[xj] Rubber in shear bushings (was Series 1 and Series 3)

Apologies - I meant to start new rubber bushing thread. Ignore
previous post and please repsond here with the points I’ve missed:

Doug, Alex, Bob (and possibly Alyn?)

Let’s get to the bottom of this one. We are 4-5 good people with a
lot of knowledge who are split into two camps on this and we can��t
both be right but we can all learn and enjoy doing so.

Sorting this kind of thing out is exactly what the forum is about
IMHO. I��ll start the ball rolling with my (non Mech Eng) view. I��m
vaguely familiar with this technology from its use 50+ years ago by
Greeves and BSA et al.

The idea of rubber in torsion suspension pivots is that you get a
waterproof and maintenance-free joint in an exposed part of the
vehicle. Bike suspension bushes often last the life of the vehicle
and quite a few cars too I guess? The main downside is that unlike
precision bearings or bushes, rubber can��t give totally precise
location and there tends to be a little ‘give’ in other planes
besides the one around which the lever is meant to rotate. They do
reduce vibration and harshness which we know Jag were trying to
eliminate. Greeves even used the rubber in torsion as the main
springing medium, let alone pivot, but that��s rare.

Points to consider:

  1. Why would a manual ever mention the strong caution of not
    tightening until mid-laden, if the sleeve can rotate on the shaft
    through has many degrees as required with no ill effects? There is
    no mention of this kind of caution for any IRS pivot, for example.
    The XJ, XJ-S and E-type manuals all say final tightening of the
    pivot bolt must not occur until the car is resting on its wheels.
    This is so that the bonded steel sleeves are clamped tight at mid-
    position and therefore the rubber does NOT need to deflect, say, 30
    degrees �V only 15-ish degrees in each direction. This is doable.
    Even the upper wishbone bushes, which have a push-fit sleeve, are
    not supposed to be tightened until the car is resting on its
    wheels, although these are not rubber-in-shear bushes AFAIK.
  2. Where else, on any assembly, is a thin plain steel sleeve
    asked to perform heavy duty, un-lubricated bearing duty around a
    plain steel pin, with no provision whatsoever for maintenance? Even
    door hinges are supposed to get a squirt of oil, but not wishbones.
    Steel on steel is not a viable bearing surface in an un-lubricated
    setting. A spring steel slipper bearing against a chain running in
    an oil bath is one thing. A steel suspension bush wearing on a pin
    with no surface treatment or lube is quite another.
  3. There is obviously zero movement once seized/rusted. If
    the sleeve was the designed pivot, then when seized all the
    suspension movement has to be taken up unexpectedly by the rubber
    bush or the pin rotating in the subframe (which it doesn��t). I��d
    expect rubber to crumble fairly quickly if it was being asked to do
    something it was never designed for. However, many bushes with
    seized sleeves are still intact.
  4. The bushes DO get shredded if people tighten the pivots
    while the car is up on stands with its wheels dangling down (hence
    the cautions in the manual to tighten only when the weight of the
    car is on them). This highlights the fact the rubber is supposed to
    be twisting, not the sleeve rotating, but it is only designed to
    twist through half the arc, not the total range of movement. If the
    sleeve were rotating on the pin it wouldn��t make any difference
    tightening up the pivots with the car on stands.
  5. The only way parts seize with rust is through prolonged
    immobility. Yet suspension bushes seize on the pivot pin even in
    cars in constant use. Un-lubricated or poorly-lubed steel on steel
    which is in constant motion typically wears rapidly �V giving clear
    wear grooves like on door hinge pins or door lock mechanisms etc.
    Has anyone ever seen a grooved pin or a sleeve worn thin from
    rotating against the pin? They either come apart as normal or are
    seized. They are never sloppy or worn. Do we check pins and sleeves
    for wear, or is there any spec for the pin OD or sleeve ID in the
    manuals? Not AFAIK.
  6. How come no Jaguar manual mentions lubricating the
    sleeves or the pin before reassembly if this is supposed to be a
    bearing? You and I may put anti-seize on but no Jaguar publication
    mentions lubrication of the sleeve or pin.
  7. If the steel sleeves rotate around the pivot pins and are
    free to spin, how come 45-50 lb/ft on the nuts doesn��t clamp them?
    Where do the nuts are tighten against if not the sleeve? If the
    sleeve is free to turn, how come there is no end float spec like
    there is for the hub carrier fulcrums at the back?

