Saga of the Crown Vic Rear Discs

ultrastang · Sep 16, 2007

I was at my mom's today and decided to take a look at her 2005 Mercury Grand Marquis GS's rear disc setup (same as 2003-present Crown Victoria's rear discs).

The rear discs are ventilated on this later C-V rear disc version. Unlike the '92-'02 Crown Vics though, the rear discs are not flip-flopped on the axle housing. Both calipers are mounted in front of the axle housing.

The 4-bolt mounting flange pattern looks to be 3-3/8" x 2", just like the older C-V versions (and the older Ford small bearing rear ends), but Ford threw a curve on this later setup. The flange is not positioned horizontally on the end of the axle housing tube. They turned the flange vertically on this later version. That pretty much screws-up the ability to take this setup and mount it directly to the end of a small bearing 8- or 9-inch housing end flange.

2005 Mercury Grand Marquis GS rear discs:

1. http://img513.imageshack.us/img513/9049/2005crownvictoriareardipd7.jpg

2. http://img513.imageshack.us/img513/2995/2005crownvictoriareardinl4.jpg

3. http://img167.imageshack.us/img167/5062/2005crownvictoriareardiga0.jpg

4. http://img174.imageshack.us/img174/8392/2005crownvictoriareardinu3.jpg

5. http://img513.imageshack.us/img513/1301/2005crownvictoriareardiem6.jpg

ratio411 · Sep 16, 2007

Where there's a will...

Does it matter where the caliper is?
Would it hurt anything to be in 12 o'clock position, as opposed to 3 and 9?

What about a custom bearing retainer plate that has a dual bolt pattern?
One for the rear, and a rotated one to mount the brackets?

D.Hearne · Sep 16, 2007

I thought the same thing, why not the 12 o'clock position, unless leaf springs are in the way ?

ratio411 · Sep 16, 2007

I don't know for sure, but it could be a simple matter of an adapter plate.

Excuse the very fast doodle, but it gets the idea across.
The red holes would mount the bracket, the blue holes would mount to the axle tubes.
Just a thought...
No patents pending either!

ultrastang · Sep 16, 2007

ratio411 said:
Where there's a will...

Does it matter where the caliper is?
Would it hurt anything to be in 12 o'clock position, as opposed to 3 and 9?

What about a custom bearing retainer plate that has a dual bolt pattern?
One for the rear, and a rotated one to mount the brackets?

Not saying it can't be done. It's just not (more or less) as direct of a bolt-on as the earlier models.

Rotating the '03+ calipers 90-degrees, to the way they are, is also going to mess the the parking brake cable operation, so that's another thing to consider.

Rusty67 · Sep 17, 2007

The simplest solution I can think of, no neccessarily easiest, is to cut the mount flange off and weld a new one on in the correct possition.

Helmantel · Sep 17, 2007

You mean on the axle? That's indeed the simplest, (but not easiest) and solves all problems.

Mounting the calipers at 12 o'clock will most likely also put the bleeder screws in the wrong place, which makes it difficult to get the air out.

ultrastang · Sep 17, 2007

ratio411 said:
I don't know for sure, but it could be a simple matter of an adapter plate.

Excuse the very fast doodle, but it gets the idea across.
The red holes would mount the bracket, the blue holes would mount to the axle tubes.
Just a thought...
No patents pending either!

The problem is, if you were just mounting the C-V anchor bracket directly to the housing's end flange, you would be loosing a little bit of the axle spline's engagement into the differential. If you have to add an adpater plate between the anchor bracket and the end of the housing's flange, you're pushing the axle even further out, which means you would be losing even more spline engagement. This may compromise the integrity of the axle's spline strength due to the reduced contact surface area.

Cutting the housing's end flanges off, re-clocking them, and welding them back on in a vertical orientation would be the most direct way to mount the '03-up C-V rear discs, but it would also be a major PITA, since it's not a simple solution, or one that just anyone could do.

I'm not sure if there's enough material/area in the factory '03+ C-V's anchor bracket to do this, but if the bolt pattern could be re-drilled on the casting, then you would be able to directly bolt it up like the earlier '92-'02 C-V versions.

Rusty67 · Sep 17, 2007

Will the new rotor fit the old Crown Vic brakes or are they bigger ? That would be an EASY solution

bnickel · Sep 17, 2007

Rusty67 said:
Will the new rotor fit the old Crown Vic brakes or are they bigger ? That would be an EASY solution

they're biger, like 11.5" for the 03+ and 11" for the earlier ones.

ultrastang · Sep 17, 2007

Rusty67 said:
Will the new rotor fit the old Crown Vic brakes or are they bigger ? That would be an EASY solution

Depending on what year model C-V discs you are talking about, the '03+ discs are 0.2" (a little more than 3/16") larger in diameter than the '92-'95 C-V rotors, and are 0.4" (a little more than 3/8") larger than the '96-2002s.

