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Converting a Jaguar MK1 to wire wheels
Converting a MK1 to wire wheels

Putting new wheels on a car- sounds simple right? Well, this is the story of what it took- and why it wasn't as simple as you might guess.

Proper wire wheels for an old Jaguar do not bolt on to the hub like wheels on a modern car; there are no lug-nuts. Rather, in the center of the wheel, there is a large spline. The wheel slides onto a matching splined hub, and the wheel is held in place with a large spinner. This kind of wheel is commonly referred to as a "knock-off" or "center-lock" wheel.

So at first glance, it is obvious that converting to these wire wheels requires (including a spare tire):

  • 4 (splined) hubs
  • 5 wheels
  • 4 spinners (also called "knock-offs")
  • Don't forget tubes (air will leak out around the spoke holes, and so you must either use tubes, or in some cases, it is possible to seal the inside of the wheel with silicone), a copper/lead hammer for installing the knock-offs, and anti-sieze, and wire wheel cleaner, etc...

    That was at first glance. Now things start to get complicated. You cannot buy splined front hubs for a Jaguar MK1. It was an option on these cars, seen most often on the 3.4L special equipment models. Splined hubs do wear out over the years, and therefore used ones (the last MK1's built were in 1959) in serviceable condition are extremely rare, and can fetch upwards of $1000 if you're lucky enough to find them.

    The solution is to use available hubs from a different car. The most obvious choice being the closely related Jaguar MK2. These hubs are very close to the original MK1 hubs, differing mostly in the internal bearing setup. What this (different bearings) means is that a different stub-axle must be fitted to the car. Unfortunately, the MK2 stub-axle does not fit the MK1 upright, and so the upright must also be replaced. Which means new ball joints must be fitted... and so on, and so on.

    In my case, I found the needed suspension parts from a Jaguar 420; totalled when the wheels fell off the car because the front hubs were installed on the wrong side and the spinners unwound themselves. When I bought the parts, I thought they were the same as the MK2 parts; later learning of a few differences I'll elaborate on later. I replaced: parts

  • Upper A-arm assemblies (420)
  • Lower A-arms (420)
  • All A-arm bushings (new)
  • Upper (new MK2) and lower (new XJ40) ball joints
  • Uprights (420)
  • Stub-axles(420)
  • Steering arms (420)
  • Sway-bar links (420)
  • My car already had the anti-sway-bar from a 3.8S installed to clear the oil sump on the 4.2L motor.

    About those differences between the 420 and MK2 uprights: the first one I discovered when I went to bolt my brakes on. The mounting points were different and my brakes did not fit. The 420 uses the larger 3-piston Girling brakes, the MK2 uses the same Dunlop brakes as the late MK1's (like mine). If doing this conversion, either upright choice offers advantages:

  • The MK2 upright allows you to use your existing brakes- which means you can also use your existing brake rotors. If you have all this stuff to use, this is definitely the cheaper solution. It also retains a more stock suspension geometry (more follows).
  • The 420 upright uses the larger (better) brakes. It is the desired choice for racing or performance driving. Using these uprights requires using (buying) the larger brakes which in turn require new rotors too.
  • Fortunately, when I bought all my suspension parts, the brakes and rotors came with them. I had to rebuild the calipers, replacing half of the pistons, but the rotors appeared to be serviceable- so aside from the cost of a few caliper parts (these brakes are the same as early 3-pistion XJ6 calipers) this wasn't much of a problem.

    Of course, with much larger front brakes, my braking system was now totally imbalanced. I could either try to use a proportioning valve to send more pressure to the rear brakes (actually, less to the front); or upgrade my rear brakes. Fortunately, there is a cheap and easy upgrade: the stock balance is obtained by fitting larger pistons onto the front calipers than on the rear. The pistons are interchangeable, and the large front pistons can be taken from the recently removed front calipers and fitted to the rear. This is a trick passed to me from some MK2 racers, and initially seems to be working well. A proportioning valve may still end up being required, but any necessary adjustment should now be much smaller.

    About that suspension geometry I alluded to: there's one more difference between MK2 and 420 uprights: one I discovered when I put my car back down on it's wheels for the first time, and the fender lips came down onto the tires. The distance between the lower ball joint and stub-axle is longer on the 420 pieces. Once mounted, the position of the stub-axle is a constant, determined only by the wheel diameter- what increasing this distance does is lower the lower ball joint, which effectively lowers the entire car. What this means is that new front springs are also required.

    The springs which fit are the S-type/420 springs. Initially, this is what I went with, only to discover that my new springs weren't properly tempered; causing my car to gradually sag. I'd shim it up (no small job) only to have it sag again. I returned these springs, but having them for a while also convinced me that I wanted a stiffer spring (the S-types and 420's were given a more luxurious ride than I wanted). The solution was to pull coil springs from a MK-X. These springs have a slightly longer free length than any of the MK1, MK2, S-type, or 420 springs and are made of very stout steel. They, of course, needed to be custom cut to retain the original ride height for my car- which stiffened them even further. However, because of the long spring length needed (because of the 420 uprights) they still weren't as stiff as they are when installed into racing MK-2's with stock uprights. It's a very liveable, yet sporty ride; one I'm very happy with.

    All this for shiny wheels.


     

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