'70 1100 4x4 Front Drum Brake: Pulling?

[Brian K]

Hi all!

I rebuilt the whole brake system on my '70 1100 4x4. It's got the uber-unobtanium lockheed front system, so I wanted to ensure that everything was a-ok in there. I ended up rebuilding the frozen brake light equalizer block, rebuilt the front wheel cylinders, repacked the bearings, and bled the system until I was blue in the face.

I then extra-carefully adjusted all the star-wheels so there is absolutely equal "just-so" rolling resistance on each wheel ......and:

upon light pressure of the pedal, the front brakes stop evenly. Upon heavier or full brake pedal, the brakes pull to the right. It's more annoying than anything, because I thought I was so careful. I don't think I got any grease on the pads and I don't believe that there is any fluid leakage from the rebuilt wheel cylinders.......

Any ideas? I'm stuck on this one.

Thanks!

Brian klea

 

[Michael Mayben]

Don't dispair dude...I now have a couplea sets of lockheeds that are "core" parts (including spindles and hub sets) that need to go to my local frictiondude for rework. True treasure thanks to dan hayes and Mike foster who I know ya met at the bee!

Does your master cylinder still have any form of residual pressure valve(s) in it? That would be between the outlet fittings and the front/rear fittings. I replaced these master cylinders with both new and remans several times and none of 'em had the valves included. In fact, I've had the same issue you describe for years and have just never got around to fixxin'!

Solution? Add "inline" residual pressure valves to both circuits such as supplied through wilwood, I think Jeff has 'em in stock. The drum/drum system needs 10 psi valves. Very inexpensive though you'll need to bleed one more time:

wilwood engineering - residual pressure valves

For info in dealing with the oem residual pressure valves (prolly more unobtanium), check a service manual of that era, if ya don't have it, I can post a .pdf of that couplea pages so ya can edjimakate yoreself.

 

[Brian K]

Michael!

Nice to hear from you! (I actually just posted some long-awaited pix of the trail ride.....I'll throw up a few of the bee when I get 'em off my camera, which means getting off my ass......)

anyway, no, no pressure valves at all. Here's what kills me: I first rebuilt that equalizer (or whatever it's called) block many months back just because I wanted that light to go out. (being a perfectionist, I couldn't just unplug it.) if I recall, you actually gave me some advice on this! Fixed it perfectly. All brakes still work great. Months prior to this, replaced master cylinder. Brakes still worked great.

Few weeks ago, sceered to death of lockheed unobtaniumness, I dig in and find that my wheel cylinders are so gunked with sheeet n' scuzz, it's a miracle they worked at all. Got new ones for the back and rebuilt the fronts. I feel great that everything is spotless, clean, and should be as good as new.

Bottom line: my "flawless" brake job made the "brakeabilty" worse. It worked better prior to me digging into the wheels. I never had any pull to one side or another. That's what I hate!

that's what kills me! The only thing I didn't do was hone the front cylinders before rebuilding them. They looked decent although not absolutely perfect. Even if that were the case, I can't figure out in my head why one side would pull now that the job's done.......

B

 

[jeff campbell]

Brian,you could take the fronts off an hnoe out an then try it?just an idea,sounds like the side doing the pulling ,the cyl.,is working better than the other side!?Jeff

 

[Brian K]

Jeff,

funny you should say that.....I think you May be on to something. I've got a feeling that the right side (the pulling side) isn't really grabbing (like when there's gunk on the shoes), rather the left side just isn't working as hard.

Unless there's some miracle "something" bit of wisdom I'm missing, that's what I'm going to try.

Thanks!

Brian

 

[Michael Mayben]

Problem ain't tha wheel cylinders! Reason it didn't pull before is 'cause tha dam front brakes weren't working! Pics of that frozen cylinder tell that story!

That valve we worked with is only a "combination valve" to operate the warning light system. Does not have any "proportioning effect".

