Brake headache!!!!

[hollywuud]

I just recently put tons under my CJ, I am using the stock 1 ton calipers on the front 60 and have done a Disc conversion to the 14 bolt to a 3/4 ton caliperin the rear. I read on Pirate that the early 80's Vette MC was the best to run with a disc/disc setup, and it's a direct bolt up to the CJ booster with no mods needed. So I tried that.... I bench bled the MC, gravity bled several times, and force bled several times. I still have a spongy pedal but I am able to stop the vehicle....poorly... but it stops. I just ran all new steel brake lines from front to back, and I did a single drop on the front axle (similar to the rear) all flex lines are new (stainless braided)

My question is this...... Might any of you have an idea of what MC to use without having to go through any major modifications? Something that won't require a small loan from the bank. ;D

 

[natedawgxj]

Reverse the brake lines on the master cylinder

 

[greenlion]

I have used a MC for a 1978 grand marquis with f/r discs before. Cheap at autozone. Has a 1 1/8" bore I believe.

 

[hollywuud]

I have the lines set as front brakes to front port, and rear brakes to rear port on the master cylinder. I will try that his afternoon.

 

[Bahama Bob]

I had the same issue. I have tried a variety of MC before due to the same problem. Best find was from Sam's off-road. It converts your 1 ton calipers to 3/4 ton. Less fluid required, much more stopping power. From there you can upgrade to the 4 or 6 piston calipers should you decide you need more power.

 

[leeman1790]

One of my buddies did the vette Mc with tons and his was same way. His steel brake lines were huge compared to most rigs. I told him that I bet if he had smaller diameter lines he might have a stiffer pedal. One of his back calipers had a problem at grayrock so we capped that side off at the T on the axle. Brakes were amazing after that.

 

[hollywuud]

This is where I am stumped... I just ran all new 3/16 steel lines from the MC to both ends.... No leaks to be found. I'm wondering if the pushrod needs to be extended, or switch to an even bigger bore MC. Something from a 1 ton truck. It makes sense to run a 1 ton MC if i am running 1 ton calipers. (does to me anyway) but perhaps I am over thinking the whole thing.

 

[Bahama Bob]

1 tom mc not the answer. Ask Brian Cole and Woodlee as well as the other guys you see changing out the Calipers. You see them going away from the 1 ton Calipers for a reason. Smaller caliper equal less fluid, but better bite.

 

[patooyee]

What exactly is your problem? Does your pedal travel all the way to the floor without much braking action or does it stop where it should just without much braking power? The solution depends on which of those is the problem.

If your pedal goes to the floor you either need a bigger MC or smaller calipers. The problem there is not enough fluid displacement.

If the pedal stops where it should but still no power you're displacing enough fluid but over too large an area. In that case you need a smaller MC.

Size of lines does not matter. Larger caliper piston dia. = more stopping power but requires more fluid to fill. Smaller caliper piston dia. = less stopping power but less fluid to fill.

A bigger MC will generate less pressure than a smaller MC with an equal amount of pedal force. Keep line pressure equal, a bigger caliper will have more "bite." (That is why the 1-ton had the big MC in the first place.) But you need big bore MC to fill that big caliper which reduces line pressure over a smaller MC using the same pedal. That is why the 1-ton also used HYDROBOOST to increase line pressure.

The GM 1-ton MC is 1-5/16 dia. The '82 'Vette is 1-1/8. That's a 3/16 difference. Pretty big. You've drastically reduced the displacement ability as compared to original setup that went with the 1-ton front calipers you are using. If you want to keep your calipers I would try the 1-ton MC but I bet you're going to need a pretty strong leg to keep that thing stopped on a steep hill because of the big bore and no hydroboost. If you want to keep your MC you might try changing to 3/4-ton or even 1/2-ton front calipers, the same you have in the rear but know that your overall clamping force potential will be less than with the 1-ton calipers. Few of us actually need that much caliper force though. Hence the reason Cole and Woodleee are probably using 3/4-ton.

J. J.

 

[Bahama Bob]

I have the Corvette master cylinder still in my shop that I used. It was for a 64 Vette with manual disc brakes. I had the same problem he is having. Pedal travels all the way, but is spongy and seems to loose pressure while traveling down hill. So I went the direction of smaller new model MC with the 1 ton calipers but still had the same issue. My buddy had the same issue and went with the 1 ton MC for manual disc brakes and still has the same issue. He says it will stop but he spends more time fighting to stop and planned what to do if it don't. Tony Black on this board that wheels the spider buggy with Julio and those guys is the one that told me about the smaller caliper conversion. He put it on his 1 ton front end and said it worked great. I just finished mine up along with a complete front and rear end rebuild. It was the answer I was looking for and now if I want to order the bigger four piston calipers I could and they would be a direct bolt on. Not trying to steer anyone wrong, but I have been in the exact same boat and tossed a lot of money at my rigs guessing about what would make it stop.

