XJ6 rear brake with original parking brake. All bolted together.
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This is strange, the MK2 handbrake pad is larger of course and, other than the MK2, only fitted to late XK150 , MK9 models , ( and incidentally to some models JCB and small dump trucks) whereas the XJS size fitts all the independent rear end models, so on potential
demand the pricing seems the wrong way round. Same for the locking plate with the different
bolt spacing.
Peter B
Should have been more specific. MK2 rear brake upgraded with XJ6 caliper. Must use original MK2 parking brake mechanism. Front brakes different story. I replaced the MK2 front crossmember with one from a 3.8S. At one time a popular conversion. 3.8S parts scarce now. The XJ6 calipers would bolt to the 3.8S upright. Also used the Marles Variomatic power steering box. A vast improvement on the original Burlen PS. Bob
Got some handbrake pads you can have when I cut off the brackets from the scrap axle I have.
You should not be fitting XJ rear calipers to a MK2 unless you upgrade the front as well. MK2 rear pistons are 1.5in. compared to the XJ at 1.69in.
A 26.7% increase on the rear.
DANGEROUS!
My Fronts are series 2 etype with uprights
With best regards
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Thanks wardell , 
I have a pair of S type rear calipers. (not 420).
These have one cylinder machined integral with the main block and one detachable cylinder. The cylinders still have the central pin, but have the conventional type of seal which sits in a groove in the cylinder. Hence much less prone to seizure. The pads are about the same size as the MK2 ones but have a thicker backing plate with a clip to fasten to the cylinder and a hole for a split pin.
I wonder if they would fit the Mk2 ? I think the bolting centres are the same
Yes , they will fit the MK2, front no problem, but the rear acting on a 1/2” disc means the pivot holes for the handbrake levers are not placed ideally.
This can be rectified on the 420 / XJ rear caliper by machining off 1/8” from one half of the caliper and fitting MK2 brass retraction levers.
Peter B
OK, but you haven’t changed anything, the fronts are still 2.125in.
To maintain your brake balance you would need to fit a cylinder of 2.38in. or greater,
C`mon Norman, Phil has series2 EType calipers up front , same as series 1 XJ,
so the system is as late S Type or 420 with single circuit hydraulics.
Peter B
S1 XJ and 420 had 2.25in front caliper pistons together with a much smaller dia. rear disc in the IRS, so the balance was much closer to the original MK2
Almost forgot, they were also heavier on the rear than a MK2.
S Type with driver only, MK2 with 4 adults up, possibly + luggage, same calipers F/R both models, MK2 with less efficient servo, but with the all important extra 1/2” approx diameter at the periphery of the rear disc?
Does one of the models have a significant brake imbalance?
Peter B
The only problem with that senario is, that more than 90% of the time, you will have a driver only onboard.
And the servo efficiency has no effect on brake balance.
The real test is a panic stop with driver only, if the rear brakes lock first, you have a problem.