Porsche wheel cylinders support braking in sportscars that pack plenty of power. In classic cars like the Porsche 356, these cylinders have pistons that are connected to brake shoes. If a wheel cylinder lacks the right surface finish, however, more than just piston ring sealing can suffer.
At the Porsche 356 Registry, an on-line community, the owner of a Porsche 356B asked for advice about honing brake cylinders. A few users suggested honing stones, but a German mechanic recommended the Flex-Hone® tool from Brush Research Manufacturing (BRM).
“I use this tool,” the Porsche mechanic explained. “This works better than all others.”
Flexible Honing for Wheel Cylinders
The Flex-Hone® is a flexible, resilient honing tool that removes cut, torn, and folded metal with a low-pressure, low-temperature, abrading action. BRM's flexible cylinder hone also breaks the “glaze” that forms on cylinder walls from the reciprocating movement of the pistons. For do-it-yourself (DIY) automotive projects, mechanics typically use the BRM Flex-Hone® with a handheld electric drill.
Flex-Hone® tools have their share of nicknames, including ball hones and dingleberry hones. That’s because these surface finishing and deburring tool feature distinctive abrasive balls or globules that are permanently laminated to flexible nylon filaments. With this unique design, each abrasive ball has an independent suspension so that the Flex-Hone® is self-centering and self-aligning to the bore.
Plateau Finishing for Peak Performance
Unlike rigid hones, Flex-Hone® tools are also self-compensating for wear. The differences don’t end there, however. Rigid hones are recommended for heavy-duty material removal, such as when cylinders have deep pits or grooves. That’s why in the discussion about wheel cylinders at Porsche 356 Registry, a user correctly noted that “If they’re pitted, they’ll need to be machined and re-sleeved”.
Flexible cylinder hones don’t remove large amounts of material, but they do they impart the ideal surface finish for optimum brake performance. Known as plateau finishing, this surface finishing technique removes peaks produced by prior honing and machining operations to create a flat, smooth, cross-hatch surface with oil-retaining valleys that promote brake fluid retention.
Flex-Hone® Selection and Use
BC Series Flex-Hone® tools are used with brake cylinders, wheel cylinders, and other bores with diameters between 4-mm and 3-in. BRM’s honing tools come in a variety of abrasive types and grit sizes that users select based on the bore material and the amount of work to perform. For complete information about Flex-Hone® selection and use, get the Flex-Hone® Resource Guide.