You may be able to machine the '03+ rotor's outer diameter down (accordingly) to fit which ever pre-'03 C-V brake setup you have, but I'm not sure the thickness of the '03+ rotor would fit inside the brake pads of the older setups. The '03+ rotor is .750" (3/4") thick. A '92-'95 C-V rotor is .500" (1/2") thick, and the '96-'02 C-V rotor is .550" (nearly 9/16") thick.

Just looking at the '98 C-V setup I have, it looks like you would have to lose close to an 1/8th inch thickness off both brake pads for a 3/4" thick rotor to fit in between. That would drastically shorten the life of the pads to have to lose that much material, initially, before you even started using the brakes.

ratio411 · Sep 17, 2007

Just thinking aloud...

I wonder if the later calipers would fit the earlier mounting brackets.
It would be nice if the later calipers were not only wider to fit the thicker rotor, but deeper too, to take up the additional diameter...
That would be too easy!

Another thing...
When you say the rotor is .200" or .400" larger diameter, that means it would only be .100 or .200 deeper into the caliper.
.100" isn't much at all. Shouldn't hit the caliper.
However this is assuming the 03+ caliper would bolt onto the earlier bracket OR the earlier caliper could take the thicker rotor without compromising pad thickness.

ultrastang · Sep 17, 2007

ratio411 said:
Just thinking aloud...

I wonder if the later calipers would fit the earlier mounting brackets.
It would be nice if the later calipers were not only wider to fit the thicker rotor, but deeper too, to take up the additional diameter...
That would be too easy!

Another thing...
When you say the rotor is .200" or .400" larger diameter, that means it would only be .100 or .200 deeper into the caliper.
.100" isn't much at all. Shouldn't hit the caliper.
However this is assuming the 03+ caliper would bolt onto the earlier bracket OR the earlier caliper could take the thicker rotor without compromising pad thickness.

I did not measure the center-to-center distance of the '05's caliper mounting bolts to compare it to the '92-'02 models, to have an idea if the '03+ caliper could be swapped onto the earlier caliper's anchor brackets. --Knowing Ford though, they probably changed things just enough to screw that possibility up. I do know that the physical appearance of the late-model C-V calipers does not look like the earlier ones, but not sure if they can be swapped onto the older brackets.

Even if the later calipers could be swapped, the mounting point distance of the caliper to the centerline of the axle is determined by the holes in the anchor bracket. Assuming the calipers and rotors could be swapped over to the older setups, there would still be machining involved to reduce the rotor's overall diameter --so that lessens the appeal of a simple swap, since it has to include machine shop cost for alterations. --this is, of course, assuming any of this can be done in regards to parts swapping.

IF this swap over would work, I'm also not sure what this would do to the parking brake cables, since the earlier version's cables run parallel to the anchor brackets, and the late model's runs perpendicular to them.

P.S. I see that we are both about to have birthdays. We are 2 years and 364 days apart --my birth date was September 30th, 1966.

ratio411 · Sep 17, 2007

Happy birfday!

You think that the .100" extra material would need to be cut off the diameter of the rotor?
I would think there is that tiny bit would squeeze in there.
However, I don't know near as much about this stuff as you do.

I am in no way arguing, just firing the brain cells in print.

ultrastang · Sep 17, 2007

ratio411 said:
Happy birfday!

You think that the .100" extra material would need to be cut off the diameter of the rotor?
I would think there is that tiny bit would squeeze in there.
However, I don't know near as much about this stuff as you do.

I am in no way arguing, just firing the brain cells in print.

I realize you're just thowing out ideas and not being argumenative. We're just having a gearhead talk session here.

If we are still talking about using the later caliper and rotor on the older setups (assuming if it can even be done), the 11.615" '03+ rotor would have to be trimmed down to the same (overall) diameter of the '92-'95 rotor's of 11.415" , or the '96-'02 rotor's diameter of 11.215" to clear the ears of the caliper's anchor brackets, --per the year model application that you would be working with.

The rotor needs to be the same diameter as the rotor it's replacing.

--and don't feel bad if I know a little more about this. After all, I have 2 years and 364 days head start on you. (wonka-wonka)

ratio411 · Sep 17, 2007

I was just thinking if you have 11.615" and 11.415" diameters, the added radius would be half the diameter difference.
Therefore the caliper would only have to swallow an additional .100".
The other .100" of the diameter difference would be on the other side of the rotor.

If the later calipers would fit the older brackets or the older calipers could handle the thicker rotors, then the additional .100" might just fit in the caliper without machining the rotor.

That's a whole lotta IFs!

88gt · Oct 31, 2007

To bring topic back to the mix...

I just recently put 2000 C-V rear disc's on my '65, one issue that I have run into was the lower caliper bolt has an interference with the leaf springs. On the passenger side the lower bolt can be installed, however, the drivers side cannot. My fix for this is to lower the rear of the car w/ 1" lowering blocks. Of course...I may end up cutting coils on my new front 620's to achieve the proper stance...

All is good though...the car will have the ability to stop when I tell it to go!!!

Jim

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