rear end and brake work
 

Hi all, I have finally given in and gently torn the rear end out of the 66. I have gotten as far as removing the brake calipers. All seems well enough so far, but I have a point to ponder. I had initially been planning on starting this project with going through the front end first but as I mentioned in the "thread about nothing", I had 73rd thoughts and finally firmly changed my mind. My car has the Dunlop system. I had earlier gotten 2 sets of the brake piston seal kits from xks. Part #sp2775 which I see now is in fact for the rears. The seals for the fronts are listed as #sp2776, but are not available as a kit, rather individual cylinder sets. Are these the same parts in both the kits? (I would call them but its Saturday night and I don't wish to be on hold that long.) More to the point- are the brake pistons all the same diameter on this car? I have not dissected the front yet and would like to leave it together till I get to that area. Ultimately I would like to use the parts that I got and am only trying to get the right parts together. Thank you for your consideration in this matter.

Also wondering if the powr lok takes any special additive.....

The rear brake pots are smaller than the fronts so the parts def won't fit the front,

The fronts should be 2 1/8" and the rears are 1 1/2"

Thanks. All I needed to know

Jerry, while you may have seal kits, do be aware that these fit on the piston and rely on a good cylinder bore surface. These brakes are an early design of the late 50s and later systems were totally different, putting the seal on the cylinder and chrome plating the piston to give a long lived surface for the seal to bear against. This later system also eliminated the piston withdrawal mechanism.

SO depending on the degree of corrosion, you will likely have to hone the cylinder surface to get a good seal. There was, at one time, a few firms that bored out badly corroded cylinders and inserted stainless steel liners. This restored the wheel cylinders, but was costly. Now one can buy complete new wheel cylinders at not too high a price, and even ones cast in stainless steel for a lot more !

Fraser, what's the piston withdrawal mechanism ?

Thanks Fraser. I do plan to hone and polish my little heart out... but not too much. The fluid that I drained was awful and I have no doubt that they desperately need it. I haven't ruled out sending them off to be professionally done if I cant make nicey nice of them. If I do, I am leaning toward either White Post or Apple hydraulics.
I plan to use this car on a very limited basis. That is as a show goer and Sunday driver. As such I am wondering about the wisdom or ease of disabling the retractors if they are not repairable.
Today I removed the axles and rotors. I had been soaking those bolts holding them in "P Blaster" repeatedly for about a week while I disassembled my way to them. Even so I had the misfortune of snapping 2 of them off. It appears that I am now faced with removing the stub axles with their mount plates to replace them all. I had hoped to not have to open the case for more than a rinse of the old gear oil. I have not dug into a differential before and have not opened this one yet. If I simply remove, clean, and replace, is there anything else I Need to do? And does this powr lok require any special lube? Thanks again for comments.

Hi, I'm having a complete brake restoration done on 62 MK2 and was told by the time you spend messing around with the rear calipers it's probably cheaper to buy the new replacement halfs they sell. And there supposed to be an improvement over the old ones. The cost was aprx. 700 usd for the rear parts expensive but for me it's also a piece of mind knowing I've got brakes I can rely on.

Thanks Lou, I do partially agree with the "just get good ones " theory, especially for the price. However I have never delved into such an oddball beast as this. My experience is mostly limited to early 60's mopars, k-cars and buicks. I want to take the opportunity to try it, and as I said if I can't make it to where I think it's safe I will go the direction of professional repair.
That all said, I got the right stub axle and its housing off last night and found that the snapped bolts can be replaced without further disassembly. I also took the diff cover off mostly just for the view. I am happy to report no other obvious problems. Parts are on order and reassembly will proceed in a few days...

I'm back. Life happened and the project got set aside. In the last few days I have replaced the inner u-joints on the half shafts and re-installed them and new brake discs to the diff. (I didn't feel any movement in the outers and don't wish to delve into the wheel bearings at This time.) This afternoon I took a few minutes to try removing the pistons from the calipers and found absolutely no movement available by simple prying. As such I will go the send-them-out route rather than chance bending or breaking them. I was planning on using either White Post or Apple hydraulics. Since I have to ship them, I don't guess it matters Too much where within the continental US. Any Comments for -or more usefully Against- either of these 2? Any other recommendations of other businesses? Thanks for comments....

Hey all, I sent them to White Post and was amazed at the turn around time of 4 (count 'em 4) days including shipping. They look Spanking new and I am now working on installing them. I find though that they are needing shims to center them. There were not any shims on either side when I took them off. I was very careful to not lose any parts OR pieces while disassembling so that I would not Have to remember quite so clearly. I don't think they were taken apart previously at Any point due to the presence of all of the aircraft wires on the bolt heads. In any case, the calipers are not centering now. My question, then, is this- Since the rear pistons are all of the same diameter will they not all push equally as hard Once they are set up and bled? or, on reflection if I put the alignment shims on the wrong sides (outboard) of the rotors, thereby causing the calipers to Appear to need centering when instead I really need to back up and move the alignment shims to the inboard of the brake rotors.... Thoughts? Chastisements?

They will push equally, but the pad closer will be pushing harder before the other pad as it is trying to distort the disc until the opposite pad applies the same pressure, so you will be introducing uneven wear in the pads before you start.

Once the closest pad wears down to a point where both pads are "centered" then all is good, but you will wear out that pad before the other. It's not critical, but get them centered as well as you can.

Ok, that sounds reasonable. I'll have to see if I can find a local who has shins that will work. Thanks

I don't think you get uneven wear because when you apply the brakes for the first time, each piston moves out until the pad contacts the disc. Then, when you back-off the brake, the piston withdrawal mechanism inside each cylinder withdraws the pad by the same amount. So next time onto the brake the pistons move the same distance.

I think the shims are used to make sure there is no possibility of the disc rubbing on the caliper slot. I remember using them on my Mark 2 in the 80s, in fact they just went back in. The workshop manual as I remember had instructions on measuring the gap either side of the disc at each end of the slot in the caliper. Machining standards were different then, and Jaguar were always very cautious about these things. The main reason, I think, was to ensure the disc was not at an angle to the pad surface, it had to be parallel.

True, but the shims are only like 10 thou, and don't change the angle relative to the disc, I wasn't clear re the wear, this will only be to a point where the pads become centralized, so we are only talking 20 thou ish, once the closer pad has worn they will be central and even wear continues.

The manual says to set the calipers to within 10 thou of center, they must have a reason for this, and the tolerance either side of the caliper body is way more than 20 thou, so it can't be just to avoid rubbing the caliper.

This is of course my opinion, and I am happy to be corrected, but I can't think of any other logical reason, but open to other opinions.

I always thought the shims were there to simply centre the caliper housing to the disc.
If it wasn't centred, then you wouldn't be able to get the "one" pad out once the pads were all the way to the rotor.

This became quite obvious when I rebuilt my brakes.

Thanks guys. All of your points have been wandering loose in my mind for some time. I do need to do some centering as I can't get one pad IN. Once I get time I will make some shims of a piece of sheet metal I have which I have measured at 12 thou. I may use one, or I may use 2 under each bolt depending o. How I feel ....

You can get the shims from SNG part no's C13198 and C13199 if that's of any help

Yes. I checked there. Honestly I should just order some up since I have become quite slow in my efforts of repair. It would probably hurt a lot less too, than trying to make washers out of sheet metal. They have a minimum order amount so I'll have to "dream up" something else this - or the other cars want too. Shouldn't. be a problem

Might be a lot less hassle, and there is always something else you simply MUST have !