What is happening is...with no residual valve to keep wheel cylinder travel "equal" each time the master cylinder actuates, one cylinder has to travel further than the other side (minute difference) under normal braking pressure. When you let off the pedal, then each cylinder "returns" an unequal amount. Next pedal app, same thing happens. We're talkin' "microsecond" difference side-to-side in actually friction material "lock-up" against the drum, thus the pull. You can reduce the problem greatly by adjusting both sides so that the wheels won't turn under hand pressure. Then go drive and you will see the problem is gone until the wheels then lock up due to heat expansion of both the friction materials and the hydraulic fluid (heated from excessive brake drag). Once it cools down, problem will diminish again.

In other words...no matter how carefully you adjust the brake shoe clearance, one side is gonna hit the sweet spot before the other. Only way to avoid that is use the rpv which is what all "split" drum/drum systems were designed to use! That keeps each shoe set "loaded" so that they move in tandem with each other at each pedal application. This has nothing to do with "proportioning".

Wheel cylinders either work or they don't (as long as they are a matched bore size). If they don't then it's because the cups are allowing slight pressure loss due to fluid bypass, thus the hydraulic pressure is not equal. If either cylinder bore is not perfect, then slight bypass will be present...only cure is replacement! The bore surface needs to be prepped with a proper hone for the cups to "seat", just like piston rings. But even if ya put new wheel cylinders on, without the rpv system, you will still have unequal braking side-to-side. It of course also affects the rear, but because the fronts generate the great majority of braking "power, unequal app of the rears is normally not noticed until the bed is heavily loaded.

Ya want the service manual pages that explain this better than I can?? This kinda stuff ain't particular to just IH crap, all drum/drum systems operate the same way.

 

[Brian K]

Michael,

hot damn. You're right! Those wheel cylinder's weren't working I bet! (duh! On my part!)

gonna order those rpv valves posthaste. I was just about to order new front wheel cylinders and re-do the whole damn job.

Thanks for explaining it to me......and saving me from taking those hubs all apart again!

Brian

 

[Michael Mayben]

I know it's too late now Brian...but for reference...

If ya do ever pull the hub/drum combo again for service, knock out and replace the oem wheel studs with new ones, simple to do! Then pull the brake drum off the hub, which is "lightly" swedged to the hub. That was done when the hub/drum combos were manufactured to make it "easier" for assembly-line assembly, no other reason.

Using a dremel with a carbide burr, lightly go around the circumference of the drum center hole and burnish the sharp edge. Just enuff to allow the drum to slip snugly over the hub.

Then clean up the hubs (normal bearing/seal service maintenance operation) and reinstall without the drum! Much easier/nicer to deal with! Then install the drum as a slip fit over the hub/studs and it will center perfectly.

I always use new dorman studs that are slightly longer than oem, and have the first three threads held back. I use enclosed acorn nuts for lug nutz so that mud and crap doesn't clog the threads for trail removal. Having the first three threads held back, simply protects the end of the studs when ya stick the wheel assembly back on. The longer studs also allow the safe use of much thicker "center" wheels such as aftermarket castings May have.

Doing this makes brake cleanup/maintenance much more pleasant for future service.

I'm in the process of working up a single replacement hub assembly to carry as a spare (complete with spindle) in the truck box. Doing this in advance makes a trail or road-side change out real simple as long as ya carry the spindle nut socket.

Joe d. Here on the forum has an even better idear for his sii spare tire mount!

He mounted a complete spare front hub/spindle assembly on his swingout tire carrier! That's how he mounts the spare on the rack! If he chunks a hub/spindle up in the sierra, then he has a fresh one ready to go! Dam kid is sharp!

You can see in the pic that I'm missing the self-adjuster hardware for the lockheed fronts, but the stuff is present in the bendix rears. Someday I will find two sets of lockheed hardware in sum oldskool auto supply, I'm always looking! Therefore I have to manually adjust the brakes every 5k or so.

The brakes on my trail/tow rig are so "touchy", Jeff don't like to ride with me, and he shore don't like to drive it! But them brakes are killers for trailer towing, just as much brakeability as discs!

Maybe it's time I practice what I preach and go get a pair of rpv for myself. The local roundy-round racing supply shop has 'em hangin' on the wall. You have now stimulated me!