This post compares center-pull and side-pull brakes.
Center-pull brakes are rim brakes with a straddle wire attaching to a set of brake arms pivoting around two independent fulcrums.
When the rider activates the brake, a cable pulls the straddle wire connected to both brake arms. The arms then move towards the rim. The friction between the brake shoes and the rim slows down or stops the bike.
Since the straddle wire is positioned in the middle, this type of brake is known as the center-pull.
Side-pull brakes are also rim brakes with brake arms pulled towards the rim via a steel cable. The difference is the position of the brake arms’ ends.
As the name suggests, the brake arms’ ends controlled by the brake cable are positioned to the side.
There are two main types of side-pull brakes – single-pivot and dual-pivot.
Single-pivot brakes (image below) have one pivot point around which the brake arms rotate.
Conversely, dual-pivot brakes have two independent fulcrums positioned either at the center and to one side (asymmetrical) or on both sides (symmetrical).
The Advantages Of Center-pull Brakes
Center pull-brakes tend to offer more tire clearance than side-pull brakes. Consequently, the rider can install wider tires and full fenders.
This is one of the reasons why you see center pull-brakes on vintage commuters and touring rigs.
- Reduced mud accumulation
The extra clearance of center-pull brakes makes it more difficult for mud to accommodate around the brake. This is beneficial because in extreme cases mud may cause the wheel to jam.
- Vintage Look
Center-pull brakes date back to the 70s. Thus, they come with a distinct vintage appearance that complements old-school bikes. People who restore vintage bicycles or simply like old-school models could find center-pull brakes aesthetically pleasing.
- Compatible With a Brake Stiffener
Since center-pull brakes attach to the frame via two bolts going into the frame or the fork’s legs, it’s possible to add a stiffener to make the brake more effective.
Stiffeners a.k.a. brake boosters are plates shaped like a horseshoe. They go in front of the brake to reinforce the entire structure. As a result, there’s less seat stay flex. (read more)
Centering is the process of ensuring that each brake shoe is at an equal distance to the rim. If one brake shoe is closer, the brake won’t be as effective and one of the pads will wear down faster.
Since center-pull brakes are installed onto two distinct bosses and pulled from the middle, they’re easier to center.
The Disadvantages of Center-pull Brakes
- Mechanically Complex
A center-pull brake needs a brake stop (usually part of the headset) and a straddle wire. This makes center-pull brakes more frustrating to install.
In different, side-pull brakes require neither of the aforementioned parts and are therefore easier to mount and adjust.
- Brake Bosses
Center-pull brakes cannot be installed on a frame or fork that doesn’t have side mounts for a brake. This makes center-pull brakes compatible with fewer components.
Furthermore, the frame and fork production processes become more complicated because the manufacturers have to weld or braze dedicated brake mounts. On a mass scale, this additional step greatly increases the manufacturing labor.
- Fork Shuddering
Another problem that may occur with center-pull brakes is known as fork shuddering (vibrating of the fork).
The explanation behind this phenomenon is as follows:
- The fork, the brake, the cable stop, and the brake cable form a bow. The fork is the body of the bow; the brake and the cable stop are the endpoints; the brake cable is the string.
2. During braking, the front wheel slows down gradually and “bites” the ground. The bike continues going forward, however, due to the inertia. As a result, the fork bends backward.
3. When the fork bends, it stretches the brake cable (the bow’s string) which in return closes the brake again. This motion triggers the same cycle. The shuddering continues until the rider stops braking or when the bike slows down tremendously.
This problem is quite common for cantilever brakes that use a cable stop that’s part of the headset. The center-pull brakes seen on retro road bikes are less likely to behave like that due to the shorter distance between the cable stop and the straddle wire.
Meanwhile, side-pull brakes do not generate the same issue because there isn’t a straddle wire. The brake cable goes directly from the lever to the brake.
- Limited Supply
The demand for center-pull brakes apart from new-school cantilever models is non-existent. Road bikes are using either side-pull calipers or disc brakes. Meanwhile, the bike models that would benefit from a rim brake with extra clearance are relying on V-brakes.
Since there’s no demand, the supply is slim too. Thus, the rider has fewer models to choose from. The prices aren’t low either due to the scarcity effect.
The Advantages of Side-pull Brakes
Side-pull brakes are mechanically simpler than center-pull brakes.
Side-pull brakes do not require brake bosses. Instead, they attach to the frame or fork via a single bolt going through the seatstay bridge or the fork’s crown. This makes side-pull brakes compatible with a greater number of forks and frames all while simplifying the manufacturing process.
Also, side-pull brakes do not need a brake cable stopper as part of the headset nor straddle wires. Thus, it’s easier to install and adjust the brake.
- Slim Profile
Side-pull brakes have a slim profile that blends with road frames and forks. Many people like the look.
- Enormous variety
Side-pull brakes dominate the caliper brake market. The greater demand stimulates competition and supply. Thus, users can choose among many affordable models.
Road rim brakes may be losing market share to disc brakes, but they’re still the norm. Companies see this as an incentive to keep making new innovative models. Or in other words, side-pull brakes have a future whereas center-pull brakes do not.
Side-pull calipers result in weight savings for the following reasons:
- Absence of cable hangers, straddle wires, brake bosses, and a second mounting bolt.
- Shorter, slimmer brake arms
- Innovative designs and materials contributing to a lighter body.
This property makes side-pull calipers a better choice for cyclists who want their bikes to be as light as possible. That said, the weight savings aren’t substantial enough to make a huge impact on the recreational scene.
- Fork and Seat Stay Clearance
- No Need For a Third-Hand Tool
Side-pull brakes are easier to set. As a result, the user is less likely to need a third-hand tool to adjust the brake.
The Downsides of Side-pull Brakes
- Limited Tire Clearance
Apart from BMX models, side-pull brakes offer highly limited tire clearance preventing the use of wider tires and full fenders.
For road bikes, this isn’t a huge problem because most models use 23-28mm tires. But for commuters, touring bikes, and hybrids, the reduced tire clearance is a massive problem making side-pull brakes unusable.
- Mud Accumulation
The arch formed by the brake arms is very close to the tire. As a result, the dirt thrown by the tire accumulates. Hence why you won’t see a side-pull brake on an off-road bike.
- Poor Centering
Single-pivot side-pull brakes are notoriously difficult to center. In the past, mechanics use to tap on the spring of the brake arm that has to go inward with a screwdriver and a hammer to center the brake.
That said, dual-pivot brakes are much easier to center because most models have a centering screw.
FAQ: Why did center-pull brakes go extinct?
Center-pull brakes went extinct because they’re heavier, more expensive to produce, and more difficult to adjust without offering additional stopping power.
When companies began making decent side-pull brakes available to the masses during the 70s and 80s, the market share of center-pull brakes had no choice but to shrink.
In addition, road center-pull brakes weren’t needed on the commuter and MTB market due to the presence of cantilevers and V-brakes.
At the moment, center-pull brakes are unlikely to make a return, although no one can predict the future.