Dia-Compe 987 Cantilever Brake: A Deep Dive

For the discerning cyclist, understanding the intricacies of their bicycle's components can elevate both performance and enjoyment. When it comes to braking systems, cantilever brakes have long been a staple, particularly on cyclocross and touring bikes, valued for their powerful stopping and adjustability. Among these, the Dia-Compe 987 cantilever brake stands out as a well-engineered piece of kit, offering a blend of durability, customisation, and classic design. This article delves into the mechanical specifics, features, and comparisons of the Dia-Compe 987, providing a comprehensive overview for enthusiasts and mechanics alike.

Dia-Compe 987: Design and Construction

The Dia-Compe 987 is characterised by its low profile design, a key aesthetic and functional element that contributes to its overall performance. The arms of the brake are crafted from a high-quality aluminum alloy, subjected to a cold forging process. This manufacturing technique enhances the material's strength and durability, ensuring the brake arms can withstand the rigours of demanding riding conditions. The arms are further finished with an anodised coating, available in a range of five attractive colours: Blue, Black, Ti Grey, Lavender, or Silver. This variety allows riders to personalise their bike's appearance, matching the brakes to their frame and other components.

Mechanical Insights: The 987's Inner Workings

A significant aspect of the Dia-Compe 987's engineering lies in its accessible and adjustable tension springs. Each brake arm houses an internal tension spring that can be easily accessed, replaced, and fine-tuned. One end of the spring securely fits into a dedicated hole on the brake arm, while the other end connects to a cadmium-plated metal nut. This nut features a hexagonal base with a 3.5mm rise, designed to accept a 13mm cone wrench for precise tension adjustments. By rotating the nut clockwise when the brake is mounted on the bicycle, riders can increase the spring tension, thereby affecting the brake's return speed and feel. To protect this mechanism, a black plastic shroud covers the spring assembly, with only the hexagonal base of the adjustment nut left visible.

The pivot point of the brake arm is equally well-considered. The aluminum arm rotates around a machined steel bushing, which is itself housed within a brass sleeve. This layered construction – aluminum arm with a brass inner sleeve, and a separate steel bushing for the mounting stud – ensures smooth operation and longevity. The brake pads are mounted to the rear of the arm, secured by a system of four steel components. These include the pad holder, a base washer for the pad to rest against, a small flat washer, and a conical steel nut, painted black. This conical nut is tightened from the front using a recessed 6mm hex fitting. Each cadmium-plated steel pad holder weighs approximately 8.5 grams. For those looking to upgrade or replace, aftermarket options like the SRP Ti pad holder (eyebolt) replacements are compatible. The short length, bulb-shaped SRP Ti holder (part number 06-91-PH) is particularly recommended as its shorter threaded post avoids interference with the 6mm wrench when tightening the conical nut, and it also happens to be the lightest Ti replacement option.

Cable Routing and Straddle Cable System

The Dia-Compe 987 employs a traditional cable carrier arrangement for its braking system. Each set of 987 brakes comes supplied with a 270mm long straddle cable. One end of this cable features two lead anchors. The primary lead anchor, a 7mm barrel-shaped piece, fits into the top of the left brake arm. The second lead anchor serves as a convenient finger hold, allowing for quick release of the brake for wheel removal. The opposite end of the straddle cable is bolted securely to the top of the right brake arm. This fastening bolt is made of cadmium-plated steel and has a 5mm hex fitting in its head. It measures 10mm in length, features 6mm by 1mm pitched threads, and weighs 3.5 grams.

The straddle wire itself is supported by a carrier stamped from aluminium plate. This black carrier utilises a "keyed" steel bolt, meaning it can only be inserted in one specific orientation, ensuring correct alignment. A hole passes through this bolt, through which the brake cable's inner wire is threaded. A black aluminium nut is then used to tighten this bolt, along with two spacing washers, to securely hold the inner wire in place. This system ensures reliable cable tension and efficient power transfer to the brake pads.

Brake Pads and Mounting Hardware

The Dia-Compe 987 is supplied with two black steel washers and two black steel mushroom head mounting bolts. These bolts have 6mm by 1mm threads and are 13mm long, each weighing 5.5 grams. The steel washer serves to protect the pivot axle beneath the mounting bolt. The brake pads themselves are a one-piece moulded design, incorporating steel reinforcement and a non-threaded aluminium mounting post. Each pad measures 53mm in length and 15.3mm in height. The rim contact surface is 50mm by 10mm, featuring a slightly arched shape designed to conform to the curvature of a bicycle rim. The pads are typically black, except when paired with the Blue or Lavender coloured brake arms, in which case they are grey. Hardness testing revealed the black pads to have an A/92 rating, while the grey pads measured A/91. Each pair of brake pads weighs 36 grams.

