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14b swap + 40" Boggers = No Brakes?

guido666

guido666

1/2 ton status
Joined
Feb 16, 2005
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Location
Longmont, CO
I have a '79 Blazer, and just swapped out my 12b for a 14bFF in the rear. I also installed a set of 18/39.5x15 Boggers on the rear only. Now I can't stop hardly at all. I bled the brakes quite thoroughly (ran about 1/2 quart through) and still it seems to take forever to stop. I was expecting some slow stops, but this seems worse. Is this just what I should expect (and what will get worse when I put on the 3/4t 10-bolt front axle) or is something wrong? Anything I can do to improve this such as putting on a 1-ton master cylinder or switching from vacuum assist to hydro assist (what is hydro assist, I see everyone talking about it)?

I know these are stupid questions, but after about 3 weeks of driving with the big rear tires, I rearended a Pontiac GrandPrix. Everyone was ok, and all it did to my truck was bend a towhook and break the glass in one of my Hella's, but I destroyed the GrandPrix. I figure that is probably bad. :doah:
 
I am sure you took care of this, but just checking. Check to make sure your pads are adjusted out. Jack up the rear of the truck and spin the tire, adjusting the pads through the backing plate until they just start to drag. That was my issue when I didn't have brakes in the 14 bolt after the swap.
 
Not to be a prick but that was a pretty stupid move man. Driving a vehicle with brakes that you know aren't adequate is flat out irresponsible to put it nicely. Replace the hardlines, have them power bled, and check the shoes.
 
The brakes are not gone, there are just much less. I was expecting some amount of increased stopping distance, I just didn't know how much. I'll try the adjusting thing, it seems plausible, because it just seems like the pedal has to travel further then it used to.

The brakes are ok for normal driving, when I hit the Pontiac it was the worst of all possibilities. Downhill, in the rain, the driver was going to turn but then stopped dead all of a sudden, and there was oncoming traffic and oak trees immediately off the road (no where to go). I know it may seem irresponsible, but like I said, I was expecting an increase in stopping distance. I'm just not sure how much. Now I'm looking for ways to beef the brakes.
 
You need to switch to rear disc brakes. They will stop my burb on 44's with no problem :D
 
Rear disc brakes will help significantly? If so I'll order them today! (While still looking for other problems of course). How much does a complete swap cost? I see in the vendors section I can get the brackets for $55-65. How much will the rest cost me? (2 calipers, either with or without parking brake, brake lines, rotors, and anything else)?

What is hydroboost?
 
disc's are nice but i can lock up my 37" ssrs on pavement with my 14 bolt drums. id diagnose what is wrong with your current setup before you spend money on a new setup.
 
Right, I tried to allude to that. I was more inquiring how much better discs are then drums. Although, these Boggers are almost 20" wide, there is a lot of meat on the pavement, I would be pleasently surprised (if even a fully working system) could lock them up.

Could someone give me an idea of how much worse this kind of swap should make my braking in general? Am I trying to fix a problem that really isn't there?
 
um, i bought all my stuff for around $200-250 i believe. i dont remember, it was a couple months ago. disc have alot of advantages over drums. find out what ur current problem is and then ge the discs ;)
 
keep in mind that disc brakes perform better if setup correctly, but it is not a plug and play deal. Many people have worse braking after a disc swap than before. If you read older threads, you'll find that different things work for different people. Hydroboost seems to be the most popular solution to the problem, but I don't think it's the booster than helps as much as the master cylinder. I know different years have different systems, but in 1990 there were JB5, JB7, JD7and JD8 braking systems that I know of. The JB5 has a smaller volume master cylinder and a vac booster all it's own. The JB7 is the 3/4 vac Boost system, but shares the same master cylinder as the JD7 which is the 1/2 and 3/4 ton Hydroboost systems. The JD8 is the 1 ton Hydroboost system and has all unique parts from what I can tell.

I guess what I am trying to say is, don't just jump into it and buy a buch of stuff expecting it to be a quick fix. Read, read, read, then ask some specific questions and you should come out better in the long run and spen d less time and money working through trial and error. And hopefully run over fewer Pontiacs in the process.

Also don't rule out the possibility of the fact that you could have toasted the seals in your old master cylinder during the bleeding process. It happened to me and alot of others. Apparently if you stroke your master cylinder much outside of it's normal opperating range (going to the floor with the pedal) You run the risk of blowing some internal seals. Something to check.
 
When working properly, those monster drums on a 14-bolt will quite easily lock up those 40's. That's especially true if you have the 13 inch brakes.
 
Ok, then a question about the seals. When I depress the brake pedal (to pump them up during bleeding) should a swirl of brake fluid rise in the master cylinder? Is this bad or is it just a pressure relief or something?

The drums on my 14bFF are quite large. I have 15" rims and the drum sits largely outside them because of backspacing, but I would guess they are 16" in diameter (outside) at least.
 
you should replace your 1/2 ton brake booster with the 1 ton booster if you feel that you have the brakes blead correctly. that is what I would do before the rear disc swap.
 
Can anyone answer my question about the master cylinder? When you press the brake pedal, you can watch a swirl of brake fluid come up in the reservoir (like when you put a hose down in a bucket of water). Is this supposed to happen? When I depress the pedal, it is not firm, but sinks slowly (2 sec?). Thanks for your help guys.
 
i know when i have the cover off, i have to press the brake pedal very carefully to prevent brake fluid SHOOTING like a fountain out of the master cylinder. it did this with the mc i bought the truck with, and when i went to replace it after a while, it still does it.

my brakes are strong though, so i wouldn't imagine i have a problem. comparing my situation to yours, its possible you aren't moving as much fluid as you should be.
 
No, it doesn't squirt brake fluid up when I let off.

If I press hard it will fountain.

The adjusters were off a bit. I tightened one of them, the other is stuck. How much of a PINA is it to replace the adjuster on a 14bFF?
 
Since the drum brakes on a 14FF are so much bigger than a normal 1/2 ton rear axle, even having them just a tad misadjusted can really cause the brake pedal to feel mushy.

The stock drums, if working properly, should provide plenty of braking power and most likely just as much as a disc conversion. The biggest issue with drums is that older setups are rarely 100% and they are harder to get setup correctly. Mud and dirt is also a big nemesis of drums, around here you always have some sort of mud to deal with on the trails and therefore I had to clean and adjust the drums on my 14FF after every ride or they got real spongy. Discs have the big advantage of being easier to work on and are not affected by mud, dirt, and water nearly as much as drums.

I now have rear discs. They don't stop any better than the previous drums when they were cleaned and adjusted correctly, but with the discs I don't have to mess with them all the time like the drums.
 
Good to know. It still sounds like it will be worth the $200, once I get this all figured out of course.

What kind of trouble am I looking at to get the drum off and replace/repair the adjuster screw?
 
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