from Rookie’s keyboard
Hello, friends
It’s been a while since I’ve done an educational post. Sorry. As they say – life happens. No excuses, though. I need to improve my posting schedule.
Today’s post is dedicated to center-pull and side-pull brakes as I think many rookies need additional information to understand the difference between each model.
But let’s start with the basic definitions first.
Center-pull Brakes
Center-pull brakes are rim brakes with a straddle wire attached to a set of brake arms that pivot around two independent fulcrums.
When you squeeze the lever, a cable pulls the straddle wire; the arms pivot and move toward the rim. The brake shoes create friction against the rim and slow down or stop the bike.
The wide straddle in the middle is behind the name “center pull”.
Side-pull Brakes
Side-pull brakes operate similarly. The main difference is the position of the brake arms’ ends.
The brake arms’ ends and the cable controlling them are….to the side.
There are two main types of side-pull brakes – single-pivot and dual-pivot.
Single-pivot brakes (image below) have a single pivot point around which the brake arms rotate.
Dual-pivot brakes have two separate fulcrums positioned either on one side (asymmetrical) or on both sides (symmetrical).
The Strong Points Of Center-pulls
- Massive Clearance
The ultimate advantage of center pull brakes is the extra tire clearance allowing you to run wider tires and full fenders. For that reason, you see center pulls on vintage commuters and touring rigs.
- Lower mud accumulation
Center-pull brakes don’t catch as much mud.
- Vintage Aesthetics
Center-pull brakes go back to the 70s and have a distinct vintage appearance that complements old-school bikes. People who restore vintage models find center-pull brakes aesthetically pleasing.
- A Brake Stiffener Can Be Used
Center-pull brakes mount to the frame via two bolts. And it’s therefore possible to add a stiffener to make the brake more effective.
Stiffeners a.k.a. brake boosters are simply plates shaped like a horseshoe that go in front of the brake to reinforce the entire structure. The goal is to reduce seat stay flex.
- Centering
Centering is simply ensuring that each brake shoe is at an equal distance to the rim. If one brake shoe is closer, the brake loses effectivity, and one of the pads wears down faster.
Since center-pull brakes have two distinct bosses and pull from the middle, they’re easier to center.
The Weak Points Of Center-pulls
- Complex
A center-pull brake requires a brake stop and a straddle wire. Hence installation is slightly more complex.
Side-pull brakes require neither of the aforementioned parts and are therefore easier to mount and adjust.
- Brake Bosses
You can’t install center-pull brakes on a frame or fork that doesn’t have mounts for a brake. This makes center-pull brakes compatible with fewer components.
- Fork Shuddering
Another issue that may occur with center-pull brakes is fork shuddering (vibrating of the fork).
Here’s how that happens:
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 end; the brake cable is the string.
During braking, the front wheel slows down and “bites” the ground. The bike continues moving forward due to the inertia. The fork bends backward.
When the fork bends, it stretches the brake cable (the bow’s string) which in return closes the brake again. The motion triggers the same cycle. The shuddering continues until the rider stops braking.
This problem is quite common for cantilever brakes that use a cable stop 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 stop and the straddle wire.
Side-pull brakes do not generate the same issue because there isn’t a straddle wire.
- Highly Limited Supply
The demand for center-pull brakes apart from new-school cantilever models is close to zero. Road bikes are using either side-pull calipers or disc brakes.
The bike models that would benefit from a rim brake with extra clearance rely on V-brakes.
Low demand = low supply. If you want more choices, stay away from center-pulls.
Side-pull For The Win?
Side-pull brakes are my personal preference for the following reasons:
- Simplicity
Side-pull brakes are mechanically simpler and do not require brake bosses.
Instead, they attach to the frame or fork via a single bolt going through the seat stay bridge or the fork’s crown.
Hence side-pull brakes are compatible with a greater number of forks and frames.
Also, side-pull brakes need neither a brake cable stopper as part of the headset nor a straddle wire. The result is easier installation and adjustment.
- Slim
SP brakes have a slim profile that blends with road frames and forks. I like the look.
- Endless variety
SP brakes dominate the caliper brake market. The greater demand stimulates competition and lowers the prices.
- Innovation
Road rim brakes may be losing market share to disc brakes, but they’re still the default choice. Companies see this as an incentive to keep making new innovative models.
Side-pull brakes have a future whereas center-pull brakes do not.
- Light
Side-pull calipers are lighter thanks to:
1/ The absence of cable hangers, straddle wires, brake bosses, and a second mounting bolt.
2/ Shorter, slimmer brake arms
3/ Innovative designs and materials
- Fork and Seat Stay Clearance
The absence of a straddle wire clears the seat stay area as well as the one between the headset and the brake. If you want to run a handlebar bag or a rack, that will be beneficial.
- No Need For a Third-Hand Tool
Side-pull brakes are easier to set. You won’t need a third-hand tool to adjust the brake.
Side-Pull Brakes Aren’t Perfect
I may like SD brakes, but I also have to admit some of their downfalls:
- Poor Tire Clearance
Apart from the 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 commuters and hybrids…need more clearance.
- More mud
The arch formed by the brake arms is close to the tire. As a result, the dirt thrown by the tire accumulates very fast. Ultimately, SP brakes just don’t work well on off-road machines.
- Annoying Centering
Single-pivot side-pull brakes are 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.
Dual-pivot models are much easier to center because they have a centering screw.
My Conclusion
Unless you are building a vintage bike, center-pull brakes are not needed and will create annoying adjustment issues. I also hate the annoying straddle wire taking up space at the front and back.
If you have a road bike, run calipers.
If you have a touring bike with brakes bosses, run V-brakes or mini Vs (if you need a short pull brake).
I know that many people will disagree, but that’s how I see things. Center-pull brakes look cool, but in practice are annoying to deal with.
Until next time,
Rookie
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