Jaguar XJ-S. Manual - part 103

 
 

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With the hub on the bench, the way to do that staking would be to screw nuts onto all five studs and set it down on a 
hard surface.  Unscrew the nut on the stud getting smacked a little bit to make sure it’s firmly against the surface, not 
held aloft by the other four nuts.  That way, the force of a smack will be transmitted straight from the stud to the nut and 
to the deck, rather than stressing the threads in the hub.  The original arrangement uses a cute X staking, like a chisel 
whacked once and then turned 90° and whacked again, but really you can use a  punch stake if you just make a little 
circle of punches on the end of the stud. 

There is one plausible scheme to use non-OEM studs here.  Buy generic studs that have a very long 1/2”-20 end and cut 
them to the overall length you need.  Then cut a shallow rounded-bottom groove 1/2” from one end, making sure not to 
cut beyond the base of the threads; the threads don’t really contribute to the strength of the stud, but you don’t want to 
neck down the solid core of the stud any.  Fashion a bit of 1/8” wire into a loop that will just fit inside the recess on the 
hub.  Cut this loop in half.  Screw in your stud (with studlock on the threads) and hold the two halves of this wire ring 
into the groove as it pulls into the recess in the hub.  This will work sorta like the collets on a valve keeper and trap it all 
together in the recess.  You can stake it if you have the hub off.  This all works, but really it’s usually easier just to buy 
the OEM studs. 

There are those who don’t care for the threaded-and-staked attachment scheme at all; there’s not much thread holding 
the wheel to the car.  If you need to replace the rear studs, consider drilling out the threads and boring the holes to a 
suitable diameter to fit pull-in studs like on the front.  You will then need to carefully trim the heads so they don’t 
interfere with the shield on the back side.  Even better idea: rather than bore out the threaded holes, drill entirely new 
holes in between them, leaving the original threaded holes in case you ever want to return to the original configuration. 

If the pull-in type of studs get loose in their press fit, the result is usually an obnoxious ticking when rolling slowly.  
This isn’t normally a problem with the XJ with alloy wheels since the lug nuts should be installed with a torque wrench. 
 A gorilla in a tire shop using an impact wrench can screw them up, though.  You can tell which ones are screwed up 
because you can usually wiggle them a bit with your finger.  The only solution that seems to work is to replace the 
studs. 

Race cars often have the heads of the studs welded to the hub so they won’t get pushed out during a fast tire change in a 
pit stop.  It’s not recommended for street cars, though; welds can cause localized stresses and cracks in the hub, and 
may also cause some distortion. 

 

LONGER WHEEL STUDS:  The OEM studs are kinda short; the fronts protrude about 1” from the wheel mount 
surface.  Whether or not you’d like longer wheel studs may depend on the type wheels and lug nuts you’re using.  If 
your lug nuts show, you probably have acorn or dome nuts and they may bottom out on longer studs before tightening 
onto the wheel.  You might still be able to use longer studs, but you’ll need to be careful and measure the depth of the 
lug nuts you’ll be using with them. 

On the other hand, the author’s car has a hubcap covering everything and would definitely be better off with longer 
studs.  The “Majestik” wheels (from a ’90 Vanden Plas) come with black nuts threaded clean through, but when tight 
the end of the stud is still way down inside the nut!  It’s better to use longer studs so they protrude through the nuts so 
you’re using all the threads in the nuts. 

For the front, you can find an auto parts shop that has a red-and-black metal cabinet of Dorman fasteners and look for 
stud #258.  As described above, it will work OK as is or it will fit perfectly if you grind a taper under the head.  When 
installed, these studs will protrude about 1-5/16” or about 5/16” longer than the originals. 

For the rear, Chuck Sparks points out that XJ40 rear wheel studs are exactly the same as XJ-S rear wheel studs except 
they are 1/4” longer.  The part number is CAC 3878. 

Of course, there are Chevy and Ford wheel studs in obnoxious lengths like 3”, apparently for racing applications.  
These can be installed using the same methods described above, and then you can cut them down to whatever length 
you desire. 

