https://www.ruffstuffspecialties.com/catalog/R2055.html reviews?

[Thewespaul]

For any brake system to function properly you need to be able to apply pressure and release that pressure, with soft brake lines they age will suck shut retaining pressure at the caliper/wheel cylinder. This makes your brakes stick, improperly bled brakes can cause this to a degree as well, I grew up with nothing but drums so I’m used to working with them, and they are NOT failure prone in these trucks, in other vehicles yes, but they are just as many disc brake systems that have design issues as drums. Pull the drums off and take a couple of pictures, I’ll be happy to point you in the right direction of your issue.

 

[jaed_43725]

Sometimes the brake lines will swell up when they get old, and that’ll cause all sorts of problems. I bet your problem is something simple that the other shop looked over.
But hey, if your set on doing a disc brake conversion, do it. I don’t think it will stop any better, but it’ll certainly be easier to work on them after they are installed.

If I do the conversion I am going to put braided lines for the mid, and both rears.

 

[jaed_43725]

For any brake system to function properly you need to be able to apply pressure and release that pressure, with soft brake lines they age will suck shut retaining pressure at the caliper/wheel cylinder. This makes your brakes stick, improperly bled brakes can cause this to a degree as well, I grew up with nothing but drums so I’m used to working with them, and they are NOT failure prone in these trucks, in other vehicles yes, but they are just as many disc brake systems that have design issues as drums. Pull the drums off and take a couple of pictures, I’ll be happy to point you in the right direction of your issue.

If I could pull them off I would. But I dont have time. I travel for work and dont get home but once a month for a weekend.

 

[snicklas]

How do people think a bad brake line is going to make them hang? It would be the opposite, I wouldn't have brakes.

I have personally seen this, so it's not a "I heard this from someone" story.

If you have a deteriorating flexible ("rubber") brake hose this can happen. These flexible lines are multi layer, I'm not sure the exact construction, but there is an inner "rubber" liner the brake fluid flows through, a strengthening layer (a braided nylon or other material) and the outside "rubber" layer. What can happen is the inner "rubber" layer can crack, and when you press the brakes, the hydraulic pressure will push past the bad area, which can act like a flapper, and apply the brakes. When you take foot off the brake, the "returning pressure" from the wheels is fairly low. Now this flapper will fall "closed" across the hose like a valve and keeps enough hydraulic pressure at the wheel(s) to keep the brake applied.

I've also had a couple of friends replace "everything" chasing a hanging brake. Caliper, pads, rotor, master cylinder, shoes, drums, "master kit" inside the drums, wheel cylinders, and flushed the lines, with no effect. Asked if they replaced the flexible lines and they said no. Had them replace the lines, and all was well. We found the bad line by blowing through the lines. One way (from the master end, toward the wheel) it blew through fine. Switch directions, from the wheel toward the master, you couldn't blow through it, or it would only "leak" a very little amount of air.

Now a bad hard (steel) line, then yes, they normally blow, all the hydraulic fluid is pushed out, and then no brakes.

 

[jaed_43725]

snicklas So you are saying I should have the lines replaced first and foremost. In that case I would get braided steel lines for both sides and the mid.

 

[hce]

Yeah, a proper disc brake setup would solve the problem as the failed part would be replaced, not because of the lack of drums. Probably have crude floating in the brake fluid, possibly from old brake lines or rust. There are two hole in each reservoir of a brake cylinder. If the tiny little bleed hole becomes plugged or if the piston is not coming back far enough for various reason, brakes will pump up and not release fully. Sometime the piston sticks, or the brake pushrod, on pedal, or master cylinder is too long. Also another area that needs to be investigated for discs of drums are the wheels seals leaking, do the sealing surfaces need a speedi sleave. I will say a hydroboost setup will increase breaking way more the the 10% claimed by discs. Could also be the residual valve acting up in the master cylinder.

 

[79jasper]

Look at semis. Only drum and they’re much higher rated than any disc.

Eh, might wanna slow your roll there. Lol
Bold part is simply untrue.
Haven't seen a kenworth in the last 5 years?

