XK 120 Taper Wedges (Between Rear Springs & Axle)

Question for the XK 120 experts:

I’m about to put the rear axle back in the '54 FHC (build date 3/54).
When I removed the axle I noticed that it had no spacers (“taper wedges”)
between the leaf springs and the axle. To be more descriptive, this is
the pad, spacer, wedge (whatever the official term) that you would place
on the top center of the leaf springs; they have a centering hole in the
middle into which a short round stub at the middle of the spring fits,
then the axle is fitted on top of that and the U-bolts are then installed
to hold the whole hoo-hah together.

I see that these parts are listed in most catalogs, and I don’t recall
any other 120’s not having them. My other Brit cars have had something
there, either rubber or a hard plastic-like material. Seems like easy
parts to skip if the axle was out before, especially since these can
deteriorate with age. Not the kind of thing repair shops worried about
back when these cars were just cheap old things to bomb around in.

BUT, is it possible, that some 120’s didn’t (and shouldn’t) have these? I
am inclined to add them on the assumption they ought to be there, but
then another voice is telling me “Well, if the car worked without them,
and you go install them now, isn’t that asking for trouble?”

Do these do much more than dampen some of the axle vibration to the
springs (and thus to the car)? It appears from the catalogs that these
are slightly wedge shaped (higher toward rear). Does that help counteract
the axle’s tendency to “wind up” the springs under acceleration? Seems
like the wedge would effect the angle of the driveshaft through the
universal joint at the front of the axle so maybe not having the wedges
has been a bad thing.

In a nutshell, to wedge or not to wedge? Thoughts? Just do it??


Dick Rowley
'54 XK120 FHC SE
'62 Mk II

Never saw one without the wedges, Dick. Just do it!

Larry Schear
Twin Cam, Inc.

Thanks Larry; that’s all the nudge I need. Wedgies it is. Unless anyone
has a definite finding or opinion otherwise it’s “case closed” in the
interest of keeping everyone’s e-mail load down. When done, if this
causes the car to run backwards I’ll be sure to report back to XK

Larry Schear wrote:>

Never saw one without the wedges, Dick. Just do it!

Larry Schear
Twin Cam, Inc.

Just don’t reverse yourself on this.–
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–GEO - W3AB - Soquel, CA. USA ------/-- http://www.mbari.org/~geo
_/ \ / \ / _/ \ / _/
_/ \ / _/

I hope I don’t ruffle any feathers by reviving a now 20 year old thread, but I’m now looking at the same scenario as the original poster, Dick Rowley, and feel compelled to add to this.

Mr. Rowley asks if it’s possible if some XK120’s have the rear axle wedge while others don’t. Subsequent posts don’t really seem to answer this. What isn’t mentioned is the Jaguar Service Manual which has a note, mid-page of H1.27, which states; “On early production XK 120 cars a wedge was fitted between the spring and axle spring pad. This wedge must be fitted so that the widest end is to the front.” This note is repeated again in the section concerning rear axle refit on the same page. In the post on this forum some say they’ve always seen it, and others not. I attribute this to being early cars were fitted with the wedge and later ones were not – as in the manual reference.

To further complicate things, Viart’s book, “XK120 Explored” states on p.150 that this wedge was not an official Jaguar “modification”. Again, referencing the previous citation in the Jaguar Service Manual, I’ll beg to differ.

Finally, I’ll reference my own XK120 here. My car is 670898 with a build date of October, 1950. Base model OTS specification. Absolutely no extra factory frills here. While performing a long needed overhaul of the whole rear end, I see that my car is fitted with these approximately 1" thick wedges – one on each side. My car has been off the road for 30+ years, is still shod with its fossilized leather gaiters and encrusted with a thick grime the consistency of hard clay so, based upon the official Jaguar reference and what I’m seeing, I’m inclined to believe that this car at least left the factory with these wedges.

Anyway, I’ve posted this as maybe it will be of some help to those with the earlier cars in particular who follow.

Regards to all –

Chris Potempa
San Jose, CA

This new version of the forum sometimes throws me for a loop when these old threads are revived and I don’t notice the date on the first posting. I don’t remember if I got involved back in '97.

Anyway, mine does not have the wedges.
The Spare Parts Catalogue says they were only used on early OTS with certain ENV axles, up to 660517 and 671097 plus six more cars a month or two later, roughly Dec '50 to Feb '51. They may have been needed because of some difference in the angle of the saddle mount as welded to the axle. Notice all five axles got an upgrade with suffix /1 added to their part numbers, and from then on the packings were not used.

Urs has a picture but does not comment on the usage.
Viart says they were a non-factory mod for racing, which would lower the body. He is partly right in that they certainly would lower the chassis and body relative to the axle centerline, and could easily have been added to any car at any time for this purpose. But he apparently missed that they are in the SPC.

Anyway, whether to use them or not, the important thing from an engineering viewpoint is that the axle pinion shaft must be nearly parallel to the gearbox mainshaft with the car at normal riding height. This is so that both u-joints make nearly the same angle in all conditions; otherwise you can get a lot of vibration.

The Hooke u-joint is not a constant velocity joint. It speeds up and slows down twice in every revolution, depending on the angle. Failure to understand this is why some off-roaders and high-rise pickups go through a lot of u-joints.

I recently saw a jacked up 4wd pickup on which the driveshafts had a large angle at the trans but no angle at the axles. I tried to tell the guy about u-joint angular velocity, but his axles and driveshafts were freshly painted purple with white pinstriping and he wasn’t about to change them.

