Help-Jag rear discs/calipers

[maverick]

I fitted a set of reasonably new calipers to my XJ12 (1981approx.) diff.
Thinking all rears were the same-wrong!
I have now seated/pinned in the pads and found that the pads sit 7- 8mm wider than the end of the disc. The inner pad edge being further out by the same amount.
The discs are the 264mm wide that should be on the year and the pads are correct for the year so obviously the new calipers sit further out than the originals(long gone) or are slightly bigger.
I have checked a mates catalogue and there are 278mm four bolt discs available on later jags and i think 295mm. The 278mm sound about right for the pad to fit better on the braking surface.
I will contact the John Gordon or Wards come Monday to check but has anyone else had a similar experience.
I hope it's just a case of buying the bigger discs but bolt hole mounts lower wishbone clearance may come into play. May have to buy a bigger pad as well.
Bolts and all are wired already - bad word!!!
John.

[maverick]

After discussion with a couple of jaguar parts suppliers I have the following info.
All rear calipers after 76 were the same and discs were the 264mm ones.
After the XJS models all the brakes were outboard I'm told so that would be after '86. The calipers were also one piston operation so I dont have a newer type caliper by the sound of it.
Has anyone had this problem of the pads hanging over the edge of the disc?

[kdavies3]

Have you got your calipers correctly bolted on?

[Clarkson]

There are 2 different types of calipers, one has a flat edge on the bolt flange and the other has a rounded bolt flange, so that it clears the diff. Hope that makes sence.

[madjohnny]

John, here's a piccy of mine taken a while ago, don't know if this helps???

[wilf]

No main pads fitted in that shot?

[maverick]

Kev,
Bolted correctly? There only is the 2 bolt holes for mounting a caliper. Bolted and wirelocked.
The ferrodo on the pads stick out by 6.6mm and out edge of pad metal frame is 15.5mm to ferrodo. There is no other holes for the pins.
I am now hearing that this problem has came up before and as the pad wears down the ferrodo part (looking in) still looks brand new.
Something isn't right and i dont know what it is - help!!
XJ12 powerlock diff. All rear calipers and pads after '76 are the same i'm told. Discs were all 264mm.
John.

[kayjayd]

Originally Posted by maverick

Kev,
Bolted correctly? There only is the 2 bolt holes for mounting a caliper. Bolted and wirelocked.
The ferrodo on the pads stick out by 6.6mm and out edge of pad metal frame is 15.5mm to ferrodo. There is no other holes for the pins.
I am now hearing that this problem has came up before and as the pad wears down the ferrodo part (looking in) still looks brand new.
Something isn't right and i dont know what it is - help!!
XJ12 powerlock diff. All rear calipers and pads after '76 are the same i'm told. Discs were all 264mm.
John.

It might be an idea to post some detailed pictures of your caliper assembly and someone is bound to know what's wrong. Without pics you might struggle for help.

[maverick]

Just put a piece of string around the outside of the disc and it measured up to 792mm approx. calculating out to diameter of 252 mm.
Was told it should measure about 264mm. This might be the problem.
String was a bit stretchy so will do it again tomorrow with wire.
The discs were brand new and came with the XJ12 when I bought it and stripped it about 8 years ago!
John.

[madjohnny]

Very observant Wilf, couldn't find a piccy with the pads fitted though!