New bracket

Backside

All views

Matching rear setup

 

[patooyee]

I have the Corvette master cylinder still in my shop that I used. It was for a 64 Vette with manual disc brakes. I had the same problem he is having. Pedal travels all the way, but is spongy and seems to loose pressure while traveling down hill. So I went the direction of smaller new model MC with the 1 ton calipers but still had the same issue. My buddy had the same issue and went with the 1 ton MC for manual disc brakes and still has the same issue. He says it will stop but he spends more time fighting to stop and planned what to do if it don't. Tony Black on this board that wheels the spider buggy with Julio and those guys is the one that told me about the smaller caliper conversion. He put it on his 1 ton front end and said it worked great. I just finished mine up along with a complete front and rear end rebuild. It was the answer I was looking for and now if I want to order the bigger four piston calipers I could and they would be a direct bolt on. Not trying to steer anyone wrong, but I have been in the exact same boat and tossed a lot of money at my rigs guessing about what would make it stop.

New bracket

Backside

All views

Matching rear setup

What 4-piston caliper is a direct bolt-on?

J. J.

 

[TBItoy]

SSBC makes 2,3, and 4 piston calipers that will swap out for GM large floating calipers (the calipers from a 3/4ton D44 that everyone uses is interchangeable with the fullsize GM car caliper), so there is lots of aftermarket bling bling stuff that would work on most crawlers...

http://www.speedwaymotors.com/SSBC-1969-77-GM-Quick-Change-Caliper-Upgrade-Kit,54977.html

 

[1TONZR2]

I had the same issue with my rig. Same MC, was running Ford dual piston calipers and rotors....very hard to stop a 5500lb+ rig on a steep hill. I switched to the GM 3/4 ton stuff and it is much better. I got my brackets from Blackbird Customs.

 

[Bahama Bob]

Great selection for upgrades should you need to, once you buy the brackets.

 

[hollywuud]

@ Patooyee. Yes, the pedal goes all the way to the floor with VERY minimal braking. I have even tried extending the push rod to no avail. I think I am just going to quit looking for a cheap way out of this and go with the 3/4 ton conversion for the front as pictured above. I am not running a very heavy rig so I feel comfortable downsizingto a smaller caliper. Prior to this axle swap, I was running a 44/60 combo with 1/2 ton calipers and it worked fairly well.

@ Bahama Bob. This may be a foolish question... I assume you had to go with 3/4 tom rotors too? Just want to get all my quacks in a row.

 

[patooyee]

SSBC makes 2,3, and 4 piston calipers that will swap out for GM large floating calipers (the calipers from a 3/4ton D44 that everyone uses is interchangeable with the fullsize GM car caliper), so there is lots of aftermarket bling bling stuff that would work on most crawlers...

http://www.speedwaymotors.com/SSBC-1969-77-GM-Quick-Change-Caliper-Upgrade-Kit,54977.html

3/4-ton calipers are what are referred to as d52's. Those are not a direct replacement for the 3/4-ton d52 calipers, they are for the much smaller d43 car calipers. I dont' know if they share the same bolt pattern. They do not appear to share the same pin style. But the d43 pad is a smaller pad than the d52. It also says for 11" rotors, I don't' know if that means that they will not seat properly on anything bigger but a 3/4-ton GM rotor is 12.5".

Wilwood makes these direct replacement d52 calipers:

http://www.wilwood.com/Calipers/CaliperList.aspx?subname=GM%20D52%20Dual%20Piston

It looks 20x more rigid than that SSBC. But I was hoping someone had found an OEM 4-piston caliper as opposed to aftermarket. I guess I can keep dreaming.

J. J.

PS: When Wilwood first came out with that D52 replacement I called them to see what type of line pressure it was rated and they said 1000-1500. Hydroboost would be at least 2000 so it wouldn't be a good swap for a hydroboost rig sadly.

 

[Bahama Bob]

@ Patooyee. Yes, the pedal goes all the way to the floor with VERY minimal braking. I have even tried extending the push rod to no avail. I think I am just going to quit looking for a cheap way out of this and go with the 3/4 ton conversion for the front as pictured above. I am not running a very heavy rig so I feel comfortable downsizingto a smaller caliper. Prior to this axle swap, I was running a 44/60 combo with 1/2 ton calipers and it worked fairly well.

@ Bahama Bob. This may be a foolish question... I assume you had to go with 3/4 tom rotors too? Just want to get all my quacks in a row.

Yes I sure did have to change the rotors as well.

 

[TBItoy]

3/4-ton calipers are what are referred to as d52's. Those are not a direct replacement for the 3/4-ton d52 calipers, they are for the much smaller d43 car calipers. I dont' know if they share the same bolt pattern. They do not appear to share the same pin style. But the d43 pad is a smaller pad than the d52. It also says for 11" rotors, I don't' know if that means that they will not seat properly on anything bigger but a 3/4-ton GM rotor is 12.5".

Wilwood makes these direct replacement d52 calipers:

http://www.wilwood.com/Calipers/CaliperList.aspx?subname=GM%20D52%20Dual%20Piston

It looks 20x more rigid than that SSBC. But I was hoping someone had found an OEM 4-piston caliper as opposed to aftermarket. I guess I can keep dreaming.

J. J.

PS: When Wilwood first came out with that D52 replacement I called them to see what type of line pressure it was rated and they said 1000-1500. Hydroboost would be at least 2000 so it wouldn't be a good swap for a hydroboost rig sadly.

Whoops,

I was looking at these D52 2 piston calipers on SSBC's website before I saw this thread, then went looking for 4 piston calipers and found the D43s...

AFAIK there is no OEM multi piston GM slider style calipers.

 

[hollywuud]

Getting ready to order my conversion brackets this week, and I already have calipers and rotors as of Sunday. Thanks for the point in the right direction, fellas. it's greatly apreciated.

Brett