Most
brake shops resurface
the rotors when mechanics replace the brake pads. By the time a car, truck,
or motorcycle needs a brake job, the rotors may have grooves or areas of wear from
the rubbing of the old pads. If a brake rotor has an uneven surface, the new
pads won’t make contact at the proper angle and the brakes may squeak or
squeal. By turning
the rotors in a lathe, brake technicians remove surface imperfections and
provide the rotor with a smooth, uniform surface.
Some
mechanics also turn new OEM and aftermarket rotors to improve the factory
finish. As with re-turned brake rotors, the proper finish is a non-directional
one where scratches on the rotor’s surface extend in various directions,
lowering harmonic vibrations and minimizing pad vibration and noise. A non-directional finish also helps the new brake
pads to seat properly. Unless all surface irregularities are removed, however,
the brake pads may skip and jump when they rub against the rotors.
How to Resurface New and
Re-Turned Brake Rotors
To
apply a non-directional
surface finish to brake rotors, automotive technicians and do-it-yourself
(DIY) mechanics use the Flex-Hone® for Rotors tool from Brush Research
Manufacturing (BRM). Named an Undercar
Digest Magazine Top Ten Tool for 8 years in a row, the BRM rotor hone
features flexible nylon filaments that are permanently laminated to abrasive
globules. As testimonials from tire and muffler shops attest, this brush tool
is ideal for new or re-turned brake rotors and finishes more rotors per hone.
As
the Flex-Hone®
for Rotors guide explains, BRM rotor hones should be held securely in a
chuck, collet, or similar holding device. Mount the disc rotor on a brake
lathe, position all guards, and rotate the lathe between 125 and 210 RPM. Then
chuck the Flex-Hone® for Rotors in a variable-speed electric drill motor or low-speed
air drill, rotate the rotor brush between 300 and 600 RPM, and bring the brake
hone into contact with the metal surface at a slight angle.
When
using the Flex-Hone®
for Rotors, work in towards the center and out to the edge of the rotor
face, applying light but uniform pressure. Dwell time against the part – and not excessive pressure – is what produces the desired
surface finish. Use the BRM rotor hone dry and work the brake hone for just 15
to 20 seconds at a time, typically 10 – 15 seconds clockwise and 5 – 10 seconds
counterclockwise. To avoid overheating, do not dwell for longer periods of
time.
DIY Rotor Turning Example
DIY
mechanics like Blue95 of CrownVic.net,
an on-line automotive forum, know that a non-directional surface finish is important,
and that the Flex-Hone® for Rotors is the right tool for the job. After
building his own brake lathe from a McMaster Carr turntable, Blue95 set his
sights on resurfacing a set of Honda brake rotors. With the Flex-Hone® for
Rotors chucked in a handheld electric drill, the amateur mechanic used the rotor
hone for “clean-up” and “to get the surface refinished”.
Like
BRM’s other flexible honing tools, the Flex-Hone®
for Rotors is not designed for heavy-duty material removal. “I checked the
before and after rotor thickness with a dial caliper”, the brake tech noted,
“and the difference is negligible”. The
homemade brake lathe offered “some wobble”, Blue95 reported, but the Flex-Hone®
tool was “very easy to use, very controllable” and ideal for imparting a
“cross-hatch or circular finish, similar to what an engine cylinder finish
looks like”.
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