I'm working with Cass (DoctorDiff) to build a Viper based front disc kit for my Duster. Plan is to test it out on my car and if it all looks good then Cass might put it into production. Here are a couple of photos showing the first prototype mounted on the bench. This setup uses a DoctorDiff hub, Baer rotor, Viper caliper and an AR Engineering caliper bracket. Looks to me like it is going to work just fine. Should have it mounted up on the car in a few weeks.

Looks great!

I agree. That looks great! Is that a disk or drum spindle that it mounts to?
Wes

Disc knuckle. I used a FMJ knuckle in the picture but the kit will also fit on A body knuckles if you want to use a short knuckle for some reason.

I'm liking what I see!! I Hope to see it made into a kit form.
What year Viper calipers is it designed for?
13" rotor?

Nice! I haven't been too keen on the drilled Mercedes rotors deal on my current brake kit. I was going to go for a 2-piece hat rotor when they needed to be changed out.

What kind of braking force improvement can you expect with this as compared to a 2.75" single piston caliper with a 12" Cordoba rotor ?

What’s the availability on the Viper rotor?:

-Used only?

-Can you buy new or used without a core? Typical Price?

-what is typical rim diameter needed?

That 2 piece 13" Baer rotor will interchange with the 1 piece Mercedes rotor supplied with my Stage 4 front brake kit.

Matching 2 piece 11.7" rotors are also available for my 11.7" rear brake kits.

That is a Baer rotor. The Viper calipers are available new from any Dodge dealer. I just bought a set of them for my car. They were $481 each at my local dealer. Not sure how much longer they'll be available but no problem buying them at the moment.

I don't know but I suppose there is a reason the Mopar engineers didn't use the Cordoba rotors on the Viper.

Cass does your 2 piece 13" Baer and 11.7" rotors come with solid discs without any holes?

If so, then I need a set!
Thanks!

Thanks. I meant to write caliper, my bad.


I prefer the Dr Diff forged aluminum hubs. And they fit large bearing spindles (Willwood doesn’t have a kit for that).

I perfer the idea of a production caliper.

I’m going to run ET minilite rims. They said the Brembo calipers tend to have tighter clearance between caliper and backside of wheel/spokes.. What is the postive or negative distance between the top of the hat to the top of caliper in this new kit?

Slotted (only) Baer rotors are also available.

I'm calling you tomorrow for a set Cass thanks!

Were the 2 piece rotors not available when I bought my spare 1 piece rotors?
Thanks again!

The front rotors, rear rotors and rear hats have always been available. Baer made me a small batch of front hats to fit my Stage 4 front brake kit. I just received them today.

How much lighter are the 2 piece vs. the 1 piece?
Need to lose more weight haha!

4-1/2" B.C.?

Robert

WEll, yeah....
I understand that weight is a big part of it, right?
I was not criticizing at all, I was wondering about the math of it. I did not see the size of the rotor or the piston configuration of the caliper so...
Thanks though.

Yes 4.5" bolt circle.

I just talked to Cass and he was trying to get pricing from Baer for my 2 piece rotors
Cass makes some great stuff! I just might have to stock some of it

I'm just copying what the factory engineers did. They put these parts on the Viper so I'm putting them on my car. The Cordoba setup is 30 years old and was designed for a car with a top speed of 120 mph.

I run Cass's Stage 4 brake kit currently.

In terms of total piston area, I believe the current calipers he offers in this kit would be similar to the 4-piston GEN II Viper calipers. The calipers Cass provides use an 03+ GEN III Viper brake pad already.

So, what am I missing here other than the (possibly) lighter, two-piece rotors? Just the ability to use the authentic Viper calipers?

I kind of agree. The Viper caliper would be a lot nicer though since its made by Brembo.

I have Cass's Stage 4 kit also but I have Carbotech pad 592 which is for a 2001-2002 Gen2 Viper and it works great! Hauls 3400 lbs. down from 140 mph with no problems.

Hey andy the viper caliper bracket looks the same as the one I bought from you years ago that fit the 13" Mercedes rotors - are these the same or is the new caliper bracket different? Whats the weight savings on going from the heavy 1 piece rotor to the new 2 piece?

