...

Go Back   Lateral-g Forums > Technical Discussions > Brakes
User Name
Password



Reply
 
Thread Tools Display Modes
  #1  
Old 07-19-2010, 05:17 AM
CreepinDeth's Avatar
CreepinDeth CreepinDeth is offline
Senior Member
 
Join Date: Jul 2008
Location: Chicago burbs
Posts: 175
Thanks: 0
Thanked 0 Times in 0 Posts
Default Trying to figure out brake problem with rear disc upgrade

I have a 1970 Olds 442 clone.
I took out the fake Olds 12 bolt 2.78 rear end, and put in a Chevy 12 Bolt Eaton Posi 3.73 I got off another member here earlier this year. It came with the Baer rear 11" disc setup. I have stock 10.75" factory front disc brakes.


I was told a 1979 Corvette Master with the 1 1/8" bore would be a great addition to make this system work. Plus an Adjustable Proportioning Valve for the rear. So far I've bled the system 5 - 6 times and I still have a mushy brake pedal. I put in a Fenco rebuilt 79 Vette master with 3/16" front and 1/4" rear lines. I'm not exactly sure if I need to upgrade to a 1" bore master cylinder, or if I'm doing something wrong here.

No matter what I have done, I still have an ultra mush pedal and I know I don't have any air left in there. I checked everywhere for leaks too, nothing. Something else has to be the problem. I was hoping maybe someone can help me figure it out. So far I've been told my rebuilt master COULD have bad seals, to order another. I just want to be sure what I'm putting in is going to really work. I've see other guys upgrade to rear discs with this master with no problems.

I have no idea if this Baer brake setup uses a big or little piston and how I should calculate this all out. I'm stabbing in the dark here.

Last edited by CreepinDeth; 07-19-2010 at 05:21 AM.
Reply With Quote
  #2  
Old 07-19-2010, 01:49 PM
Apogee Apogee is offline
Senior Member
 
Join Date: Aug 2007
Posts: 394
Thanks: 0
Thanked 1 Time in 1 Post
Default

Quote:
Originally Posted by CreepinDeth View Post
...I have no idea if this Baer brake setup uses a big or little piston and how I should calculate this all out. I'm stabbing in the dark here.
The Baer brake kit you have uses 1993-1997 LT1 F-body rear calipers if I'm not mistaken (the same as the 88-96 C4 Corvette calipers except for the direction of pull for the parking brake cables). These calipers have 45mm [1.77"] diameter pistons which are relatively small compared to your fronts. Balance is going to be a little tough to achieve with a single master cylinder, but I'd probably be more inclined to run a smaller bore (1" or 1-1/16") MC with the adjustable proportioning valve on the rear.

Spongy but no air eh?...that's a neat trick. Could be a bad MC, however that still won't typically feel spongy but rather a sinking feeling cause by fluid bypassing the seals. They'll still usually pump-up, if not just temporarily, at least until they get really bad. Fill us in on how you know you don't have any air in the system with special attention given to how you bench bleed your master cylinder before installing it.

Tobin
KORE3
__________________
www.kore3.com

Last edited by Apogee; 07-19-2010 at 01:51 PM.
Reply With Quote
  #3  
Old 07-19-2010, 04:24 PM
CreepinDeth's Avatar
CreepinDeth CreepinDeth is offline
Senior Member
 
Join Date: Jul 2008
Location: Chicago burbs
Posts: 175
Thanks: 0
Thanked 0 Times in 0 Posts
Default

Quote:
Originally Posted by Apogee View Post
Fill us in on how you know you don't have any air in the system with special attention given to how you bench bleed your master cylinder before installing it.

Tobin
KORE3

Man, I really don't know. LOL

I bled EACH caliper at least 5 times with a vacula, then my hand with a 2nd person (old fashioned way), and then with the 1 man bleeder bottle with help again. I don't see anymore bubbles coming out. So I just ASSUMED there was no air because hell it should have came out by now I thought. If I couldn't get it out that many times, I figured it will never come out so it's GOTTA be clear.

