[Diy_efi] OT: ABS retrofit into older car...

[Eric Byrd]

On a low friction surface, such as wet pavement, less of the car's weight
"shifts forward" during a hard stop, perhaps 60/40, so the brakes have to
be biased no more than that, so that the rear brakes won't lock up. 
However, on a high friction surface, you can stop harder, but that causes
more of a weight shift, so that the brakes could be more biased, say
70/30.  But if you bias the brakes 70/30, the car has more likelihood of
locking the rear brakes when stopping hard on a wet surface, which is
twice as dangerous.  Generally car manuf'rs compromise with something
like 65/35, depending upon the CG of the car.

You might be right about the transient response of the front brakes, but
brakes don't lock at all except during hard braking, and given a choice,
it is definitely better to lock the front than the rear.

On Thu, 5 Dec 2002 13:07:50 +1100 (EST) Mos <mos at sydney.net> writes:
> (This is off topic, but nonetheless interesting).
> 
> I would've thought the front brakes are more prone to locking up 
> first
> upon a heavy stomp, as they have more braking power to start with, 
> and the
> front wheels are unloaded relative to when the car is actually 
> slowing
> down rapidly.
> 
> What does properly biased mean? The correct bias (in reference to 
> the
> force a tyre can hold) changes with deceleration magnitude, does it 
> not?
> If you bias for maximal deceleration, then the fronts will be 
> overbiased
> in slower deceleration, right? (And wont help you with stomping at 
> all).
> 
> Mos.

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