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14b SF disc brake conversion questions.

S

sniperthx1

1/2 ton status
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I'm going to be putting disc brakes on my gm 14b SF axle, and need to keep my 15 inch aluminum wheels.

I'm having a hard time finding which calipers and rotors I need for this.

I've seen 79 eldorado calipers, 77 k20 calipers and rotors, and all sorts of other things.

Just hoping to hear from someone who has done it and knows what will work.

Again, I need to keep my 15" wheels as there's no way I can afford new wheels and tires for the foreseeable future.
 
Can't speak to wheel fitment as I've never done one on 15" wheels, nor have I done one on a semi-float.

All the kits and brackets I've seen for the 14-bolts use the large style GM calipers. The 10/12-bolt kits use a smaller size caliper, but the whole point of the 14-bolt axle is stupid strength :D

To get a parking brake, you'd use the 76-78 Eldorado calipers. Note that it's extraordinarily difficult to find remans at parts stores for the last coupla years; TSM sells new ones, but they aren't cheap.

If you don't want a parking brake, you use the K20 fronts. These are the same size and mounting as the Eldorado units, but don't have the parking brake function. These are a dime a dozen anywhere in the free world.

At least for the full-floater axle, you use front rotors off a similar K20. Again, donno about semifloaters, and this may affect your choice of brackets. Where were you planning on sourcing the brackets?

-- A
 
Was thinking of either getting some weld on brackets from virginia 4x4, or having a machinist friend fab some.

This guy seems to have done it with 89 K1500 rotors (12") which don't appear to exist, and 76 k20 calipers, and after some mild grinding, he says he fit his 15" wheels on it.

http://tharf.com/wordpress/?p=17

But at that point, I worry if the bracket I get or fab will work the same as his is set up.

He has the rotor on the outside of the wheel mounting face, where others do the rotor pressed in like the front rotors.

I'm just confused and don't wanna buy parts and have them not work.
 
Hmm, yes. I of course blithely assumed that a 14 bolt meant 8-lug, but if you're talking about 15" wheels you're prolly thinking six lug. Then yeah, the 70's K20 rotors won't do you so much good. :doah:

The 14bff disc options are well-documented 'cuz lots and lots of people have done them. I can't say the same about the 14bsf's, as many more folks just go with the big momma. (Little known fact: the 14BFF doubles as a trench digger :haha: )

You *will* be doing some of your own figuring it out and fabwork in this case.

I *can* contribute that, regarding the guy you linked to, having more brake pad area than rotor surface is not optimal. At the very least, you end up wearing down PART of the pad, leaving the outer edge of the rotor rubbing against your now irregular pad, which IMO borks up the calipers' ability to slide and make a whole buttload of noise. I did a try-it-myself disc conversion on my dually, and I ran into this problem. It's one of a few issues I either have to sort out, or go back to drums.

I may well end up doing the latter, so if you want a simple bolt-up you may want to rethink your tires/wheels ideas. I'm just sayin'...

-- A
 
I was looking through that link I posted earlier, and saw where he mentions you could use a rotor from a 76' K10 but they would need to press to the back of the axle flange.

Looking it up, that rotor is exactly .25" larger in diameter than the 89' k1500 rotor he used.

Seems to me, even with the larger rotor, the caliper would stay in the same place, and it seems that the rotor should fit inside the caliper as well.

That should alleviate the partial pad wear problem.

I guess it would give me a reason to more regularly maintain my diff oil too. :rolleyes:
 
I used 1/2-ton front rotors on 1/2-ton front backing plates. Slapped on mid-90's 1/2-ton front rotors, which fit perfectly on the outside of the 6-lug axle shafts. There were no problems fitting inside 15" aluminum wheels. The only fab was enlarging the hole in the backing plate and coming up with a spacer. If you are using a pre-made bracket, it's even easier. I bet one of the 10/12 bolt brackets would work with very little effort.


