Anyone know what sort of ratio modern car brake servo's run?

Spent a few hours out in the Jaguar over the weekend, and the brakes feel crap, yet are working properly, even have EBC Grooved disks and green stuff pads. I know the servo is 3-1, so just wanted to compare to modern ratios, and whether its just me not applying enough boot.

Hi Mate,

Modern servos can be in the order of 4 or 5:1 so that may be part of the problem.

The other part is the 'jump-in' setting which is set up during initial development. The 'jump-in' setting is the booster output compared to the input but only over the first millimetre, or so, of pedal travel.

This can make the brakes feel very sensitive and is very popular on modern cars - particularly recent Audis.

So long as it stops when you push the pedal and you can lock the wheels you've got it about right

I was told modern ratios are 5:1.

E type servos are crap a really bad design at least on the series 1 and 2 --- unless it changed on the the later series it was a single circuit to the servo but dual circuits front/rear from the servo.

I have seen an early series 2 with the servo only working on one circuit.

Couldn't agree more BT, just got my head round how the reaction valve works, checked everything out and its all working perfectly, just seems an absolute lack of assistance, almost like a modern car with the engine not running.

Mine's an S1.5, the circuit from the pedal MC, runs the front brakes via the servo MC, and also pushes a further piston via the fluid to operate the back brakes!!!!

I feel some sort of upgrade comming on, using a modern servo/MC.

[Edited on 4/5/10 by r1_pete]