Topics covered in this article are as follows -
Rob's brake adjustment method -
My shoe adjustment method is to adjust the stars (one at a time for the complete process here) until that shoe JUST starts to touch (spin the wheel to hear the scrape). Pump the brake pedal to realign the shoes [the stars push only one side of the shoe so they go off-centre as the stars are turned) and tighten that star again until the shoe JUST touches, then back off 1-2 clicks.
I have disc front brakes of course, so for drums all round, try it at one click loosened, rather than two. Discs run VERY close to the pads and so have very little movement before they work so the drums can be a fraction looser -- two clicks). If you feel the drums are still scraping a little, THEN back off an extra click, but this of course increases the piston movement inside the master cylinder before the brakes work, so you want the minimum shoe clearance that will still prevent brake-binding.
Dave wrote to Rob -
I adjusted the brakes, all around. The front ones are hard, because the lower strut support interferes with your screwdriver and you can't move the adjusting star on the front shoe. A screwdriver won't work unless it's bent 30 degrees or so. A while back I bought my son a handy-dandy adjusting tool and was excited to try to out; discovered the ends were too wide to fit in the holes! Frustrations!
I finally found a brake adjusting tool that's slim enough to go through the holes -- works great!
Interestingly (and I can't figure why this should be so), both of the rear brakes were quite a ways out of adjustment (four clicks or so).
Rob responded -
It could be just the shoes wearing in. That was obviously part of the pedal travel problem.
I find it better to remove the drum and de-dust the brake drums and then do the adjusting from the outside, rather than crawl under and use the adjuster holes. There was plenty of dust to remove too -- drums about 1/2 worn I'd say. Removing the dust reduces any noise or squeal from the back brakes. Not a problem for the front discs of course - they're exposed so no dust hanging around.
Dave wrote -
You gotta help me out here. I agree with the de-dusting -- and while I had the drums off I took the adjusting stars out and cleaned them up so they would turn readily -- but I'm not understanding how you adjusted the brakes with the drums off.
Rob responded -
I tighten the adjuster a couple of clicks and slide the drum back on and then spin it. Pull the drum off and tighten again until it just binds with the drum back on. Tramp on the brake pedal hard to centre the shoe again, then spin the drum again - sometimes then you need one more click before it binds. Once I'm sure I have it JUST binding, I back off one click so it spins free. I do this with each shoe separately. Tramping on the brakes I've found to be important if you need more than 1-2 clicks, since only one side of the shoe is being moved and it will then be fractionally off-centre (tramping on the brakes makes the shoe slide to the centre between the star adjuster and cylinder pushrod).
Sounds complicated, but it means I can sit on a stool next to the wheel instead of crawling under several times (so I can do it just on the jack, and not bother with axle stands since I won't be underneath), and it's actually quite quick, since I can see the stars and don't have to find them with the screw driver through the hole.
Dave wrote to Rob expressing concern over the excessive pedal travel his son was experiencing in his Bug -- the pedal goes almost all the way to the floor before there is any actual braking action. His son found that if he pumped the brakes several times it would bring the brake pedal up. Dave read the Bentley Manual (in the troubleshooting section) that this problem probably because the linings are worn and the brake shoes are in need of adjustment.
Note: The pedal travel being discussed here is not to be confused with "brake pedal freeplay," the 5-7mm of play at the top of the brake pedal (which translates to 1mm of play between the brake push rod and the piston in the master cylinder). See discussion of brake pedal freeplay at the link above.
Rob responded with a little treatise on brake pedal travel -
Pumping the pedal usually means air in the lines -- not good. A thorough bleeding of the braking system should take care of that problem. After that, the next thing to check is the reservoir -- maybe it's lost enough fluid for one or both sections to be uncovered. It may be as simple as a leaky slave (wheel) cylinder; if so, you can at top up the reservoir so you get SOME brakes until you can get it fixed. I don't like the idea of "needs a couple of pumps in the morning" to get it working!