 

 
 

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WHEEL BALANCING:  Incompetence is rampant in the retail tire industry, at least here in Florida.  Left to their own 
devices, most of the meatheads in a tire store will happily mount your Jaguar alloy wheels on a balance machine 
incorrectly, give them a static balance only, then beat the weights onto the rim with a BFH. 

The first challenge is getting the wheels mounted on the balance machine correctly.  When you mount the wheel on a 
machine that spins it to check the balance, it must be mounted centered properly -- meaning centered the same way it is 
centered on the car.  On the XJ-S (and on just about any other car), correctly-fitting wheels will be centered by the back 
side of the center hole fitting closely around a machined diameter on the hub.  If the wheel is a style in which the center 
hole is a couple of inches deep and has a motif cap clipped into the outer opening, note that the inner half inch or so of 
the center hole of the wheel has probably been carefully machined, while the rest of it may not have been machined as 
carefully or even machined at all.  In the worst case, the two portions of the same hole might not even be concentric, 
although one would hope that they are very close.  The point is, the wheel needs to be held centered on the inside 
portion of the center hole -- not the outside portion, nor any other part of the wheel.  The inside portion of the center 
hole is how the hub on the car holds the wheel centered, so it must be the basis for the balance machine to hold it 
centered as well.  As you watch the balance machine operator pick through the selection of adapters he has to mount 
your wheels on his machine, you will understand why it is important to keep an eye on what he’s doing and raise 
objections if he’s doing it wrong. 

There are two basic types of imbalance.  The old-fashioned bubble balancing, which engineers refer to as static 
balancing, only corrects one type of imbalance -- the type that causes the wheels to hop.  This is generally adequate 
only for wheels that are very narrow, and should be considered unsatisfactory for any modern automobile. 

The other type of imbalance, dynamic imbalance, is the type that causes wobble.  A wheel that is statically balanced 
may still be dynamically imbalanced by having a heavy area on the outside edge of the wheel and an equivalent heavy 
area 180 degrees away on the inside edge.  Although the wheel would appear balanced on a bubble machine, when 
spinning the two diagonally opposite heavy areas cause the wheel to wobble.  It’s usually not too noticeable on the rear 
wheels, but on the front wheels it can cause steering wheel shudder.  And you may eventually wanna rotate the rear 
wheels to the front, so it’s kinda nice to have them all correct. 

To correct a dynamic imbalance requires that weights be placed in two separate planes -- usually (but not necessarily) 
the inside and outside edges of a wheel.  It requires more lead than static balancing.  It also requires a machine that 
actually spins the wheel; the bubble balancer is out.  Use of these machines has come to be called “computer 
balancing”.  However, note that a switch on the machine allows the operator to specify a static balance only, so asking 
for “computer balancing” does not guarantee a proper dynamic balance. 

The meatheads generally understand that the owner of alloy wheels is not thrilled about balance weights on the visible 
outside surface of the wheel.  They will often ask: “Do you want the balance weights hidden inside the wheel?” and 
when you answer “Yes” their response is to set the balance machine on “static” and apply all the balance weights to the 
inside rim of the wheel.  This actually makes the dynamic imbalance worse, since even in the days of the bubble 
balancer the operator knew to put half the weight on the inside edge and half on the outside. 

Insist on watching what is going on.  The machines normally operate in “dynamic” mode, and there are two displays 
showing the amount of weight that needs to be added to each side of the wheel.  There is also a button or switch marked 
“static”, and when selected the machine will read imbalance values on one display and the other display will go blank.  
If you see this happen, you need to politely interrupt the balance operator and instruct him to put it back in dynamic 
mode. 

At this point, there will probably ensue a discussion with the balance operator.  He will often insist that you have two 
choices: either you want a static balance, or you have to put up with weights that show -- but he is wrong, you are not 
limited to those choices.  If this discussion deteriorates into an argument, you may have to take your business elsewhere 
until you find a balance operator willing to work with you to get the balance right. 

Eventually, it will probably be necessary to show a balance operator how to do his job.  Set in dynamic balance mode, 
the machine will specify the amount of weight to be applied to each side of the wheel, but you’re not going to be 
applying any on the outside surface.  Instead, select a piece of “stick-on” balance weight of the size specified by the 
machine for the outside edge, but install it on the ID of the rim as far outward as possible, right up against the inward 

 
 

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side of the center structure.  Then install the weights on the inside edge using either clip-on or stick-on weights, 
whichever you prefer. 

