109 rear brake shoes query

[Iain]

I'm just fitting new brake shoes to the rear of my 109.

I've noticed that although the metal part of each shoe is identical, the actual friction material is positioned differently on them. In the set of four, there are two with the pad closer to the fixed end, and the other two have it closer to the slave cylinde end. (See the attached photo)

The ones that came off are the same, and although I carefully noted whuch holes the springs belong in, I didn't not which way wound the shoes were fitted (and it was me who fitted that set 15+ years ago, and I'm not sure I knew the right answer then either!)

I one type must be the leading shoe and the other is the trailing shoe, but which is which?

Thanks,

Iain

[simonb]

Be better if you photographed them flat on the ground  - so each pair makes a circle, but the ones with the longer linings will the leading shoes.

The leading shoe at the front of the axle, will have the lining closer to the cylinder and shorter at the pivot end. The rear shoe will have more lining at the pivot and less at the cylinder end.

 

Edited August 6, 2019 by simonb

[Iain]

Thanks!

Here's a side on photo, of them now fitted to the right rear, so the one on the right is the leading shoe with the lining closer to the piston.

Thanks the help. I couldn't find it in either green or blue bibles.

The new shoes, although apparantly genuine, came from a well known supplier with no packaging at all.

[Iain]

And here's the left side.

Edited August 6, 2019 by Iain
Incorrect text posted.

[Snagger]

I’ve not noticed that before.  Interesting.  If you have them the wrong way around, the adjusters don’t work, with one cam never pushing the shoe tight against the drum and the other cam never backing off enough, so that should confirm if you have them the right way.

[simonb]

Yes, that's also correct and the tell tale that the shoes are the wrong way round.

On the leading shoe, at the fixed pivot there is less force than at the cylinder. For the trailing, there is more force at the pivot and the least force of all at the cylinder. Hence as an economy measure the linings are cut short at the "low force" points.