Doctor Diff Viper-Style 13" Front Disc Brake Kit

[DoctorDiff]

Thanks, I see how the bracket is aligned now.

I searched my email and didn't find anything from you, not even in the spam folder. Well, thanks for trying, and replying to this thread.

On 7/1/25 you Emailed me the following: "Your website says 2003 and newer calipers must be sourced, but I've been advised on the forbbodiesonly forum that the kit actually uses the 96-2002 Viper caliper. Can you clear this up?"

Four minutes later, I replied: "The 13" kit uses 2003 and newer calipers. The 11.75" kit uses 2002 and older calipers. Cass"

This is the only message I received from you. I just re-sent you the Email chain for reference.

My Email address is doctordiff@gmail.com Do not abbreviate the word "doctor". The abbreviated version is an Email address for another guy.

 

[autoxcuda]

On 7/1/25 you Emailed me the following: "Your website says 2003 and newer calipers must be sourced, but I've been advised on the forbbodiesonly forum that the kit actually uses the 96-2002 Viper caliper. Can you clear this up?"

Four minutes later, I replied: "The 13" kit uses 2003 and newer calipers. The 11.75" kit uses 2002 and older calipers. Cass"

This is the only message I received from you. I just re-sent you the Email chain for reference.

My Email address is doctordiff@gmail.com Do not abbreviate the word "doctor". The abbreviated version is an Email address for another guy.

Thanks for clearing that up and making note of the email address.

 

[JR_Charger]

On 7/1/25 you Emailed me the following: "Your website says 2003 and newer calipers must be sourced, but I've been advised on the forbbodiesonly forum that the kit actually uses the 96-2002 Viper caliper. Can you clear this up?"

Four minutes later, I replied: "The 13" kit uses 2003 and newer calipers. The 11.75" kit uses 2002 and older calipers. Cass"

This is the only message I received from you. I just re-sent you the Email chain for reference.

My Email address is doctordiff@gmail.com Do not abbreviate the word "doctor". The abbreviated version is an Email address for another guy.

Well that's interesting. I've got the 7/1/25 email I sent, which you've quoted, but no replies. I believe you when you say you replied to it - obviously you're making the effort to reply here. So there's a technical problem somewhere. I'll use a gmail account in the future.

FWIW I sent an email on May 23, 2022 asking about the Spicer "Trac Loc" differential - Mopar 8 1/4" Spicer "Trac-Lok" Differential

You probably replied to that one, and I didn't get that reply either.

 

[JR_Charger]

My first Viper caliper has arrived -

O'Reilly's could not get the rebuild calipers they advertise on their website. I got on eBay and found a pair of OEM calipers. Pricey compared to the Cobra calipers, but mmmmm . . . Viper logo. That said, I'd prefer these be gloss black with a gold logo. O'Reilly's phantom calipers would have been gloss black, with no logo, but I found a high temp vinyl Viper decal in gold. I thought, heck, if brake caliper decals are possible, that's probably how Chrysler did it. I'm surprised to see the logo is actually painted on.

These things are frickin' huge too. I did not expect them to be this big! I don't recall the two piston calipers on my Silverado being this big - maybe they are and I've forgotten. I bet these are bigger though.

So, these are 4 piston calipers, but they have opposing pistons, and IIRC Andy Finkbeiner's book says to measure the piston cylinder area by the pistons on one side of the caliper, in this situation, not all four. By my math, the Viper front calipers have a piston area of 4.29"s vs 4.0"s for the Cobra calipers.

The Eldorado rear calipers I currently have, have a single piston, but an area of 3.46 inches. I believe the rotor is 11". There are no performance pads for that caliper, so, although the piston area is larger than half the piston area of the Viper calipers, maybe the non-performance pads and lesser leverage will get me close to the 2:1 brake bias? I don't currently have a proportioning valve, and the distribution block is the drum brake block. The master cylinder is Doctor Diff's aluminum unit, without a booster. I'm assuming it will be possible to add the booster later, if needed. I've read that driving purists prefer the feel of manual brakes, and yet the Viper at least had the option of power brakes.