Having the rotor outside of the WMS was an important criteria for me when I did it, so I wouldn't have to drain the differential to replace the brakes. That being said, I am still running the originals since 2001.
 
So you used the backing plate from 1/2 ton, with the calipers attached, and just another 1/2 ton rotor from an IFS chevy?

Did you weld the backing plate to the axle or did you bolt it on?

If you have pics of your setup, would you mind sharing? Keep in mind I can't see attachments. :whistle:

And 72BlazerGuy, thanks for the link to TSM. I didn't know they had the six lug kit.

They are extremely spendy, and if I hadn't gone on a recycling spree a few months ago, I would have the backing plates, calipers, and rotors for he job.

My wife wonders why I never get rid of things.
 
Yes, I got the backing plates from a junkyard, had the center hole enlarged to fit over the 14B tube and drilled the new 4-hole pattern for mounting. I made 1" solid spacers out of aluminum and then added about 1/2" tube spacers to get the caliper in the right place. The exact spacing depends on which axleshaft you have. There were different lengths for different brake options. I meant to go back and make "good" spacers, but never got around to it. Of course now that I weld, I would just move the mounting surface out and skip the spacers.

Those IFS rotors fit so well the the holes don't even touch the wheel studs. All of the parts were cheap - the whole conversion cost less than new drums, spring kits and wheel cylinders would have cost. I also used some stock (short) front brake hoses to connect to the hard lines - the fittings match right up. Everything is replaceable at any local parts store. If a vendor has a bracket that fits, that could be as cheap as junkyard backing plates + machining.

The downside to using front calipers is that the pistons are too big. You have to adjust the proportioning somewhere and you will always have more pedal travel than when using a smaller caliper in back. And of course no parking brake.
 
Alright, that's the kind of information I was looking for. :D

There's no plus machining for me on the spacers. I have a buddy who will do if for me.

How did you adjust the proportioning on your setup? Did you get an adjustable proportioning valve or something else?
 
I just used one of these and set it by trial and error. The stock combo valve is still in there.

proportioning_valve.jpg


I actually have it mounted under the floor, in front of the gas tank where the rear brake hose drops because the fittings matched. I understand that someone makes adapters to plumb it right to the master cylinder - I just couldn't find them when I was doing it.

It would be cool to work in one of the load adjusting units from a 'Burb, but I figured that you can't get any real axle droop with one of those.
 
Quick question, what are the backing plates made out of and can they be welded to the axle tube?
 
sniperthx1 said:
Quick question, what are the backing plates made out of and can they be welded to the axle tube?
Click to expand...

If by "backing plates" you mean the 4-5" square flange, it's mild steel and they're welded to the axle at the factory.

If you mean the sort of circular plate that holds the drum hardware and bolts to said flange, they're waaay too thin to weld on. Plus they're no good for a disc conversion.

If instead you mean the bracket that holds the caliper, then yep, you can get them in weld-on or bolt-on, at least for the 14bff. The bolt-on ones often have bends in them or come with spacers to account for the distance from the flange to the rotor surface.

Does that make sense?

-- A
 
They're plenty thick for welding.

It's either weld it on or spend a lot of time making spacers and drilling holes I'll inevitably screw up. :whistle:

Thanks for the help.
 
Sounds like a lot of work for arguably slightly better brakes. Why the desire to change the brakes?
 
C clips. Break an axle shaft with the drum brakes on a c clip axle and tire and all goes it's own route.

Calipers hold everything together, gives you the ability to limp home.
 
When I swapped one into my 00 Silverado, I just bolted everything from the (disked) 10 bolt onto the 14 bolt using a new flange that I welded farther out on the axle tube.

Perched.jpg


Perched3.jpg


Perched4.jpg


complete.jpg


I forgot I used an Easter egg basket for an oil catch can.:haha:
 
Don't wanna be hiding eggs with that basket. :haha:

I assume you had a disc brake 10 bolt before you swapped in the SF?
 
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