Brake upgrade options

cloneman315

Active member
Guys so I am thinking about upgrading my brakes on the truck. I am eventually going to put coil overs on the front so keep that in mind. I know there are a ton of threads out there of different type of brake upgrade options. What is the most effective easiest route to go? I don't necessarily want the cheapest but the Best option. I know I saw people mentioning F body C5 and C6 brake upgrade options. Also some information of what is exactly required for the swap. I don't really want to hack anything up or Jerry rig anything to make it work.
 

Static

Member
Re: Brake upgrade options

LS1 brakes here. ABS delete and I modded the prop valve for the rears. Brakes have saved the truck a few times. Fbody going to probably be the easiest to find in the yard also. Vendor has the brackets, e brake cables if you want to retain that.
 

overS-10ded

Donating Member
Re: Brake upgrade options

How did you mod the prop valve for the rear? I found a 2002 Blazer Extreme at a yard and used the front and rear disc setup off that, front dual cyl caliper and larger disc and all bolted up and I used the 2002 lower control arms also because I wanted the 33mm front sway bar too which mounts different than my '91. I am coil over-torsion bar delete also. I even used the master cylinder too as I needed clearance and the stock '91 master cylinder is long! I'm ABS delete as well. Mine setup works great but I think I would like a bit more balance to the rear on the proportioning but don't want a adjustable thing.

Good times!
Bruce
 

Static

Member
Re: Brake upgrade options

How I did the proportioning valve mod: Remove the bleeder looking thing from the front of the prop valve. This is the section for the rear brakes. Remove the valve and spring that are inside. I used a #8 screw and tapped the bleeder and threaded in the screw. Reinstall the bleeder and bleed the brakes. This resulted in more even braking.
 
Re: Brake upgrade options

How I did the proportioning valve mod: Remove the bleeder looking thing from the front of the prop valve. This is the section for the rear brakes. Remove the valve and spring that are inside. I used a #8 screw and tapped the bleeder and threaded in the screw. Reinstall the bleeder and bleed the brakes. This resulted in more even braking.

I know this is an older post but I wanted know you what problem you had with the proportioning valve... I have a big problem with the brakes after installing Wilwood discs on the front and ABS delete. When I bleed them (4 times now) brakes work fine until I start the car - no brakes at all...
Any help would be much appreciated.
Thanks
 

Static

Member
I know this is an older post but I wanted know you what problem you had with the proportioning valve... I have a big problem with the brakes after installing Wilwood discs on the front and ABS delete. When I bleed them (4 times now) brakes work fine until I start the car - no brakes at all...
Any help would be much appreciated.
Thanks
When I did the swap I had the truck up on 4 jack stands. When we were testing the brakes we noticed as the pedal was pressed the front wheels stopped nearly immediately while the rear wheels were still spinning until the pedal was fully depressed. Modifying the prop valve just takes the bias out between the front and rear.
On your truck are the bleeders on your calipers facing up? When you say no brakes at all, pedal goes right to the floor no resistance?
 
Yes, I used the calipers facing up. I get pedal pressure only with the engine off. As soon as I start it - no brakes whatsoever...
 

corsair231

Active member
You must still have air in your system somewhere. As long as this is a traditional vacuum assisted power brake set up and not a hydroboost or powermaster type system the only thing starting the car would have to do with the brakes is supplying the vacuum for the booster to assist and lessen your pedal effort. You may not have enough strength to compress the air with out the assist thus giving you the pedal pressure with the engine off and when you have the engine on you have the assist and you are actually compressing the air.

The only other things I can think of is did you get rid of all of the ABS control components out of your system? If the pressure relief valve for the abs system is still in place and getting energized when you start the truck it could be letting the pressure bleed off. That or possibly a bad master cylinder that when the pressure goes up with the truck running it may be enough to force the fluid past the internal seals so you have pedal travel but no fluid movement.
 

DaveP's Ghost

Active member
You didn't say how long it takes for the pedal to reach the floor. If it doesn't "free-fall" but takes a brief period of time for it to sink all the way down, I think your master cyl is bypassing. With the engine off apply the brake with about 25lb of force. And wait. If the pedal slowly sinks, the master is bypassing. Replace it.

Starting the engine allows the booster to assist with the foot-pressure, and the "sinking pedal" becomes more noticeable, where with the engine off, the sinking pedal may not be.

Modifications to the Combo Valve are only necessary when installing REAR disc brakes. The residual pressure valve must be removed/disabled. Rear pad life is drastically shortened if you don't because the rear brakes will always be applied with 5psi of line pressure.
 
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You must still have air in your system somewhere. As long as this is a traditional vacuum assisted power brake set up and not a hydroboost or powermaster type system the only thing starting the car would have to do with the brakes is supplying the vacuum for the booster to assist and lessen your pedal effort. You may not have enough strength to compress the air with out the assist thus giving you the pedal pressure with the engine off and when you have the engine on you have the assist and you are actually compressing the air.

The only other things I can think of is did you get rid of all of the ABS control components out of your system? If the pressure relief valve for the abs system is still in place and getting energized when you start the truck it could be letting the pressure bleed off. That or possibly a bad master cylinder that when the pressure goes up with the truck running it may be enough to force the fluid past the internal seals so you have pedal travel but no fluid movement.
  1. The Master cylinder is new - replacing it made no difference. MC was bench bled and the the whole system was bled afterwards (again).
  2. The power brake is standard GMC vacuum type.
  3. I removed the entire ABS unit and installed the ABS delete kit. Is the pressure relief valve part the ABS unit? Or is it somewhere else I may have missed?
 

90SLGND

New member
Modifications to the Combo Valve are only necessary when installing REAR disc brakes. The residual pressure valve must be removed/disabled. Rear pad life is drastically shortened if you don't because the rear brakes will always be applied with 5psi of line pressure.

I bought my Ty about 4 years ago and it came with a C4 rear brake conversion (done in the mid 90s). How do i know if this mod to the combo valve was done? I've changed the rear pads once since owning it, and i drive it a lot, almost daily.
 

DaveP's Ghost

Active member
How do i know if this mod to the combo valve was done?

Look at the end plugs. If the valve has been modified, the pin will be gone, and the hole in the other end will have a plug in it. Some guys thread and install a screw in the holes, I welded the holes closed with a TIG.
 
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