C3 Rear Bearing Assemblys

[John D.]

Hi:

I just read an article on C3 rear bearing assembly problems. Is there any way to tell the condition of the bearings without pulling them apart? Any telltale signs the bearings are going? Obviously I don't want to shear off a spindle.

I have had my C3 for a little over a year and I have no clue when or if the bearing assemblys were ever changed or pulled out.

Also any suggestions on a company who rebuilds the assemblys? Any experience with Van Steel?

Thanks for the advice, John

[Joe L.]

Re: C3 Rear Bearing Assemblys

John-----

Usually, when things get real bad with these, you can detect it by jacking up the car and trying to "rock" the wheel with your hands planted at the 12 o'clock and 6 o'clock positions or the 3 and 9 o'clock positions. There should be very little "play" observed. A very small amount is ok, since the bearing end play should be somehwere between .001" and .006". However, if there is more than just a "scoche", you need to have the bearings serviced.

Van Steel of Clearwater, FL , Bair's Corvette of Linesville, PA, or Carter's Corvette of Livermore, CA are excellent places to get the trailing arms rebuilt. All have EXTENSIVE experience with these and, for these, experience is everything.

[Joe L.]

Re: C3 Rear Bearing Assemblys

John-----

Usually, when things get real bad with these, you can detect it by jacking up the car and trying to "rock" the wheel with your hands planted at the 12 o'clock and 6 o'clock positions or the 3 and 9 o'clock positions. There should be very little "play" observed. A very small amount is ok, since the bearing end play should be somehwere between .001" and .006". However, if there is more than just a "scoche", you need to have the bearings serviced.

Van Steel of Clearwater, FL , Bair's Corvette of Linesville, PA, or Carter's Corvette of Livermore, CA are excellent places to get the trailing arms rebuilt. All have EXTENSIVE experience with these and, for these, experience is everything.

[Gary S.]

Re: C3 Rear Bearing Assemblys

Excellent advice from Joe. I followed this advice diagnosing a noisy rear end in my 72 last fall. Another poster on this forum suggested that I pull the brake caliper on the suspect trailing arm and rotate the assembly by hand. Sure enough - there was enough bearing noise, without the caliper and pads in the way, to make me suspect a failed/failing bearing. I did the same test to the other side and it was quiet.

Gary

[Gary S.]

Re: C3 Rear Bearing Assemblys

Excellent advice from Joe. I followed this advice diagnosing a noisy rear end in my 72 last fall. Another poster on this forum suggested that I pull the brake caliper on the suspect trailing arm and rotate the assembly by hand. Sure enough - there was enough bearing noise, without the caliper and pads in the way, to make me suspect a failed/failing bearing. I did the same test to the other side and it was quiet.

Gary

[Jim T.]

Re: C3 Rear Bearing Assemblys

South of you in PA is where Bairs is located that Joe Lucia mentioned. You can contact them and they will sent you the containers to send your complete trailing trailing arms from your 68 and they will take care of everyting. What I like about Bairs is that they can attach the disc to the spindle with rivets like your car came from the factory if yours has been removed. This will assure no air pumping of the rear calipers a definite safety feature. Most likely if the revits are missing from your rear discs if your bearings have been serviced. If the service facility has the right tools to disassemble the bearings the removal of the revits are not neccessary.

[Jim T.]

Re: C3 Rear Bearing Assemblys

South of you in PA is where Bairs is located that Joe Lucia mentioned. You can contact them and they will sent you the containers to send your complete trailing trailing arms from your 68 and they will take care of everyting. What I like about Bairs is that they can attach the disc to the spindle with rivets like your car came from the factory if yours has been removed. This will assure no air pumping of the rear calipers a definite safety feature. Most likely if the revits are missing from your rear discs if your bearings have been serviced. If the service facility has the right tools to disassemble the bearings the removal of the revits are not neccessary.

[Michael W.]

To rivet, or not to rivet- one of the issues that

just won't die.

Presence or absence of the rivets does not directly or indirectly cause air pumping. Lateral runout of the rotor surface does. The two main contributors to run out are:

1)poor matching/machining of the spindle and rotor combo which allows more than .005" TIR
2)excessive bearing clearance that allows the rotor assembly to 'wander' back and forth with respect to the caliper.

Neither of these points is addressed by riveting the rotor.

The ONLY reason GM riveted the rotors was for ease of final machining of the rotor surface once mated with the spindle or hub, and convenience of subsequent transportation to the assembly line. After completion of this operation, the rivets became superfluous. They are not required and serve no purpose during operation of the car.

A more modern OEM assembly method, used on almost all cars today, is to precisely machine the hub mating surface to almost perfect perpendicularity with respect to the axis of the hub. The rotor is separately machined as flat as possible. The stack up tolerances of the two operations results in a maximum runout that is well below the threshold of pad knockback and air pumping.