Happy to hear the opposite side of course, so I learn more stuff
myself. Over to the ��spinner�� camp ��–
66 2+2, 73 OTS, 76 DD6 Coupé, 93 XJ12
Cambridge, United Kingdom
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In reply to a message from PeterCrespin sent Mon 31 Mar 2008:

Peter. You already know that I 100% agree with you on every single
point you have made. I have held this point of view all through the
numerous other times this has been discussed on this list. I
believe also that Alex and I have had a few exchanges on this exact
subject in the past.

It is my belief that the inner sleeve is there for two purposes.
One to be a stable part of the bushing enabling the rubber to
torque in either direction and the other to be a spacer preventing
the rubber from being crushed when the long bolt is torque to spec.

Another thing that you did not cover was that if the Inner metal
bushing was supposed to be allowed to pivot around the shaft. It
would not make the slightest difference to the feel of the car when
poly bushings are installed in place of the original rubber. But it
does, there is a lot of difference, the ride becomes a lot harsher
and to my mind unacceptable.

In the rear suspension where the swing arm was intended to pivot
directly on the shaft. Jaguar installed roller bearings to allow
this movement to be made without undue wear taking place. They also
installed grease fittings in order to allow these bearings to be
lubricated. Why then would they change to an altogether different
design for these front pivot bearings if they were to function in
exactly the same way as those in the rear.–
The original message included these comments:

Let’s get to the bottom of this one. We are 4-5 good people with a
lot of knowledge who are split into two camps on this and we can��t
both be right but we can all learn and enjoy doing so.


Bob
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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In reply to a message from Peddlarbob sent Mon 31 Mar 2008:

Err, actually I didn’t Bob but I’m sure it’s very nice to know! :slight_smile:

I’m not personally aware that this specific point has been
discussed in the past, publicly or privately, although I daresay it
would have been because everything else has. It’s the first time
I’ve pitched in anyway.

The polybush ‘feel’ issue is true, but I could argue that merely
having a stiffer material that resists radial deflection better
would result in more precise handling at the price of a less
refined ride - regardless of how the bush actually pivots.

Since the poly bushes are not bonded to the sleeves I believe there
is a rotational action with those, rather than a ‘poly-in-shear’
equivalent to the rubber bushing scnario. But evne there the sleeve
is not rotating around the pivot bolt but hte bush rotates around
the sleeve I believe. I deliberatley kept away from poly bushes
though, in order that we clarify between us all what is, or isn’t,
happennig with the OEM stuff. I think most of the numbered points I
made are unarguable, but there may be others people can bring to
the discussion which hint at some other mechanism. I’m sceptical
but open-minded :-)–
The original message included these comments:

Peter. You already know that I 100% agree with you on every single
point you have made. I have held this point of view all through the
numerous other times this has been discussed on this list. I
believe also that Alex and I have had a few exchanges on this exact
subject in the past.
Another thing that you did not cover was that if the Inner metal
bushing was supposed to be allowed to pivot around the shaft. It
would not make the slightest difference to the feel of the car when
poly bushings are installed in place of the original rubber. But it
does, there is a lot of difference, the ride becomes a lot harsher
and to my mind unacceptable.


66 2+2, 73 OTS, 76 DD6 Coup�, 93 XJ12
Cambridge, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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  1. Why would a manual ever mention the strong caution of not
    tightening until mid-laden, if the sleeve can rotate on the shaft
    through has many degrees as required with no ill effects?

I’ve wondered the same thing. I understand the logic of your position but
wouldn’t rely on the ROM to support it. This is the same manual that, for
instance, mis-identifies relays, has two completely contradictory entries on
rear wheel bearing adjustment, has diodes pointed the wirng way in diagrams,
etc.