Yes, I can see exactly what you mean about the gearbox-driveshaft-rear axle pinion housing all being in the same rotational plane. If I was to have discarded the axle wedge in the mistaken belief that it was an aftermarket performance mod it would really throw the alignment of the above assemblies off. Of course, mine is one of those early cars you reference with the ENV axles so I can’t speak with any authority for what followed such as Salisbury axles with wires, different saddle angles, etc. I hadn’t considered the speeding up/ slowing down of an off-center u-joint but as soon as you explained it in relation to those off-roading trucks, it became immediately clear. Thank you for that Rob.


They were originally used [ by jaguar and everyone else] on the front axles , when they were beam axles , as a way of setting the caster.
My understanding of their use on XKs was to lift the nose of the diff up for a bit more clearance under suspension movement[ As the brakes are applied the nose of the crank will move downwards under torque reaction .Similar, in a different way, to putting track rods on the rear for acceleration wind up.

Well, the packings were only used by the factory with the first set of five ENV axles, only until the end of 1950, not with the subsequent 10 axles from ENV nor the 9 from Salisbury. Porter believes they were deleted because the axle casing was modified.

The leaf springs were unchanged until about Dec '52, the new springs being stiffer. They are mentioned in several Service Bulletins as being stiffer and suitable for racing, but spring windup is not mentioned.

However, there is a tapered fiber wedge mentioned in the XK140 and 150 parts books, apparently used with all 140s and 150s. Regretfully this is not mentioned in the Service Manual Supplements. I have not found any mention of them in connection with XK120 in the factory literature.

BTW my car is 679187 from Nov '51 and I believe has the C.5150 ENV axle.
Christopher, if you have your axle out and happen to notice, can you say if your spring saddles are parallel to the pinion shaft, or at a slight angle?
If I ever have mine out I will look for this and it might go some way toward answering this 20 year old question.

My 120 FHC is a 1953 build and when I stripped it there were no wedges. My understanding is that they are not fitted on the later cars. My 150 however does have them, and as previously mentioned I understand that all 150’s had them.

It would make sense in a logical world to have mounted the spring pads on the axle at the angle o incorporate the wedge angle… In a perfect world . It might have been the wedges were found to be needed and were an intermediate solution until axle casing could be ordered with a modified angled pad. Or the tooling was shared with Mk Vs for a while. Or someone forgot . Or …

Yes, after all these years we still haven’t really figured them out completely.

To summarize…
We are talking about two different wedges.
C.3829 is the thick tapered aluminum wedge pictured in Urs Schmid Vol. 1 pg 119.
He shows an early ENV axle on which it appears that the spring saddle is very close to the axle tube.
Here is my later ENV axle, and you can see there is some clearance, the saddle is taller. This may explain why the thick wedge is not used on my car.

C.3186 is the thin fiber wedge listed only in the 140 and 150 SPCs and without explanation in the Service Manuals.
Curious that it has such a low part number, in proximity to a lot of Mark V chassis parts, suggesting it was designed about the same time. But it does not seem to have been used on Mark V, not listed in the SPC anyway.
Makes you wonder if it was a service part used on an “as needed” basis, like for adjusting caster angle and diff nose angle on individual cars.
Perhaps we are making an invalid assumption in thinking they were on every single 140 and 150?
We discussed them in 2014.

Rob, to my eyes, the spring saddles slope down towards the front in relation to the pinion shaft which slopes slightly up. Also, there appears to be no gap between the saddle bottom and axle tube as shown in your picture. I’m in the process of removing the whole shebang and once out in the sunlight and cleaned up, I’ll reference the areas in question with a straight edge along with pictures.

As a side note, upon removal of the mummified gaiters I found this:

How long the previous owner had been driving it with only one leaf secured to the forward mount is unknown but if it too had let go, then it would have made for one hell of a squirrely ride. Several sources mention these earlier springs as being prone to breakage and needless to say, I’ll be ordering a new set. Also, yet another reason why I lean against having gaiters on my springs.

This picture will have to do for now. Definitely no gap between axle and saddle like in Rob’s picture.

I took these photographs 3 years back to show the assembly parts of my XK120 OTS Dec '53.

I believe the aluminum spacers/wedges were only on early cars.

Front suspension parts here:

(the Konis, disc brakes, NTN bearings & thick sway bar are not original of course.


One woudhave thought that there was some indication that one of the ain leaves had broken , BUt maybe it was just ignored [ too hard] I recall that a few owners have complained that new springs are too hard … well maybe more than a few. It seems that spring steel is not avaulable/ made in the original range of sizes , and Metric are also a factor. here it just 6mm steel . Recently I needed leaves of [ original] 3/16"thick and 6 mm would have been far too stiff ,As it was as the car had been sitting on springswith s/hand 1/4"leaves from another car. So I went to the spring works, bought 4 leangths of the 6 mm steel , un-tempered and straight , I took them to a place that did grinding wet [ under a stream of water. an d had both sides ground down to leave the 3/16’thickness and at the same time ground the edges back to the correct 1 3/4" { imperial] width.
Then back to the spring works and had them made up into leaves and worked perfectly , It was important that they were ground wet to cool them and stop the grinding process from tempering them. It wasn’t expensive , the grinding was $120 cash for the lot. well worth it.
I do like the gaiters as they keep the road dust out and stop it mixing with the grease and making something like valve grinding paste between the leaves. The spring leaves wear a lot. The rollers don’t roll for long and end up wearing ridges in the leaves. The SS s had a better system . The U shaped stripped simply went through a flat plates with slotsin it and were bent over , The wear was then over a larger area and the corners can be radiussed and not as likely to tear the leather gaiters. There may have been a reason for the change , cost possibly , The U bars need to be bent over cold and so flat strip as purchased is too brittle and cracks , so one needs to have it lasered into strips from sheet in the right orientation to the grain. Then it’s easy. But probably it was hard to find lasers in the 40s-50s.