Self adjusting rear drum brakes

ramona300

ramona300

True Classic
After several heavy braking moments on last Wednesday's track day where I often felt I needed more from the rear brakes, I pulled the drums off. There was no dust and it looks like there has been very little contact between the shoes and the drum. I've ordered new shoes but I need to understand how the self-adjusting bit works. I have the workshop manual and two other manuals and just re read this thread. https://xwebforums.com/forum/index....0-850-spider-fix-up.36791/page-22#post-335558
I'm still no wiser. The hand brake is adjusted but probably could be tighter. The two-pot callipers on the front work exceptionally well but rear brakes would be nice!
 
Since you have good front brakes I'd suspect (you are using a dual MC?) no pressure to the rear. If using the older single circuit MC look elsewhere as if worn seals there would be no braking anywhere. On older manual adjusting cars I've always switched to the late self adjusting type without any problems. Use brake grease (high temp) on the "adjusters" but if binding I'd expect they're NOT releasing rather than not engaging. If you run a manually adjustable front/rear brake bias possibly there is air in the rear circuit past the valve. I had similar problems when not properly bleeding the rears. Thinking (happens slower at my age) I seem to recall having used a 4-wheel disc brake master cylinder and having rear drum problems but I'm fuzzy on how that went. Something to do with the drums requiring a tiny bleed hole in the relaxed (not braking) position. I think (fuzzy again) that one led to dragging rear drums though.
 
It does rely on the hand brake being adjusted to lock the wheels up with three clicks or so this preloads the adjuster bar between the shoes. The self adjusting part is done by the friction washers under the coil springs on each shoe.

Rear brakes as you know don’t do a whole lot but they should be doing something :)
 
Maybe convert to rear discs. I am using bigger discs on the rear than the front in my track X.
 
I'm sticking to drum rears because they are much lighter than discs. I still use the single master cylinder {new} and the rear wheel cylinders are new and the hoses are new, SS on the front. Looking at them yesterday there is a possibility I have the top bar fitted incorrectly [the one next to the handbrake lever]. I have it the same as the photo in the workshop manual but the line drawing on the same page is different. The only wear on the shoes and it's only slight, is at the top near the wheel cylinder. Those friction washers under the coil springs are just for centring the shoes. The only adjustment for the shoe to drum that I can see in the workshop manual is two clicks up on the handbrake and tighten the cable till the wheels stop then ease off a little. At the bottom where the shoes normally pivot on a self-adjuster there are just two bolts. Normally with self-adjusting drum brakes, you just drive backwards and hit the brakes and the adjuster tightens up a few clicks. With this version of the 850 brakes the only thing I can see is a regular adjusting of the handbrake cable and the adjuster bar takes care of balancing the drum to shoe clearance evenly.
 
No they are not like the self adjusting units which have a pawl which pulls down or the rotating adjusters approach one often finds on more modern designs.

It is all about the hand brake adjustment in my experience. My car has the dual master but I don’t think it makes any difference in the way the rear brakes work.
 
kmead said:
No they are not like the self adjusting units which have a pawl which pulls down or the rotating adjusters approach one often finds on more modern designs.

It is all about the hand brake adjustment in my experience. My car has the dual master but I don’t think it makes any difference in the way the rear brakes work.
Click to expand...
I agree. They are certainly not self-adjusting!
 
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