Technical Straight axle truck steering gets stiffer when brakes are applied

Here:

 

Yes, in the picture you provided when you step on the brakes in reverse the secondary shoe self energizes, moving off the anchor which pulls the cable, lifting the self adjuster lever, as soon as the brakes are released the lever moves down adjusting the brakes.


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I had never cared how it work just that I was told by my Dad that the adjusters tightened the slack when you apply the brakes when backing up. Good enough for me. But since you made the point to ask, refer to the picture. When you apply the brake when backing up and the brakes need to be adjusted, the secondary shoe is forced off the pin at the top. The cable pulls on the adjuster. When the brakes are released, the adjuster is turned.

Here is the link where I found the picture that I used. In that article I found this statement. "In some cases, the master cylinder may contain residual check valves to prevent air from being drawn past the wheel cylinder cup seals when the shoes are retracted by the return springs."
https://www.knowyourparts.com/techn...ponents/importance-drum-brake-self-adjusters/

Just a passing thought. How did you figure the front brakes were adjusted? No parking brake there that I know of.

 

I am not on this board to argue.

I am giving my truth. You can take it, or leave it.

That's on you.

 

If this is the case, how is the adjustment of front brakes maintained? (not stirring up sh*t, serious question).

 

Drum brakes are adjusted by the self adjusters which are activated when you back up.

 

Yup.

 

I just did it on the bench, with the backing plate that I posted.

One sharp pull of the cable gave one tooth turn on the star wheel. I cannot get enough leverage to pull very far, but with a pedal or lever, you can probably get 2-3 teeth.

They very much adjust when the parking brake is applied. This is how I have been equalizing shoe drag for over 40-years, including on trucks that require break function inspections.

Like I have said, not here to argue. Go try it yourself. You have nothing to lose.

 

Yes they will also adjust with the park brake as well as when applying the brakes in reverse.

I’m not here to argue either


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They do adjust when applying the brakes in reverse, I've done it a hundred times at least, and it definitely works.

 

I never knew setting the parking brake would adjust the rears, cool. I never had a car with 4 wheel drum and adjusters, always disc/drum or changed a rear to a newer one that had the self adjusters.

 

My procedure is to manually ball-park the shoe drag, and then cycle the parking brake to get it as close as it can be, short of arcing/grinding the shoes. I do this before even bleeding the brakes.

Why before? Shoe drag sets pedal feel. If you have low or no drag, you will have a pedal that feels soft. Worse, you might have trouble fully bleeding the brakes.

Relying on the back-up-and-stab-the-brakes method means that you have a car on the road that has improperly adjusted brakes. I am not sure I need to mention what a bad idea this is.

My shop has a 10-foot wide sidewalk, and a 12-foot wide parking lane, before you are immediately in the fray of a very busy 4-lane one-way city street, with a floating parking lane, and a protected dedicated bike lane. It is 100-feet from an intersection with a stop light.

One delayed braking action will result in impact. When you are entering a road from off--street, you NEVER have the right-of-way. That presumes that I got across the sidewalk without running down a pedestrian. I have to watch the live feed of my security cameras on the phone, of the outside, while backing out, every time, just to get out.

Most of the streets near my shop are one-way. They are all busy, except for late at night. Finding any place in a 46.2 square-mile city with 845,000 people to drive a car with improperly adjusted breaks, where it would be safe to repeatedly back up and stomp the pedal, would be a neat trick.

Maybe at 3am, but they I would be explaining to a cop what I am doing, and how I am not drunk, high, or both.

Doing it my way gets the brakes adjusted before the vehicle ever moves, not after you have had a chance to find out the hard way.

I don't have the "luxury" of living 16-1/2 miles West of the middle-of-nowhere. Knowing how to do what I need to do safely, within the extant parameters, is critical.

 

the auto adjust when backing up is intended to replace manual adjustments that were required before. Not a service procedure after brake work. That's what the star wheel is for.
I use an old tool, quite similar to this to get really close before putting the drum on.

 

Exactly

 

X2.
Anything that moves the trailing shoe off of the anchor will move the cable. If the brake shoe is within the correct range of adjustment, the cable will not move enough to spin the star wheel. If the adjustment clearance exceeds what is required, the shoe moves farther, moving the cable farther, rotating the star wheel. Either reversing, or park brake application will move the rear shoe. However...
An application of the park brake may only move the rear shoe 50% of the distance needed to move the star wheel.
Best practices is to manually adjust the star wheel with a brake spoon upon assembly. This assures a proper starting point on a fresh brake job.

 

I have not used anything but my method in several decades. That's enough data to say that it is a successful methodology, not just speculation.

 

I think 99% are in agreement here. Now, back to regular scheduled programing. What was this thread about?

 

Can't and won't argue with success, but am curious as to how you do front drums?

 

Post 28 talks about the OPs findings.