I think we’re better off deciding the issue without the manual’s help :slight_smile:

This is so that the bonded steel sleeves are clamped tight at mid-
position and therefore the rubber does NOT need to deflect, say, 30
degrees �V only 15-ish degrees in each direction. This is doable.

This is one of my points of contention. I don’t the the design and and/or
the torque spec allow enough clamping effect of lock the inner metal sleeve
into a stationary position. If that was the intent I would think A) two
individual pivot bolts would be used, so as to allow reliable clamping on
both sides of each bushing B) somehting more positve by way of locking the
inner sleeve stationary and C) a much thicker bushing. That is, more more
rubber

  1. Where else, on any assembly, is a thin plain steel sleeve
    asked to perform heavy duty, un-lubricated bearing duty around a
    plain steel pin, with no provision whatsoever for maintenance? Even
    door hinges are supposed to get a squirt of oil, but not wishbones.
    Steel on steel is not a viable bearing surface in an un-lubricated
    setting.

Hmmmm. I have to agree there. I’ll give that one some thought :slight_smile:

  1. There is obviously zero movement once seized/rusted. If
    the sleeve was the designed pivot, then when seized all the
    suspension movement has to be taken up unexpectedly by the rubber
    bush or the pin rotating in the subframe (which it doesn��t). I��d
    expect rubber to crumble fairly quickly if it was being asked to do
    something it was never designed for. However, many bushes with
    seized sleeves are still intact.

Despite my TIC remark a few postings back, you’ll never see one rust solid
in that respect. The rotational movement and wieght of the car would prevent
seizing in the rotational aspect. However, rust will build up on the shaft
on either side of the sleeve, making the pivot shaft impossible to withdraw.

  1. The bushes DO get shredded if people tighten the pivots
    while the car is up on stands with its wheels dangling down

They do ? I don’t recall mine shredding :slight_smile:

More later. Gotta get ready for work !

Cheers

Doug Dwyer
Longview Washington USA
1995 XJR
1990 T-Bird SCFrom: “PeterCrespin” jag@thewritersbureau.com

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In reply to a message from Doug Dwyer sent Mon 31 Mar 2008:

All good stuff Doug, thanks :slight_smile:

  1. Why would a manual ever mention the strong caution of not
    tightening until mid-laden, if the sleeve can rotate on the
    shaft through has many degrees as required with no ill effects?

I’ve wondered the same thing. I understand the logic of your
position but wouldn’t rely on the ROM to support it. This is the
same manual that, for instance, mis-identifies relays, has two
completely contradictory entries on rear wheel bearing adjustment,
has diodes pointed the wirng way in diagrams, etc.

Fair comment. However, the E-type manual says the exact same thing
for a different suspension set up (torsion bars) using the same
system of rubber in shear bushings. The XJS manual has the caution
too. I think the X300 one does too and the X308 and all the Haynes
ones which do not use the exact Jag wording in these assembly
sections. That’s an awful lot of mistakes for something that to me
seems an obvious caution of tightening up the sleeves with
suspension at around mid-travel.

This is one of my points of contention. I don’t the the design and
and/or the torque spec allow enough clamping effect of lock the
inner metal sleeve into a stationary position. If that was the
intent I would think A) two individual pivot bolts would be used,
so as to allow reliable clamping on both sides of each bushing B)
somehting more positve by way of locking the inner sleeve
stationary and C) a much thicker bushing. That is, more more
rubber.

I think they allow plenty of clamping considering there are no
shock loads to dela with because the rubber damps any rotary
twisting load. Why would you want tangential clamps each side?
You’d need a split bushing to clamp the shaft and it would all take
up more room either side of the bush and make the wishbone wider,
which would affect steering lock probably. The bush does not need
clamping mega tight (although 50lb ft sounds plenty to me!) as the
pivot action is not that extensive because the suspension doesn’t
move far enough. Even when it is excessive (bushes clamped with
wheels unloaded) the sleeve stays tight enough to damage the rubber
eventually. Not instantly, but it shortens the life of the
bushings, hence the caution. The reason they have to compromise on
bush thickness is that too thick makes the handling sloppy, even if
it helps refinement. So for the chunky radius arms and subframe and
IRS mounts they can go quite thick, up to nearly an inch of rubber
as these don’t control precise geometry so directly.