The brake pedal "travel" (as opposed to the "freeplay") is the amount of piston movement (taking up the adjustment gap in the shoes/drums) before the brakes start to bite. That's maybe 10mm on my pedal -- it can be much worse if the brakes are out of adjustment.
The total pedal movement can't be much more than that, just so that if one brake circuit should ever fail you have enough pedal travel left for the remaining circuit to work (one circuit failing will always result in the pedal sinking closer to the floor as it bottoms out the "dead" piston in the master cylinder).
The slack has to be the brake shoe adjustment -- it's the only place to take up the slack between the piston starting to move and the brakes starting to work. Try the shoe adjustment routine before you replace anything else. I know it's a pain with four shoes to adjust, but that SHOULD fix it.
After that, the Brake Troubleshooting section of the Bentley Manual gives only three possible reasons for excessive pedal travel -- worn linings, insufficient brake fluid, and defective master cylinder.
After completely replacing all of the brake components in his '73 SB and bleeding the brakes several times, Dave found that he still had excessive brake pedal travel (i.e., travel in the pedal before braking action begins). Rob wrote to say that with all new components and the brakes properly bled, the only thing that could be causing excessive brake pedal travel is the brake adjustment, since the pedal travel is directly related to the distance between the brake shoe and the drum that must be traversed before braking can begin.
Dave's experience confirmed this. He recalled only partially adjusting the brakes after replacing the front brake components and before bleeding the brakes. When he remembered this and then completed the brake adjustment per the Brake Adjustment Procedure, the brake pedal travel was reduced to within normal limits.
Where the pedal cluster meets the floor there is an adjusting plate and attendant bolt. See the lower picture on this Old Beetle Web page (go to Item 60 in the left menu) - items 18-21 show the brake pedal adjuster that is bolted to the floor pan.
From the sketches it appears to me that the "elongated hole" is in the clamp, allowing the clamp to slide forward and back on the stationary bolt in the floor.
Indeed the Bentley Manual says, "To adjust pushrod clearance, simply loosen the clamp bolt and move the brake pedal's stop bracket... Tighten the bolt when freeplay is correct." Does the whole pedal assembly then move? No, it looks like the little stop bracket impinges on the bottom of the brake pedal shaft, thus affecting only the brake pedal.
Moving the clamp in and out moves the brake pedal back and forth, thus changing the distance between the end of the pushrod and the piston in the master cylinder. (See Fig. 4-4, p. 5-5 in the Bentley Manual). At least that's the way I think it works.
However, the right-hand drive (RHD) pedal cluster has a different arrangement. The clamp on the outer end of my cluster does not appear to have any adjustment to it at all -- in fact there doesn't appear to be any method of adjusting the pedal cluster and/or brake pedal at all. I've used the pushrod for the adjustment of the freeplay, and it's always worked (I've only needed to touch it 2-3 times in 30 years, so there's not been much need to fiddle with it anyway).
I took a look at the left-hand drive (LHD) and RHD pedal cluster designs on the "Old Beetle" page. The two are completely different. My pedal cluster (RHD) is a lot longer than yours (LHD), since it has the throttle arm projecting right through the middle of the cluster and has to go right across the tunnel to the throttle cable link on the left side -- same place your cable is (your throttle pedal "surrounds" the clutch operating "tube" I think), and the outer clamp on mine is just to fix the outer end of the cluster.
In the LHD design the brake pedal is offset slightly to the left and there is a ring of metal around the shaft that the RHD design does not have. It is this ring that has irregular cam-like shape that the adjusting clamp impinges on.
The RHD cluster has three concentric tubes, one for each pedal, and both the clutch and throttle cables have to work on the left side of the tunnel (so they go right through). The brake pedal has a short tube as the master cylinder is about one inch to the left of the pedal.
Disclaimer stuff: Rob and Dave have prepared this information from their own experiences. We have not assumed any specialised mechanical knowledge, but we DO assume that anyone using this information has at least some basic mechanical ability.
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Last revised 4 May 2004.
