Springer Automotive Restoration
Chris Springer (408) 857-2088
Chris Springer (408) 857-2088
The GM hub/rotor assembly has not been available for a long time now and NOS inventory is nearly depleted.
Regarding the hub/rotor assembly, the GM Service Manual clearly states, “the indicator reading should not exceed .002
inches. If runout exceeds this amount the hub and disc assembly should be replaced.” (1966 Chevrolet Chassis Service
Manual). A true GM quality replacement part is largely unavailable in the aftermarket.
Regarding the hub/rotor assembly, the GM Service Manual clearly states, “the indicator reading should not exceed .002
inches. If runout exceeds this amount the hub and disc assembly should be replaced.” (1966 Chevrolet Chassis Service
Manual). A true GM quality replacement part is largely unavailable in the aftermarket.
1965-1982 Corvette Hub/Rotor Issues
To build a better product one must first understand how the original was created. After putting several NOS units in the
lathe, it becomes apparent that GM was rough machining the cast iron hubs and riveting them to a rotor, then turning
the entire assembly on a lathe. The original rotors were cast so poorly that they had to use balancing “weights,”
inserted into the rotor vanes to compensate for poor casting/machining. The original hubs (without rotors), when placed
on a lathe (with new or old races) usually have a runout of at least .005” and sometimes up to .015”. The entire
assembly was then joined by rivets. Lastly, the friction surfaces were machined together as one unit.
lathe, it becomes apparent that GM was rough machining the cast iron hubs and riveting them to a rotor, then turning
the entire assembly on a lathe. The original rotors were cast so poorly that they had to use balancing “weights,”
inserted into the rotor vanes to compensate for poor casting/machining. The original hubs (without rotors), when placed
on a lathe (with new or old races) usually have a runout of at least .005” and sometimes up to .015”. The entire
assembly was then joined by rivets. Lastly, the friction surfaces were machined together as one unit.
The process was not perfect. There were balance issues. And there were service issues. When the rivets are drilled out
and replaced with an aftermarket rivet, the rotor and hub assembly would have to be shimmed and checked for runout
with a dial indicator. This method is not very easy for the at-home restorer and inefficient for a professional restoration
shop. Also, by drilling out the rivets, the authenticity of the part is lost. During subsequent servicing, the process is
repeated indefinitely, with time-consuming efforts to attempt to reduce the runout with shims. So after several attempts
and continuing progress toward perfection and repeatability, it seemed the foundation (hub face and bearing surfaces)
was the place to start to build a better hub/rotor assembly.
and replaced with an aftermarket rivet, the rotor and hub assembly would have to be shimmed and checked for runout
with a dial indicator. This method is not very easy for the at-home restorer and inefficient for a professional restoration
shop. Also, by drilling out the rivets, the authenticity of the part is lost. During subsequent servicing, the process is
repeated indefinitely, with time-consuming efforts to attempt to reduce the runout with shims. So after several attempts
and continuing progress toward perfection and repeatability, it seemed the foundation (hub face and bearing surfaces)
was the place to start to build a better hub/rotor assembly.
After a bit of consultation, and a few missteps, we found the ultimate partner: Tab Bell, a Corvette enthusiast/owner and
local businessman whom devised the ultimate solution: to use a modified Corvette spindle as a fixture. This method
eliminates the repeatability problems with tapered universal cones designed for the entire automobile industry, and
differing levels of operator skill found nationwide.
local businessman whom devised the ultimate solution: to use a modified Corvette spindle as a fixture. This method
eliminates the repeatability problems with tapered universal cones designed for the entire automobile industry, and
differing levels of operator skill found nationwide.
Remanufacturing the assembly is the only way to ensure a part which meets both the quality and appearance standards
of a discriminating restorer. After countless attempts and seven special fixtures and tools, the process has been
simplified to eight steps- with 100% repeatability.
of a discriminating restorer. After countless attempts and seven special fixtures and tools, the process has been
simplified to eight steps- with 100% repeatability.
Step one is to drill the rotor off the hub and solvent wash the hub to clean it up. It is then inspected for damage
(specifically the race seats, seal seats, and wheel studs). Inferior cores must simply be destroyed. Additionally, the old
bearing races must be pressed out, along with the wheel studs.