Weight and Specifications

In terms of performance metrics, the Dia-Compe 987 cantilever brake achieves a Bike-Pro brake profile measurement of 51mm. This measurement is a standard way to compare the physical dimensions and potential clearance of different brake models. The 987 is versatile, suitable for use as either a front or rear brake. The total weight of a single Dia-Compe 987 brake unit is approximately 155.5 grams. Adding the straddle cable and carrier (15.5 grams) and the mounting bolts and washers (13 grams), the complete system weighs in at roughly 184 grams. When ordering, specifying the desired colour is essential.

Comparison with the Dia-Compe 986

It's beneficial to compare the 987 with its sibling, the Dia-Compe 986, as many of their components and design philosophies overlap. The 986 also features cold-forged aluminium arms, but is available in a more limited palette of three colours: Black, Ti Grey, or Silver. A notable stylistic similarity exists between the 986 and the Ritchey Logic cantilever brake, which is no coincidence, as Dia-Compe manufactures the Ritchey brake. The two were developed concurrently, reflecting shared design principles.

Mechanical Similarities and Differences

The mechanical aspects of the 986 mirror the 987 in many ways, making the 987's description largely applicable. The internal tension springs in the 986 are also accessible, replaceable, and adjustable, using the same parts as the 987: the plastic shroud, cadmium-plated nut, spring, and inner machined steel bushing. Consequently, a 13mm cone wrench is used for tension adjustments on both models. The system for holding the brake pads is also identical, with only a minor, non-functional difference in the conical nut's finish – it is silver on the 986, compared to black on the 987, though the components are otherwise the same. As with the 987, aftermarket SRP Ti pad holders, particularly the short, bulb-shaped ones, fit and function well on the 986.

The cable carrier and straddle wire used on the 986 are also identical to those on the 987. However, the aluminium plate and nut on the 986's carrier are silver, contrasting with the black components on the 987. This silver colour scheme extends to the mounting bolts and washers, which are also silver on the 986, despite being functionally the same as those on the 987. The straddle wire is secured in the same manner, using the same cadmium-plated bolt found on the 987.

Brake Pads and Final Weight Comparison

The Dia-Compe 986 is supplied with grey brake pads, which are the same as those used on the 987. Therefore, the primary differentiating factor between the two models, apart from colour options, is the subtle weight variation in the arms themselves, given the near-identical nature of most other parts. The 986 has a Bike-Pro brake profile measurement of 61mm, slightly larger than the 987's 51mm. Like the 987, the 986 can be used as either a front or rear brake. The weight of the 986 brake unit is 156.5 grams. Adding the straddle cable and carrier (15.5 grams) and the mounting bolts and washers (12.5 grams – slightly lighter than the 987's set), brings the total system weight for the 986 to approximately 184.5 grams. This makes the 986 only half a gram heavier than the 987, a negligible difference that highlights their shared engineering.

Frequently Asked Questions

What are the main advantages of the Dia-Compe 987 cantilever brake?

The Dia-Compe 987 offers excellent adjustability due to its accessible tension springs, durable construction from cold-forged aluminium, and a classic, low-profile aesthetic. The availability of multiple colours also allows for customisation.

Are the brake pads on the 987 interchangeable with other brands?

While the 987 uses standard mounting posts, aftermarket pad holders like the SRP Ti options are known to be compatible. For the pads themselves, their specific dimensions and compound would need to be matched with other brands.

Can the Dia-Compe 987 be used for both front and rear wheels?

Yes, the Dia-Compe 987 is designed to be versatile and can be used effectively as either a front or a rear brake.

What tools are needed to adjust the Dia-Compe 987 brakes?

A 13mm cone wrench is required to adjust the spring tension, and a 6mm hex wrench is needed to tighten the brake pad retaining nut.

Where are Dia-Compe brakes manufactured?

The Dia-Compe 987 and 986 brakes are manufactured in Japan.

What is the key difference between the Dia-Compe 987 and 986?

The primary differences lie in the colour options for the arms and minor aesthetic details on the cable carrier and mounting hardware. The overall weight and mechanical functionality are remarkably similar, with the 986 being only marginally heavier.

In conclusion, the Dia-Compe 987 cantilever brake represents a solid choice for cyclists seeking reliable, adjustable, and aesthetically pleasing braking performance. Its thoughtful engineering, from the cold-forged arms to the easily tuneable springs and robust mounting hardware, ensures a dependable braking experience. Whether you are maintaining a classic bike or building a new one, understanding the details of components like the 987 allows for informed choices and a deeper appreciation for the mechanics that keep us rolling.