Aug 19, 2023 Disc Brake Conversion Update - So, like others, I bought a "Bolt In" front disc brake conversion kit and didn't read the fine print well enough. First couple pictures shows that the transmission mounting cross member is in the way. Never mind that the fine print says it won't work with a manual transmission linkage. However, I did read in the forums the idea of moving the location to behind the cross member and lengthen the arm. So, spent the time to figure out what I need today.
I took the booster off, and bolted it to the original bracket to see how the arm ran to the brake pedal (as seen in the first two pictures). The centerline of the arm to the edge of the frame is about 7 1/2" (picture #3) and the arm ran at an angle instead of straight on perpendicular to where it attached to the brake pedal, but seems to operate without any binding. I bolted in the old brake cylinder for comparison. The centerline of the original was approximately 6" from the edge of the frame (picture #4). I should mention the brake cylinder bracket angles into the frame rail such that the measurement of where the rod links to the brake pedal measures 5" from the centerline of the brake pedal to the edge of the frame. Between the original and new brake cylinders there seems to be some dimensional play in how perpendicular the arm is to the brake pedal.
Now, in consideration of moving the brake booster and cylinder assembly back, I have to account for the frame getting wider as it goes back. I measured the total frame width just in front of the brake pedal mount and got 31 1/2". Measuring at the rear of the transmission cross brace I got 34", so the frame widens by 2 1/2" from the brake pedal mount to the new brake booster/cylinder location which translates to 1 1/4" wider from the truck centerline. Pictures 5 and 6 show how much clearance I have from the cross brace with the old and new brake cylinder. The old is not looking good, but plenty of clearance with the new, but would still like to minimize the angle away from perpendicular of the arm to the brake pedal. The measurement of the outside of the new brake booster bracket to the centerline of the brake booster is about 2 3/4". So if I take the 6" centerline of the old brake cylinder (Picture #2) and add 1 1/4" for the new location and take away the 2 3/4" for the bracket I get 4 1/2". If I do the same math with the new booster I get 6". So, I figure if I get a piece of 6" HSS, I can make a new bracket to bolt to the frame from that.
Last consideration is to angle the bracket back to the brake arm like the original, or at least angle it to run parallel to the frame. I plan to cut a wedge out of the HSS and bend the open space closed and get it welded up. The wide end of the wedge will be a 1/2" and I'll cut it approximately 4" long on a 5" length of angle iron. If I make it perpendicular to the frame, the rod should end up at less of an angle than the new booster installed on the original mounting bracket. Also giving consideration that the original rod mounted with a y connection on the center of the brake pedal, whereas the new rod mounts on the side of the brake pedal (towards the centerline of the truck) so that gives an extra 1/2" to 3/4" to the 5" the brake pedal measures from the edge of the frame.
Will be looking to do this work this week, so will post how it turns out.
