C-Body Front Disc Conversion Prep

[SGVert]

My 68 Sportsgrain Newport came with 4 wheel drums. When I restored the car in 2003, I converted to SSBC 4wheel discs. I have never felt that they would safely get me to a stop in a panic situation. After going on the Illinois River Run cruise a week ago, I've decided to change the front brakes out to start with and go with one of the 69-73 C-Body disc swaps.

I had bought 2 pretty complete sets from different people a decade ago and brought the set that was most complete home from storage this week to start going thru it to see if I have what I need to get started.

I'll post pics of the major parts in a couple of posts for comments:

SPINDLES: Widest diameter of spindle appears to be 1 3/8" (1.375)
Are these the 70-72 or 73? I'm having a hard time making out the complete part numbers that are stamped on the spindle side.

 

[SGVert]

CALIPERS:

 

[SGVert]

ROTORS: I would probably source new, but the guy sent me these when I bought the parts

 

[SGVert]

DUST SHIELDS (in great condition, started to de-grease them and they are in great shape)
BRAKE PADS: (were new when I got the kit from the guy)

 

[Davea Lux]

The 1.375" inner bearing mount would be from a '73 spindle. A couple of questions:
1.) What did you use for a booster when you did the conversion? To adequately stop a C-Body beast you really need a '68-'70 Bendix dual diaphragm booster. A lot of the after market conversion kits have a 1" smaller booster that is not really powerful enough to get the job done, neither is the factory drum booster.
2.) An adjustable proportioning valve should be present as part of the conversion. Having that item properly adjusted can make a lot of difference in how the vehicle stops.
3.) All of the disc brake equipped C-Bodies used 15" wheels to accommodate the large diameter factory calipers. If your conversion kit was set up to retain the 14" wheels, the rotor diameter was about 1" smaller and had less friction area to stop the car.

Police cruisers and cars with the heavy tow package used the riveted pads, most others were bonded. The riveted pads held up a lot better in high brake temp situations. The rotors in the photo appear to also be the one piece cast units used on the '73 application. Check to see if the bearings fit the spindle. Pin type calipers are correct for either the '72 or '73 application.

Dave

 

[SGVert]

The 1.375" inner bearing mount would be from a '73 spindle. A couple of questions:
1.) What did you use for a booster when you did the conversion? To adequately stop a C-Body beast you really need a '68-'70 Bendix dual diaphragm booster. A lot of the after market conversion kits have a 1" smaller booster that is not really powerful enough to get the job done, neither is the factory drum booster.
2.) An adjustable proportioning valve should be present as part of the conversion. Having that item properly adjusted can make a lot of difference in how the vehicle stops.
3.) All of the disc brake equipped C-Bodies used 15" wheels to accommodate the large diameter factory calipers. If your conversion kit was set up to retain the 14" wheels, the rotor diameter was about 1" smaller and had less friction area to stop the car.

Police cruisers and cars with the heavy tow package used the riveted pads, most others were bonded. The riveted pads held up a lot better in high brake temp situations. The rotors in the photo appear to also be the one piece cast units used on the '73 application. Check to see if the bearings fit the spindle. Pin type calipers are correct for either the '72 or '73 application.
Dave

I have the dual diaphragm booster installed from when I did the SSBC conversion.

I have an adjustable proportioning valve installed also.

I have 15 x7 Magnum 500’s installed.

Will do on the bearing check. I’m probably going to source new rotors and get new bearings, etc. anyway just so those are brand new.

thanks for once over!

 

[furious70]

Mark, no reason to not take the rotors to be checked if thick enough to be turned. I'm not sure who does it by us now, the car quest on Lake near the Elgin O'Hare did before it closed. Probably the Napa by the Brunswick still does?

 

[SGVert]

Mark, no reason to not take the rotors to be checked if thick enough to be turned. I'm not sure who does it by us now, the car quest on Lake near the Elgin O'Hare did before it closed. Probably the Napa by the Brunswick still does?

