Problem with rightstuff 4-wheel discs, please help!

[fasjac]

I to have seen this issue. And there may be some threads here about it. Seems that Wilwood recommended 15/16’s bore.
On my 73 cuda (original power disc) , I used Wilwood front disc/calipers, factory master cylinder and booster, rear drums. It will lock up all 4 tires when you want to.
I believe it to be a master cylinder issue as well.
Good luck and let us know your progress.

 

[rasmus westlin]

I to have seen this issue. And there may be some threads here about it. Seems that Wilwood recommended 15/16’s bore.
On my 73 cuda (original power disc) , I used Wilwood front disc/calipers, factory master cylinder and booster, rear drums. It will lock up all 4 tires when you want to.
I believe it to be a master cylinder issue as well.
Good luck and let us know your progress.

okey but rightstuff and willwood Said 1” bore MC was enough, and some other guy here Said if i get bigger bore master cylinder this would reduce the line pressure and likely make the brakes worse.

I wish i kept drums back and only disc in front. Because now when it has 4 wheel discs, it really sucks to brake with.

 

[Mopar Nut]

Are your hardlines and softlines new?

 

[Huskidrive]

I had the same problem with a Right Stuff brake conversion kit. In my application a larger vacuum booster and a smaller bore master cylinder fixed everything. Remember, a smaller bore MC increases pressure at the wheels. This guy fixed all my problems..........ABS Power Brake, Inc.

 

[Mopar Nut]

 

[rasmus westlin]

Are your hardlines and softlines new?

Yes everything is new

 

[rasmus westlin]

I had the same problem with a Right Stuff brake conversion kit. In my application a larger vacuum booster and a smaller bore master cylinder fixed everything. Remember, a smaller bore MC increases pressure at the wheels. This guy fixed all my problems..........ABS Power Brake, Inc.

Hmm okey, the booster is 8” now, did you change to 9” booster? I have 1 inch bore MC now, willwood sells 15/16 Bore MC. But its with pushrod. I need it without pushrod because the pushrood is coming out from my booster.

 

[Huskidrive]

I don't remember what the setup abs sent me. All i know is if a fly lands on the brake pedal you'll wind up on the hood........

 

[moparleo]

The brakes will never have the feel that a modern cars brakes have. It also takes time for the disc pads o completely seat into the rotors and transfer the proper amount of friction material to the rotors. The brakes will get better with time unless they have been overheated. Brake system break-in is very critical just like piston ring break-in. If done improperly the rings never seal, the brake pads never seat.
Modern vehicles use abs modules, computer controlled. Larger rotors, designed for modern friction materials. The braking systems are engineered for the specific application. Rotors tend to be much larger since most new cars of equal size to the Muscle cars, like a new Challenger have 18" wheels on the lowest SXT models.
Your calipers look nice painted but still just 70's technology single piston floaters, factory units.
Want real performance braking you need a performance brake system. Just like going fast the saying is "speed cost money, how fast do you want to go."
You never want the brakes to lock up anyway, the idea behind A.B.S. Antilock Brake System.
No wheel lockup just a computer modulating the brakes.

Link Is It Better To Have More Pistons In Your Brake Calipers?

 

[Bret Schneider]

A bigger master cylinder bore moves more fluid as compared to a smaller bore, so the same amount of pedal travel will cause the slave cylinder (caliper piston) to travel further with the bigger bore master cylinder. However it is true that a larger caliper piston will result in less travel given the same amount of fluid movement from the master cylinder. Have you considered the size of the caliper pistons? Maybe mismatched to the master cylinder?

 

[fasjac]

okey but rightstuff and willwood Said 1” bore MC was enough, and some other guy here Said if i get bigger bore master cylinder this would reduce the line pressure and likely make the brakes worse.

I wish i kept drums back and only disc in front. Because now when it has 4 wheel discs, it really sucks to brake with.

okey but rightstuff and willwood Said 1” bore MC was enough, and some other guy here Said if i get bigger bore master cylinder this would reduce the line pressure and likely make the brakes worse.

