Dr Diff 13" Cobra front disc kit...Anyone here have any feedback?

[Kern Dog]

I'm looking at the Cobra front disc brake setup that Dr Diff offers.
Funny story...Back in 2006 when I bought his 10.7" rear disc kit, he offered to let me use a prototype of this front 13" kit at no expense. He said If I wanted to keep it, we'd work something out. He was looking for real world feedback on whether it was worth further investment for sale to the public. I politely declined because I was sure that I would like it but didn't want to spend the money for it at that time.
Here we are, 15 years later and I am ready now.
I have had the ubiquitous 12" Cordoba rotors (Actually 11.75) on 75 Dart knuckles with single piston iron calipers with a 2.75" bore pushing carbon metallic pads. It stops okay but not fantastic like some stock front disc-rear drum A body cars that I have had.
I want to change to a NON power master cylinder at the same time. I have been using this bulky booster and master cylinder for over 20 years now...

The Dr Diff master cylinder I want to use looks like this...

Aluminum, 15/16" bore and 2 bolt mount. It comes with a 4 to 2 bolt adapter plate.

The Cobra kit uses an aluminum hub, a lighter rotor and a twin piston aluminum caliper. The weight savings could be 10 lbs per side compared to what I have now while providing better braking.
Who has experience with this kit?

 

[Ottmundr]

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[72bluNblu]

I run the 13" DoctorDiff Cobra disks on my Duster. I installed them back in 2014, I wanna say I probably have about 25k miles on them?

I was originally running the Duster with 10.95" disks, 2.6" calipers and 10x2.5" drums, then 11.75" disks with 2.75" calipers and 10x2.5" drums, then 11.75 disks with 11x2.5" drums, then to the 13" Cobra disks and 11x2.5" drums, and most recently added DoctorDiff's 11.7" rear disks. Pretty much all have been with the 15/16" master cylinder from DoctorDiff. I think the current version with the 13" Cobra kit and 11.7" rear disks stops best, but it's not a night and day kind of difference when compared to the 11.75" disks and 11x2.5" drums.

I have to say that as far as "bang for your buck" goes, the 11.75" disks with 2.75" calipers and an aggressive set of pads is it. I like the 13" Cobra kit, and I do think it provides better braking. But it's not a dramatic improvement compared to the 11.75's. I ran the 11.75's and 2.75" piston calipers on my Challenger for all of the 70k+ street miles I put on it, and a decent chunk of that was with 275/40/17's on all 4 corners. And I have to say that I'm not sure that going from 11.75's and 2.75" calipers to 13" rotors and Cobra calipers is as big of an improvement as going from 10.95" rotors and 2.6" calipers to 11.75's and 2.75's.

Full disclosure, I've already bought the 13" Viper caliper kit to upgrade from the Cobra's. Part of that was the Viper kit popped up here and was local, the other part was that I still wanted more braking. So if I had to do it over again, I would probably just go straight to the Viper kit. I haven't run it yet, so I can't add a ton on that front.

There is also a guy at Invincible Extremes that makes brackets for the GT500 Brembo's Invincible Extremes Muscle Cars Garage . I think most of his brackets are based off of the 73+ disk knuckles and a stock hub, like you take a 10.95" disk or 11.75" disk and turn the rotor off and use that hub as the basis for your floating rotor. He's done kits from 13" all the way up to 15" using the GT500 stuff. I believe you could also use the aluminum hubs from DoctorDiff for that purpose, based on the offset the aluminum hubs are basically the same as a 73+ hub minus the rotor.

So that's my general impression of them. It's a good kit, not as great on the performance to price scale as the 11.75's but overall a better performer. Lots of pad options out there too, I'm just running what comes with the kit (semi-metallics). I can probably answer any specific questions you have, the install is pretty straight forward.

You can also shoot me a PM if you want, if I ever finish re-wiring my car the Viper calipers will be going on and I'll have the 13" cobras laying around. I think I'm gonna keep the hubs, partly because it's easier to just swap on the new rotors and partly because I want a set of hubs as spares. But Cass sells the hubs by themselves and I might be willing to let the calipers, brackets and lines go for a reasonable price if you're not in a hurry.

 

[dano]

I too have the 13" front, 11.6" rears, and 15/16 Master Cylinder from Dr Diff. I have a history with Fox and SN95 Mustangs so this was a familiar territory for me. I like it a lot and I consider it pretty much the most bang for the buck when you step outside OEM parts. 17"+ wheels are a must but with that you get way better tire options with furthers your braking ability. I will say the 13" rotors are anything but light weight, which is good.

I'm considering a Hydro boost to aid the system further but that's just me as I prefer a power brake feel after driving many manual brake cars and trucks.

 

[Kern Dog]

I think that I will skip the swap for now. I might still switch to the manual master cylinder though.
Thanks for the feedback, people.

Cheers!

 

[moparmarks]

My buddy just put them on his 72 Cuda road track car but it is still under construction.
On my Dart I have 11.75 on the front with the MBM GM disc on the back using a 1.03" manual cylinder. Stops great for me. I don't care for the weight of either setup though.

 

[72bluNblu]

I think that I will skip the swap for now. I might still switch to the manual master cylinder though.
Thanks for the feedback, people.

Cheers!

View attachment 1715939074

I think you’ll like the 15/16”
manual master cylinder. Brake feel is so much better with it. Plus it’s better to only change one thing at a time anyway so you know what was responsible for which changes.