 

Lol, fortunately the truck stops fine now. My issue is steering. Did some experimenting today. Couldn't find any 90's Dodge wheels to match the calipers/rotors but I snagged the spares off both mine and my Dad's mid-90's Chevy 2500's. These are 16x6.5 with I believe +22mm offset (so about 1/2" more than what I've been running) and ~4 1/2" backspacing. Side note, the tires cleared everything just fine; caliper, drag link, fender wells. I thought I would have had trouble with this much backspace, but the disc conversion pushed the WMS out plus I had the spacers. These wheels should have pushed the scrub in at least as much as the disc brake conversion pushed it out. I tried them with and without spacers and I had the same (actually seemed to be worse than the previous wheels) rotation of the tire when static steering indicating I still had significant positive scrub even though my overall scrub radius was back to stock. Now I'm not so sure my steering issues are a result of the scrub radius, or at least that the truck must have been set up with positive scrub from the factory. I tried eyeballing the kingpin angle and it looks like there's 1-1.5" of positive scrub. I think I'm going to mess with the steering pump some more and see if I can get a little more pressure and/or flow. Might just still be under-spec? I don't remember if I opened up the idle flow orifice in the spool or just shimmed it for pressure.

I'm going to recheck the toe-in and caster as soon as I can find a helper and see if that helps the twitchiness. What are you guys running for toe-in? I believe I set the truck to 1/8" last time I checked it.

 

I don't install them. I remove them.

 

Toe in 1/8", Caster 6 Deg.

 

I was wondering about the front brake adjustment as well. Not to argue about the parking brake adjusting the rear, that will obviously work.

Front drum brakes of course can't be adjusted by using the park brake. The self adjusting drum brakes are not meant to adjust the brakes after brake services have been performed, but rather to keep the brakes in adjustment between service intervals. All service manuals explain the advised procedure to keep the brakes adjusted is to brake firmly in reverse. Far too many vehicles on the road with 4 wheel drum brakes to not have as many people that may need to know this information think otherwise.

 

He said he had disks on the front

 

I would also put more caster in ( 6 degrees)
I would also take it to an alignment shop to confirm your measurements.
I also think you should put the original manual steering box back on temporarily and drive it to rule out the new box. It seems odd to me that you had to boost the pressure to 1400 to get it to work correctly, I alwayes thought 11-1200 was more than adequate, but I may be wrong.
I've used the scarebird conversions before and never noticed any difference in drivabilty
JMHO, Good luck

 

I've been thinking about temporarily reinstalling the manual box. It's a pain because the column had to be relocated ~1" for the power box, but I could convert it manual and back to power in a weekend I'm sure if I can find the original column lower mount plate and the old pitman arm. I put a couple hundred miles on the truck with the discs and the manual box and I don't remember any twitchy handling, but it sure was hard to steer. That was also with the ugly American Racing rims it came with, which I think might also still be kicking around the shop if need be. I tried to get a local place to check the alignment but they insisted on charging me the full $85 for an alignment even though they can't adjust it and I only wanted it measured. I'll try and find a place more willing to work with me...

 

You can check the toe in with nothing more than a pencil, tape measure and jack plus a helper to hold the end of the tape on the line you scribed on the other tire. I've done it hundreds of times and that was how we set the toe in in one shop I worked in. Just jack the tire up a couple of inches off the garage floor, use something to steady the hand you hold the pencil with so your hand doesn't move, hold the pencil tip to the center of the tire tread and slowly spin the tire with the other hand and do the same on the other side. Set the tires back on the shop floor, bounce the front bumper a few times to settle thigns out and measure from center of the line to center of the line at the back side of the tire about as high as the tape will go across in a straight line and then at the same height in the front. figure the difference and if the front is more or less than the back. You want 1/8 inch less at the front to have 1/8 toe in.
Few guys can do anything about camber on an I beam them selves so that shouldn't be an issue. You can get a reasonable idea of the caster by holding an angle finder to the spindle or maybe on the axle beam it's self. As long as what you are holding the angle finder has top and bottom spots that are even with each other to get a somewhat accurate measurement.

I still think you are trying to make something that is not much of anything a big ass problem though.

 

That's not a bad idea about checking the caster at the axle instead of the wheel. I've got a decent digital angle finder. Would take the guess work out of the bubble gauge. As for the toe, I have a set of toe plates with the little standoffs that touch the wheel bead and have notches for two tape measures. I've set toe on a number of cars (including my DD Honda CR-V) with it and I'm confident it's good to better than 1/8".

 

Getting ready to tack in some spring pads on a tube axle, I’ve been giving this some thought lately. Assuming you have good kingpins, here’s my approach.
I’m going to take a piece of flat bar, 1/2 in thick, 4 inches wide, cut it into a square “C” put on the spindle bosses and use my angle finder on the opposite edge. I’ll have the weight of the truck with the engine in it with the axle at ride height blocked up on each end.