Brake dilemma, need advice
 

I'm sick of my brakes! No matter what I do my brakes just don't stop the truck fast enough. I just put dual piston Wilwood D52 calipers, drilled and slotted 12" rotors, and steel braided hoses on the front and no matter what speed I'm at they still won't lock up no matter how hard I push the pedal.

I have the right MC , I have the rod adjusted correctly, I have the right proportioning valve, I have a good booster, I have a vacuum reserve canister, and I have bled them too many times to count. What am I missing?


The only thing I can think is my MC isn't putting out "enough" pressure. Do I just need to spend the money and get a hydroboost setup? Normally I wouldn't worry too much about this but if some kid runs out in front of me I honestly don't think I could stop fast enough.

Re: Brake dilemma, need advice
 

Do you think and adjustable porpotioning valve in the rear line would help you dial it in?
Which bore master cylinder? 1" or 1-1/8" bore?
Also disc/drum or 4 wheel disc?

Re: Brake dilemma, need advice
 

What is the vacuum level @ the vac can?

Re: Brake dilemma, need advice
 

I have an adjustable prop. valve on the rear line, I'm not sure on the bore size, and it's a disc/drum setup.




SCOTI ,I'm not sure what the vacuum level is at, I don't have a guage.

Re: Brake dilemma, need advice
 

You know someone that does. Let's try & get together this weekend maybe & see what it is??

Re: Brake dilemma, need advice
 

I'll try, but I have another problem that developed on the test drive for the brakes. My elec. fan decided to come loose and put a small hole in my radiator so now I have to get that fixed.


I swear this truck hates me.

Re: Brake dilemma, need advice
 

Basically there are 2 ways to improve the brakes.

1- Use a bigger booster, or use a Hydaboost. The Hydraboost are the most powerful booster you can get.
2- Use a larger rotor. The CPP 13” kit or the Willwood 14” kit will improve the brake performance.

FYI: The D52 caliper has almost the same piston area than the OE caliper.

This web address shows the output of different boosters. http://www.classicperform.com/PDFs/B...ssureChart.pdf

Danny Nix CPP

Re: Brake dilemma, need advice
 

Just to throw my 2 cents in, I was working on my buddy's Chevelle recently and he had a booster that was less than a year old that we had come to find out was blown. Also the check valve was blown. If you ever experienced any backfire while tuning your truck that could have blown out your booster. My buddy had the canister and new brake system on his car too. I took the booster out and she was toasted. I'm sure you've checked your drums already too, but just in case, make sure those axle seals aren't leaking onto the shoes.

Re: Brake dilemma, need advice
 

I find it odd that you can't get enough pressure to lock up your brakes, especially with the upgrades you have made. Has the problem always been there? Is that the reason you upgraded the brakes to begin with? If the problem was present before the upgrades, what components have NOT been replaced yet?

Re: Brake dilemma, need advice
 

You're preaching to the choir brother, I find it odd too. The problem has always been there and yes that is why I did the upgrade. Originally three years ago "everything" and I mean "everything" was replaced, mostly with parts from O'reilly. Even then the brakes behaved the same way, I just assumed it was the way it was going to be.


To the best of my knowledge the rear brakes work perfectly it's only the front ones that seem to just not get enough pressure. The lines aren't clogged ,I get plenty of fluid when I bleed them just not enough pressure I guess. Could I possibly need a new MC ,maybe one that has more pressure than stock.


I do know for sure it's not the calipers, rotors, hoses, or pads they only have about 4 miles on them and they are brand spankin new.:lol::lol:

Re: Brake dilemma, need advice
 

Have you broken in the pads? some times it takes quite a while for them to seat in. Four miles doesn't sound like enough. Maybe somebody else has some info on breaking pads in. good luck

Re: Brake dilemma, need advice
 

Interesting infor no one told me before I purchased mine -- hop emine work better! I have had the same basic problem -- and setup -- was kind of hoping the new calipers would help the issue a little.....

Re: Brake dilemma, need advice
 

Do you feel it when your booster gets vacuum with your foot on the brake and starting the truck? I thing something is up with your booster. Also really double check the brake push rod adjustment. You have some component not working, the stock disc drum stuff should lock up no problem! You don't need a more powerful mastercylinder or booster.

