoming increasingly popular on cyclocross, electric-assist and road bicycles (and are now finally approved for UCI road racing). Disc brake calipers are located on one side of the wheel (left side) and are mounted to the frame and fork nearer to the center of the wheel where they straddle the disc (literally a metal disc, normally 140 or 160 MM in diameter which is mounted directly to the hub). The calipers on better brakes are activated by a hydraulic (rather than steel cable) line and squeeze the disc (much as a rim brake squeezes the rim) causing friction and slowing progress. Disc brakes are not complicated and can be serviced by a competent and disciplined DIY cyclist. That said, wear is less obvious and on disc brakes. I emphasize the importance of routine service and maintenance checks, as the ramifications of poor attention to system maintenance can be significantly more acute than with rim brakes. Additionally, installing the wheel is somewhat more finicky and MUST be done correctly. It’s not complicated, but you need to have patience and base level of mechanical aptitude to enjoy the fruits of your investment. The most positive attributes of disc brake systems are the counterpoints to the most negative attributes of rim brakes, which is to say that wet weather performance is superior and a mildly damaged wheel does not impact the braking action. Third, most agree that modulation, in general, is better on the top disc brakes, meaning you can operate the brakes with greater finesse for a more controlled deceleration with less tendency to lock the wheel, which can result in a rapid loss of control. Just as a last comment on wet weather braking: to be clear, once you lock the brakes or loose grip based on slippery conditions, your brakes are not going to make a difference!

Disc Brakes and Bike Design

Good disc brakes are powerful, but because they are mounted on a single side of the bike and not at a normal apex or confluence of structural members, actuating the brakes induces a significant force into the frame/fork on one side only.  In the case of the front fork with conventional design, this place a huge force that is about 1/3 of the way up the fork leg with absolutely no other support.  Without proper design consideration, braking can cause poor handling due to the uneven or unsupported loading or premature failure of the frame, or worse, catastrophic failure of the fork.  All three of these ‘downsides’ have presented themselves in various brands over the past five or so years as, in all too common fashion, the road bike industry was paying more attention to generating new product demand then taking the time to fully explore and understand the impact of this design shift (rather than paying enough attention to similar lessons learned more than 10 years ago in mountain bikes). 

All of this is to say that if a bike is being outfitted with disc brakes, achieving structural integrity takes a different path than with rim brake bikes.  Rest assured, the disc brake AModoMio has a stouter rear triangle and front fork, both, very specifically designed for the purpose. Done right, the frame and fork will be a little heavier and a little less supple then the rim brake counterparts.

RIM BRAKES

Rim brakes still have been the go-to brake style for the majority of all bicycles for the last 80 years, and are still the preference of a lot of cyclists. As the name indicates, the brake is actuated by small brake pads squeezing the rim of the wheel, causing friction, and slowing the bike. In the last decade, design improvements to the brake calipers, the brake pad materials and rim braking-surface have significantly enhanced over-all braking performance. Rim type brakes (cable actuated) are pretty simple to observe, adjust, and maintain if you are a DIY cyclist. The right choice of rims and brake pads provides very good modulation for controlled braking. The two prevailing negatives being wet weather braking, which without question, can be less than confidence inspiring and reduced performance if the rim/wheel becomes slightly bent or damaged.

Rim Brakes and Bike Design

Because rim brakes are mounted near the circumference of the wheel, the standard frame and front fork designs almost naturally provide an optimal structural configuration so that when the brakes are applied with force, the added “load force” from a rapid deceleration is effectively transferred through the structure without unduly affecting handling of the bikes nor causing potentially hazardous overload (leading to failure). This simple yet important benefit allows bike designers to focus more on the ‘feel’ of the bike rather than whether it is strong enough. In fact, if weight is a central issue in your consideration, the braking system itself is a little lighter. Back in the late 1970’s when aerodynamics was reintroduced into bicycle design, it was not uncommon to find custom bikes (including some Serotta TT bikes) with rim brakes that were ‘hidden’ in the frame and fork. This style choice has resurfaced again, and while it can have a very clean look, it requires more cleaning based on the brake location and is more inconvenient to work on. Personally, I’d rather spend my spare time riding rather than fiddling with finicky equipment, so AModoMio bikes with rim brakes have calipers located in the traditional, easily accessible locations.

Point / counterpoint with no BS, but a little soapbox

If you waded through the above, you may have the impression that I am less of a fan of disc brakes, but that’s not the case. Here’s the thing, the primary reason why disc brakes are being heavily marketed in road bikes is that bike companies are desperate to have you believe that whatever you have is obsolete. Whenever manufacturing capacity and supply outpace demand, the bicycle industry puts most if its energy into trying to convince the already-believers into buying another bike by creating a new category (or categories) of product, rather than pooling resources to promote growing participation (and therefore demand). Bike companies who sponsor racing, have been pressuring the UCI to allow disc brakes in the pro peloton, a primary marketing tool to more sales.  My guess is that the shift will become the general standard over the next year or two based on current momentum alone, but based on the fact that you can still purchase new quill style handlebar stems (broadly deemed outdated more than 20 years ago) I am confident that rim type brakes will be around for a long, long time, albeit on a minority of new bikes.

 

 

Rim brakes are your choice if:

  • You rarely ride in the rain;
  • You want lighter weight;
  • You are less diligent with maintenance;
  • You prefer or don’t mind what is becoming
    a more ‘classical’ look.

Disc brakes are your choice if:

  • You hope to set a new speed record descending L’Alpe d’Huez
  • You want the absolute best braking performance in any condition;
  • You are diligent about routine maintenance;
  • You prefer (or don’t mind) fitting in with a growing trend.
 

 

As for Ben, himself?  Fortunately, Ben is not limited to one bike and he is constantly trying new components.  However, if Ben could only own one road bike, he confesses that it would have disc brakes.  Group conformity is also a consideration, not from a position of status, but of safety. Cyclists who really know their disc brakes often brake later and harder into a turn and you may not be able to readily adjust your timing coming into a hard turn at higher speed.