Can someone please explain what servo brakes are. Yes I know, stupid question. It indicates how little I know about mechanics. How do they work? And how superior are they, if at all, over non-servo brakes? And if you were going to add a little more power to your bus (say double the power) are the standard servo brakes good enough to cope with it?
servo's do not improve the brakes, they reduce the amount of effort required by the driver to push on the pedal... basically it's a multiplier... so in essence, you press the pedal and the servo doubles your effort.. that said, the servo mc is bigger in bore than the non servo version
they make a vast amount of difference to the driving experience as its more 'modern car' than '1950's tractor' The servo works off a vacuum which is created by the engine - you have a pipe off the intake manifold, when the engine is running it 'sucks' the air out of the servo, creating a vacuum. As you press the pedal the difference in pressure within the servo from front to back assists by multiplying the amount of energy you put into the pedal When I first bought my current van the servo wasn't connected - braking was normal for a bus, I just built up a larger thigh muscle in my right leg (it ended up matching my right bicep, enlarged for other reasons ) When connected the servo it made the braking so much easier ;D
the front callipers, discs and pads fitted to these buses were also fitted to the Porsche 911 so using standard brakes for your stoppies is not an issue. It would be a different thing if you had drums up front though ;D
Easy check for your Servo. With the engine off, pump brake pedal half dozen times, you should feel pedal getting harder. Make sure you are out of gear, put foot on brake pedal and push, at the same time start the engine. As engine starts you should feel the brake pedal move further down, this is due to your second working. If your brake pedal doesn't move your Servo, if fitted isn't working and needs checking out.
A bit more info - had enough, yet ? - I think the servo ratio of the ones in buses was 2.1:1...something like that. Meaning that they effectively halve the pedal effort. As above, they don't increase the braking force - just give your leg a rest. Requires the same amount of energy-getting-rid-of-ability to stop your van, whether you've got a stock engine or a 911 with extra cheese (assuming the weight's the same), so I've never really understood this get-bigger-brakes thing. The amount of joules of energy you've got to dump for a given mass is the same. Front drums would be dodgy tho
Nothing wrong with front drums Snotty - have you ever driven a servo'd drum brake bus? They work a treat. If you've ever had to emergency stop from high speed in a fully loaded camper you may well find it impossible to lock the brakes without a servo. Not the same as testing in empty camper at 20mph. Just saying.
I've got servo brakes in my van, and although they looked connected when I bought it, the pipe to the manifold was blocked, so braking was scary (and involved pulling on the steering wheel at the same time as pushing on the pedal!!). When I changed the engine, it was connected up properly, and a working servo was a revelation. Long term, I'd like a Scooby conversion, because I'd like to take the van on a grand tour, but I won't be changing the brakes. The conversion, in my case, is not to allow me to drive the van faster and drive like a lunatic, but is for reliability and a van stops in the same way from 60, regardless of whether it's powered by an aircooled type 1, a subaru engine, or a large wound elastic band.