Re: Brake dilemma, need advice
 

I'm using the same pads I already had and there's plenty of miles and material left on them. It's not the pads.

I was hoping that too
I do feel the vacuum, it doesn't and never has felt very strong. The only thing left is the MC or the booster I guess I'll try those next.

Re: Brake dilemma, need advice
 

Look at Wilwoods website.
There a FAQ section and a troubleshooting section.
Seems like master cylinder bore size is an important part of brake pressure produced by the master cylinder.

Re: Brake dilemma, need advice
 

I agree w/reviewing the troubleshooting section. Also consider this....

I've yet to have an issue w/brakes when using the correct GM parts (calipers, rotors, master, & booster). If they are (were) sourced correctly, I think the vacuum issue needs to be verified. Vacuum is what these brake systems require to 'boost' the pedal pressure. A vacuum system w/o vacuum will not hit it's intended pressure range. Sure the rears will lock up but that can be a result of limited weight & the natural weight transfer that occurs during harder braking.

Re: Brake dilemma, need advice
 

Doesn't sound like pedal ratio.

http://www.hotrodheaven.com/tech/brakes/brakes6.htm

Re: Brake dilemma, need advice
 

THANKS for all the help guys.

Who the hell knows what's going on or exactly which MC or booster I have, like I said I got them at O'reilly's. I guess I'll look into the bore size of the MC and go from there. If all else fails I'll just replace both the booster and MC with some good aftermarket parts and see if that fixes it.


Right now I have other issues with the truck when I was on the test run for the new brakes not only did I put a small hole in my radiator I think I knocked a lobe or two ,or three off the cam as well. I was "wanting" to do an engine swap anyway ,but that "want" may become a reality pretty quick.

Re: Brake dilemma, need advice
 

Sure sorry to hear about your other problems. I am doing the same kind of build as you -- but plan on driving around in primer for a while to get all the little issues and bugs worked out before i paint. I painted and did the interior on a truck almost 20 years ago -- drove it to work to show it off and broke down on the way to there!! Anyhow -- looked at your thread and will have to say your build is AWESOME..love the blue!

REAL interested in hearing what your brake problem turns out to be -- mine sounds EXACTLY the same....

Re: Brake dilemma, need advice
 

I just noticed I missed your call. I'll be in touch tomorrow. Maybe if the roads are ok, I'll swing by your place & we can brainstorm the possibilities on Sat?

Re: Brake dilemma, need advice
 

Try this method of bleeding:
1. Open at least one if not both front bleeders and put a vacuume hose from the bleeder into a plastic drink bottle (to keep from making a mess).
2. While the front/s are open, bleed the RR and then the LR. Keep checking the master cylinder to make sure you don't run dry.
3. If you have the LF open, close it.
4. Bleed the RF.
5. Bleed the LF.
If your pedal is not rock hard after trying this, try it again at least once. If still not rock hard, replace the master cylinder. FYI, even if your booster is bad, if you stand on the brakes hard enough, you should be able to lock the brakes.

Re: Brake dilemma, need advice
 

I've had a bad "new" booster from O'Reilly before. I would start there, sounds like all the other variables are covered.

Re: Brake dilemma, need advice
 

I got a vacuum guage and here's what it read "at the booster".

At idle in gear it's pulling 10in. hg vacuum
At idle in park it's pulling 13in. hg vacuum
When I rev it up it goes up to about 20in. hg vacuum

I don't know if those readings are good ,bad, or normal but that's what they are. While I had it running I pushed the brake pedal with the booster hooked up and without it hooked up ,and I can definately tell it's working when it's hooked up. I just don't know if it's working up to the level it needs to be at.


What do you guys think?

Re: Brake dilemma, need advice
 

What cam do you have? 10" of vacuum is not enough to run your brakes properly.

Re: Brake dilemma, need advice
 

UUGGHH ,I cant remember the exact specs of the cam it's somewhere around .511 lift.


Not sure if it matters or not but I used to have a more mild engine setup with a less aggressive cam in it, and the brakes acted the same way then too.

Re: Brake dilemma, need advice
 

I recall reading somewhere that a minimum of 17" vacuum is needed for full brake pressure. Although the 14" sounds close when the motor is reving, you won't have rpm's up when the brake pedal is applied.