I'm going to bench bleed the master though because while I had it hooked up to the booster , I left it unplugged while I was flaring some new fittings. It's possible air got back in the MC. Thanks for replying to my email too bro. I will try that, then if it's fine, I'll just install the new Raybestos premium 79 new MC I just ordered. My Camaro used the same MC and went like a BREEZE the 1st time around. This one is being a real bitch to me.

Quote:
Originally Posted by Apogee View Post
Balance is going to be a little tough to achieve with a single master cylinder, but I'd probably be more inclined to run a smaller bore (1" or 1-1/16") MC with the adjustable proportioning valve on the rear.
BTW what did you mean by "A single master cylinder" ??
The 79 Vette MC has 2 equal size chambers and is 1 1/8".....so you lost me. I'm still kinda new to this so excuse my ignorance.

Last edited by CreepinDeth; 07-19-2010 at 05:58 PM.
Reply With Quote
  #4  
Old 07-19-2010, 09:42 PM
Apogee Apogee is offline
Senior Member
 
Join Date: Aug 2007
Posts: 394
Thanks: 0
Thanked 1 Time in 1 Post
Default

Quote:
Originally Posted by CreepinDeth View Post
Man, I really don't know. LOL

I bled EACH caliper at least 5 times with a vacula, then my hand with a 2nd person (old fashioned way), and then with the 1 man bleeder bottle with help again. I don't see anymore bubbles coming out. So I just ASSUMED there was no air because hell it should have came out by now I thought. If I couldn't get it out that many times, I figured it will never come out so it's GOTTA be clear.

I'm going to bench bleed the master though because while I had it hooked up to the booster , I left it unplugged while I was flaring some new fittings. It's possible air got back in the MC. Thanks for replying to my email too bro. I will try that, then if it's fine, I'll just install the new Raybestos premium 79 new MC I just ordered. My Camaro used the same MC and went like a BREEZE the 1st time around. This one is being a real bitch to me.



BTW what did you mean by "A single master cylinder" ??
The 79 Vette MC has 2 equal size chambers and is 1 1/8".....so you lost me. I'm still kinda new to this so excuse my ignorance.
Wow...I should buy some stock in whatever brand brake fluid you're using.

By single master cylinder, I meant a single tandem master cylinder, one with one bore size and two pistons and outlets so that you have some safety should one circuit fail. The alternative being dual master cylinders like those used in a race pedal setup with a balance beam between the two. These setups allow you to run different bore MC's front and rear, giving you the flexibility to run huge caliper mismatch's should you want to and still getting the bias you want/need.

As for the MC fittings, I'll usually bleed the MC fittings first by cracking them one at a time while under pressure just so I don't have to push those air bubbles all the way through the system, especially if it's already been filled. It also helps if you run your hard lines to the MC slightly uphill so that they hold more fluid prior to installation. The air that I've had difficulty bleeding from the MC at times seems to be tiny bubbles trapped in or around the seals. No amount of moving fluid through the MC seems to remove them without some tapping with a dead-blow hammer to help dislodge them.

Tobin
KORE3
__________________
www.kore3.com

Last edited by Apogee; 07-19-2010 at 09:44 PM.
Reply With Quote
  #5  
Old 07-19-2010, 10:20 PM
CreepinDeth's Avatar
CreepinDeth CreepinDeth is offline
Senior Member
 
Join Date: Jul 2008
Location: Chicago burbs
Posts: 175
Thanks: 0
Thanked 0 Times in 0 Posts
Default

Quote:
Originally Posted by Apogee View Post
Wow...I should buy some stock in whatever brand brake fluid you're using.
I've killed a gallon already......wasn't fun.


Okay, so I guess the '79 Vette MC is a single. I hope this new MC works out better.
Quote:
Originally Posted by Apogee View Post
As for the MC fittings, I'll usually bleed the MC fittings first by cracking them one at a time while under pressure just so I don't have to push those air bubbles all the way through the system, especially if it's already been filled.
So let me make sure I understand this.
You crack the 2 fittings while pressing the plunger in on the MC.....to get the air out.
Then before releasing the plunger you tighten the 2 plugs ???

....or did I misunderstand that ??