If you have a 5-spoke wheel or some such, you can take this idea one step farther and hide the stick-on weights behind 
the spokes -- even if the machine tells you to put them between spokes where they show.  Simply split the balance 
weight into two portions, and put portions behind the spokes on either side of the correct location. 

Usually, after spinning the tire once more, the machine will indicate that the wheel is balanced.  However, in theory 
both installing the outer weights a couple of inches inwards and splitting a weight into two pieces and spreading it 
actually require slightly more weight to be used.  You can either anticipate this and use a slightly larger weight than the 
machine calls for to begin with, or you can wait and see if the machine tells you you didn’t install enough.  Either way, 
always insist that the balance machine indicates zeroes (0.00 or “Ready” or whatever) on both indicators before the 
wheel is taken off the machine and installed on the car.  At this point, the balance operator will probably be astounded; 
he has never seen an alloy wheel get a workable dynamic balance without the weights showing, and is wondering why 
nobody showed him how to do it before. 

There are newer balance machines that actually have both of the procedures described above built into the machinery.  
They can properly balance the tires by applying weights in any two planes, not necessarily the outer edges; the desired 
location for the weights is a separate setting in the balance procedure.  They also can “split” a balance weight callout 
into two smaller weights, telling the operator where to put them both.  But if you understand what’s going on, you don’t 
need to find this fancy machine; the more basic dynamic balance machine will do the job. 

Finally, if you are less than impressed with the competence of the shop balancing your wheels or of the condition or 
calibration of their balance machine, you can ask to have one of your just-balanced wheels put back on the machine and 
spun up again.  Balanced is balanced, folks: if they’ve done it right, it should come up all zeroes again, even if mounted 
rotated to a different position on the machine or even mounted on a different balance machine altogether.  If it comes up 
calling for weights, either their centering procedure for installing the wheel on the machine is NFG, or their balance 
machine is out of calibration, or something else -- but you don’t really care what, you only know that you are not 
getting a viable balance job here, you might as well head on to another shop. 

 

BALANCE WEIGHTS -- STICK-ON VS. CLIP-ON:  Steel wheels commonly use “clip-on” weights that are 
hammered onto the rim.  Some alloy wheels are designed with a rim that can accommodate clip-on weights, but they 
may not attach as well to the thicker aluminum.  And use of a hammer to install is not good for aluminum, especially if 
the meathead responds to difficulty with a bigger swing. 

When the steering on an XJ-S is turned full lock, the clearance between the inside edge of the wheel rim and the front 
anti-roll bar is very small.  If wider-than-original wheels are used, clip-on balance weights may actually hit the bar, 
resulting in a blip-blip-blip as you roll around a tight turn.  And, of course, the balance weights may actually get ripped 
off. 

The proper balance weights to use on alloy wheels are called “stick-on”, and are attached to the inner surface of the 
wheel with a layer of foam tape attached to the back side of the lead weight.  One problem is that they are not reusable; 
once peeled off, the tape is not reusable, and the shops customarily throw them away.  I guess using generic foam tape 
has not occurred to them, or just isn’t worth it, even though they often complain loudly that these weights are expensive 
and charge the customer accordingly. 

The problem is exacerbated by the meathead not knowing how to use the machine properly and having to do a by-
guess-or-by-gosh balance job.  With the clip-on weights, he can just keep prying them off and reinstalling them until he 
gets it right, but he can waste a lot of stick-on weights.  An intelligent operator, of course, will be able to set the 
machine up properly and get the correct weight applied the first try. 

Owners of alloy wheels should always insist on dynamic balancing using stick-on weights in two planes within the 
wheel -- one near the inner edge, and one just inside of the outer face of the wheel.  Since these planes are closer 
together than the edges of the wheel, more lead will be required to correct imbalances.  But the weights won’t show, 
and nobody will need to use a hammer to install them.  Always insist that the balance machine shows zeroes on both 
indicators before the balance is accepted. 

