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Rear axle disc brake master cylinder/booster which one?

Posted By: 472 R/T SE

Rear axle disc brake master cylinder/booster which one? - 01/14/12 10:18 AM

I'm gonna update the wheels/tires on my Charger this spring. It was that or a 671 or 871. Maybe the next upgrade?



They'll be 17's on the rear & 16's up front
-17's all the way around
-18's on the rear & 17's up front.
No bigger than that.

I haven't decided yet. It will have plenty of rubber though. Just say no to rubber band tires is my motto.

I'm sure there's several folks who question me ruining this car. I do have the #'s drivetrain. But all my mods will be easy to change over. With this latest endeavor I might try & find a Ford truck Dana to mod or another 8 3/4. Since I'm running Cal Tracs I don't need to worry about the truck Dana not having a pinion snubber.

So my questions:

-Which rear would be easier on the wallet to add disc brakes to?

-My booster & master cylinder. Do I have to go with hydroboost?

-Is there a factory appearing master cylinder that has 2 big reservoirs' that would mount to the Bendix booster?

I'm not concerned about vacuum as I already am running a pump.

I've seen a few rides using the factory disc/drum master cylinder with the two different size reservoir's. Just because they're doing it doesn't make it right.

TIA
Posted By: astjp2

Re: Rear axle disc brake questions. - 01/14/12 10:28 AM

If you run a mopar axle, you can use the jeep grande Cheorkee rear discs. If you run a dana, get the ford ends and use the Ford explorer discs. They are both the same brake calipers and rotors, the only difference is in the parking brake hardware but the pad and shoes also interchange. If you want killer fronts, use the explorer front calipers and crown vic rotors. This is all stock parts and can be found in most parts stores. Tim
Posted By: BrianShaughnessy

Re: Rear axle disc brake questions. - 01/14/12 03:39 PM

If I had to do things over again...

I'd still go Dana 60. But I'd just call up DoctorDiff and tell him to build it with torino ends and his rear disk kit with a truetrac diff.

No green bearings, no tracloc. No local friend that doesn't work on mopars cutting up a junkyard ford truck dana, and no aerospace rear disks with $200 warped wilwood rotors.
Posted By: AndyF

Re: Rear axle disc brake questions. - 01/14/12 05:41 PM

Just talk to Cass at DoctorDiff. He can set you up with a good rear disc kit at a reasonable price.

Attached picture 7018134-cass.jpg
Posted By: racealittle

Re: Rear axle disc brake questions. - 01/14/12 05:50 PM

Andy, whose rear sway bar set up is on the car in the picture? Looks like a fair amount of choice for setting it up.
Posted By: 67autocross

Re: Rear axle disc brake questions. - 01/14/12 05:52 PM

You could also try Kore3, they a rear kit for a 8 & 3/4 a guy local to me has them on his 42 Plymouth.

www.kore3.com
Posted By: AndyF

Re: Rear axle disc brake questions. - 01/14/12 07:15 PM

Quote:

Andy, whose rear sway bar set up is on the car in the picture? Looks like a fair amount of choice for setting it up.


The rear bar was custom built by Tim who owns the Valiant. Firm Feel can build you a similiar bar if you want one.

Attached picture 7018312-bar.jpg
Posted By: tallzag

Re: Rear axle disc brake questions. - 01/14/12 07:20 PM

On our Lemons car we run the Dr. Diff rear disc brakes and they work fantastic. We use our car harder than anybody (4000 pound C-Body) and they never fade. The brakes are Mustang Cobra sourced.

On wheel size you pretty much have to run at least 17's to get a decent tire choice. We run the Dunlop Direzza Star Specs, best track day tire for the money out there. They are a summer/performance tire only however. The other tire guys are really liking right now is the Falken Azezzi's (sp?) but have heard they tend to work better on lighter cars. Hoping to experiment with both tires this summer.
Posted By: autoxcuda

Re: Rear axle disc brake questions. - 01/14/12 08:14 PM

Quote:

...
On wheel size you pretty much have to run at least 17's to get a decent tire choice. We run the Dunlop Direzza Star Specs, best track day tire for the money out there. They are a summer/performance tire only however. The other tire guys are really liking right now is the Falken Azezzi's (sp?) but have heard they tend to work better on lighter cars. Hoping to experiment with both tires this summer.