Last edited by CreepinDeth; 07-19-2010 at 10:22 PM.
Reply With Quote
  #6  
Old 07-20-2010, 08:52 AM
Apogee Apogee is offline
Senior Member
 
Join Date: Aug 2007
Posts: 394
Thanks: 0
Thanked 1 Time in 1 Post
Default

Quote:
Originally Posted by CreepinDeth View Post
...So let me make sure I understand this.
You crack the 2 fittings while pressing the plunger in on the MC.....to get the air out.
Then before releasing the plunger you tighten the 2 plugs ???

....or did I misunderstand that ??
That's about right, except I just do one fitting at a time since I'm usually juggling a rag and trying not to get brake fluid everywhere. Have someone press and hold the pedal while you crack open and then close one fitting at a time and repeat until you're satisfied. I've found that 1-2 times per fitting seems to be plenty most installations.

Tobin
KORE3
__________________
www.kore3.com
Reply With Quote
  #7  
Old 07-20-2010, 10:02 AM
GregWeld's Avatar
GregWeld GregWeld is offline
Lateral-g Supporting Member
 
Join Date: Jul 2005
Location: Scottsdale, AriDzona
Posts: 20,642
Thanks: 504
Thanked 1,076 Times in 384 Posts
Default

I bench bleed the M/C on the bench rather than on the car. It's hard to get all the air out of the M/C sometimes. I use a large phillips screwdriver as the push tool... and that way I can really bottom the plunger. I have a set of lines I use that hook up to the outlets and return to the M/C reservoir and I can SEE that there is not a single bubble left before the install. I cap it -- and leave the lines on - get it bolted up - toweled up - and swap the lines over.

One other thing that is a mistake I've found several times trying to help someone with "brake issues".... Not every M/C is the same line configuration - i.e., some M/C's run the front reservoir to the fronts and some run the front reservoir to the rear. The way I've found to check for this is while I'm bench bleeding it - I plunge slowly while looking for the fluid flow FIRST in which bowl of the reservoir - that reservoir should be to the fronts. If you do this a couple of times - you'll see what I'm talking about - you'll see fluid just a nano second before in one bowl or the other. That wouldn't give you a mushy pedal - I'm just adding this since you're using parts you may or may not be familiar with...

If you bench bled the M/C - and went thru a gallon of fluid - I say you've got a bad M/C and should probably just get a new one.
Reply With Quote
  #8  
Old 07-20-2010, 11:01 AM
CamaroAJ's Avatar
CamaroAJ CamaroAJ is offline
Lateral-g Supporting Member
 
Join Date: Mar 2010
Location: San Antonio, Tx
Posts: 851
Thanks: 102
Thanked 241 Times in 116 Posts
Default

just going to throw this out there since i know first hand this can happen. do you have the rotors bolted on or the wheels bolted on? it may sound like it shouldn't matter but this just happened to me the other day and then i remembered i didn't have the rotors bolted onto the hub. but i blead the system then had a soft pedal. bolted the wheels back on and have nice hard pedal. the rotor being able to move side to side even though its just a little bit is enough to push the pistons back and give you problems
Reply With Quote
  #9  
Old 07-20-2010, 12:31 PM
GregWeld's Avatar
GregWeld GregWeld is offline
Lateral-g Supporting Member
 
Join Date: Jul 2005
Location: Scottsdale, AriDzona
Posts: 20,642
Thanks: 504
Thanked 1,076 Times in 384 Posts
Default

Just one last thought on this problem... I think we'd all ASSume that you know how to bleed brakes.... which is the furthest away first -- so passenger rear first - then driver rear - then passenger front - then driver front....
Reply With Quote
  #10  
Old 07-20-2010, 04:09 PM
PRRC PRRC is offline
Senior Member
 
Join Date: Jun 2006
Posts: 344
Thanks: 0
Thanked 0 Times in 0 Posts
Default

I would say that 1 problem with this set up your running is the 1/4 line to rear calipers. It's just to large of a diameter for a disc. set up.
__________________
www.paradise-road.com
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 09:34 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright Lateral-g.net