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angus

Drum brake adjustment

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I`m going to be doing some work on the old GMC 2500 today. It has drums on the rear and I would like to check the adjustment.... In the past I have always dialed them in to the point of installing the drum and not being able to feel any friction.. My understanding was that should self adjust any time you back up with the brake applied??  

 

I`m just looking for input from anyone who might have a different theory..

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I've always made sure everything is clean and freely moving and properly fitting.  Then adjust out the star so that the drum barely slips over the shoes.  Then adjust the star out some more so that when spinning the drum by hand I can barely hear a slight contact of shoes to drum surface.  You dont want to feel any drag in that contact either.

When using the brakes in reverse the stars are supposed to click a notch as long as there's enough room for that much automatic adjustment.  Problem is the stars quickly stop moving from corrosion or dirt, so use some anti-seize on the threads. :thumbup2:

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31 minutes ago, KATOOM said:

I've always made sure everything is clean and freely moving and properly fitting.  Then adjust out the star so that the drum barely slips over the shoes.  Then adjust the star out some more so that when spinning the drum by hand I can barely hear a slight contact of shoes to drum surface.  You dont want to feel any drag in that contact either.

When using the brakes in reverse the stars are supposed to click a notch as long as there's enough room for that much automatic adjustment.  Problem is the stars quickly stop moving from corrosion or dirt, so use some anti-seize on the threads. :thumbup2:

The last time I worked on them the adjusters were froze up.. I got them cleaned up and working free again.  I never thought of anti seize?  That's a good tip!  I`m getting ready to go it now.

 

Thanks! 

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2 hours ago, KATOOM said:

I've always made sure everything is clean and freely moving and properly fitting.  Then adjust out the star so that the drum barely slips over the shoes.  Then adjust the star out some more so that when spinning the drum by hand I can barely hear a slight contact of shoes to drum surface.  You dont want to feel any drag in that contact either.

When using the brakes in reverse the stars are supposed to click a notch as long as there's enough room for that much automatic adjustment.  Problem is the stars quickly stop moving from corrosion or dirt, so use some anti-seize on the threads. :thumbup2:

 

What he^^^^ said!!!!  This is how I've always adjusted rear drums!!!  Anti-seize is a must for drum brakes!!

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7 hours ago, dorkweed said:

 

What he^^^^ said!!!!  This is how I've always adjusted rear drums!!!  Anti-seize is a must for drum brakes!!

yeah I use anti seize on all kinds of stuff... but never thought of it on this one... sure enough I had one of the adjusters froze up again today.

 

4 hours ago, Royal Squire said:

I have always adjusted shoes out tight against the drum and then back them off. Don't know if it matters though

I think you are on to something RS. Went for a drive down the dirt road, and I think the rears are still a little loose..  Its 

really kind of hard to tell where your at without running them all the way out.. Question is how far do you run them back down?  

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Today I adjusted the shoes all the way out, then backed them down about half a turn. went for a test drive and no real difference... I think I was already pretty close.

I decided to try @Mopar1973Man comment in another thread and unhooked the load proportioning valve and tied it back..

This made a noticeable improvement!  This old truck is so stiff in the rear you would have to seriously overload it to ever get the full effect from the rears.

 

Thanks Mike!

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1 hour ago, angus said:

Today I adjusted the shoes all the way out, then backed them down about half a turn. went for a test drive and no real difference... I think I was already pretty close.

I decided to try @Mopar1973Man comment in another thread and unhooked the load proportioning valve and tied it back..

This made a noticeable improvement!  This old truck is so stiff in the rear you would have to seriously overload it to ever get the full effect from the rears.

 

Thanks Mike!

 

Please keep me posted as to how this works for you.  I've considered trying this just for sake of curiosity but since my brakes work really well, its not something I think about every day.  But.....it would be interesting to see if it did anything.

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8 hours ago, KATOOM said:

 

Please keep me posted as to how this works for you.  I've considered trying this just for sake of curiosity but since my brakes work really well, its not something I think about every day.  But.....it would be interesting to see if it did anything.

@KATOOM this old truck seemed like it was biased 80/20 or more toward the front. When I tied the valve back I noticed an immediate difference when I backed out of the shop.

I drove quite a ways on a gravel road just to see if the rear was going to be over sensitive or lock up.. it feels more like 60/40 now and The fronts will lock up before the rears. I think in my case disabling the valve is a good thing.

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I have always felt my truck stops fine, I always wondered why my front brakes only lasted about 60k when my rear brakes lasted 285k. I changed them out them because of all the rust on the backing plates. The pads were thin but were still working fine.

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For all you guys who've disconnected and tied up the rod or valve lever, can you take a picture and show me what you did or how its positioned?  I'm going to try removing the rod from the axle and see if it helps braking power but I'm not exactly sure at what point the proportioning valve is "fully open".  Thanks. :thumbup2:

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2 hours ago, KATOOM said:

For all you guys who've disconnected and tied up the rod or valve lever, can you take a picture and show me what you did or how its positioned?  I'm going to try removing the rod from the axle and see if it helps braking power but I'm not exactly sure at what point the proportioning valve is "fully open".  Thanks. :thumbup2:

I'm curious on this too

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My 03 Dodge doesn`t  have a load valve. My old 85 GMC did,, So it might be a little different. The theory behind it seems to be the more the rear end squats the more brake pressure is diverted to the rear brakes. In the case of my GMC the valve was connected to the rear axle by a linkage arm. The valve itself has a arm with a stroke that runs roughly 12 o'clock to 5 o`clock. after removing the linkage arm,  I used a zip tie to tie the valve arm up at 12 o`clock which would simulate towing a very heavy load. The result is I now have full brake pressure to the rear drums. 

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I appreciate that but the angle of the arm is what I'm looking for conformation on.  On these trucks, at what position is the proportioning valve fully open?

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In my case turning the valve counter clockwise to 12 O`clock applies full brake pressure. In any case look at the valve and the linkage as if the truck was loaded heavy and tie the valve back in that position. You might tinker with it and take a few test drives to see if you like the different feel. I was surprised at how much difference it made on my rig.

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So I finally got some time and crawled under the Dodge and popped the lever off the load adjustment valve. I raised it all the way up and it actually fell back to the 11:00 position so I just tied it down there and went with it. Took it for a test and It stops what I would say is normal. Even at 50 mph on gravel road it did not want to lock up on moderate braking. So thanks for the tip guys :wink: my lazy rear brakes finally woke up and are going to start pulling thier weight

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Weird part is that valve only was on a few years of trucks and then disappeared again. It was like let's see if we can do this better? Nope... Just yank the valve back off because it made things either worse or created issues. 

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1 hour ago, Mopar1973Man said:

Weird part is that valve only was on a few years of trucks and then disappeared again. It was like let's see if we can do this better? Nope... Just yank the valve back off because it made things either worse or created issues. 

that's the next step is just to take the valve off completely, and splice the lines together.

I agree just another example of over engineering

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On 8/28/2016 at 8:33 AM, 01cummins4ever said:

that's the next step is just to take the valve off completely, and splice the lines together.

I agree just another example of over engineering

 

Unfortunately the brake line from the axle to the valve doesn't have the normal brake line fittings so I believe you have to get that specific replacement line and cant use any universal line.

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