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The eBearing News
September 15, 2000
CR/SKF Recalls Defective Automotive
Wheel Hub Units, Files NHTSA Petition
copyright © 2000 eBearing Inc.
Chicago Rawhide (USA) division of SKF (Sweden) has initiated an unprecedented suspension of
sales and total customer recall of all BR930070, BR930053, BR930089, BR930093, CBR930093 and GBR930093 automotive
wheel hub units manufactured by Precision Automotive Industries and sold by CR since August 1999.
Precision Automotive Industries is an aftermarket manufacturer; the recall involves only hub units which CR has been sourcing from Precision since August 1999. Until then, CR was buying these units from a different vendor; those
units are not subject to the recall.
The six part numbers of wheel hub units involved are all rear wheel applications, fitting 1989 to 1996 model years of various midsize GM front-drive cars.
[ go to SKF's web site for details of the recall and related information ]
The failures are apparently related to an engineering/design issue and a related machining issue, both of which surfaced
when warranty return units were examined by SKF Engineering Center in Plymouth, Michigan.
The engineering/design issue relates to the wall thickness of the spindle where the bearings are pressed. To accommodate
the bearings Precision chose to use, the wall thickness is believed to be too thin, compromising the structural integrity
of the spindle at the point where it flares out to create the flange where the wheel is mounted.
The machining issue relates to that same area of the spindle where it flares out to create the flange. The inside corner
radius machined into the spindle was found to be too sharp, creating a stress riser and potential failure point.
Not only is CR publicly recalling these hub units, but they have taken two other steps, again unprecedented since
aftermarket hub units came on the market over 20 years ago.
First, CR is offering to pay for their distributors and installers to track down and all costs of replacing the affected
units on customer vehicles.
Second, CR has taken the extremely rare step of filing a petition with the National Highway Traffic Safety
Administration (NHTSA) for a hearing on whether Precision Automotive Industries had properly addressed its
obligations under the National Traffic and Motor Vehicle Safety Act (i.e. that Precision manufactured the units
to meet or exceed the necessary safety specifications).
eBearing has spoken to a number of sources, trying to assemble a clearer picture of the situation.
CR's Response
Bill Diggory, VP/GM of CR's Aftermarket Business Unit, who wrote the recall letter to CR's customers, told eBearing
that the letter essentially speaks for itself, declining further comment.
Precision's Response
eBearing then spoke to John Rice, President of Precision Automotive Industries. He took the opportunity to clarify some
of the issues involved and indicated his surprise at the intensity and level of CR's actions.
Mr. Rice first indicated that, although CR's letter lists AQ/Transcom dba Precision Automotive as the manufacturer
and vendor of record, in fact Transcom and Precision are two separate entities. He wanted to clarify that Transcom is
not involved in any way in the recall, but that Transcom's automotive and industrial seals do compete with CR's seals
in the market. Precision Automotive, not Transcom, is the manufacturer of the hub units.
Out of over 19,000 of these units Precision sold to CR under this program, he said they have information about failures in
only 12 units, with one of those failures unfortunately resulting in a rollover accident. 12 failures out of 19,000 is .06%,
below what we would expect to see, including installer error and accident damage. The rollover accident is apparently what
caused CR to initiate a detailed engineering analysis by SKF and eventually recall the units.
Mr. Rice also told eBearing that, as part of the process which certified the Precision hub units as suitable quality for their
product line, CR/SKF had conducted thorough engineering analyses and quality audits before purchasing the first unit.
All of the affected hub units had passed CR/SKF engineering analyses and quality audits.
Others
eBearing also knows of at least two other aftermarket hub assembly manufacturers (Precision competitors) who were asked
to asses the Precision hub units' metallurgy, engineering, machining and assembly. Both manufacturers apparently also
expressed their concern with those same wall thickness and chamfer radius issues.
Our Experience
eBearing management, unfortunately, has some experience with this type of flange failure. A crack initially
forms at the stress riser created by the sharp corner radius. The crack quickly works around the inside diameter of the hub
flange where the center of the vehicle's wheel is located.
When this failure occurs on a drum brake-equipped vehicle, there is little or nothing to stop the flange portion with the
studs, the brake drum, wheel and tire from separating from the vehicle.
This happens almost instantly, with little warning and giving the driver little opportunity to react.
On a vehicle equipped with disc brakes, there is some containment from the rotor locating within the caliper, but
it may not be sufficient to prevent wheel separation.
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- by Bruce A. Carr
from individual research,
tips and commercial sources.
Unauthorized reproduction is prohibited.
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eBearing.com ... for everything that moves™
Entire contents Copyright 1999-2008, eBearing Inc. All rights reserved.
eBearing.com and "... for everything that moves" are registered
trademarks of eBearing Inc.
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eBearing.com ... for everything that moves™
Entire contents Copyright © 1999-2008, eBearing Inc. All rights reserved.
eBearing.com and "... for everything that moves" are registered trademarks of eBearing Inc.
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