About 5 years ago, we installed an EGR rear disc conversion in place of the stock drums. The kit uses 70s caddy style calipers w e brake. It's been decent, but never stopped great. The pedal felt spongey most of the time, and you had to use about 3/4 pedal before it started to get firm. I attributed this to the fact that the caddy calipers are huge and take a lot more fluid to move than the drums did.
A few months ago, things started getting worse. I would need to pump the pedal and the abs light kept coming on.
I decided to replace the master cylinder and hydro booster. I ordered an 01 MC instead of the 99. The 01 is physically larger, and the piston is close 3/16 larger in dia. When I went to install it, I realized that it was too big to slide into the spacer on the hydro booster. I had a buddy w a CNC machine open it from 1 5/8" to 1 3/4". After that, the MC slid in wo a problem. The next issue was that the actuator rod that sits in the HB was too long. I trimmed it down and it worked perfect.
I proceeded to adjust the rear brakes and bless all the way around. It was a huge improvement. It was still not as good as I thought it should be, so I called EGR to ask how to get a better pedal feel. They now have a one way check valve that keeps 10psi pressure in the rear brake lines. After installing this valve and bleeding the rear again, I'm finally happy with the pedal feel and how the truck stops now.
If anybody else has upgraded from drums to discs and had an issue, I'd recommend this upgrade.
A few months ago, things started getting worse. I would need to pump the pedal and the abs light kept coming on.
I decided to replace the master cylinder and hydro booster. I ordered an 01 MC instead of the 99. The 01 is physically larger, and the piston is close 3/16 larger in dia. When I went to install it, I realized that it was too big to slide into the spacer on the hydro booster. I had a buddy w a CNC machine open it from 1 5/8" to 1 3/4". After that, the MC slid in wo a problem. The next issue was that the actuator rod that sits in the HB was too long. I trimmed it down and it worked perfect.
I proceeded to adjust the rear brakes and bless all the way around. It was a huge improvement. It was still not as good as I thought it should be, so I called EGR to ask how to get a better pedal feel. They now have a one way check valve that keeps 10psi pressure in the rear brake lines. After installing this valve and bleeding the rear again, I'm finally happy with the pedal feel and how the truck stops now.
If anybody else has upgraded from drums to discs and had an issue, I'd recommend this upgrade.