(specifically the race seats, seal seats, and wheel studs). Inferior cores must simply be destroyed. Additionally, the old
bearing races must be pressed out, along with the wheel studs.
Step two is beadblasting the hub, re-inspecting, and installing new bearing races.
Step three involves placing the hub in a lathe and machining it true. This requires using a special made Corvette
spindle fixture. Two fixtures had to be made, one for the small bearing cars (1965-1968), and one for the large bearing
cars (1969-1982).
spindle fixture. Two fixtures had to be made, one for the small bearing cars (1965-1968), and one for the large bearing
cars (1969-1982).
Step four is to install new wheel studs (originals are now 40+ years old).
Step five requires bolting the hub assembly to the new rotor to check for runout. This requires the use of the special
spindle fixture again, and ensures that the rotors to be used are within specification. The higher-quality Raybestos 5500
rotors used were advertised as “No turn- guaranteed,” so they seemed like a logical choice. After a phone call to a
Raybestos engineer, they clarified the guarantee to be within .002” runout. We found that after bolting the rotor to the
remanufactured hub, the rotors were within .001” runout. Unfortunately, the Raybestos 5500 rotors do not have the pre-
drilled and counter-bored rivet holes.
spindle fixture again, and ensures that the rotors to be used are within specification. The higher-quality Raybestos 5500
rotors used were advertised as “No turn- guaranteed,” so they seemed like a logical choice. After a phone call to a
Raybestos engineer, they clarified the guarantee to be within .002” runout. We found that after bolting the rotor to the
remanufactured hub, the rotors were within .001” runout. Unfortunately, the Raybestos 5500 rotors do not have the pre-
drilled and counter-bored rivet holes.
Step six is simply drilling and counter-boring the rivet holes to prepare for final assembly.
Step seven is when the new rotor is installed and riveted to the hub. This is not an easy task, and a special fixture had
to be made to support each rivet for 20 tons of pressure each, in a star-pattern.
to be made to support each rivet for 20 tons of pressure each, in a star-pattern.
Finally, the eighth step is to re-install in a lathe and check runout to ensure a measure of less than .001”.
Satisfaction has been finally achieved! As an added benefit, because of the custom fixtures and tools made, the
hub/rotor assembly can be re-machined while indexed off the bearing/races, as Chevrolet originally intended. This
allows the owner/shop to have the assembly re-machined and returned to OEM specification.
hub/rotor assembly can be re-machined while indexed off the bearing/races, as Chevrolet originally intended. This
allows the owner/shop to have the assembly re-machined and returned to OEM specification.
Pressing new bearing
races in using a special
tool.
races in using a special
tool.
The rotors have been removed and
discarded. The hubs have been inspected
and cleaned. The wheel studs and bearing
races have been removed.
discarded. The hubs have been inspected
and cleaned. The wheel studs and bearing
races have been removed.
The hub/rotor assembly has been
installed on a 1965 Corvette (small
bearing).
installed on a 1965 Corvette (small
bearing).
The hub/rotor assembly has been
installed on a 1969 Corvette (large
bearing).
installed on a 1969 Corvette (large
bearing).
Hub assembly with longer wheel
studs for a vintage racing Corvette
after machining of the hub faces.
Vintage racers choose not to rivet
the hub/rotor assembly together but
still need hubs/rotors with zero
runout.
studs for a vintage racing Corvette
after machining of the hub faces.
Vintage racers choose not to rivet
the hub/rotor assembly together but
still need hubs/rotors with zero
runout.
Custom bearing
tools.
tools.
Two factory spindles had to be
sacrificed to complete the task: one for
the small bearing cars, and one for the
large bearing cars.
sacrificed to complete the task: one for
the small bearing cars, and one for the
large bearing cars.
Here is a hub/rotor assembly for
a 1966 Corvette that awaits J-56
calipers.
a 1966 Corvette that awaits J-56
calipers.
Typical professional shim made to compensate for an out of true
hub face.
hub face.
Our current price for this service is $275 per hub/rotor assembly.
Written by Chris and Kyle Springer. This article has appeared in Corvette Magazine and The Corvette Restorer magazine.