Setting up Laverda drum brakes - Tips?

S

Smartv11

Full member
Location
Meopham, Kent
After reassembling the drum brakes on SF, I would like to put some time into setting them correctly.

I'm not sure what is a correct set-up, should both lever arms work in parallel, or does the first lever move more than second?

Any tips on how to set up, would be appreciated.

Paul
 
I for one would be most interested to have access to a step by step process (and to know if there is any difference in the set up procedure between front/rear brakes and different types). I've adjusted up car brakes easily enough (Minis; MGs, landRovers/Landcruisers and the like) but bike brakes have me baffled and am often left wondering if i have brake shoes made of stone and cables made of spaghetti...
 
When I did the gold 750 brakes it was a balls ache.
Assemble wheel and brake cables/rods/whatever.
But before assembly cover all the friction surface with chalk.
Spin wheel, apply brakes, disassemble, check where the chalk has rubbed away.
Flat down with sandpaper.
Lather, rinse, repeat until the friction surface seats evenly on the drum (which had been skimmed true before respoking the wheel.
Balls ache because each wheel took 15 to 20 iterations before I was happy it was as good as it was going to get.

3 different types of drum brake were fitted to twins and triples.
First was a Grimeca drum, second was a mk1 Laverda where the cable sort of self centred 2 independent actuating arms and then the last one was the type with an adjustable rod connecting the 2 arms.
 
Thanks Grant - I have the first MK1 laverda brakes, so interested in tips on these.

I'm not setting up new brake shoes, as old were fine and evenly worn, I even made note of each shoes position, so think its all ok on the 'inside'.

Its how the actuator arms should be set up, that's the main part of my query.

Also, what is the purpose of the stop adjuster?

Paul
 
Paul,

The first series drums are easy...

Hoist the front wheel free, loosen the front axle so the drum backing plate is free to move (it doesn't need to slop around, the axle tension just needs to be reduced a bit), spin the front wheel and apply brake hard.  Keep applied and tighten axle nut.  You now have a base line to work from, the plate/shoes are now centred in the drum, irrespective of condition, wear, etc...

Adjust the stop screw until a shoe touches the drum surface, back off slightly until wheel is entirely free to rotate.  Lock the stop screw.  You can now adjust the cable to your requirements.  Finished.  In action, the lever limited by the stop screw is actuated first, further tension on the cable pulls the rear lever tight.  You should make sure the levers move in that order, if the rear lever moves first, either the bushes/axles are binding or the return springs have stretched unevenly.

The included angle between levers and cable should not exceed 90? when brake is applied.  If you end up with more, you are sacrificing leverage, the linings are worn.  When replacing the wheel, after tyre change e.g., it pays off to repeat the centreing process to retain the proper adjustments.

Ideally, new linings can be machined to fit the drum exactly, decreasing break-in time radically.  This is where Grants efforts turned into the ball-ache... we misjudged the adjustment range of the 2nd. series drums slightly and he had to painstakingly fit the linings by hand because I had left the linings too thick.

piet
 
If I was setting the arm angles, if they go on splines I?d assemble them so that they are almost at 90deg to the cable pull, giving maximum leverage.
On ANY drum brake it is most important to apply firm pressure on the lever whilst tightening the axle nut. This centralises everything around the shoes. Piet posted while I typed this, so I second what he says.
 
Tippie said:
If I was setting the arm angles, if they go on splines I?d assemble them so that they are almost at 90deg to the cable pull, giving maximum leverage.
On ANY drum brake it is most important to apply firm pressure on the lever whilst tightening the axle nut. This centralises everything around the shoes. Piet posted while I typed this, so I second what he says.
Click to expand...

Yes Lee, but the Lav levers are located on a sqare drive, so cannot really be adjusted any differently.

I'm simply amazed by many drum brakes that pass through the shop.  Horribly set up, worn out, dirty... generally, scrap.  No wonder the Lav drums don't have the best reputation.  Imho, they can be made to work extremely well, can, and often does, cost a fair bit! :D

piet
 
sfcpiet said:
spin the front wheel and apply brake hard.  Keep applied and tighten axle nut. 
Click to expand...

Same here: I think it's this part <above> I've been missing...

thanks all.. 8)
 
Thanks Piet,

Is there a different process for setting up the series 2 Laverda drum brakes that you could share - having issues setting up front brake of SF1.  Wolfgang provided all new backing plate, linkages and shoes..

Yogi
 
Yogi said:
Thanks Piet,

Is there a different process for setting up the series 2 Laverda drum brakes that you could share - having issues setting up front brake of SF1.  Wolfgang provided all new backing plate, linkages and shoes..

Yogi
Click to expand...

Yogi,

The trick is to get both shoes to contact the drum simultaneously.  Often requires lots of fiddling with the actuating rod to the short lever.

I set the wheel on a vertical axle in a vice and place the brake plate in the drum.  With the rod connected only to the longer lever, both levers are acutated with a 13mm spanner and the shoes pressed to the drum.  Looking through the clevis bore, you can determine in which direction adjustment is required.  Problem is, you cannot adjust the rod without removing the short lever, may take several attempts.  Repeat till the clevis pin simply drops into the clevis and lever, with both shoes hard up against the drum.  Be sure to consider/compensate any wear in the pin bores.  By centralising the brake plate upon re-fitting the wheel, you should be pretty close to as good as it can get...

The brake levers will need to done up quite tight, do be sure to fit substantial (2.5mm thickness at least) washers under the fixing bolts.  I often find thin tinny shit washers there, with the levers slopping around on the square of the fulcrum axle.

Someday I'll get around to making clevis and rods with RH and LH threads, will make adjustment a doddle.  I've done this with all my rearsets, really cool. :D

piet
 
The last time I adjusted a TLS brake was on a '69 Bonnie I used to own. Trick was to completely slacken off the adjuster between the cam arms, tighten up the cable as tight as it will go, then tighten the adjuster arm fully, and then finish off by slackening the cable to the required slackness.
 
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