Dual Pivot Brake Service
Properly adjusted brake systems require attention to small details. This article will discuss caliper arm adjustment, brake attachment to the frame, pad adjustment to the rim, pad centering, and pad clearance. For purposes of this article, the terms "left" and "right" will be from the "mechanic's point of view," not from sitting on the bike.
This article discusses primarily Shimano® brakes, but the concepts also apply to Campagnolo® and other dual pivot type brakes.
The dual pivot caliper rim brakes are used on many modern road bicycles. It is a combination of a “center-pull” and a “side pull” brake. One caliper arm has its pivot off of wheel center, the other arm pivot directly over the wheel center.
Left side and right side dual pivot brake caliper arms move on separate pivots. Pads move in different arcs as they approach the rim. The left side arm acts as a sidepull. This pad swings downward as it travels toward the rim. As this pad wears thinner, it will travel downward even more. The right side acts as a centerpull. The right pad will travel upward as it approaches the rim. Set the right pad lower on the rim braking surface, and the left pad high on the braking surface.
The calipers secure to the frame with a threaded stud and nut. Next, we install the wheel and make sure it is fully seated, centered, secured and true.
Hold the brake centered to the rim, and secure the nut to manufacturer’s specifications, typically 6-7 newton meters. Getting the calipers close to center now helps with adjustments later.
Feed the cable through the barrel adjuster, and through the pinch mechanism. Back the barrel adjuster out two or three turns to allow for later adjustments. Make sure the quick release is in the closed position. Squeeze the pads to the rim and secure the pinch bolt to manufacturer’s specifications, typically 6-7 newton meters.
Loosen and lubricate threads of pad bolt/nut. Adjust height of right pad to strike lower edge of braking surface. Adjust height of left pad to strike the upper edge of braking surface. Most dual pivot pads adjust only for height and tangent. Vertical face and toe alignments are not typically adjustable on dual pivot calipers. Tighten pad-fixing bolts.
An important pad setting is height. For dual pivot calipers, we pay attention to the swing.
This arm is moving upward to the rim, so the lower edge of the pad should strike the lower edge of the braking surface. As the pad thins and wears, it’ll move up the rim surface.
The other arm is moving downward toward the rim. Set the top edge of the brake pad to the top edge of the braking surface, but never so high that it contacts the tire.
On the dual symmetric system, both arms of the caliper move upward as they approach the rim. Set both sides low on the braking surface.
This is the only procedural difference between the dual symmetric caliper and the dual pivot caliper, so from here on, we’ll work only with the dual pivot system.
Other pad settings include adjusting the face of the pad to match the face of the rim, although not all pad systems allow for this alignment. There’s also tangent: we want to make sure the front and back edge of the pad are even.
Finally there’s toe, which adjusts the pad so there is a slight gap at the back. Setting toe in the pad can help reduce brake squeal, but if the brake doesn’t squeal when ridden, toe is not needed.
A useful way to achieve toe is to apply a shim at the back of the pad using a rubber band. Note that your pads need to have a convex and concave spacer system for this to work. We squeeze the lever gently and loosen the pad screw. The pad will self align because of the gentle pressure we’re adding at the lever. Secure the pad to manufacturer’s specification - typically 5 Newton meters. We remove the rubber band and we have our toe.
Another way to add toe is simply to loosen the pad, manipulate the arm, hold it, and re-secure the pad.
A test to see if it’s tight enough is to try and twist the pad. Twist hard with one hand, and if it doesn’t move, it’s tight enough.
NOTE: It is generally not recommend that dual pivot brakes be bent for “toe.” On less expensive brakes with thin caliper arms, it is sometimes possible to bend the arm so the leading edge of the brake contacts the rim first. This can help in reducing brake squeal. If the caliper arms are thicker and stiffer, as with better quality brakes, there is a risk that the caliper arm will snap and break rather than bend. If squeal is a problem in the brake, consider filing the pad so there is a slight gap at the back of the pad.