Got a quote from Cass. Whoa these rotors are pricey haha!
Andy can you please post up the 1 piece vs. 2 piece rotor weight? Trying to justify cost to weight, need vs. want ratio haha!

Thanks!

The offset on the hubs is different between the kits. The kit I used to make pushed the wheel surface out so that Mustang rims would bolt on. Cass has his wheel surface in the stock location. So no, the caliper brackets will not interchange.

Two piece rotors are 4 lbs lighter per side. So 8 lbs of unsprung weight off the front end.

Cass will have to answer that. From what I understand there might be a supply issue getting the knockoff caliper. The OEM design should be around for a long time since Vipers will be around for a long time. Downside is cost of course.

Thanks so much Andy! Unfortunately the 2 piece rotors and shipping to me would cost nearly $120 bucks per pound so the price is hard to justify as Cass's Stage 4 kit works great just heavy. I also have a spare set of his 1 piece Mercedes rotors already. I would rather spend that money on more track days.

If someone were to start from scratch I would definitely recommend your kit with Cass's 2 peice slotted only rotors!

Viper calipers are a radial mount?
What is the ctr to to ctr stud spacing and/or is it common to other caliper options?

All of the high end calipers are radial mount. Take a look at any Porsche or Ferrari and you'll see radial mount Brembo calipers. The Corvette was the only super fast car that was bucking the trend but I think GM engineers finally saw the light on the track cars.

Center to center on the Viper caliper is 130 mm. That is a fairly common measurement but I wouldn't bet that all Brembo calipers use the same dimension.

All of the current Chrysler "super cars" use what appears to be radial mount Brembo calipers but I don't have access to the tech info so I'm not sure. But just a casual look at the calipers on the SRT, Hellcat, Demon and Viper cars look like Brembo calipers to me. So there is probably some sort of corporate edict that says once the power to weight ratio gets greater than X then the car has to use Brembo calipers.

What do you guys mean by "Radial Mount" ?

The mounting adapter bracket that bolts normally to the spindle and connects/bolts to the caliper one of two ways with two bolts/studs, perpendicular, or parallel to the rotor, ie radially, the later allows additionally, small adjustment of tuning the caliper operating radius. A pic is worth a thousand words, the pic in this thread unfortunately is not overly clear, hence my original question. As mentioned, radial mount is the current preferred method.

Here is a radial mount caliper bracket. This one is from Baer for their race caliper. They use the same bracket for all of the rotor sizes and just use a spacer to adjust the caliper height. So you can have a 13 inch, 14 inch or 15 inch rotor all with the same bracket. Just use a 1/2 inch or 1 inch spacer to adjust the caliper height.

Thank you for that. That is a great idea, allowing for future upgrades.

Andy -- T/Anks for posting the new option for us.

I'm at a point now in updating to the 'Cordoba 11.75 diameter, using my pin-type original calipers... just have to order the 11.75 rotors and bearings (spindle updated to later a-body). Just still wondering what could be better than that... while still keeping the allowable usage of the factory 15x7 rally rims. I tried that rim onto a Viper caliper setup (thanks to a local cool Mopar guy having the setup on his awesome '70 Charger!) with the 11.75 rotor and the inside of the rim hit the Viper caliper (would possibly clear by using a ~1/4" spacer for the rim-to-hub... not something I want to do). Also, I have SuperLight brand 15X8 mini-light rims for street/hwy-cruising and they have barely any inside diameter clearance against the top of the Viper caliper (especially the inside tape weights -- they touch the caliper during wheel rotation. I really wanted to go with the Viper setup and 11.75 rotors (and I have a set of the correct spindles aside), but the interference issues cautioned me away. 16" rims are not a problem which I've checked and confirmed. I'll probably just use the cast iron pin-type calipers and be done with it.

Rim clearance with Viper calipers can really vary from rim to rim. The older factory stuff being the highest risk for interference. Newer stuff does seem to have some additional space built into them these days. I've had trouble with OEM era rallyes, magnums, and steelies. I've had not trouble with most new purpose built race wheels, a couple of billet styles, and even cast aluminum that is within 25 years old, all in 15" diameters.

Any updates?

anything available for a mustang 2 spindle?

