Installing C5 brakes on my 1970 Corvette
Part 2
Part 2
Everything is back together and the brakes are bled. Time for the first drive. Needless to say I am a little bit nervous. I get in the car and go around the block and the brakes suck. The pedal is extremely hard to push, but for the time being I am convinced that they are indeed better, just harder to push. Afterall they came from a C5 so it has to be better, right?
Looks like I should have done a little math proior to slapping on some new calipers. I am only going to talk about the fronts here and neglect that the new rotors are larger. The stock calipers have 1 7/8" pistons where as the C5 calipers have 1 9/16" pistons. These smaller pistons are what is making my extremely hard pedal. In fact, my brakes are now only 70% that of stock. Now I am starting to understand that hard pedal thing.
The best way to adjust for this is to change the master cylinder. So I will add a C5 master cylinder.
After finding out a remanufactured C5 master cylinder costs $300+ I went to my favorite auto parts store (ebay) and found a 2001 master cylinder for ~$35 shipped.
Looks like I should have done a little math proior to slapping on some new calipers. I am only going to talk about the fronts here and neglect that the new rotors are larger. The stock calipers have 1 7/8" pistons where as the C5 calipers have 1 9/16" pistons. These smaller pistons are what is making my extremely hard pedal. In fact, my brakes are now only 70% that of stock. Now I am starting to understand that hard pedal thing.
The best way to adjust for this is to change the master cylinder. So I will add a C5 master cylinder.
After finding out a remanufactured C5 master cylinder costs $300+ I went to my favorite auto parts store (ebay) and found a 2001 master cylinder for ~$35 shipped.
I had an adapter plate machined out of 1/4" aluminum that spaces the master cylinder out from the firewall and lowers it 1". The spacers are 1" for the upper and 3/4" for the lower ones. This angles the master cylinder down slightly in order to clear the hood. The master is spaced out from the firewall to ensure a good angle for the pushrod and also for hood clearance.
This master cylinder has a shallow hole for the pushrod instead of the deep hole you would find on a typical manual master. Some people have showd concern with my design because they think the pushrod will fallout of the master if you quickly let off the pedal. I just wanted to clear that up here. The bracket was designed to place about a 1/16" preload on the master cylinder. That means there is always tension on the pushrod even with the pedal fully retracted. Also there is a lip that extends beyond the master piston so if for some reason the pedal were to pull back faster than the piston, the pushrod could not fall out of the master.
Here is the master installed and ready for bench bleeding. The front brakes attach to the rear port and the rear to the front. This is backwards from the C3, but the lines have to be tweeked to fit anyway. The front brake line uses a 12x1.5mm ISO bubble flare on a 1/4" line. The rear uses a 12x1mm bubble flare on a 1/4" line. And both feed to the stock distribution block.
When first installed, I was not completely satisfied with the performance. I think part of this was I was still chasing a little air in the lines since the rear calipers actually have to be un-mounted to bleed properly. And part was the pads were not broken in yet (I re-used the pads that came with the calipers).
After several hundred miles, I am pleased with the performance. The car stops great. It is still a manual brake car, but I actually prefer the firm solid feel of the manual brakes.