Squeeze lever to test pad clearance. Use barrel adjuster to adjust pad clearance. Set clearance for approximately 3-4mm (1/8") per side from pad to rim. Draw slack from system using inner-wire pinch bolt if barrel adjuster is set out to its limit.
Next we set pad clearance, which is the gaps between the rim and the pads. Begin by pulling the lever with force to test the cable pinch bolt and settle in the cable system. Don’t worry about centering the pads, that will come next.
Set pad clearance not by looking at the gaps, but by feel up at the lever. A brake that is too tight will mean that we are just barely squeezing the lever and the pads immediately contact the rim. In this case we bring the barrel adjuster down into the brake, which gives us more cable slack, and moves the pads away from the rim.
On a brake that is too loose, you’ll squeeze the lever and nearly contact the handlebar here we won’t have enough stopping power. We never want to touch or get close to the handlebar. We turn the barrel adjuster counterclockwise, drawing out slack and bringing the pads closer to the rim.
This is adequate - the pads strike the rim with at least an inch of travel left at the lever, and we have enough space between the pads and rim to allow easy centering.
Normally, front and rear brakes are set to feel the same.
Pads will wear out with use and require replacement. Pads will also harden and become ineffective with age. Pads may also become embedded with aluminum or other contaminants. Inspect and remove as necessary. Pads that are aligned too low on a rim will tend to develop a lip on the low edge. This lip makes correct alignment impossible.
View pad centering to rim. If right pad appears closer to rim, tighten setscrew. If left pad appears closer, loosen setscrew. For Campagnolo® dual pivot type brakes, the centering screw is located on the left caliper arm. See image below.
We will now center the pads to the rim. Depending on the model, there are different techniques to do this.
Some models will have a centering screw on the side. Use this screw to move both pads left or right. If the brake looks centered, it is centered.
Some models lack a centering screw. In this case, we move the brake with two wrenches: one on the centering flats, and another wrench on the mounting nut. Move both wrenches the same direction, and the same amount.
Finish by trimming the cable and installing an end cap. We only need enough cable to grab with a fourth hand, a little over an inch is fine. And this brake is ready to go. I mean stop.
Caliper Arm Pivot Adjustment
Because each arm has a separate pivot, each arm pivot is adjusted separately. Neither arm should have play, or a back and forth knocking. Additionally, neither arm should bind as it moves. The caliper arm bridge behind each arm is threaded for each arm pivot bolt. Behind each pivot bolt is a locknut. Dual pivot use a spring to push open the side-pull type arm. A setscrew in the side-pull type arm pushes on the center-pull arm to open it.
- To adjust the center pivot of the right arm, begin by removing the brake from the bike.
- Loosen set screw located under bridge. Not all brands and models use a setscrew on this bridge. Campagnolo® uses a setscrew in the locknut behind the brace.
- Release spring tension by un-hooking the spring from the right caliper arm (center-pull type arm). Use care not to damage plastic spring-guide.
- Loosen locknut at base of mounting bolt. It is not necessary to remove locknut. Shimano® typically uses a 12-point 13mm nut. Other brands vary.
- Mount a L-shaped hex wrench vertically in a vise. This will act to hold the pivot bolt and free up your hands.
- Pivot center pull side inward to expose center bolt. Place brake down on hex wrench. Center bridge is threaded, and can also act as its own lever. Turn brace clockwise slightly (10-15 degrees) to tightened adjustment. Hold brace and fully secure locknut (about 70 inch-pound torque). Test center-pivoting arm for knocking and play. Test arm for adequate free movement. If the arm binds, loosen locknut and loosen bridge slightly. Re-secure locknut and test again. Repeat as needed.
- Move caliper arm to full open position and re-attach return spring. Use care not to damage plastic spring-guide.
- Mount brake to frame, or use soft jaws in vise to hold mounting bolt.
- Use hex wrench to hold right-arm adjusting bolt, and loosen locknut on backside of arm. Tighten adjusting bolt slightly. Hold bolt and secure locknut fully. Test for play in arm, and squeeze arm to rim and test for adequate free movement.
Mount caliper to bike and adjust pads as described above.