So that Dunlop is the current HOT street tire everyone is going to right now??

Duly noted. Thank you. Going to get some 275/40/17's soon.
Posted By: RodStRace

Re: Rear axle disc brake questions. - 01/14/12 09:11 PM

Just as a note on the green bearings; I asked about the Hotchkiss RR rear discs at MATS last year.

It uses discs with green bearings. He said that they have to replace them every 6 months!
You probably won't be running the laps they do, but I would not be happy with that kind of lifespan!
Posted By: AndyF

Re: Rear axle disc brake questions. - 01/14/12 09:17 PM

That is a good point. Many of the rear disc kits require a switch to the green bearings. That is one of the reasons why I always recommend the DoctorDiff kit. He is one of the few guys who actually bothered to design his kit to work with the stock tapered bearings. Many mfgs just rebox a Chevy kit for the Mopar application.

With the DoctorDiff kit the bracket replaces the backing plate and the thrust clearance is set just like a drum brake.

Attached picture 7018501-brg.jpg
Posted By: jcc

Re: Rear axle disc brake questions. - 01/14/12 09:26 PM

That's a transport tie down eye on the u bolt plate?
Posted By: 472 R/T SE

Re: Rear axle disc brake questions. - 01/15/12 01:33 AM

Thanks for the responses, really appreciated it.

What about booster & master cylinder?
Posted By: AndyF

Re: Rear axle disc brake questions. - 01/15/12 02:25 AM

Quote:

That's a transport tie down eye on the u bolt plate?



Chassis dyno tie down, but it also can be used for trailering.
Posted By: autoxcuda

Re: Rear axle disc brake questions. - 01/15/12 03:07 AM

Quote:

That is a good point. Many of the rear disc kits require a switch to the green bearings. That is one of the reasons why I always recommend the DoctorDiff kit. He is one of the few guys who actually bothered to design his kit to work with the stock tapered bearings. Many mfgs just rebox a Chevy kit for the Mopar application.

With the DoctorDiff kit the bracket replaces the backing plate and the thrust clearance is set just like a drum brake.



What thrust clearance did you shoot for on Tim's Valiant?

Dan W. with the Hotchkis RR complains about pad knockback with tapered and green bearing. I think he's going to a floater rear end. Wonder what Tim W. opinions and experiances on this issue.
Posted By: dangina

Re: Rear axle disc brake questions. - 01/15/12 02:34 PM

Quote:

On our Lemons car we run the Dr. Diff rear disc brakes and they work fantastic. We use our car harder than anybody (4000 pound C-Body) and they never fade. The brakes are Mustang Cobra sourced.

On wheel size you pretty much have to run at least 17's to get a decent tire choice. We run the Dunlop Direzza Star Specs, best track day tire for the money out there. They are a summer/performance tire only however. The other tire guys are really liking right now is the Falken Azezzi's (sp?) but have heard they tend to work better on lighter cars. Hoping to experiment with both tires this summer.



some of the guys here have been running the star specs - until we discovered the hankook ventus RS - unbelieveable tire and the price is just as unbelieveable - will be running them this summer again...only downside to them is not a huge range of sizes...
Posted By: tallzag

Re: Rear axle disc brake questions. - 01/16/12 12:04 AM

Quote:

Quote:

...
On wheel size you pretty much have to run at least 17's to get a decent tire choice. We run the Dunlop Direzza Star Specs, best track day tire for the money out there. They are a summer/performance tire only however. The other tire guys are really liking right now is the Falken Azezzi's (sp?) but have heard they tend to work better on lighter cars. Hoping to experiment with both tires this summer.



