Brake shoe wear

[kentishvanman]

Hi,
Brake shoes are down to 2.5mm but only in one place, top edge of the secondary shoe. The rest of the shoes are fine ie. 3 to 4mm.The
piston is, or appears to be, working fine in fact only replaced it 24 month ago.
Don

[California Dreamin]

I'm not sure what you class as the 'secondary' shoe but what you are probably seeing is normal 'self servo' action of the leading shoe and the extra wear from this normal shoe action.
The 'leading' shoe works around 40% more than the trailing due to this action and on the top edge as that is the point at which the wheel cylinder works (the lower part of the shoes just pivot).
Martin

[bigherb]

The shoes weren't centralised when they where fitted.
The leading shoe will self centre as it follows the direction of rotation, the trailing shoe won't unless you drive a long way in reverse
I've seen it quite a few times.

[Aidan]

are the drums in spec ? if overly worn then you will also see more uneven wear on shoes on a single piston set up like ours

[kentishvanman]

Hi,
Thanks for that.
It's just like the photo so that is probably the reason.
I will check the other drum now.
Don

[California Dreamin]

A couple of possibilities:
Cheap & inaccurately made shoes which alters the geometry of where the friction lining touches the drum.
As Aidan said, overly worn drums which also alter the angle at which the lining touches.

Martin