how does the rear ratchet work? GIRLING brake drums

[Richard309Sri XU5JA 205GTi 8]

Just wondered If I am understanding how the rear brake drum auto wind out "ratchet" works? 

 

GIRLING brake drums 

 

so it's when the brake pedal is used - creates space for the L shape metal elbow to move into 

via the spring tension 

 

that then winds down the notches? 

 

as per photo? 

[Tom Fenton 1,542]

Yes. They don't always work that well.

[309SRiguy 15]

I ended up adjusting mine manually. As Tom says, They don't always work that well.

 

The thin metal piece can be distorted so that the pawl does not sit in the teeth of the ratchet. They can be adjusted with careful bending. Some kits supply a star washer that holds the plate on the roll-pin to keep everything in place.

Make sure the ratchet wheel turns easily on the rod when unloaded. (They do get hard to turn manually when the springs are pulling the shoes together against the rod)

 

Clean off any ridge on the drum where the shoes don't wear. The drums need to slide on and off without a ledge or lip. Check the lip on the inside also. Slightly difference width shoe could rub there and prevent the shoes sitting right down on the drums friction surface. 

Click the ratchet up with a screwdriver. Slide drum on. Nip up the axle nut.  Apply pressure to pedal to centralise the shoes. Try handbrake. It should be firmly applied at between 5 and 7 clicks on its ratchet. First time will probably come up more than that.

Remove drum and click up the brake ratchet more. Refit drum,  centralise and try handbrake again. 

Eventually you will find you have gone too far and friction will occur. Remove drum and back off a click or two. Reach a balance between too much friction and the handbrake not locking up soon enough. 5 - 7 clicks is the range you want at the handbrake on the 309 according to Haynes. I recall reading a different number of clicks for 205.

Doing both wheels together might make the job easier. You can compare the binding on each brake and feel if the torque needed to spin the drums is similar.

 

If high spots show on the shoes they can be carefully trimmed with a suitable file. It will speed the bedding-in process.

 

Bedding the shoes is quicker using the handbrake. You can drive the engine against the rear brakes only. Using the full brakes puts most of the load to the front discs.

Don't overheat the drums or shoes. A bit of on/off/on/off action then a bit of cooling before repeating.  When you can pull the brake on and feel the rear pull down (and evenly on both sides) you will be pretty much there.

Your full-on handbrake might not be between 5 and 7 notches. Go back to the start and click the "self-adjusting" ratchet up as required. The shoes should be bedded by now and not much further adjustment necessary.

Do not adjust this with the cable adjuster. It alters the geometry of the handbrake leverage away from optimum.  If shoes are adjusted to rub and handbrake is at correct height then you could look at adjusting the cable length.  

 

 

Off track a bit:   A really good scraper can be made from a triangular file about 7 - 10mm width.  Snap the finer part off the tip. Stone the milling off the file while also grinding the broken tip back to a point. Taper the tip down over the final 10mm or so. Quench often to avoid overheating the steel. Don't overheat and lose the temper. It needs to retain its hardness to keep a good edge. The point can be sharp but curve down to it so it is not too thin and brittle. Once all three sides are cleared of teeth you can go to a finer stone or work down to finer grades of emery paper on a flat surface. Work until you have three nice sharp edges.

You should end up with what looks like a small 3 cornered bayonet. A small wooden handle is good for control and safety.

Very handy for scraping. Place the flat on whatever surface and push or pull it while easing the trailing edge off the surface until you get cutting action on the leading edge. It works more like a wood- plane rather than by dragging it across the surface. 

 

 

 

  

[Tom Fenton 1,542]

I have found the best way to adjust manually is through a wheel bolt hole. A good torch so you can see the ratchet wheel and you can wind it round with a screwdriver. Much quicker to get the shoes right up to the drum without keep taking it on and off.

[Richard309Sri XU5JA 205GTi 8]

brilliant thanks @309SRiguy  & @Tom Fenton

[309SRiguy 15]

@ Tom Fenton    While writing my post I had a vague recollection of adjusting through the drum on a previous vehicle. I thought it was a special hole but I couldn't remember which car.

 

When I saw the "through a bolt hole" it came back to me that it was my Simca 1000 from many years ago. It too had bolts rather than studs.

 

It also reminded me that it needed the adjuster backed off to get the drum off if there was a lip on the drum.

 

Richard, keep up the good work on the SRi. It is nice to have another around. They were never common here in NZ.