Proper Drum Brake Adjustment-- Tire On or Off?

[The Critic]

Here's a question that I've always wondered about.

To perform a proper adjustment of a vehicle's rear drum brakes, should the tire be on or off?

I've seen some techs do it with the tire on, while others do it while the tire is off. I personally do it with the tire off. Which one is the correct method?

Also, for the actual adjustment of the shoes, I've been taught to tighten the star wheel until the drum won't move, then back off six to eight clicks. Some videos have said that the proper procedure is to adjust the shoes until the drum can only move one full rotation. Who's right?

Thanks!

 

[chrome]

I used to do it with the wheels off. That way, as I rotate the drum and tighten the adjustment click by click, I will feel the drag immediately once the shoes contact the drum surface. I then back off 1 or 2 clicks.

The trick is to get the shoes as close to the drum as possible without dragging.

 

[ls1mike]

On my 1 ton I usally leave a little drag. They wear out sooner but it is nice for towing the 5th wheel.

 

[The Critic]

http://www.youtube.com/watch?v=FpxQN2esZnU&feature=channel_page

Seems like Richpin is following the "one rotation method" with his video-- the drum only spins once after he adjusts the shoes.

 

[ls1mike]

That is about what I get when I do it on the 1 ton.
Seems to work well.

HOlY COW! I wish the truck's brakes were that small!

 

[Familyguy]

It's a bit of a PITA to adjust drum brakes with the tire on if you don't have access to a lift. So I just leave the wheel off.

 

[mechtech2]

It should make no difference [wheels on or off]. Maybe if the drum alone[by itself] is not seated right, you could have a false set-up.
Also , a heavy wheel assembly may mask some drag, if you are not careful.
Automatic adjusters will stabilize things anyway, if you have them.

The reason you tighten the star tight is to make sure the shoes are really seated, not just some incidental drag.
Then backing them off 6-8 points/clicks is about right on a cold drum.
You do not want any drag.

 

[swalve]

I'm not a professional, so I usually just hack it. Get the shoes "eyeball" adjusted (but left a little loose), and then let the auto adjusters to their job. A couple of hard (slow) stops in forward and reverse, combined with application of the parking brake, and I'm good to go. But I hate working on drum brakes, and the less fiddling around that I have to do with them, the better. I would hate to accidentally adjust them too tight and have to redo the work...

I think the only caveat with that is that the shoes have to be close enough to make some contact with the drum- if they are way loose, they never make contact and never set up the auto adjust mechanism. (It has something to do with how the shoe contacts the drum- if it's too loose, when it strikes the drum, some kind of movement in the assy clicks the autoadjuster over one click. The size of one click is roughly the size of the adjustment tolerance.)

But if I was going to do it the right way, I would think that you would have to adjust it by the book once, go out for a drive and get the pads seated in, and then remove the tire and do a final adjustment to double check. If I remember from what I read, there will always be a touch of drag if they are set up right. Something about the geometry of the shoe, drum and the pivot points.

 

[labman]

If I already have the tire off, I do it with the tire off. Yes it is easier with the tire off, but taking it off isn't worth it.

 

[eljefino]

I do it by ear, listen for the bzzzt bzzzt of a flake of rust or something rubbing every turn.

I also check e-brake tightness and pedal feel. If that's all good, the brakes are good.

 

[mechanicx]

I think technically you are suppose to use a guage that measures the inside of the drum and the shoes circumference. Or you could just adjust the shoes till the drum slides on with a little friction. I think it makes little difference whether the tire is on or off if you are going by just check the drag. You want a light drag, and if the adjusters are working the shoes won't have to wear much before the adjuster take over keeping the adjustment right.

 

[paulo57509]

I use a similar tool:

http://www.brandsplace.com/0384-kdt3377.html

This gets them close. Then, I just let the self adjusters do the rest.

If I'm adjusting them using spoons, I tighten them until I just can't turn the wheel any more (tire/wheels installed) then back off the adjusters 12 "strokes".

 

[Gary Allan]

The main thing you're trying to achieve is making sure that when the proportioning valve allows flow to the wheel cylinders ..that they don't have to reach too far. 2mm or 5mm won't make a difference. If the operator learns to drive like they're not out to test brake endurance, they'll never see use in most cars.

 

[tom slick]

They are self-adjusting; all you have to do is get them close enough to work until they adjust themselves as the friction material wears to the radius of the drum. Nothing scientific.

I adjust them until they stop the drum then back off to free spin then adjust to a slight drag, they'll take care of the rest.

 

[eljefino]

... and how do we think they put these things together at the factory? They probably turn the adjuster x number of threads and call it good!

 

[Vikas]

I thought they self-adjust only when you brake hard while going in reverse. They do NOT self-adjust if going forward.

 

[mechanicx]

It depends. many will adjust properly with any forward movement. A lot of later model GM are that way, what models that still have drums. Some others adjust when braking in reverse.

 

[tom slick]

Originally Posted By: Vikas
I thought they self-adjust only when you brake hard while going in reverse. They do NOT self-adjust if going forward.


what car never goes in reverse?

Old toyotas adjust when the parking brake is applied.

 

[The Critic]

So, based on what you folks are saying, it's pretty much impossible to overtighten the drum brakes when you adjust them. Is that correct? As long as the tire/wheel assembly still spins, and there's a slight drag of the shoes, then the shoe-to-drum clearance is adjusted properly?

Originally Posted By: mechanicx
It depends. many will adjust properly with any forward movement. A lot of later model GM are that way, what models that still have drums. Some others adjust when braking in reverse.


Assuming that the self-adjusters still work, which is quite rare.

 

[labman]

Yes, if the wheel turns with very little drag, It isn't too tight. Getting both the same or in the past, all 4 may, not be as important with ABS to correct any uneven application.