I have no plans of ever making anything for a Mustang II spindle. Lots of other folks make brake kits for Mustang II. You shouldn't have any trouble finding stuff that will fit those spindles.

Shut up and take my money!! I have had gen 3 calipers since I got them from you before you stopped making the last kit.

Give DoctorDiff a call. I think he has all of the parts on hand now for these new Viper kits.

Why the FMJ knuckle vs the 73-76 A-body knuckle?

It seemed like everything was geared toward those before. For the 11.75 upgrade they even warned against using the FMJ knucles, "Do not succumb to the temptation to use “lookalike” knuckles from later Mopars, such as 1973-up B/R-bodies, F/J/M bodies, etc. These parts, while visually very similar, are taller, altering suspension geometry (camber change, bump steer, etc.), and possibly forcing the ball joints beyond their designed range, a/k/a “over angling”."

Just wondering if that was incorrect information or what the deal is as a layperson. Plus I already have a pair of the A body knuckles. This would be for a '68 Charger.

If you have A body knuckles then use them. Given a choice, I prefer the FMJ, but A body should work. You might need to grind a little clearance for the caliper bracket when using the shorter A body knuckle. Just depends on the forging.

Is the potential grinding the only reason you prefer the FMJ Knuckle?

The A vs FMJ spindle issue has been rehashed here repeatedly.

It boils down to preference really. The quote you provide was an incorrect, off the cuff comment that had zero facts to back it up.

If you want numbers and facts

https://www.bigblockdart.com/techpages/spindles.shtml

Thank you for that page, I don't need it now but it might come in handy later down the road.

The later FMJ knuckles are taller and lighter than the A body knuckle. Both of those are good things for a serious build. For a street car it doesn't matter what you use.

I am reading it now, thanks! My car will be more protouring than race so I will probably just stick with my A-body Knuckles, but keep an eye out for some FMJ if I happen upon them.

You are more likely to happen upon FMJ spindles than A body ones.

Is anyone re-popping the FMJ spindles? Dr Diff sells re-popped A body ones.

No need to repop FMJ spindles, but yes Fatman Fab makes a dropped one.

The FMJ spindles have been in production from 1973 till 1989 in B, F, M, J, R bodies.

The A body spindle is 73, 74, 75, 76.

Probably 15 FMJ spindles for every A spindle made.

Good to know, I've got both so I'm not looking.

There are a couple of different "FMJ" knuckles. I use the later style which is lighter weight. Either will work, but the latest ones are 1.5 lbs lighter. I think some engineer at Mopar finally learned how to use finite element analysis in the 80's since the last version of the knuckles shows that they took weight out of areas with no stress.

i'll bet i've done, and advised/supervised around 100 or so FMJ spindle conversions to date, and have encountered absolutely NO problems what so ever, including bump issues and "ball joint overextension". i respect e-boogers wisdom and knowledge, and really appreciate him writing up these articles [right now, he is doing a two part rear disc conversion in mopar action, using late model jeep components.] but his concern about the FMJ knuckle, in my opinion, is without merit. as to the fatman lowered knuckle, that is, from the pics i've seen, a pressed in pin to a flat piece of steel, welded to an upper balljoint tapered bung. i have never held one in person, nor do i know what material the plate, spindle pin, or balljoint bung, are made from.

Already did the rear disc swap myself on an 8 3/4.

Not too difficult.

Ordered my setup from Cass, went with the 2 piece drilled/slotted bear's. Very happy to have another part of the Charger equation solved. Thanks to all involved.

The Fatman units are a bit scary looking, but they were designed for the street rod, fairgrounds cruising crowd. I did speak to someone once who had these and I asked him to weigh them. IIRC, they are something like 1.5-2# heavier than the A body spindle.

I had a set of the Fatman knuckles for a while. I refused to put anything that ugly and stupid looking on my car so I sold them. I don't know if they work or not but they are as ugly as a high school shop project.

Cool deal. I have my set all mounted up but not sure when the car will move under its own power. I've been focused on other projects for a bit now so it could be another 6 months.

That is funny. Great insult !

Been busy doing other stuff but got back to work on the Duster the other day. Here is the Viper kit mounted on the car. Just need to mount up some wheels and drop it back on the ground.

