Brake dilemma, need advice

[Painter D]

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.

[lolife99]

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?

[SCOTI]

What is the vacuum level @ the vac can?

[Painter D]

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.

[SCOTI]

Originally Posted by 69chevyshort

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.

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

[Painter D]

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.

[DKN]

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

[skoffice]

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.

[PBFAB.COM]

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?

[Painter D]

Originally Posted by porterbuilt

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?

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.

[bikertim]

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

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.....

[lolife99]

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.

[SCOTI]

Originally Posted by lolife99

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.

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.

[Painter D]

Originally Posted by SCOTI

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.

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?

[LONGHAIR]

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

[Painter D]

Originally Posted by LONGHAIR

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

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.

[Hart_Rod]

Doesn't sound like pedal ratio.

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

[Painter D]

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.

[SCOTI]

Originally Posted by 69chevyshort

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.

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?

[Longhorn321]

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.

[LEEVON]

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

[Longhorn321]

Originally Posted by Longhorn321

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.

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.

[bikertim]

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....

[lolife99]

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

[SCOTI]

Originally Posted by lolife99

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

He's using factory drum lines on a disc system. I suggested getting a front line kit for a 71-72 & go from there....