I think the guy I bought them from had them turned before he sent them to me. They’ve got some flash rust on them but could probably be done. I checked online and Rock Auto has new Raybestos Rotors for $36 each so it may be better to just get a new pair.

I’ve got to do a test fit for caliper clearance with the rotor, caliper and spindle together to make sure there’s not an issue before I go any farther. Otherwise I’ll have to go with different rims... I’ll do that tomorrow

 

[Davea Lux]

I think the guy I bought them from had them turned before he sent them to me. They’ve got some flash rust on them but could probably be done. I checked online and Rock Auto has new Raybestos Rotors for $36 each so it may be better to just get a new pair.

I’ve got to do a test fit for caliper clearance with the rotor, caliper and spindle together to make sure there’s not an issue before I go any farther. Otherwise I’ll have to go with different rims... I’ll do that tomorrow

When you decide to purchase new bearings, be sure to specify Timken. The China crap at Autobone and CarCrap are not up to the task. I would inspect the old bearings if they are not pitted, they are better than anything you can buy today, so reuse them.

Dave

 

[SGVert]

When you decide to purchase new bearings, be sure to specify Timken. The China crap at Autobone and CarCrap are not up to the task. I would inspect the old bearings if they are not pitted, they are better than anything you can buy today, so reuse them.

Dave

Sounds good Dave, I will

 

[FURYGT]

If you need rotors and don't want to buy cheap Rock Auto junk let me know as I have some New Rotors that were made long ago in the US or Canada.

 

[BAD69FURY]

I’ve done this conversion too and yes best to use factory parts from a c body that came with disc brakes. Word to the wise if you use the larger 11.75 rotors that are 1.25 inches thick make sure the matching pin calipers are the “wide mouth” to bite over the larger rotors

Make sure you have a matching pair that are both 2.5 inches wide shown here

 

[BAD69FURY]

To the naked eye you can accidentally buy pair that are not the same size width one will be a 2.5 width and the other a 2.1/4 like this below.

 

[BAD69FURY]

I’ve had this happen to me a couple of times from the auto parts stores, there mixed and matched out there. Very frustrating! So pay attention to what your buying.

 

[SGVert]

When you decide to purchase new bearings, be sure to specify Timken. The China crap at Autobone and CarCrap are not up to the task. I would inspect the old bearings if they are not pitted, they are better than anything you can buy today, so reuse them.

Dave

The bearings are Timken! They look pretty new and spin freely, I can probably reuse them.

 

[SGVert]

To the naked eye you can accidentally buy pair that are not the same size width one will be a 2.5 width and the other a 2.1/4 like this below. View attachment 458813

I measured from the black boot around the cylinder to the opposite edge and they are both 2.5”, should be good to go with these.

 

[SGVert]

I’ve got to do a test fit for caliper clearance with the rotor, caliper and spindle together to make sure there’s not an issue before I go any farther. Otherwise I’ll have to go with different rims... I’ll do that tomorrow

I assembled each spindle to the rotor and installed each caliper respectively, then mounted each assembly to my spare 15x7 magnum 500 rim/spare tire to test for clearance...

Fits well, caliper does NOT rub on the rim anywhere, have about 3/16 clearance all around! I was concerned about this, but I’m happy with the results! Good to go with remaining parts I need to get. I’m going to get new rotors, I measured these and one is thinner that the other, they have both been cut in the past, so I’d rather have new.

Thanks for all the tips on what to watch out for. I’m comfortable doing this at home in my garage but I like to be prepared in advance so I don’t have to make multiple trips to auto parts/tool stores while the install is in progress!

 

[furious70]

Are you buying new hoses? They look old.

 

[SGVert]

Are you buying new hoses? They look old.

Yes, they’re toast. I may be able to transfer the hoses from my SSBC front calipers to these. I’ve got to measure their length. If not I’ll get new. Any idea how long the hoses need to be?

 

[furious70]

The same as the old ones?