MKX Front Brake Upgrade

Hello all, I have a 1963 MKX that I have adapted a XJ6 brake booster, master cylinder assembly and pedal but I can not get the brakes to stop to my satisfaction. The pads are new front and back. I was told that the front caliper mounting holes are the same on the 1963 MKX and the Series 1 E Type. If this is true then any upgraded brake caliper and rotor kit for a series 1 should bolt up to the MKX uprights. I measure 3 inches from center of bolt hole to center on my MKX caliper. Does anyone know dor sure if the bolt holes measure the same on the MKX and the Series 1?

Have the pads bedded in sufficiently as you say they are new?

I have been driving the car for several months, I can not get the tires to ever lock up and have significant brake fade if I push the brakes too far.

Is there much difference with the vacuum removed? And brake fade? That can be associated with contaminated brake fluid (water) due to high temperatures indicating that the brakes are working hard.

Brand new fluid, been bled several times, brand new booster and master cylinder for a 1986 XJ6.

Under 40 miles an hour the car seems to brake fine, the issue is a panic stop from 70 mph that im concerned about.

It appears the series 1 e type caliper mounting holes are the same 3 inch as mkx, so the calipers might interchange. Dont know if the 14 inch rims will clear.

I cant directly answer your question, however,

The front brake pads on the 3.8MKX have a smaller surface area than 4.2 MKX and 420G

One fix is to try and find calipers from the later cars

My 420G brakes very well

DO NOT EVER attempt to swap in XJ uprights, steering arms and calipers, it utterly ruins the steering

If the 420G brakes are bigger, then I wonder if I can exchange the uprights from a 420G?

dont need to…same part num

420G has 1/2" front discs, earlier cars had 3/8"

I got new discs and pistons from David Manners UK a couple of years ago

420G calipers are a rare & expensive item though

cant remember the name of them but those fancy aftermarket 4pots will fit I am pretty sure

just make sure your rears are working, mine were siezed

I am not 100% sure on whether there was a caliper/pad change from 4.2MKX to 420G, pretty sure there was and 4.2MKX also have the 3/8" front discs

will check my parts manuals later if i have time

This is what I had in mind since it appears the etype caliper mount holes are the same, this kit should work on the MKX. The only issue will be clearance on the stock 14 inch wheels.

I believe, but have no proof that kit will fit on the vehicle

As to wheel clearance on the 14" wheels, I think the only way is to write to the suppliers and ask whether they know, or have sold any for that application.

I have 15" XJ wheels on my 420G, and I think that they may actually be ever so slightly inboard to the original 14" wheel & tyre combo

be absolutely certain the rears are working before bothering with fronts
have they been out & apart in the last 10yrs ?

front caliper clearance is very tight on my car, its an issue

The rears are working. I can bleed them and have plenty of pressure when an assistant is pressing the pedal. I can also feel the heat on the calipers after a short run on the road. I had them out this year when I removed the differential and installed a XJ6 rear end because of the gearing.

I cant recall whether anyone has fitted Willwoods to a MKX from this list but I would search the archives, and perhaps PM @peder

He has a few well sorted vehicles, and may have done this

I went under car and the clearance between the stock caliper and 14 inch wheel is minimal, so I cant see installing bigger brake components and keeping the stock wheels.

Maybe worth trying a diffrent compound pad , ask on the racing forum !

ok, checked my parts manuals, here is the situation

  • 3.8 has a 3/8" disc

  • early 4.2 has a 3/8" disc, but disc, caliper, brake pad different to 3.8

  • late MKX-420G has 1/2" disc, different caliper, even bigger pads

So clearly Jaguar recognised and upgraded the front brakes
I believe there may be a MKX or 420G front end on USA Ebay atm

A complete front end upgrade to the later steering and brakes would be my aim if I had an early model

My 420G brakes very well, I can easily lock up the brakes, and they are very progressive
These cars will never brake as well as an XJ, as they lack the anti-dive front suspension

Thank you for your response.

The calipers on the MK X suit 1/2" discs while the E caliper is only for 3/8" discs.
Early MK X’s (1st 1500) were fitted with the same size cylinder as the S1 E, but later ones were upgraded to 2.25" cylinders. The cylinders are interchangeable, it was an upgrade I used to do to the S1 E back in the 60’s.
I woud assume that your 63 MK X would be fitted with the 2.25" cylinders unless some one was naughty and swapped them with the 2.125" E ones.

This isnt totally the case, its very confusing actually

3.8 MKX have 3/8" discs

most 4.2 MKX have 3/8"

late 4.2 MKX and 420G have 1/2"

this is outlined in the Parts Manual, at what Chassis number this took place

I got slightly caught when I bought a wreck '66 MKX for $300, turns out the brake discs were 3/8", and XJ calipers and discs had also been fitted, (which badly affects steering)

Most of the replaced parts were in the boot

I would reiterate that the latest incarnation has the larger brake pad area, as well as 1/2" discs, and is quite adequate for spirited braking, imo, if you want to drive harder than that, you probably ought do it in a more suitable vehicle