Sent from my SM-G892A using Tapatalk

 

[jaed_43725]

Yeah, a proper disc brake setup would solve the problem as the failed part would be replaced, not because of the lack of drums. Probably have crude floating in the brake fluid, possibly from old brake lines or rust. There are two hole in each reservoir of a brake cylinder. If the tiny little bleed hole becomes plugged or if the piston is not coming back far enough for various reason, brakes will pump up and not release fully. Sometime the piston sticks, or the brake pushrod, on pedal, or master cylinder is too long. Also another area that needs to be investigated for discs of drums are the wheels seals leaking, do the sealing surfaces need a speedi sleave. I will say a hydroboost setup will increase breaking way more the the 10% claimed by discs. Could also be the residual valve acting up in the master cylinder.

The fluid is perfect. I bled the whole system and put in perfect DOT-3 fluid less a year ago. The front lines are all new, so that eliminates that. Master cylinder is only a few years old as well. As for the leaking it was not the last time it was rebuilt. And hydroboost wouldn't do me any good as I can normally get the brakes to lockup without much trouble.

 

[hce]

The fluid is perfect. I bled the whole system and put in perfect DOT-3 fluid less a year ago. The front lines are all new, so that eliminates that. Master cylinder is only a few years old as well. As for the leaking it was not the last time it was rebuilt. And hydroboost wouldn't do me any good as I can normally get the brakes to lockup without much trouble.

Check that tiny 0.030 inch hole. After pedal is release, is the pressure still in the lines, crack a bleeder and find out. Pressure should just be noticeable in the rear and practically zero on the front. Pull the two bolt on the master cylinder make sure the pushrod is not pushing the piston in when brakes are not applied. If not checked the pushrod and its the problem may follow to discs.

 

[Thewespaul]

Eh, might wanna slow your roll there. Lol
Bold part is simply untrue.
Haven't seen a kenworth in the last 5 years?

Sent from my SM-G892A using Tapatalk

Depends on what axles they got, but eventually even heavy side will be going to discs, but drums are still tried and true

 

[Sidewinded_idi]

Depends on what axles they got, but eventually even heavy side will be going to discs, but drums are still tried and true

This. I’ve seen em but 90% are still drum. Not saying a switchover isn’t coming but can’t say ones better than the other like the op stated. Both have heir advantages and disadvantages

 

[jaed_43725]

Check that tiny 0.030 inch hole. After pedal is release, is the pressure still in the lines, crack a bleeder and find out. Pressure should just be noticeable in the rear and practically zero on the front. Pull the two bolt on the master cylinder make sure the pushrod is not pushing the piston in when brakes are not applied. If not checked the pushrod and its the problem may follow to discs.

I dont have access to the truck right now, and wont until its back from the shop.

 

[IDIoit]

Is that the kit you have? If so what options did you get and how do you like them?

I havnt finished up the e-brake yet, but the truck stops great
yes that's the kit I have

 

[nelstomlinson]

Interesting. I drive older vehicles with rear drum brakes, and in 30+ years with many vehicles, including VWs and light and medium trucks, I've never had a problem. Drum brakes just work, same as the discs up front.

I can't help with your question about the conversion kits. I'll second the suggestion that you have mechanical problems you are overlooking.

 

[nelstomlinson]

I have personally seen this, so it's not a "I heard this from someone" story.

If you have a deteriorating flexible ("rubber") brake hose this can happen. These flexible lines are multi layer, I'm not sure the exact construction, but there is an inner "rubber" liner the brake fluid flows through, a strengthening layer (a braided nylon or other material) and the outside "rubber" layer. What can happen is the inner "rubber" layer can crack, and when you press the brakes, the hydraulic pressure will push past the bad area, which can act like a flapper, and apply the brakes. When you take foot off the brake, the "returning pressure" from the wheels is fairly low. Now this flapper will fall "closed" across the hose like a valve and keeps enough hydraulic pressure at the wheel(s) to keep the brake applied.

I've seen this, too.