The following question is related/relevant the the following thread where we are discussing the possibility and merits of fitting the XJ81 front brakes to the X300:

https://www.jaguarforums.com/forum/x...brakes-136498/


The reason I'm positing here is to see if anyone has driven an XJ40(XJ81) V12 and an X300 XJ12 and compared braking feel and performance?

We are curious if the upgraded brakes that only appeared on the XJ81 (dual piston, potentially larger rotor at 325 or 335mm) perform any better than the X300 (single piston, 305mm) that were on all X300 variants.

A back to back comparison of an XJ40(XJ81) XJ12 and X300 XJ12 is likely the best opportunity to compare the two braking systems.

So, has anyone driven an XJ81 and X300 XJ12 and have any observations on braking?

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I have test-driven the XJ81 a couple of years ago, and I have a feeling that my current X305 has better brakes. But that XJ81 was not in the best shape, so I am not sure that my comparison is valuable...

 

Thanks, definitely interested in any other experiences as well.


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I've got a question about the comparison. First off, the X300/X305 cars use vacuum brake boosting, while XJ40s use a Hydraulic Brake Booster with Accumulator, correct?

When I first got my '96 XJ12, one of the first things that I noticed were how "spongy" the brakes felt. My '92 XJ6 (with hydraulic assisted brakes) has a VERY firm pedal, it becomes almost rock hard at the bottom of it's travel, and even panic stops feel reassured, like there's never any limit to the amount of braking force I can apply.

On the other hand, my XJ12 has brakes more akin to my past GM cars, never dangerous, but quite spongy, and lots of pedal travel. I definitely feel more confident in the braking system of my XJ6 over my XJ12.

There may be variations with the level of care given to each car, the increased weight of the XJ12, etc, but the pedal feel is night and day... Just my $0.02.

As an aside, this reminds me of the Rolls Royce Silver Shadow's that used a multiple-circuit hydraulic-boosted brake system. The brake pedal was so firm that there was almost no feedback when braking. The solution was to put a rubber stop on the floor under the pedal to give it something to squish into when the driver applied the brakes, giving them the "feel" of traditional brakes.

-Nick

 

The spongy feel of the X300/305/306 brakes comes up often in conversation.

It takes some getting used to. Drove me a bit batty in my early XJR/6 ownership. I must've bled the system ten times before accepting "that's just they way it is".

To increase your confidence I suggest getting out there and making some very hard stops from speed. Assuming no correctable faults in your system, and decent brake pads, I think you'll find the brakes work very well.

The brakes on my XJR/6 would "Stop on a dime and give ya two cents change"

Cheers
DD

 

I would concur, with the XJ40 V12 and the X305. I got around the vague braking by changing the rotors to a drilled and slotted variant & EBS Red Stuff pads. All I can say is what a difference! Ya the pedal is still a bit spongy, but the whole stopping things comes about a lot quicker. There's no doubt you just stepped on the brake pedal.


And at speed, to a exuberant stop, no fade, and not a linear stop either. the closer you get to zero, the harder the car wants to stop. Oh, and the best thing. virtually no brake dust. Yeah me!!


I was so pleased with the performance and especially the lack of brake dust, I replaced the brakes on 3 of my 4 XJ's The forth, I'll need extra stiff soles on my shoes. YABA-DABA-DOOOO!!!


for whatever it's worth.

 

Yeah I think I've finally reached a point of 'comfort and familiarity' with the X300 brakes where their feel is no longer an issue. I just had to get used to it.

They do feel different in initial bite than some other cars I've driven (and still drive) but the X300 brakes are fine now. In fact they stop great now that I am used to their feel.

It just took some time..

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