Another question - other than the quiet aspect of the posi-quiet calipers what is the difference in the physical dimensions of that caliper compared to the standard?
I’d there any performance differences between the posi-quiet and a standard caliper and pads?
Can I swap this caliper for a standard caliper?
Sure Norman,
you have to have excessive braking power to make any control system work, unless you want to reduce it to specific road conditions (ice, snow, slush, water). Much like you only need a t-stat if you have excessive cooling power.
I usually don’t feel uncomfortable with new cars that respond quicker to pedal effort. The thing I don’t like though is that they cheat on you. You caress the pedal and the car seems to throw an anchor. So you’ll be inclined to think that if you stomp on the pedal braking effect will grow proportionally - wrong!
Good luck
Jochen
75 XJ6L 4.2 auto (UK spec)
Yeah, I hate that. I remember GM was famous for that trick with the gas pedal. Give it 1/4 throttle and it leaps like a scalded cat. Man, this thing must have lots of power! Not so much; the remaining 3/4 throttle does diddly.
As I understand it, competition drivers prefer a brake pedal that requires a considerable amount of force because it’s easier to modulate. I understand that Granny needs a pedal you don’t have to push too hard, but my parents had a Chrysler that would lock up all fours at the slightest tap. Maybe somebody needs to develop an adjustable brake response.
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It’s sort of unnerving when you are used to the smooth braking of my Jaguar, Jochen - one sort of wonders if the brakes are contaminated…
Don’t know if it is related to earlier onset of servo assist - or increased brake piston dimensions…?
Frank
xj6 85 Sov Europe (UK/NZ)
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is it correct or incorrect that the brake caliper threads changed from Imperial to Metric sometime during S3 production ?
On the XJ-S, the rear calipers are Imperial while the fronts are metric. They are both Girling. The inboard rear calipers had been around a while, but the fronts were updated from 3-pot to 4-pot sometime before the XJ-S was introduced. I’m guessing Girling switched from Imperial to metric in the meantime.
Indeed, I’m quite satisfied with the Jaguar brakes. The few occasions I needed to step in braking power was sufficient to instantaneously lock up the fronts - and MOT tells me the rears aren’t doing bad.
Anyway, over years most driver trainings were focussing on braking trials teaching drivers to step in with their full foot and the calves of a fighting bull to take advantage of the braking power available. Most rear-end accidents occur because drivers fail to make use of the first third of the deceleration time, getting on the brake too late and too little. In the end there isn’t enough space left. Car manufacturers help out with brakes that react briskly on the first centimeter of pedal movement, help out with brake assistants identifying quick manouvres and the like.
Best
Jochen
75 XJ6L 4.2 auto (UK spec)
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There is a fine line on braking, Jochen - and situation awareness can only be taught up to a point…
It’s simplified with ABS; there is no risk of lock-ups - you can keep control of the car even if you give an almighty pedal push. Of course, the guy behind you will then rear-end you if you suddenly stop - but that is his problem.
Then of course there is the road surface, and no ABS; if slippery you need to use all the time available for maximum. But heavy initial braking may cause lock-up - at which stage the braking distance grows (a lot), and loss of traction means loss of control. Which becomes your problem…
Of course; I am an experienced winter driver! The experience was gained by getting it wrong often enough and cheaply enough to live and learn. The main lessons learned was; don’t paint yourself into a corner - and to identify such corners…
Frank
xj6 85 Sov Europe (UK/NZ)
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