Re: Brake dilemma, need advice
 

Either way you look at it shouldn't I be able to push the pedal hard enough that at some point they lock up? Even if I had no power brakes at all? If I have to I'll just spend the bread and get a hydroboost setup if I can't get enough out of my current setup.



BTW SCOTI thanks for telling me about Entropy ,I ordered some elec. fans and a nice aluminum shroud from them today.

Re: Brake dilemma, need advice
 

Glad you found what you were looking for.

As for the pressure issue, I would think they should still lock up but it may not be the case (a pwr steering set-up w/o the pwr assist is more difficult to steer vs. a manual steer set-up). My guess is a manual brake set-up has the internal valving calculated for that specific design requirement as does a power brake master cylinder. Take away the 'boost' assist from the system, & it may be more difficult than we think to get them to lock-up.

Re: Brake dilemma, need advice
 

HHMMM, interesting you may be on to something there. Well where do I go from here hydroboost ,or should I wait until I get my new engine (probably a 502) and see if that motor makes enough vacuum?


Decisions, decisions.

Re: Brake dilemma, need advice
 

You could also look into an electric vacuum pump. GM used them on Caddys & such plus they're available via the aftermarket for applications where consistent vacuuum is an issue.

Re: Brake dilemma, need advice
 

Here's a good way to check your vacuum. Hook up the vacuum gauge at the engine. Now, adjust your timing until the gauge reads the highest reading. Next, back your timing off 2 degrees. This will show you two things, the highest amount of vacuum your engine is capable of producing, and you will be shockingly close to the correct timing for your engine. Gone by this method a few times before and it works perfectly. Also a couple things, have you thought about a residual valve? If it's an aftermarket MC its common for them to not have it built in. Also, fire up the engine in the evening sometime, then come out the next day and pull the check valve. There should be vacuum still holding in the booster even overnight. Also, I had one of those vacuum pumps, it worked alright but it was very noisy :(

Re: Brake dilemma, need advice
 

Yes, you should.

Re: Brake dilemma, need advice
 

Dude ,don't even get me started on timing. The engine in my truck is the only engine in the world that refuses to have the timing set correctly. Amongst other engine issues timing is the absolute last thing I want to mess with on my truck. That's (one of the many reasons) I'm ditching this engine and getting a new one.:lol:


I think I'm just gonna wait a little longer and get a new Wilwood MC and get rear disc brakes. If that doesn't do it I'll invest in a hydroboost setup.

Re: Brake dilemma, need advice
 

Sounds like the problem your having is... You need more horsepower!!!!

Re: Brake dilemma, need advice
 

Thinking back, my brakes were like this before I had a big cam and my motor was essentially stock. I don't know what the vacuum readings were then but they should have been alot better than they are now. Which would only leave the MC and proportioning valve to check into.


Is there any way I can test those two things out?

Re: Brake dilemma, need advice
 

If the master cylinder is bad you should be able to tell by bench bleeding it again. It may show air bubbles from a leaky seal or something. The proportioning valve I think you'd just have to replace to find out..

Re: Brake dilemma, need advice
 

Did you try bleeding it like this? My dad who has forgotten more about cars than I will ever know (I am a technical instructor for BMW) told me that these old trucks have something wacky in the M/C that will not let the rears bleed very easily if you don't have the fronts or at least one of the front bleeders open. Too much pressure in the cylinder wont let the piston bottom out in the rear portion? Or it bottoms out too early in the front portion? I don't think even he remembers exactly why it's wacky...it just is and you will have a lot better luck with the fronts or at least one front bleeder open when you do the rears.

Re: Brake dilemma, need advice
 

http://www.markwilliams.com/braketech.aspx
good luck with the 'problem' ..thought this might shed some light on the subject..

Re: Brake dilemma, need advice
 

THANKS for the link.



Update: Upon closer examination of my brake system with the help of board member SCOTI over the phone I may have found the culprit of the problem. Years ago when I plumbed the system I may have used too small of a brake line for the front after all that one line feeds two calipers so it probably doesn't need to be undersized. I'm going to order some nice stainless steel lines and try that and see if that fixes the problem.

Re: Brake dilemma, need advice
 

What are you calling too small?
Smaller than 3/16" or 1/4" brake line?