OK, after fighting with my brakes for over 2 years I've have finally won the battle and have managed to get my junk stopping very nicely.
After completing my front solid axle swap converion (SAS), I first started out with single 2-15/16" piston, GM front calipers for a 1975 1/2 ton pickup truck, 12" GM front rotors, SOS rear disc brake kit, Wilwood rear proportioning valve, factory brake booster, and the factory 13/16" master cylinder. With this set up the truck would kind of stop, but the brake pedal was pure mush and would actually hit the floor board.......in other words, my braking sucked in a major way
! This poor performance was due to the need to move an increased amount of brake fluid to accomodate the larger volume of the GM calipers.
The next step I took was to change out the factory brake master cylinder for a new 1-1/8" GM master cylinder for a K5 Blazer. With this set up my truck would kind of stop, but the pedal was like a rock and had very little modulation.....so this set up also sucked.
Next I went to Howe Racing 2-piston aluminum GM style front calipers and kept everything else the same. This set up stopped slightly better due to the increased clamping force from the front calipers, but overall still had major suckage for brakes.
Then I change out the front GM rotors for some Stainless Steel Corp. slotted rotors with Hawk pads. This too gave me slightly better stopping power due to the brake pad material, but my pedal was still extremely firm and braking was poor.
This next rendition kind of happened due to me switching over to custom 1-ton front and rear axles.....this resulted in my set up consisting of the 12" slotted front rotors, Howe Racing front calipers, GM 1-1/8" master cylinder, factory Tundra booster, Wilwood rear proportioning valve, Wilwood 12" rear disc, Wilwood forged Dynalite 4-piston rear calipers with internal parking brake, Wilwood BP20 pads, Lokar parking brake cable kit (Ford Explorer style). Yet again, better braking........but no freakin cigar
!
The next step was to switch out the 12" slotted rotors with 13" GM rotors and changing the front Howe Racing calipers for some massive Wilwood forged Superlite 4-piston front calipers & Wilwood BP20 pads.....surely this would give me Formula F-1 stopping power......NOT! My breaking performance did improve, but not up to my expectations. So at this point in my journey I decided to actually attempt to apply some of my engineering background to figure out why the h*ll I had a $250k brake system that essentially didn't stop any better than a 1968 VW Bug (yes, I know because I owned one
)!!!! There was good news though, I found out that one of my front Howe calipers had the mounting ear snapped off of it.....glad I found that in time
!
My first step was to purchase a Mityvac hand vacuum pump and double check if the booster was functioning properly - I had already tried all the normal tests (start truck with foot on brake to see if pedal drops a little, turn truck off with foot on brake to see if pedal kicks back, unplug vacuum line on booster and see if there was a difference) and it passed them all. So I pulled 15" hg vacuum on the booster and it held....so the diaphram wasn't ruptured.
I then started working with a fellow named Eric that hangs out a lot over on the Pirate board to figure out what else could be going on. After calculating the proper hydraulic ratio of my master cylinder/front calipers
Brake Upgrade, I realized that I was running way too large of a master cylinder and also found out that for some reason the Tundras came from the factory with a single diaphram brake booster (where the Tacoma 4x4's & T-100's ran a dual diaphram booster which requires less input force on the pedal).
So I started out by swapping out my factory Tundra booster with a dual diaphram booster for a 1997 T-100 (all the years for the T-100 and the V-6 Tacoma 4x4's are the same) and threw on a 1-1/16" bore master cylinder for a 1997 T-100 (1-ton chassis). The new booster had the same firewall stud pattern & size, but due to it's increased thickness I ended up not using the small aluminum spacer that the factory Tundra booster used between it and the firewall and also ended up having to cut approximately 1/2" off of the new booster threaded rod so my brake linkage clevis on the pedal would end up at the same point. With the new booster I no longer needed to use my homemade plunger part since the booster and master cylinder were facroty interfaced. This produced substantially better braking right off the bat, but the pedal was still a little firm for my taste.
The next change was to try a 1" master cylinder for a 1998 V-6 Tacoma and I also went ahead and threw a 2 psi Wilwood residual valve on the rear brake line, due to the anticipation that the smaller bore master cylinder could possibly allow excessive brake pedal travel. Bingo......finally I have real brakes again - I am able to achieve a nice bias with the adustable proportioning valve on the rears, minimized brake pedal travel with the rear residual valve (which I could have probably done without it, but I'm tired of bleeding brakes, so the h*ll with it
!), and stopping power is as good or better than stock while running 35" tires and heavy steel wheels
!
I also changed my fluid over to ATE Super Blue and purchased the best tool ever created (a Motive Power Bleeder Pro kit
!).
The only real improvements came when I actually sat back and calculated what I needed, although I would have gone with the Wilwood calipers anyways, I believe that the real deciding factor was correctly matching up the size of my master cylinder bore to my front caliper piston surface area. I have a friend with a SAS 1998 V-6 Tacoma who runs the GM calipers, 12" rotors, adjustable proportioning valve & 2# residual on the rears, stock dual diaphram booster and 1" MC and his brake work well also.
Anyways.......the moral of this long, expensive story is to do your homework up front and save a lot of time and $$ down the road!