Squeezing a few more percent out of the rear drum brakes
 

Hi everyone - my Saxo failed MOT recently on the rear drum brakes only being at 46% efficiency instead of required 51%. I’ve bought some new brake shoes for it, but was thinking - is there an easy way I might be able to bring the efficiency up over the magic 51% without having to start replacing stuff? Maybe just clean the drum up and rough the shoes/drum surface with some sandpaper? Or is there a way to adjust the shoes so they press a bit harder?

I haven’t looked at them yet so it could well be they’re worn out and need replacing, but equally I’d like to just get it through the retest and then maybe do a full replacement of shoes + cylinder when I’ve really got the time.

Cheers!

…also, weight in the back - I’ve got some heavy stuff in the boot, would that bring down efficiency during the test? Haha!

if anything weight in the back will help, depends if you have a load compensator on the axle or the usual brake pressure limiters built into the wheel cylinders, the latter is most likely on the drum brake vehicles.

best bet is to pull the drums off, grind off any lip on the drum off, make sure nothing is seized, peel back the dust seals on the wheel cylinders and check they are dry, any sign of dampness and they need renewing before they contaminate the brake shoes.

when re-assembling you need to slacken the handbrake cable adjuster, wind out the shoe adjusters till you can just get the drum on, fit the nut, stomp the brake pedal HARD a few times, then through a wheel bolt turn the adjuster out till the shoes just start to drag, then take up any slack in the handbrake cables and check the wheels still spin freely.

The old shoes looked acceptable, so I greased up the contact points and manually adjusted them out a couple of notches so they’re closer to the drum. Cleaned out the brake dust too. Passed the re-test with 57%, haha. I’ll replace the cylinders and fluid when I get the chance too since I think they’ll need doing before next test.