Problem with rightstuff 4-wheel discs, please help!

[rasmus westlin]

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!

 

[Challenger RTA]

You might need a 1 /8" master cylinder. Here are some post from here to read

Wilwood Disc on a 73 Challenger​

through.https://www.forebodiesonly.com/forum/threads/wilwood-disc-on-a-73-challenger.15216/

Cannot solve hard pedal issue Cannot solve hard pedal issue​

 

[Challenger RTA]

By the way your challenger looks absolutely great!

 

[Chryco Psycho]

I have run into this many times the brakes simply will not function , I wish I had a good solution , I believe it has to do with the master cylinder , the Willwood master doesn't work , you may need a bigger bore , every time Ihave run into this the system has the wilwood master .

 

[Challenger RTA]

I'll tell you how to fix it if you post more pictures of your Challenger. No really I would like to see the brake pluming and vales used. I or others may see some thing in question.And more of a description of brake pedal pumping reaction. Believe it or not probably air in the line.

 

[Steve340]

You need to start by measuring the line pressures at the callipers. Once you know what you have you can make the right move.
Until you do that you are just guessing.
By the way if you fit a bigger bore master cylinder this would reduce the line pressure and likely make the brakes worse.

 

[Challenger RTA]

4 wheel disc require a larger master cylinder bore,then a disc drum or drum drum set up. Was this a drum drum car?

 

[rasmus westlin]

Thanks for your answears!

If it was air in the system the brake pedal should get firmer if i pump it 3-4 times, and it dosnt. Its the same all the time.

The car passed inspection and the brake test. The car Will stop but it wont lock up in a emergency situation, thats why i am worried.

Both willwood and rightstuff says 1” bore MC is enough. I read another thread here on the forum and he had similar problem. He changed from a 8” booster to a 9” booster and the problem was fixad. Can it be that maybe?

Some more photos on the car.

 

[Challenger RTA]

Ok as Steve 340 said:

You need to start by measuring the line pressures at the callipers. Once you know what you have you can make the right move.
Until you do that you are just guessing.
By the way if you fit a bigger bore master cylinder this would reduce the line pressure and likely make the brakes worse.

You might need to adjust proportioning valve for more pressure to the front brakes.Did the install instructions give any pressure guide lines? This set should be correct with no residual valves installed. Again was this a drum drum car?

 

[Challenger RTA]

Drum drum car brake pedal set up different. Thanks for the pictures

 

[rasmus westlin]

Ok as Steve 340 said:

You might need to adjust proportioning valve for more pressure to the front brakes.Did the install instructions give any pressure guide lines? This set should be correct with no residual valves installed. Again was this a drum drum car?

It was a disc/drum car. I have tried with adjusting the proportiong valve with no better resultats.

 

[Challenger RTA]

Are there 2 holes on you brake pedal arm? one is for disc and one is for drum. in the late 70s and early 80s I knew of a few brake change over problems. that was the issue.

 

[rasmus westlin]

Are there 2 holes on you brake pedal arm? one is for disc and one is for drum. in the late 70s and early 80s I knew of a few brake change over problems. that was the issue.

No only 1 hole on the brake pedal

 

[Challenger RTA]

As Steve said: Did you adjust you pressure using gauges. 600 psi for front come to mind. don't want to say for sure. Have to look up or someone here may know for sure,contact manufacture. You have to know were you are at and where you are going to get it right.

 

[Challenger RTA]

No only 1 hole on the brake pedal

Ok then that should be good if no one changed it before.

 

[Challenger RTA]

As I looked at the big meats on you car. I don't think you are going to get them to lock up and skid. there is a lot of bite there. what size rotors? a bigger rotor will lock em up. F=MxA

 

[Challenger RTA]

This always goes back to the point.Rear drum brake where always adequate for the rear. Disc on the back are over kill ( not a bad thing) Easier to maintain,just sometime a problem. not basing on your set up,It's great when you get it setup. One of Chrysler's 4 wheel disc setup was on a Land yacht. It need it.

 

[rasmus westlin]

As I looked at the big meats on you car. I don't think you are going to get them to lock up and skid. there is a lot of bit there. what size rotors? a bigger rotor will lock em up. F=MxA

Yeah i know it wont lock up the rears but it should do it up front , i cant adjust the front brakes eaither. The adjuster is Max pressure on back brakes and i tried screw it up also but no diffrent result.

Its 15-12.5 wide rim with 315 tires in the rear. Rear rotors is 11.25 in./285.75mm and front is 11.00 in./279.40mm

 

[rklein71]

Obviously, you need to give the Challenger to me. Seriously, I have not been happy with my four wheel discs on my 71 Barracuda either. Same issues. I am working on painting it, so I have kicked the brake issues to a later date.

 

[rasmus westlin]

Obviously, you need to give the Challenger to me. Seriously, I have not been happy with my four wheel discs on my 71 Barracuda either. Same issues. I am working on painting it, so I have kicked the brake issues to a later date.

Hehe , its a really anyoing problem.. it should work better..