The benefit of manufacturing this way is to ease replacement of rotors in the field, being that any rotor can now be fitted on any hub with no final machining required. There are no rivets holding these rotors to the hubs.

[Michael W.]

To rivet, or not to rivet- one of the issues that

just won't die.

Presence or absence of the rivets does not directly or indirectly cause air pumping. Lateral runout of the rotor surface does. The two main contributors to run out are:

1)poor matching/machining of the spindle and rotor combo which allows more than .005" TIR
2)excessive bearing clearance that allows the rotor assembly to 'wander' back and forth with respect to the caliper.

Neither of these points is addressed by riveting the rotor.

The ONLY reason GM riveted the rotors was for ease of final machining of the rotor surface once mated with the spindle or hub, and convenience of subsequent transportation to the assembly line. After completion of this operation, the rivets became superfluous. They are not required and serve no purpose during operation of the car.

A more modern OEM assembly method, used on almost all cars today, is to precisely machine the hub mating surface to almost perfect perpendicularity with respect to the axis of the hub. The rotor is separately machined as flat as possible. The stack up tolerances of the two operations results in a maximum runout that is well below the threshold of pad knockback and air pumping.

The benefit of manufacturing this way is to ease replacement of rotors in the field, being that any rotor can now be fitted on any hub with no final machining required. There are no rivets holding these rotors to the hubs.

[John H.]

Re: To rivet, or not to rivet- one of the issues t

Good point, Mike - the Viper is a good example of this, as the design is very similar. We take hub/bearing/knuckle assemblies out of a container from one supplier and install them, take rotors from another supplier and install them to the hub, then install the fixed 4-piston calipers from yet another supplier(Brembo) over the rotor to the hub/knuckle and bolt it up. At this point the rotor is still loose on the hub, and is secured against the hub surface when the wheel is installed and torqued. No runout problems, no knock-back or air-pumping. Machining tolerances are much better today than they were 35 years ago.

We also build the Viper engine right next to the car assembly line, and we buy the block and crank finish-machined, and the pistons already ringed and assembled to the rods (different suppliers for each); one bore size, one piston size, one size of main and rod bearing shells - this kind of tolerance control was unthinkable even ten years ago, but it's commonplace today.

[John H.]

Re: To rivet, or not to rivet- one of the issues t

Good point, Mike - the Viper is a good example of this, as the design is very similar. We take hub/bearing/knuckle assemblies out of a container from one supplier and install them, take rotors from another supplier and install them to the hub, then install the fixed 4-piston calipers from yet another supplier(Brembo) over the rotor to the hub/knuckle and bolt it up. At this point the rotor is still loose on the hub, and is secured against the hub surface when the wheel is installed and torqued. No runout problems, no knock-back or air-pumping. Machining tolerances are much better today than they were 35 years ago.

We also build the Viper engine right next to the car assembly line, and we buy the block and crank finish-machined, and the pistons already ringed and assembled to the rods (different suppliers for each); one bore size, one piston size, one size of main and rod bearing shells - this kind of tolerance control was unthinkable even ten years ago, but it's commonplace today.

[Craig S.]

Re: To rivet, or not to rivet- one of the issues t

Mike - you are absolutely correct....but if you stay with GM spindles they need to be accurately faced to be true. International Axle spindles are held to I believe 2-3 ten thousandhs of an inch trueness in their CNC process, and are a higher grade forging than GM's, so they are a great choice for replacements. Of course, the rotors need to equally be trued or be of high grade manufacture in the first place. Otherwise, the rivet and true afterwords process is a sure fire way to insure accuracy.....Craig

[Craig S.]

Re: To rivet, or not to rivet- one of the issues t

Mike - you are absolutely correct....but if you stay with GM spindles they need to be accurately faced to be true. International Axle spindles are held to I believe 2-3 ten thousandhs of an inch trueness in their CNC process, and are a higher grade forging than GM's, so they are a great choice for replacements. Of course, the rotors need to equally be trued or be of high grade manufacture in the first place. Otherwise, the rivet and true afterwords process is a sure fire way to insure accuracy.....Craig

[Michael W.]

What I was driving at was

that the act of riveting does not eliminate runout- it was simply GM's way of holding stuff together while the final machining was done.

In the field a much simpler way is use the lug nuts reversed and torqued on the studs to secure the rotor to the hub while truing the surfaces.

Rivetless and Loving It In Montreal, Mike

[Michael W.]

What I was driving at was

that the act of riveting does not eliminate runout- it was simply GM's way of holding stuff together while the final machining was done.

In the field a much simpler way is use the lug nuts reversed and torqued on the studs to secure the rotor to the hub while truing the surfaces.

Rivetless and Loving It In Montreal, Mike