I wish i kept drums back and only disc in front. Because now when it has 4 wheel discs, it really sucks to brake with.

Hang in there, you’ll get it to brake and lock up/stop to your liking. Keep working
with your resources.
I picked up a 70 cuda for my boss with 4 wheel disc, ssbs calipers with a wilwood master cylinder (restomod). The first test drive after inspection was will it stop all that HP.
It did. The calipers weren’t big enough for his taste so, brembo’s went on. They too worked great.

 

[rasmus westlin]

A bigger master cylinder bore moves more fluid as compared to a smaller bore, so the same amount of pedal travel will cause the slave cylinder (caliper piston) to travel further with the bigger bore master cylinder. However it is true that a larger caliper piston will result in less travel given the same amount of fluid movement from the master cylinder. Have you considered the size of the caliper pistons? Maybe mismatched to the master cylinder?

Willwood and rightstuff says 1” bore mc is enough. Someone with same problem tried go up in bore size, but with the same problem. Maybe try a smaller one , but i cant find a 15/16 bore MC without pushrod.

 

[Chryco Psycho]

Personally I would use hydro boost if you have power steering

 

[rasmus westlin]

Personally I would use hydro boost if you have power steering

Yes iam thinking of it. How does it work ? Two lines to my steering pump? But i still would want to know what is causing my brake problem.. someone must had same problem?

 

[Chryco Psycho]

Lack of pressure being developed to clamp the calipers .
Hydro boost runs a loop so it goes to the power steering then to the hydro boost unit & back to the reservoir

 

[mebeblown]

Hello everyone!

I have rightstuff 4 wheel disc brake kit on my -70 challenger, the car is completly renovated and everything is new on the car. I use willwood booster and mastercylinder 1” bore. The problem is that the brakes dosnt work as good as i think they would..

I have done all this

:bleed the brakes 100 times, its no air left, if i pump the brakepedal it dosnt get firmer as it should if it still was air in the system.

: i have adjusted the parkingbrake arm as they recomend.

: I checked if the gap between the pushrod from the booster to my mastercylinder was to big. It was perfect gap there also.

The car stops when i brake, but it wont lockup the brakes even if i stand on my brakepedal. I am out of ideas now and would really appreciate help with this! Is it just bad quality or will it get better the more i drive the car and let it brake in the parts?

Please help!

Best regards Rasmus!

View attachment 94979

If it's not right, don't drive it. Investagation & repair.
I have found the only thing that gets better with time is a " Divorce "....

 

[BSG]

I literally went through the same crap on my car. I changed out the master cylinder 3 times before I got the correct feel and brake quality. It because of that, I left the 4 wheel drum setup on my 71 RT I'm putting together now. I cant remember exactly what the difference in the cylinders were but the piston size was definitely a factor. The masters are cheap like 30 or 40 dollars at the chain stores.

 

[rasmus westlin]

I literally went through the same crap on my car. I changed out the master cylinder 3 times before I got the correct feel and brake quality. It because of that, I left the 4 wheel drum setup on my 71 RT I'm putting together now. I cant remember exactly what the difference in the cylinders were but the piston size was definitely a factor. The masters are cheap like 30 or 40 dollars at the chain stores.

Hmmm, i use a willwood mastercylinder with 1” bore. And they say its enough..

 

[BSG]

okey but rightstuff and willwood Said 1” bore MC was enough, and some other guy here Said if i get bigger bore master cylinder this would reduce the line pressure and likely make the brakes worse.

I wish i kept drums back and only disc in front. Because now when it has 4 wheel discs, it really sucks to brake with.

When you get it sorted it will stop on a Dime. I struggled for a minute with mine and I repair cars for a living. I feel ur pain ride it out it will all be worth it!

 

[Mopar Nut]

How’s the distribution block? New? Rebuilt?