Who has done the disc brake conversion on their 14 bolt

[elyon]

who has done the disc brake conversion on their 14 bolt? Was the results positive? I just did it and the results were less than expected. I have hydaboost brakes and prior to the conversion my brakes were very responsive. Now they are marginal. I have not changed the proportioning valve yet but am considering it.

 

[frankin5]

Make sure it not tripped before you change. It is a common problem in rear disc conversions. Once you open the rear for conversion and fluid is lost, the valve will trip. You will get fluid out of the rear, but not the trapped air. Also make sure the bleed screw is pointed straight up on the calipers.

 

[bigjimmy82]

I think my brakes are ok, but how does one check the proportioning valve for a trip?

For the OP, 3/4t brakes all around and truck stops great, panic brake will lock rears 1st. Worth it for me just to rid my life of drum brakes!

 

[chris85]

I think my brakes are ok, but how does one check the proportioning valve for a trip?

For the OP, 3/4t brakes all around and truck stops great, panic brake will lock rears 1st. Worth it for me just to rid my life of drum brakes!

You have to pull the proportioning valve off the truck then take off the safety switch on the top (see below). That is what it looks like open. If closed that hole will be blocked by the valve, blocking fluid to your rear brakes, and you have to reposition the valve.

If your tears are locking up then you should be good. I caught mine while trying to bleed. Fluid would trickle out but would not pressurize.

 

[elyon]

My brakes seem to be working all round but I have a lot pedal travel. I took the master cylinder off and bench bleed it until it was solid. Put it back on and bleed the system until no air. I am using a vacuum bleeder at the caliper. I probably pulled 3 quarts of fluid through it in the process. My proportioning valve is the original one. Well, at least it seems that the set up should work once I figure out what's my problem is.

 

[Fastereddie]

I believe you have to gut the residual valve or replace with a disc/disc prop. That shouldn’t be your pedal issue but that residual is supposed to keep 3-5 psi or something like that on the shoes. You don’t want that with your discs.

 

[elyon]

I'm not sure where the residual valve lives. There is a valve inline above the rear differential mounted to the chassis with linkage connected to the differential. I always assumed it was a load dependent proportioning valve.

 

[diesel4me]

^ It is..the more load in the bed,the more pressure it allows to the rear brakes--less load it reduces pressure to avoid rear wheel lockup..

I've deleted more than one of those on my trucks,never noticed any real difference,if anything it felt like the brakes were more responsive and I had to use my foot to keep the rears from locking up by using lighter pedal pressure..

 

[Fastereddie]

I'm not sure where the residual valve lives. There is a valve inline above the rear differential mounted to the chassis with linkage connected to the differential. I always assumed it was a load dependent proportioning valve.

The residual valve is on the end of the prop valve

 

[elyon]

Thought that was what it was.

 

[elyon]

The residual valve is on the end of the prop valve

Is it the larger diameter threaded portion that the rear brak line threads into?

 

[Fastereddie]

Is it the larger diameter threaded portion that the rear brak line threads into?

Yeah. If you remove that and gut the little spring and disc and reinstall.

 

[K85 Octane]

Not worth the money and headache to get them working "OK".
Even without any valves etc, straight tubing to the 4 calipers, it still sucks.
Good luck getting any real product support too, from whomever you bought it

 

[skunked]

Mine work well but I ran all new lines and added a wilwood adj. prop valve when the body was off.

 

[elyon]

Not worth the money and headache to get them working "OK".
Even without any valves etc, straight tubing to the 4 calipers, it still sucks.
Good luck getting any real product support too, from whomever you bought it

Well that's depressing...... why would anybody want to go to the trouble of converting to disc if it was not a better set up? Why would anyone go to the trouble of making all the bracketry up.......

 

[K85 Octane]

I can only see one way to fix my own personal beef with my rear disc set up. I want a firmer pedal feel. I might reduce the 1/4" lines on the truck to 3/16". This would increase the pedal firmness. Would it help stop the truck or just firm up the pedal.....I dunno.

 

[JoshHefnerX]

You have to gut or buy a 'gutted' combo valve to make the system work at all. If you have a long/soft pedal push then you need to look at swapping master cylinders to something w/ a larger bore. I went to a 2004 2500 on my setup. Its in my build thread someplace. I'll see if I can find it.

Old bore 1.1" new bore 1.4"

80 Jimmy - The Monkey Paw (Time to finish interior)

 

[6.2Blazer]

I have a 14FF rear with the typical disc brake conversion using stock 3/4 ton rotors and calipers. The front is a D60 with the stock brakes, along with the stock hydroboost system. It works great and will stop the 39.5" Swampers in a hurry. Can't really give an honest comparison to the original stock setup because the rig went through several tire and axle iterations before doing the rear disc conversion, but overall I think it is better than the stock D60 front and stock 1-ton (big version) drum brakes. The biggest thing is that the mud just destroyed the drum rear brakes....I'm not a mud bogger by any means but the trails we ran in the midwest always had some mud holes or water crossings to go through even in the middle of a drought, and by the end of every ride I would start getting a soft pedal until I cleaned and adjusted the rear drum brakes.

Overall you really don't change to disc rear brakes for better stopping power, rather you go to disc because in an offroad vehicle because they withstand dirt, mud, and water much better. On a street driven car the main advantage is disc brakes shed heat better, and are not as affected by heat build-up. Drum brakes are still really common on heavy trucks (semi, dump trucks, etc...) because they have good stopping power.

 

[bigjimmy82]

You have to gut or buy a 'gutted' combo valve to make the system work at all. If you have a long/soft pedal push then you need to look at swapping master cylinders to something w/ a larger bore. I went to a 2004 2500 on my setup. Its in my build thread someplace. I'll see if I can find it.

Old bore 1.1" new bore 1.4"

80 Jimmy - The Monkey Paw (Time to finish interior)

Yes, I almost forgot, I also switched to a p-30 step van master cylinder after swapping to rear disks.

 

[6872xtc]

@elyon I agree that you should eliminate the extra valve above the rear axle. Then investigate your combination/porportioning valve. Depending on the size of your rear calipers, you will need to get the master cylinder which supplies the proper volume AND pressure to the whole system. I converted a '90 to rear disc and kept the original master cylinder. I believe that it had the 1/2 ton calipers, but not sure. Lots of years ago.
Josh has a great idea of using what GM did. I have a company truck with 4 wheel discs and hydroboost which is very good. GM did their research on that system.

The only reason to stick with drums brakes is that they are cheap. Not good, just cheap. Semi trucks are moving to air disc brakes as liability risks have gone sky high from accidents. Disc has more stopping power. We have a truck at work with 6 axles, all air disc. It spends all day doing round trips, 7 miles each way, weighing 100,000 lbs when loaded. It has great stopping power compared to the older trucks and better durability.

I know that you can get your truck dialed in, it may just need some research. Sorry that I don't have much personal experience to share yet on this swap. I am planning to do my rear axle this spring. I just looked at @JoshHefnerX thread last week and will probably be following it. Not sure yet because of my hood clearance. He has an '80 and I don't know how the hood on the '81 and up slope is comparatively.