Remote brake servo for VW drum brakes

[Andy1433]

Hi all , I want to put a servo on my trike for rear brake drums . Can someone recommend which unit I need , ratio or pressure. So many to choose from . All help greatly appreciated. Cheers

[Deep Diver]

I find my drum brakes work fine without one.
Check your shoes and cylinders are working ok.

[gorbee01279]

I find my drum brakes work fine without one.
Check your shoes and cylinders are working ok.

It's funny this has cropped up,i took mine down the road today to test the brakes etc & my rear brakes are still hard on the pedal after renewing everything except the master cylinder with next to no stopping power? only thing it could be is the master but it bled ok when changed, hand brake works fine so looks like i will be changing master cylinder tomorrow weather permitting got a couple of new land rover ones.

[Mal]

How long is your brake pedal, ie, leverage, fulcrum to push rod. It makes a hell of a difference on VW set up.

[gorbee01279]

How long is your brake pedal, ie, leverage, fulcrum to push rod. It makes a hell of a difference on VW set up.

It's about 6inches it all looks to be unchanged from original build from pedal to master cylinder it's the only thing i can think of causing the problem as all is new & good on the rear plus i double checked everything was ok when i done them pedal even felt better with more play than before while it was standing, when i bled the brakes the pedal travelled freely around 4inches & bled fine, adjusted brakes so they just started binding & came of half a turn on all four adjusters so i am scratching my head with this at the mo for some reason my head is telling me it's master cylinder but as i said the pedal travelled freely when bleeding????? would coming of the adjusters another 1/4 turn help i wonder????

[gorbee01279]

Sorry Andy didn't want to hijack your thread i will use mine for any answers.

[Deep Diver]

I'll measure Hermans pedel tomorrow.

[Mal]

Its possible with new cylinders to get an air bubble trapped behind the pistons, try pulling the brake adjusters right back to close the pistons then bleed again. If you have a good pedal though its probably not that. Get Barry to post a pic of Hermans pedal set up, you do need a lot of leverage. Sorry Andy for hijacking although i wonder if you have a similar problem.

[Deep Diver]

Here is Hermans setup.


From the bottom peg its 250mm to the centre pivot, and 43mm from the centre to the cylinder pivot. The master cylinder size looks to be around 19mm ? This is on a linked brake system for front and rear wheels.

[Kawazuki]

Bloody hell! - You couldn't have got the master in a worse place No wonder they don't work well! The lever ratio looks to be about 8:1 which ain't bad but would be soft compared to recommended 6 or 7:1. But the worst bit is the angle between the lever and the master ! ! ! Imagine the arc the lever bolt travels and how it pushes on the master push rod - you are probably loosing half the lever movement and hence piston travel! Lever to master push rod should ideally start a little less than 90 deg, hit 90 deg when pressure starts and finish a little more than 90 deg. for best effect!