The Shimano BR-6700 [paid link] brake calipers, part of the Ultegra 6700 series, are designed for high-performance road cycling. However, even well-regarded models like these can develop a spongy feel over time. This soft brake lever response undermines confidence and performance during descents and high-speed maneuvers. In this detailed guide, we’ll examine the specific causes of spongy brake feel in the BR-6700 [paid link] calipers and offer effective, model-specific solutions to restore crisp, predictable braking.
Understanding the “Spongy” Brake Feel in BR-6700 [paid link] Calipers
A spongy sensation at the brake lever often signals a loss of mechanical efficiency between lever actuation and pad contact. This vague modulation can arise from several interrelated issues including cable stretch, housing compression, pad alignment, and caliper centering. On the BR-6700, which relies on a dual-pivot symmetrical design, precise adjustment is key to achieving the intended braking response.
Riders experiencing spongy feedback should not dismiss it as mere cable wear. When left unresolved, this issue reduces braking control and can lead to uneven pad wear or rim damage. The first step is understanding the specific areas that contribute to braking inconsistency.
Common Causes of Sponginess in BR-6700 Brakes
Cable actuation systems like the BR-6700 are vulnerable to several mechanical inefficiencies:
1. Inner Cable Stretch and Housing Compression:
With prolonged use, inner cables elongate microscopically while housing can compress, especially under high loads. On the BR-6700, this reduces the mechanical advantage at the caliper, increasing lever throw before pad contact.
2. Dry or Frayed Cables:
Cables with corrosion, kinks, or fraying drastically impact the smooth transmission of force. Even minor cable degradation affects the precise spring-loaded operation of the caliper arms.
3. Caliper Arm Centering:
The BR-6700 features a return spring that balances the pivot arms. If the caliper becomes misaligned or the centering screw drifts out of adjustment, one arm may resist compression, causing uneven pad contact and a mushy lever feel.
4. Pad Wear or Misalignment:
Worn pads or pads that are improperly toed-in can create a perception of sponginess. When the pad contacts the rim surface inconsistently or too late in the lever stroke, the system loses tactile feedback.
5. Rim Contamination or Deformation:
Brake feel is also influenced by the braking surface. Rims that are dirty, oily, or uneven due to damage or manufacturing variance can reduce friction and increase stopping distance.
How to Instantly Improve the BR-6700 Brake Feel
Addressing the spongy response on BR-6700 brakes involves systematically evaluating each contributing factor and applying precise corrections. This section outlines the model-specific techniques for improving brake response.
Cable Replacement and Lubrication
Start by replacing the inner cable and housing if they show signs of wear, rust, or resistance. Use pre-lubricated, low-friction cables compatible with Shimano systems. The BR-6700 performs best when paired with stiff, compressionless housing to eliminate play and maximize lever efficiency.
Once installed, apply a silicone-based or light PTFE lubricant inside the housing before threading the new inner cable. This reduces drag throughout the lever stroke.
Fine-Tuning Lever Cable Tension
Use the barrel adjuster at the brake lever or the inline adjuster (if present) to tighten cable tension. The pads should sit about 1–1.5 mm from the rim surface when properly adjusted. Excess gap introduces slack, while too little clearance can cause rub.
Caliper Centering Adjustment
Utilize the centering screw on top of the BR-6700 caliper. With the wheel spinning, tighten or loosen the screw until both pads engage the rim symmetrically. This ensures even pad wear and uniform brake feel.
Brake Pad Positioning and Toe-In Adjustment
Align the pad so it contacts the braking track squarely and doesn’t extend above or below the rim. Slightly toe-in the pads—meaning the front edge of the pad touches the rim slightly before the rear—by about 0.5 mm. This minimizes squeal and creates progressive braking force.
Cleaning and Decontaminating the Rim Surface
Thoroughly clean the rim with isopropyl alcohol and a clean cloth. Remove all residue from previous pad compounds and oils. If the rim surface shows ridges or warping, consider resurfacing or replacing the rim to maintain pad engagement integrity.
Testing the Brake Response After Adjustment
After adjustments, apply firm lever pressure while stationary. The lever should engage resistance within 1/3 of its full throw and reach a firm stop. On-the-road tests should confirm a predictable, strong response with no mushiness or uneven modulation.
If lever throw still feels excessive, double-check the cable anchor bolt at the caliper for slippage, and inspect the lever pivot for excess play. The BR-6700’s performance is largely determined by precise mechanical contact, so every interface matters.
Preventing Future Spongy Feel in BR-6700 Brakes
Routine inspection and adjustment are key to maintaining brake performance. Lubricate the pivot bolts and cable path quarterly, check for housing cracks, and recenter the caliper after each wheel installation. Replace cables and pads annually or sooner if used in wet or mountainous conditions.
Proper pad compound choice also plays a role. Use Shimano’s recommended R55C3 pads for aluminum rims, as they are designed to complement the BR-6700’s spring tension and pad holder geometry.
Final Thoughts
A spongy feel in Shimano BR-6700 brakes isn’t just an annoyance—it’s a performance liability. By methodically replacing worn components, fine-tuning adjustments, and maintaining rim and pad interfaces, cyclists can restore a firm, responsive brake feel. The result is improved control, safer descents, and a more confident ride.