Center pull brakes are often standard equipment on vintage bicycles. Their design can allow more clearance for fenders and wide tires, and based on where the pivots reside, they may have more mechanical advantage than standard sidepull brake calipers.
But, centerpull brakes are sometimes viewed as more challenging to set up than side pull brake calipers. How long should the straddle cable be? How close should you set the brake pads to the rim? What is the ideal angle for the straddle cables? How much torque should go on the mounting bolt? What about lubrication of the pivot points and cables? Should the straddle cable be thick or thin? And, most important, how can you eliminate brake squeal on these often very noisy calipers.
For over twenty years I cycled on a bike that had the best centerpulls you could find – brazed on centerpulls were standard equipment on my 1976 Centurion Pro Tour. While this advantage went unnoticed by me in my youth (I had nothing to compare this to), I have definitely noted the extra care and adjustments needed to the bikes I currently ride which feature center pull brakes, but which are not brazed on to the frame. The above photo shows brazed on Dia Compe centerpulls on a 1978 example of a Centurion Pro Tour.
Brazed on centerpulls have been around for a long time. The above examples show Jeay centerpulls on a 1947 Peugeot, and a more custom example from Follis on a 1953 frame.
If you are ordering a custom bicycle, you can most definitely specify for this braze-on feature. Using the brazed on version of centerpull brakes keeps the brakes centered, and undoubtedly improves the overall performance of the brake.
What is the best way to set up centerpull brakes? Sheldon Brown offers some guidance, as well as Park Tools. But the instructions on these sites do not address some puzzling issues such as the proper length and angle for the straddle cable and the proper distance of the pads to the rim. Nor is the cable width and pivoting characteristics of the straddle cable discussed (a la Mafac).
For the question regarding the ideal pad distance to the rims, I can turn to both my own personal experience, as well as to one of my favorite resources – Glenn’s New Complete Bicycle Manual. The distance to set the pads to the rim is recommended at 1/8 inch, according to “Dr. Coles” (aka “Dr. Glenn” – the author whose white coat visage inspired my affectionate homage). That’s about 3 mm. Seems about right to me, based on my many decades of cycling with centerpull brakes.
The length and width of the straddle cable is another important element to consider when setting up these brakes. For Dia Compe and other non-Mafac centerpulls, it may appear that you have no choice in selecting the straddle cable, but these cables actually come in all different lengths, not just the one included with whatever caliper you are working with. The angle and width of the cables can impact the performance of the brakes. More flexible and moveable cables (a la Mafac and Compass) will provide better performance. One of the nice features of Mafac brakes is that the straddle cable is actually a shifter cable cut short, so it is easy to replace and adjust these straddle cables for Mafac brakes, at will.
The above Daniel Rebour drawing shows a custom frame with unusual braze-ons for the rear centerpull calipers, resulting in a very long straddle cable. In my experience, the length of the straddle cable is not so important as its angle – a wider angle at the yoke being more advantageous. The angle will decrease as the brake lever is applied. Also, pads should be set parallel to the rims, and with no upward or downward angle for best results (unlike some cantis which may need a slightly upward angle).
For Mafac enthusiasts, one issue is the flex characteristics of the fork and seatpost hangers. These hangers are not very stiff, so that when braking pressure is applied, the hanger can flex significantly, reducing the performance of the brake and providing for a “mushy” feel. Because of this, I have sometimes replaced the Mafac hangers with more robust hangers on my bikes with centerpull brakes, and with good results. The above photos show the Mafac hangers.
Brake pads are important to any brake set-up. While Kool Stop does make Mafac replacement pads – both in orange and black compounds, I have found that I prefer using Velo-Orange pads for my centerpull brakes. They are quieter and yet perform equally well. I usually lubricate all the pivot points on any centerpull brake I am setting up, as well as lubricating the straddle cable and yoke. It’s critical to check your cables and the bolts securing them for wear and proper torque on a routine basis, and if any cables show degradation, replace them immediately. You never want to apply the front brake, only to have it fail. That’s 70% of your stopping power.