Re: New disc brake conversion doesn't work
[Re: Dads426]
#58214
05/13/08 01:44 PM
05/13/08 01:44 PM
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Joined: Jan 2003
Posts: 28,096 Irving, TX
feets
Senior Management
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Senior Management
Joined: Jan 2003
Posts: 28,096
Irving, TX
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It's a combination of pedal ratio and MC size.
I went through the no-stoppy thing when I dropped a truck MC on the "big" Dippy rotors. Stopping the car required both feet on the pedal and my butt in the air. It was pretty hard on the steering column too. That MC was WAY too big and caused a super-hard pedal. When I went to the larger calipers, the MC was the perfect size and the pedal effort dropped to normal.
Dropping the bore of the MC will reduce the pedal effort. Maybe one of the K-car MCs would work?
We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind. - Stu Harmon
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Re: New disc brake conversion doesn't work
[Re: DoctorDiff]
#58217
05/13/08 03:45 PM
05/13/08 03:45 PM
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Joined: Jan 2003
Posts: 16,376
dogdays
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,376
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Re: New disc brake conversion doesn't work
[Re: timinator]
#58223
05/22/08 08:46 AM
05/22/08 08:46 AM
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Joined: May 2007
Posts: 1,445 Maryland
Dads426
pro stock
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pro stock
Joined: May 2007
Posts: 1,445
Maryland
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I just bought a new brake pedal. It should be coming today or tomorrow. I posted a question about 62-65 brake pedals and a member measured thiers and it was about 3" shorter, so I found a manual brake car and got that pedal. If we get it on the car this weekend I'll post the results.
If your car had power brakes, measure the brake pedal from the pivot to the bottom of the footrest, and the pivot to the brake pushrod attachment point. Divide that number into the first measurement and that is your pedal ratio. Find someone that has a true manual brake car and ask them to measure their pedal and compare. From the measurements that I got, on the early B-bodies the pedals are different.
The smaller master cylinder will help, but not solve the problem if the pedal ratio is incorrect. Been there, done that.
2012 422 Allstars NSS Champion 2013 422 Allstars NSS Champion 2014 422 Allstars NSS Champion
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Re: New disc brake conversion doesn't work
[Re: AndyF]
#58228
05/24/08 09:08 PM
05/24/08 09:08 PM
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Joined: May 2007
Posts: 1,445 Maryland
Dads426
pro stock
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pro stock
Joined: May 2007
Posts: 1,445
Maryland
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I picked up a brake pedal for a manual brake car. Noticeably different. The ratio is closer to 6-1 versus 3-1 for the power brake pedal. There are two pivot holes in the hanger for the pedal, but we had to drop the steering column and remove the hanger to get the pedal out. The brake pushrod mounts higher than on the power brake pedal; luckily the firewall had holes and a cutout for a higher mount. But, I had to remake the brake lines to the proportioning valve and line lock. I put the 1-1/32" master cylinder back in and brake effort is noticeably better. Not nearly as good as a power brake car, but much better. I'm sure the 15/16 master cylinder would reduce effort further, but I like the lightweight master cylinder better.
2012 422 Allstars NSS Champion 2013 422 Allstars NSS Champion 2014 422 Allstars NSS Champion
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Re: New disc brake conversion doesn't work
[Re: Dads426]
#58229
05/24/08 10:21 PM
05/24/08 10:21 PM
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Joined: Jun 2003
Posts: 4,872 connecticut
pnypwr
master
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master
Joined: Jun 2003
Posts: 4,872
connecticut
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A residual vlave in the front will keep the brakes applied and not release...not a good idea! Have you all checked to make sure the rears are working? increase the rear line pressure it sounds like the fronts are not getting help from the rear...also are the rears adjusted correctly? I know sounds simple but you never know! Ive done a few conversion with no troubles im about to put a set of ford cobra brakes on my early mustang 4 wheel disc 13 in front rotors 11.65 rear fronts dual piston 38 mm 15/16 master is whats recomended...im thinking a hydro boost setup will be the way to go. its basically the same system on late model cobra mustangs and that car stops on a dime and gives u back 8 cents!
"Are you gonna bark all day lil doggy? Or are you gonna bite?"
05 ram 2500 ctd 74 gremlin x 360 65 mustang 347 70 coronet R/T 440 03 Mach 1
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