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I'm asking because I found a better selection of rear brake parts for the XKE than XJ6.
Here is a link to what I found:
The prices for the ceramic and higher end brake pads don't seem to be terrible. And they have slotted rotors.
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Hoping they are really a direct fit for an XJ rear. I plan on rebuilding the calipers and getting new main and e-brake pads. Then hopefully these rotors or something similar.
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So far all I can tell is my rotors are just shy of 10.5 inches in diameter, just like the ones in the two links.
My concern on the rotors is how thick the rotors are for spacing and how much offset there is.
The other concern I have is, are the pads, will the pads fit the Girling Calipers I have.
Might be time to do some research on another and post back what I find...
Last edited by 303Radar (8/19/2013 8:48 am)
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Still trying to research what I can. I have a link to EBC and their catalog (in Excel format) is here:
They don't show they make Red Stuff (ceramic) for the Jag Series 1 rear but they do have Green Stuff and Yellow Stuff pads.
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I think I found what I'm looking for in pads. After studying the EBC spreadsheet, it looks like the Series 1 Jag rear from an XJ6 or XJ12 can use the Red Stuff ceramic pads from EBC. While studying their spreadsheet, I noticed almost every European car (Aston Martin, Alfa Romeo, AC 428 (67-74), and many more) through the late 60's and early 70's used a Girling Caliper and had the same part number for the Green and Yellow pads, including the cars which had a part number for the Red pads. They also had the same link to view relevant product image:
What I realized was, the higher end and/or sportier cars had the same part numbers and Red Ceremic pads available. Having heard that Ceremic pads have slightly less bit and need more pressure to work effectively, I've come to the conclusion the main reason the Ceremic pads don't show up for the XJ6 or XJ12 is, the braking systems on these cars were inconsistent. I've seen several used rears with nearly new looking pads. The reason is, the stock system didn't always apply proper pressure to the rear brakes.
I would expect, anyone with a modern power braking system who ensures there is proper pressure and possibly a proportioning valve would be able to use ceremic brakes.
Just need to find out about those ventilated discs...
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I got this update from "Frank" at Jag-lover's forum regarding ceramic pads and availability:
'Inconsistent' is not really the right word, sir - 'incompatible' with
harder pads would be more appropriate...
The pad force is a function of 'gearing'; the fulcrum-to-pedal at driver's
input - and the master cylinder-to-caliper piston area. 'Our' master
cylinders and pads give a 'gearing' factor of 7+ - ie 1 'm/s pound' gives 7
pounds on each pad, and a pedal pound some 15 'pad pounds'. In addition; the
booster has available some 400+ pounds to be delivered to the ms - giving a
whopping 2800 pounds on each pad. To have the same effect you need nearly
200 pounds of pedal pressure - which explains the superhuman effort required
when the booster fails...
Basically; the piston areas front and rear are equal, but the dynamics of
driving, and common weight distribution patterns, usually leads to the front
wheels doing most of the braking during 'normal' driving - less less wear on
the rear pads. This is perfectly normal and common on all cars - and does
not imply that the system applies unequal pressures front and rear,
pressures are identical. All of which is one reason why Jaguar stayed with
the unvented discs at the rear...
The actual braking force on the road wheels then depends on disc diameter
and the pads' friction coefficient - which is the only 'free' variable
available to us, the other factors are fixed, unless the braking system is
modified. To some extent the Jaguar system is a compromise for driver
comfort - perfectly adequate for the speeds and weight of the car with the
usual pad hardness. Softer pads require less driver effort, but harder pads
are more resistant to wear and overheating - requiring more pedal force,
and increased disc wear...
Integral to driver 'comfort' is pedal travel - the initial pedal movement is
to seat the pads to the discs - the pads being fractionally retracted as
pedal is released, increasing with disc runout. This requires moving fluid
from the ms to the calipers - at the cost of pedal travel. With 8 pads to be
moved the volume required is not negligible - and the relationship with ms
and piston area must not be excessive lest the driver feels uncomfortable
with the pedal travel. An inevitable trade-off - halving the ms piston area
to double the brake force doubles the pedal travel...as does doubling the
piston area...
That Jaguar is not listed for 'ceramic' pads by the company in question may
have various causes. One being of course that Jaguar owners did not want
them, lack of market - or indeed that other makes had set-ups more suitable
for a wider variety of pad material, and greater driver tolerance...
Frank
Frank - Thanks for the information and clarification.
Since the aftermarket brake systems for a '59 Chevy are quite a bit different than a '70 Jag, I'll wait until I have the brake booster and master cylinder in hand. This way I can verify how much pressure I can/will be putting to the pads.
After all, I'd had to have a brake system which isn't optimal for my vehicle.
Thanks again!
Ragan
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In short, there are ceremic pads a Series 1 Jag can use.
The better question which should be asked is, should they be used for the application at hand.
The answer really depends on, is the braking system optimal for desired brake pads.
I'll update this post (much) later once I have parts and can run through the calculations to see if my brake system will be suitable for ceramic pads.
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Ragan -
Thanks for sharing that fine treatise on brakes. A lot of that applies universally as well as your specific efforts.
Good Job - Cheers - Jim
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So I was at Napa last night picking up an air filter when I asked them if they happen to have 1970 Jag XKE rear rotors on hand, I wanted to take a look at them. So they pulled up info in the computer and said no, they are a special order. I told the guy I was curious if the rear would fit an XJ6/12. He pulled up the cross reference guide and low and behold, the XKE rear rotors are cross listed for at least Series I and Series II Jag. I don't know about a Series III, they certainly won't fit the five bolt mounts.
In short good news, I can feel more confident about ordering the cross drilled rotors for an XKE. However, before I place the order, I have one last item to confirm. In their computer they had the measurements for the rotor, diameter, thickness, etc. I plan on taking the existing replacement rotors I have with a metric ruler (all the sizes were metric in the computer) and double checking. After I do that, I'll post how well the sizes match up.
That is a benefit of going to a friendly parts store when they are not busy!
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