Drum brake Eccentric bolt play

[Cyriel]

How much slack may the eccentric bolt have in the Bush bronze on a series 2 Laverda drum brake?
has anyone measuring values for me?

2 eccentric bolt i`m using have surface wear by rust. I`m thinking of chroming them.
has someone done that here earlier? Has anyone values for grinding them?

Or making the bolts smaller on the lathe and new bronze bushes?

 

[gibbo-123]

I've not started working on the brakes on my Laverda project yet but had a similar problem on a previous bike. I wasn't chroming the bolts so just machined them parallel taking off the minimum of material and made up new bushes to suit. Along with all the other pivot points, lever etc, it made a big improvement to the feel of the brakes.

Stuart

 

[sfcpiet]

How much slack may the eccentric bolt have in the Bush bronze on a series 2 Laverda drum brake?

As little as possible Cyriel...

Not easy repairing these axles.  They are hardened and don't machine easily.    Just restoring a series 2 drum, went through all that.  New internal oversize pins, new bushings throughout... a real pita!   Was totally clapped, should work OK now, though.

I clean the axles up with a tool post grinder on my lathe and make undersize bushes to suit.  The little linking plates usually need attention, as do the pins and the fit of the brake shoes on the post in the brake backing plate.

piet

 

[sfcpiet]

Stefan,

You'll find the brake shoes won't contact the drum on the entire lined surface.  Mount he whole caboodle in a lathe, pre-load the system slightly and turn to size.  The result is complete contact from the word go!

The problem of these brakes not releasing properly is due to the slop so often encountered.  You need to take it up when braking, but it's also there going in the other direction!  The servo effect keeps the shoes in contact long after the brake lever has been released.  Only when the external return spring has taken up the slop will it lift the shoes from the drum.  The springs you fitted will help overcome this.  Standard fitment for the US, specified by the DOT btw, on twins only asfaIk!  Apparently they weren't very happy either.  They did keep the smaller ones though.

Don't particularly like those dry bearings, a bit too soft for high pressure applications.  I needed to bush the large pivot bores of the shoes, they were worn oval, as were the small linkage bores (Linings were still very good.  Pity actually, new shoes would have made the job a lot easier).  They were reamed out to fit over-size pins.  After turning down the linings slightly, the backing plate now fits snugly in the drum without the need for juggling and pushing, hopefully it will work as well as it turned out.

piet