Looks great Andy. Eagerly awaiting updates.

What size wheels will fit with these? I like the idea.

17 inch minimum. The hub design that Cass uses has stock dimensions. The rotor hub is 0.300 thick so that means the wheel mounting surface is moved outboard by 0.300 inches. So if you want the center of the wheel to be in the stock location you need 0.800 inches of offset. Obviously if you want something else then you just order what you want/need.

Cass puts a long flat section on his hub so you can use a fairly wide spacer to move the wheel location around. I designed up some 1/4 inch spacers that will be hub-centric so a person could stack them if wanted.

My Duster is more of a street/strip type of car so I'm going to run 17x6.5 wheels with 205/55-17 tires. For a B body car that was street driven I'd recommend a 17x8 wheel with a 235/55-17 tire. If it is a track car then go hog wild with whatever you can stuff under the fender.

Thank you!

I got the hoses installed. The hose brackets on my car were a D shape so the new hoses wouldn't fit. I didn't want to drill out the frame bracket so I sent the hoses to the machine shop and had them machined to a matching D shape. Other than that it was a simple bolt in operation!

The Weld wheels finally showed up. Took about 5 weeks from the time I ordered them. They are 17 x 6.5 with 4.80 inches of backspace. That gives me a small amount of room for a spacer so I should be able to put the wheel on the car exactly where I want it. I'm planning to run a 205/55-17 tire up front. I'm thinking that will clear the Duster fender and still provide me with decent handling.

Looks good.

Beautiful and purposeful looking, nice choice!

Will the FMJ spindle work on an A-body?

Kevin

Don't they look like they work in the pictures?

Here are a couple more pictures. The wheel needs to be chosen with care. You'll need clearance for the caliper and you'll need a deep enough center to cover up the long nose on the hub. I'm using a Weld S71 wheel in this picture. The wheels are 17x6.5 with a 215/50-17 tire.

Looks great Andy. Any idea when the kit is going to be available and if you can get it without the calipers?

The new Viper brake kit is currently available without calipers. See below:

https://www.doctordiff.com/viper-style-13-front-disc-brake-kit.html

Hi Cass thanks for getting that up, just a quick Q. Is that only for the 03-05 Viper Calipers? Thanks, Steve

Hi Steve,

The kit uses '03 and newer Viper front calipers.

Cass

I use caliper part number 5136152AA and 5136153AA. Those are for the red ones. I think there is another part number for black calipers but I've never bought the black ones.

I'm not sure what years they fit. Some online catalogs show them as 2005 to 2017 while others show them fitting other years.

I thought they didn't fit the latest 5th Gen 2013-2017 Viper brakes?

In any case...

According to most parts books, FRONT Viper calipers interchange from 2003-2017.

I have read that in general the "FMJ" knuckles are lighter than the 73-76 A body knuckle but are you saying that later versions of the "FMJ" knuckles are lighter still? If so, what years/models does one need to target for these even lighter 'FMJ" knuckles?

The hubs shown in the picture with this post look like they are made of steel and have a factory style grease cap. I assume they are not the hubs that come with the kit. What is the story with them? Are they machined down hub/rotors?

I'm not sure on the years with the lightweight knuckles but I think it is near the end of production. You can tell them apart once you're familiar with these knuckles. A body ones are short and squat, B body are tall but heavy and the FMJ are tall and lightweight.

That is true, I used a set of steel hubs so I could move the car around in the shop. Those are steel hubs left over from my Coronet. I used steel hubs when I designed the brake system for the Coronet. I prefer steel hubs since it is easier to maintain a tight tolerance press fit for the bearing race in steel but Doctor Diff and Baer both use aluminum for their hubs. I think Wilwood also uses aluminum for their hubs. When I made hubs I used steel.

Here are a couple of pictures of my Duster with fresh paint. The brake kit looks nicer when the fenderwell has just been painted.

Shot some new pictures today after installing a set of Firm Feel upper control arms. I also ordered a set of reproduction upper arms from Doctor Diff but I think I'll end up running the Firm Feel arms for the extra caster.

That looks really clean. I like that.

Article in Hot Rod: https://www.hotrod.com/articles/dustbin-duster-love-big-brakes-cannot-lie/