Drum to Disc Brake Conversion Question

chevy 68 · 09-09-2010, 07:12 PM

I have converted my brakes from drum to disc, but the peddle goes all the way down to the floor with 800 PSI. If I pump up the brakes it gets better. The rear shoe is adjusted correctly,there are no leaks and there is no wear. I wonder if I have to change the Master Cylinder? I am supposed to be at the Nitro Jam race tomorrow and any help I get would be greatly appreciated. Thanks!

Dgal · 09-09-2010, 07:44 PM

When we converted a car from drums to disc brakes we were advised to replace the master cylinder with 1.125" bore over the 1.032" bore since the brakes took more volume of fluid. I don't know what your stock master cylinder bore is, but you may need to replace it with a more robust version like we did.

The brakes work great after following all of the instructions.

Ed Fernandez · 09-09-2010, 09:50 PM

Are there two holes in the upper brake pedal,where the brake swith mounts?If so try using the other hole.It will increase the brake pressure.Hope this helps.

Dave1695 · 09-10-2010, 10:49 AM

If you have a fixed caliper (as opposed to a floating caliper) DO NOT use anything larger than a one inch bore master. Your problem sounds like you still have air in the system. Did the master cylinder run dry while you were making the change over or if you installed a new master was it bench bled before installing. On a Camaro the upper hole in prdal arm is for manual brakes.

09-09-2010, 07:12 PM	#1
chevy 68 Junior Member Join Date: Aug 2009 Posts: 9 Likes: 0 Liked 0 Times in 0 Posts	Drum to Disc Brake Conversion Question I have converted my brakes from drum to disc, but the peddle goes all the way down to the floor with 800 PSI. If I pump up the brakes it gets better. The rear shoe is adjusted correctly,there are no leaks and there is no wear. I wonder if I have to change the Master Cylinder? I am supposed to be at the Nitro Jam race tomorrow and any help I get would be greatly appreciated. Thanks!

09-09-2010, 07:44 PM	#2
Dgal Member Join Date: Dec 2009 Posts: 169 Likes: 0 Liked 0 Times in 0 Posts	Re: Drum to Disc Brake Conversion Question When we converted a car from drums to disc brakes we were advised to replace the master cylinder with 1.125" bore over the 1.032" bore since the brakes took more volume of fluid. I don't know what your stock master cylinder bore is, but you may need to replace it with a more robust version like we did. The brakes work great after following all of the instructions.

09-09-2010, 09:50 PM	#3
Ed Fernandez Veteran Member Join Date: Nov 2001 Location: NOO JOISEY nexta NOO YAWK Posts: 5,879 Likes: 38 Liked 100 Times in 45 Posts	Re: Drum to Disc Brake Conversion Question Are there two holes in the upper brake pedal,where the brake swith mounts?If so try using the other hole.It will increase the brake pressure.Hope this helps. __________________ Former NHRA #1945 Former IHRA #1945 T/SA

09-10-2010, 10:49 AM	#4
Dave1695 Member Join Date: May 2009 Posts: 160 Likes: 0 Liked 15 Times in 11 Posts	Re: Drum to Disc Brake Conversion Question If you have a fixed caliper (as opposed to a floating caliper) DO NOT use anything larger than a one inch bore master. Your problem sounds like you still have air in the system. Did the master cylinder run dry while you were making the change over or if you installed a new master was it bench bled before installing. On a Camaro the upper hole in prdal arm is for manual brakes.