So that Dunlop is the current HOT street tire everyone is going to right now??

Duly noted. Thank you. Going to get some 275/40/17's soon.



That is the size tire we currently run in the Dunlop's (although we just picked up a set of 18's ). The problem with tires like the Hankook is we run the 24 Hours of Lemons and they require a 190 tire treadwear or higher, the Hankook's are 140.
Posted By: Kern Dog

Re: Rear axle disc brake master cylinder/booster which one? - 01/17/12 05:37 AM

My combo defies logic, but it works.
1970 Charger with 12" Cordoba front discs, 11.7 rear discs with a power booster and Master cylinder spec'd for a 75 Dart with disc brakes. In reality, I expected it to be overly biased to the front brakes, but it really works well.
Posted By: Rick_Ehrenberg

Re: Rear axle disc brake master cylinder/booster which one? - 01/21/12 11:04 PM

Quote:

My combo defies logic, but it works.
1970 Charger with 12" Cordoba front discs, 11.7 rear discs with a power booster and Master cylinder spec'd for a 75 Dart with disc brakes. In reality, I expected it to be overly biased to the front brakes, but it really works well.



What are piston sizes? I'll bet that's what you did right, without realizing it!
Posted By: Kern Dog

Re: Rear axle disc brake master cylinder/booster which one? - 01/21/12 11:13 PM

Thats high praise, Rick. You are well respected.
I used front calipers spec'd for the master cylinder/power booster 75 Dart. I think that I read in Mopar Action that they changed the A body caliper in 1976? When I ordered the rear kit from Dr Diff, I told him of my existing combo which had 10" drums in the rear. He thought that it would work with the 75 A master cylinder and it certainly has.
I love the bias, but I am tempted to eliminate the booster. While the combo works great from 20 mph and up, the minimal vacuum from the '509 cam makes slow speed braking a bit nerve wracking.
I just had the car out for about 45-50 minutes, taking corners and doing a little flexing of the muscles. I really enjoy this car!
Posted By: DRAG-ULA

Re: Rear axle disc brake master cylinder/booster which one? - 01/23/12 05:54 PM

I just did this setup for about 100 bucks.



Why does everyone stay away from the green bearings? I've had them on my street car for 10+ years with no problems.
Posted By: amxautox

Re: Rear axle disc brake master cylinder/booster which one? - 01/23/12 06:16 PM

Supposedly green bearings can't handle too much side load, like what is seen in autocross and roadcourses.
Posted By: Kern Dog

Re: Rear axle disc brake master cylinder/booster which one? - 01/24/12 03:38 AM

When I bought my Moser axle shafts in 2003 I went with the green bearings, thinking that the originals may be a pain to adjust. Within 5000 miles I trashed the left bearing and replaced them both.... with Mopar Performance bearings of the same design. If these fail within the same time frame, I'll go back to the Timkens.
Posted By: AndyF

Re: Rear axle disc brake questions. - 01/24/12 03:45 AM

Quote:

Quote:

That is a good point. Many of the rear disc kits require a switch to the green bearings. That is one of the reasons why I always recommend the DoctorDiff kit. He is one of the few guys who actually bothered to design his kit to work with the stock tapered bearings. Many mfgs just rebox a Chevy kit for the Mopar application.

With the DoctorDiff kit the bracket replaces the backing plate and the thrust clearance is set just like a drum brake.



Dan W. with the Hotchkis RR complains about pad knockback with tapered and green bearing. I think he's going to a floater rear end. Wonder what Tim W. opinions and experiances on this issue.



I set the thrust play up at middle of the book. Nothing special. I don't think Tim has ever complained about pad knock back. The rear disc aren't really required on his car and he runs it up past 155 mph on the straight. But rear discs are more linear and they reduce both rotating and unsprung weight a little bit so it is all good.

What thrust clearance did you shoot for on Tim's Valiant?
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