MK2 Brakes , what way to go?

I like to do something to the MK2 over the winter , as most of the time it’s off the wet roads ,
I keep thinking about the brakes , will changing them be much of a improvement ?

I have quite a few ways to go

1 , volve 4 pots
2 I have some 420 uprights , so could go Jaguar 3 pots
3 , COOPERCRAFT 4 pot’s , Alloy or cast Iron ?

I am quite happy with the brakes now , but better would be a improvement !

What are your thoughts :thinking:

I put the standard Wilwood calipers and s/s lines onto my stock front rotors, with the stock rear brakes. Did nothing special other than install and bleed the lines. The car now stops HARD and confidently in a straight line. I’m honestly very impressed by the difference. The downside is I feel much more confident driving in a spirited fashion, as a trust the brakes so much!

Well sorted, the original Dunlops are adequate, the 420 3pots are a little bit easier to dose.

But the key is to have everything working properly.

If you upgrade the stopping power at the front you should do something at the rear. One solution is to swap to larger Dunlop cylinders at the rear.

Having the 420 uprights I would go that route, some 420 / series one XJ calipers
should be available. Change the back calipers also to 420 / XJ.
If you can source one, change to the S type servo…
Peter B .

Don’t forget drilled and slotted discs for the front/ As far as I know they are not available for the rear. I can stop on a dime, Euro, etc.! Heat dissipation is important

i am going the exact route peter has suggested

also going that way with an early mk2 but have no experience or details. do you know if i can get away with using original master cylinder and servo? is there a thread or write up you would recommend ? also have volvo 4 pot stuff unused but not as good all round i think? not expecting more than hard slow road use.phil and peter you probably are exposed to better variety than i .

I thought 4 pistons all the same size would be more affective then 1 big one and 2 smaller ones , not sure why Jaguar did that .
At the same time Girling had the 4 pot , as used on the Volvo’s !

They used one big one and 2 smaller ones because 4 big ones wouldn’t fit within the radius of the wheel. As least I think that’s the reason!

Ian have you calculated the pad area and total piston area of the Volvo 4 pots v Girling
3 pots?. As to cost, it must be less to go the Girling 420 route than other make
calipers.
Although more involved, have you given thought to fitting the complete 420 dual
circuit system?
Slightly off topic. I take it that you might fit the variomatic power steering . The downside
re MK11 is using the dynamo/pump combo. I have carried out a conversion by moving
the servo to the left side inner wing, then using the 420 engine mount, power steering
pump crank damper and water pump although you could then use a large impellor
XJ pump as your engine has the correct timing cover. this setup then enables a alternator to be fitted.
Peter B

This brings up an interesting hypothetical question. Can Series I XJ uprights be fitted to a S Type? Might make my steering rack conversion work better.

Lot’s of diffrent ideas on what way to go , that is good , still have lot’s of time to decide !
Girling makes the Volvo 4 pot and the Jaguar 3 pot .
4 pot must be better as all the later Jaguars XJ6 XJS have them ?
Only way we would realy know is to have MK2’s with diffrent brakes at a rolling road to test them , on the same day .

Hello John, XJ uprights are approx 5/8"- 3/4" shorter than MK11 / S type / /420 uprights,
therfore if the bottom wishbone position remains as per ,the top wishbone is obviously
angled downwards. this results in positive camber upon suspension compression.
I have considerd repositioning the top wishbone mount downward, this just to
utilise readily available XJ vented discs/ calipers. But all in all it is probably less trouble
to obtain specialised discs etc to fit the MK11 upright.
Nonwithstanding the above, I do not see how fitting XJ uprights will help to improve
your rack conversion, for the steering arm position remains the same…
With a rack conversion attention to bump steer is required I check this by removing
the suspension spring /, loosening the wishbone nuts so the wishbones can move freely, then, clamping a straight edge to the wheel hub observe the amount of defllection ( if any ) while you articulate the suspension. If deflection is observed removing the lower
steering arm / caliper bolt and loosening the stub axle nut so the steering arm can
be repositioned might effect a change for the good… When I am satisfied with the
optimum position re steering arm / track rod end, my method for the fixed position i leave to your imagination !
Peter B

Peter, Thanks for your reply. I have spent many, many hours trying to understand this issue that comes about when converting a 3.8S (or a Mark II for that matter) to a steering rack. The issue is that the design of the suspension/uprights (called a sub axle carrier in the WSM)/ and steering arm (called a tie rod lever in the WSM) is somehow not fully compatible with the retrofit of a steering rack. I do not suffer any what you call bump steer, but the Ackermann effect is lost which results in tire scrubbing on tight turns giving early inner tire wear and a reduced turning circle. I do not see how the tie rod lever can be re positioned in any way as it is solidly located by two nuts, one for the stub axle and one other one. (both of which are safety wired). If these levers are the same length and in the same position on a S Type and an XJ there is no advantage for a change in the stub axle carrier. There is something else different between the S suspension and the XJ suspension. I would love to learn what that is and why it makes a rack work properly on an XJ and not so much on an S Type.
John F. Quilter
Eugene, Oregon USA

One difference between the MK11/‘S’ and XJ is the upper wishbone mounting can be reversed on the former which drops the pivot point down, effectively pulling the top of the wheel into a negative camber situation I believe.

Yes, and flipping them lowers the upper fulcrum by something like 3/4".

Just fitted Zeus 4 pot vented discs to my MK11 and zeus rear callipers, seem to work well

Five years ago I replaced the servo with an ‘uprated’ version from SNG Barratt which is claimed to produce 30% more power. I’m very happy with it mated to the factory Dunlop calipers.

  • 1 for that. I did the same a couple of years back, now the limit is the tyres not the brakes!