[urq] bomb test variation with S4 brakes?

[Buchholz, Steven]

... no argument from me ... in fact as I see it you are supporting my original statement ... that it is overly simplistic to assume that you can bolt up a new set of brakes and expect to see no difference in pedal travel.  

The effect of the area of the different pistons is a fact ... paper or no ... to move a piston a particular distance you need to supply more fluid for a larger piston diameter.  (Unless you make a similar compensation at the M/C) more fluid needed at the caliper means that the master has to move farther.  OK, maybe the distance will be different depending upon the calipers ... but you could argue that even changing the pad material could well change the amount of distance the caliper will need to move ... so even a pad change might lead to a situation where you have a larger master cylinder piston travel.  Bringing everything back to the original question ... you might well see a difference in the number of pedal applications to deplete the bomb by using a different type of brake pad ... even with all factory calipers and M/C ...

I think the message I was originally trying to get across was not to worry too much about the observation that it seems to take less pedal applications to deplete the bomb.  Use dynamic functionality to guide you ...

Steve B
San José, CA (USA)
> 
> I beg to differ with you.
> Increase in piston number is theory on paper.  In real life this is actually
> a bit different.  There are many things to consider including how good the
> callipers are (how far they retract after brake application) and how good
> the sliders themselves are.
> 
> Previous car was '83 with G 60s up front and the travel was minimal.
> The difference would be something your foot would not even register, not to
> mention reduce # of pumps from 30 to 10!
> 
> BTW S4/V8 rear callipers use the same piston as Ur-q and in fact use the
> same pads as well!!
> Oh and my '85 with SQ callipers (4 piston fixed) has the shortest pedal
> travel of them all.. probably because of lack of slider.