 

[autoxcuda]

My first Viper caliper has arrived -

View attachment 1892591

O'Reilly's could not get the rebuild calipers they advertise on their website. I got on eBay and found a pair of OEM calipers. Pricey compared to the Cobra calipers, but mmmmm . . . Viper logo. That said, I'd prefer these be gloss black with a gold logo. O'Reilly's phantom calipers would have been gloss black, with no logo, but I found a high temp vinyl Viper decal in gold. I thought, heck, if brake caliper decals are possible, that's probably how Chrysler did it. I'm surprised to see the logo is actually painted on.

These things are frickin' huge too. I did not expect them to be this big! I don't recall the two piston calipers on my Silverado being this big - maybe they are and I've forgotten. I bet these are bigger though.

So, these are 4 piston calipers, but they have opposing pistons, and IIRC Andy Finkbeiner's book says to measure the piston cylinder area by the pistons on one side of the caliper, in this situation, not all four. By my math, the Viper front calipers have a piston area of 4.29"s vs 4.0"s for the Cobra calipers.

The Eldorado rear calipers I currently have, have a single piston, but an area of 3.46 inches. I believe the rotor is 11". There are no performance pads for that caliper, so, although the piston area is larger than half the piston area of the Viper calipers, maybe the non-performance pads and lesser leverage will get me close to the 2:1 brake bias? I don't currently have a proportioning valve, and the distribution block is the drum brake block. The master cylinder is Doctor Diff's aluminum unit, without a booster. I'm assuming it will be possible to add the booster later, if needed. I've read that driving purists prefer the feel of manual brakes, and yet the Viper at least had the option of power brakes.

How much $$$ where they for the two?

 

[JR_Charger]

I got a "deal" on the left side, but it looks like it would normally cost around $800 for both with taxes and shipping. There aren't many available, so don't expect them to get cheaper, or to find many options for color.

 

[JR_Charger]

The driver's side caliper has arrived, and now I've got a decision to make -

As you can see, the colors don't match. The dullest one even has silver overspray on it from the logo.

They appear to be the same side caliper -

The only way to tell the difference is by the size of the pistons. Otherwise, they look like the same part.

Here's the problem I'm faced with. I can install them as-is, and 99.9% of the people out there will not notice, or care about the paint issue.

Or, I can have them repainted gloss black so they match, and put this pretty gold sticker on -

Maybe a mask could be made from the sticker, and the logo could be painted gold, and cleared over?

Just more time, money, and trouble to get what I really want.

What issues could there be in disassembling and reassembling these calipers?

It'd be super sweet if they both had the matching gold finish fasteners and brake line too.

 

[Mopar Hunter]

The only way to tell the difference is by the size of the pistons.

Two size pistons? One caliper will grab quicker than the other.

 

[JR_Charger]

Two size pistons? One caliper will grab quicker than the other.

LOL, each caliper has two different size pistons. It looks like the bigger one goes to the rear and bites first, than the little piston eats its leftovers.

 

[Kern Dog]

Me? I’d paint them. Black, too. When I got my kit from DrDiff, I specified BLACK since the rear calipers are dark gray. I didn’t want the fronts to stand out against the rear.

 

[Mopar Hunter]

LOL, each caliper has two different size pistons.

That makes sense. Paint them fire red, make them stand out.

 

[JR_Charger]

That makes sense. Paint them fire red, make them stand out.

You see this hat? This is our color palette, as much as possible.

Here's one with some chrome on it, which will be my excuse for having a chrome front bumper, a chrome lip on the rims, and polished aluminum window trim. But I will have a chrome bumper in front and a black bumper in back until someone shows me a Richard Petty hat with a chrome piece in the back.

He had a hat with a bit of Petty Blue worked into the chrome piece, so I tried to incorporate that -

My paint job isn't the best, but that emblem wasn't in the best shape either. I'll revisit it later, but it looks like the idea works anyway.

Hmm, I also made this graphic for the bulge hood I don't yet have -

and I've got this little diorama on the dash -

And I've got his signature on my glovebox -

Well, that settles it. Now I've got to have the calipers repainted and the Viper logo redone in gold.

I can't believe I'm actually going to disassemble new Viper calipers that cost hundreds of dollars. This is insane.

 

[Kern Dog]

REDline at 4100 ? Is that a slant six in the car ?

 

[JR_Charger]

REDline at 4100 ? Is that a slant six in the car ?

Pay no attention to what the tach is set at - redline would be zero for the the engine currently in the car.

BTW, how wide are your front rims?

 

[Kern Dog]

18 x 9. 4 3/4" back spacing.

275-40-18 tires.