Assisted Steering / Brakes - What weight?

[Sicob]

I was thinking back to cars of the 80's, obviously ABS was somewhat new then, and I presume servo'd brake assistance was in it's relative infancy in the mainstream manufacturing, (although I'm not sure and can't be arsed to wiki).

My point is, in the 80's cars were generally a lot lighter, see VW Golf / Cavalier / Sierra etc,and power assisted steering and brakes were not necessarily required anyhow due to vehicle gross weight being sufficiently light enough and therefore relative ease of turning and braking. Even now, light weight sports cars are mainly without power assistance.

So, what is the tipping weight for a car to have
a) Power assisted steering
b) Power assisted braking

I would have thought a vehicle of a gross ton in weight or less can do without, and the opposite is true. Any thoughts, is weight the only factor? Do we actually care a jot?

[trickywoo]

Sicob said:

I would have thought a vehicle of a gross ton in weight or less can do without, and the opposite is true. Any thoughts, is weight the only factor? Do we actually care a jot?

IIRC on original Griffiths (which are pretty light) without PAS, you had to be pretty strong to turn the wheels at parking speeds. Not much fun.

[bigdods]

My first car a 60's austin 1100 had front disk brakes with Servo assistance. No PAS but it did have an enormous steering wheel to compensate. Being very light with skinny tyres it spent a lot of time with the front wheels locked up (me being 17 and crap at driving at the time)

[The Black Flash]

Size of steering wheel and the steering rack ratio will be the other obvious factors.

[flemke]

A major factor in steering weight is mechanical trail, which is the thing that you change when you alter caster.

For the brakes, pedal travel (when pressurising fluid, not mere slack in the system) equates to leverage. So does distance between your foot on the pedal and the pedal fulcrum. Both directly affect brake pedal pressure.
Also, disc diameter - the bigger the disc, the more leverage the pad/caliper will have on the rotating mass, which will reduce required pedal pressure.

[HellDiver]

Drive a current model Focus. Get out of it and get in to a Mk3 Escort. See if you can get the Escort to stop anywhere near as quickly as the Focus can. I'm pretty sure it'll be impossible.

Servo assistance isn't the only thing that has changed in the last few decades when it comes to brakes.

[Major Fallout]

My landrover didn't have pas. And cheaper than a gym membership!