Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Post 93 rear drum auto adjusters

Well, some how my brain can not get itself to understand how these work.


Obviously I can see the knurled edge & see how that would hold. But can not see how it adjusts as the shoe is pushed out how does the adjuster move ?

Sorry for an idiotic question.
Thanks for any insight, to ease my mental block.

According to the manual they auto-reset every 18th June (first one for RHD, second one for LHD) .😆

K

I've always found auto-adjusters on any car a black-art and just make sure all the bits are clean, and free moving and let them do their voodoo in their own way.

I can only theorise, although I've used a screwdriver to self adjust with the shoes on the axle after replacing the cylinders.

In the image.......when the footbrake and or handbrake is applied.......the pivot point, left end, moves "North East", and rotates clockwise.

The smaller section has to react so moves in anti clockwise around the "drill pivot" and so the "heel" on the top right presses against the shoe, and the knurled edges rub against each other just hard enough to click one tooth, thus holding the shoe just a bit further from the cylinder, and closer to the drum.

How's that sound?

As you'll be aware most is hidden when the shoes are fitted



What's missing from your shot IcePack, is the little spring that pulls the pawls together, so when you operate the brake after re-assembly if there's play the serrations on the pawl take up this slack but can't release back when you let off the brake - essentially taking up the shoe to drum gap and give a nice short hard pedal 'feel'

You can just see the spring here (opposite side under the Y47 mark)

Thank you for your replies. Dave are you saying that once the two pieces have moved a “notch” when you release the brakes & the shoes reverse direction the adjuster is held in it’s adjusted position by a geometric lock ?

perhaps this foto helps?

Yep Spot on icepack, as the adjuster is allowed to take up a new position so does the cylinder pistons. so more brake fluid from the reservoir remains present in the cylinder body but unlike the front calliper pistons the extra fluid required to hold the pistons in the rear drums in an Extended/ing position is negligible in comparison to the front ( hence brake fluid level drop).
This effects the position of the shoes within the drums as they wear but still keeps the contact of the friction material fully in contact with the drum surface. The metal part of the shoe which holds the friction material is circumferentially similar in diameter to the mean internal diameter of the hub, so initial wear to new brake shoes tends to be to the outer ends of the shoes and this then equals out as the shoe wears in. Eventually as the shoe reaches its lowest permissible thickness it will be very close to leaving an equal 1-2mm around the whole shoe. These wear patterns allow you to make an informed diagnosis of what might be wrong with your rear drum brakes. For example a worn shoe showing equal amounts of friction material left at both outer ends of a shoe yet worn so there is hardly any material left in the central area would indicate that your drums have gone beyond their maximium wear diameter, ie, the internal drum diameter has worn and now its internal size is to large. Of course there are several indications on this theme and it's probably worth looking them up as so many times you see rear drums having had work done to them yet clearly the initial problem was never addressed. Yes I suppose it is a bit of a dark art but probably self adjusters didn't help. When shoes had to be manually adjusted to bring the friction material into the desired position, more of us were aware of our brakes performance and to a greater extent what was probably needed to sort them out. It was not unusual for your dad to get you out on a Saturday afternoon when he got back from work to just watch him show you how to adjust the brakes. Nor was it unusual to end up stripping the whole thing down to service a piston........ But that's for another day!

Oh the memories of adjusting a Ford 105e drum brakes. Two each on each front, one each on the rears. Assuming none were seized. They often were. Setting up, road test, and setting up again to get a perfect hard pedal along with perfectly straight emergency stops. This was a dark art. Nothing gets a hard pedal with no slack other than 4 properly adjusted drums without a servo!

Oh how true Dave!..... The seized adjusters of yesteryear, What a nightmare!