 
 

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The only real problem with stick-on weights is a reputation for getting lost.  Since clumps of mud and other debris 
sometimes gets dragged around the inside of the wheel and jammed between the wheel and the brake caliper, the foam 
tape can be ripped away.  Two suggestions are in order, and neither is likely to be done by the tire shop, so the owner 
should bring the materials necessary and do them himself while the wheels are off:  First, mark the locations of the 
stick-on weights with a permanent marker.  Then, secure them with a piece of aluminum tape (available at air 
conditioning shops).  Don’t use duct tape; it quickly dries up and falls off, often taking the balance weight with it.  The 
aluminum tape appears to be light enough to not affect the balance when added; or, to be safe, you could simply add a 
dummy piece of tape on the opposite side of the wheel. 

 

WHEEL MOTIFS:  If you wish to replace the growler motif on an 80’s XJ-S wheel, you’ll find that the puddy tat itself 
and the retainer holding it are two separate parts.  The puddy tat is C42191 or CAC6502 or CBC2660, and the retainer 
is CAC5073.  However, in the late 80’s Jaguar switched to a single-piece item, CCC6347.  The one-piece motifs also fit 
the earlier wheels, but may not match the two-piece motifs well; you’d probably be well-advised to get a set of four. 

Also note that Jaguar apparently had some really bad quality control problems with the one-piece motifs around 1990; 
some of them look really bad, with the puddy tat face distorted as though it has melted, and some of the motifs even fall 
apart and lose pieces on the highway.  Within a couple of years after that, the motifs started looking a lot better, with a 
clearly-defined and attractive puddy tat face. 

The one-piece motifs are available in five different colors; if you need to buy a couple anyway, you might consider 
finding a color you like. 

 

TICK, TICK, TICK:  Chip Lamb had an irritating tick from one of his wheels.  He was all set to tear into bearings 
when Roger Homer pointed out that it may just be the Jaguar logo in the center of a wheel cover coming loose.  “Pulled 
both hubcaps  - it was the kitty on the right rear.  Quick fix with duct tape and some black RTV!” 

 

TIRES:  If you want to maintain the originality of the tires on your car, you’d better take them off now and store them 
in the attic!  Tire manufacturers change their models regularly and discontinue the older designs.  The XJ-S has been 
out of production long enough that it’s unlikely you’ll be able to find an “original” new tire for any of them, even the 
mid-90’s models.  If you drive your XJ-S, you will have to find a modern tire to fit. 

Be very careful when mixing tire types, sizes or makes on a Jaguar.  The XJ-S and the XJ6 have a suspension design in 
which the entire suspension assemblies are attached to the car with flexible mounts, and the relative stiffness of the 
mounts is premised on all the tires being the same.  Mixing tire types, even outwardly similar ones, can result in 
dangerous instabilities in this suspension system.  This is no joke; having one type of perfectly good tire on one end and 
another type of perfectly good tire on the other can result in you being rudely introduced to a tree when you aren’t even 
travelling that fast.  If you must put different tires front and rear, take the car for a test drive and put it through its paces 
away from traffic and trees before accepting the arrangement as safe. 

The problems with mixing tire types, combined with the fact that tire manufacturers are constantly discontinuing tire 
models as they design newer and better tires, means that you will probably want to keep an eye on your wear rates and 
rotate tires as required to get them all to wear out simultaneously.  If you wear out the pair on one end first, you are not 
likely to find a replacement pair of the same model, so you will be well advised to replace all four tires with a new 
model -- and you’ll end up pitching two tires with good tread still left on them. 

When replacing tires as a set, you don’t have to stick with the brand of tire that came on the car.  In fact, it may be 
better to change brands according to Michael Neal, who works on Jaguars for a living:  “I’ve seen hundreds of the 
215/70 Pirelli P5s rip out at the sidewall near the bead.  These are the original equipment tires on the US-spec XJ6 
Series 3s and early XJ-S’s.  Sorry, but I would not even consider buying a set of these.  The 235/60 P600s had the same 
problem.”  Reportedly the still-later Pirelli P4000’s were better. 

If you have internet access, you can check for tire availability and prices online.  Peter Cohen suggests