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.