Duo servo vs leading trailing drum brake

[tortron]

Just noticed the original diff in my ute had duo servo brakes, and the second gen diff has leading trailing drum brakes (and a few small hose differences).

They have the same slave cylinder bores but the small amount of discussion I can find online shoes that the duo servo brakes are more efficient.

Am I likely to notice any difference in the real world?

As it is I can lock the rears, all too easily on a wet road but that's expected, the pedal is a little hard but that's life.

[Carsnz123]

Being rear brakes probably not. The old cars with drums all round and no boostingn, it's very notisable when they have self wrapping brakes. 

[sr2]

Duo servo was an early single wheel cylinder design that floated the pivot point between the brake shoes in an attempt to transfer some self-energising from the leading to the trailing shoe. They were cheap to manufacture, were forgiving re-adjustment but required uneven pad thickness and area to wear uniformly that reduced their effectiveness. The real breakthrough in drum brakes came with the advent of the twin leading shoe which ran two wheel cylinders finally achieving uniform pad wear and self-actuation on both shoes.  Never underestimate how effective twin leading shoes were; it took quite a while for them to be surpassed by disks.

The leading/trailing design (despite creating less friction, i.e. braking force) has a big advantage to the above in working equally well in both forward and reverse and lending itself to working with an additional mechanical (handbrake) system operated from a cam or similar mechanism.

Rant over, (I used to work on this stuff many moons ago!). In my opinion (i.e. suck it and see) there should be no major shift in front/rear bias. If you do have a bias issue it will more than likely be from using a commercial vehicle with little or no payload. If you have any problems feel free to contact me, I’ll be able to point you in the right direction.