For actual wishbone pivots which have to transmit steering and
braking loads for a 2-ton car there’s only room for a few
millimeters of rubber without compromising wishbone twisting and
wheel geometry and having impossibly mushy handling IMHO. See how
people rave about the steering directness when removing even a few
millimetres of rubber and going to poly. Can you imagine the land
yacht feel of the car if the bottom bushes had, say, half or 3/4 of
an inch of rubber?

Have a nice day at work. See if you can find me one of those steel
on steel lube-free suspension bearings on a GM car :slight_smile:

Pete
Despite my TIC remark a few postings back, you’ll never see one
rust solid in that respect. The rotational movement and wieght of
the car would prevent seizing in the rotational aspect.

If they rotated, I’d agree totally. The E-type rubber in shear
bushings rust onto the shaft all the time. It’s the norm. My shock
bushings in the X300 did the same. But if they are constantly
moving with no lube, how come we have no worn pins and no worn-out
sleeves even on rust-belt cars? I wonder if anyone has ever
reported a pin worn down or a collapsed worn sleeve? Has anyone
ever failed inspection because there was slop between the sleeve
and the shaft, or do they fail because the rubber has perished? If
this steel on steel unlubed bearing exists, how come in all the
pages of technical detail to the nearest few thou, we have no spec
for the pin OD or bush ID? How come this bearing has no lube
assembly instruction in any manual, or lube maintenance
instruction, or reports of squeaking fro ma dry sleeves? How can
the major pivots of the front suspension be steel on steel and
unlubed where the IRS has all grease nipples?

The bushes DO get damaged eventually if people tighten the pivots
while the car is up on stands with its wheels dangling down.
This is reported fairly often on the E-type list which uses the
same style of bottom bushing. It can actually affect the ride
height slightly on those cars as the rubber with excessive shear
becomes part of the de-facto springing of the car. I suspect the XJ
is a little heavy for that?–
The original message included these comments:

I think we’re better off deciding the issue without the manual’s help :slight_smile:


66 2+2, 73 OTS, 76 DD6 Coup�, 93 XJ12
Cambridge, United Kingdom
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In reply to a message from PeterCrespin sent Mon 31 Mar 2008:

Anyone:

I am certainly not a ME.

I think the word ‘‘complaint’’ best describes rubber v steel.

Although it is not in torsion the forward control bushing on the
rear IRs of these csars is an illustration of a compliant jont.
It allows a degree of movement in more than a specific arc or
plane.

Literally, a rubber joint allows a certain degree of ''controlled
wallow in the arc traveled by that joint.

The poly bushes still allow that controlled wallow but at a slower
rate as they are stiffer.

Yes, a poly or rubber bush must be locked in place at the
aproximate center of it’s intended travel. A lubricated brass joint
is free to move to it’s center from the outward limits of it’s
travel.

We probably lube for the ease in installation or removal. The
factory has specialized tools to force the assembly clean.

Steel on steel in a moving joint is a poor choice. Oil only slows
the inevitable. Kinda like bone to bone in a human joint when the
cartilage is gone.

Just spinning the grey matter.

Carl–
The original message included these comments:

The idea of rubber in torsion suspension pivots is that you get a
waterproof and maintenance-free joint in an exposed part of the
vehicle. Bike suspension bushes often last the life of the vehicle
and quite a few cars too I guess? The main downside is that unlike
precision bearings or bushes, rubber can��t give totally precise
location and there tends to be a little ‘give’ in other planes
besides the one around which the lever is meant to rotate. They do
reduce vibration and harshness which we know Jag were trying to
eliminate. Greeves even used the rubber in torsion as the main
springing medium, let alone pivot, but that��s rare.
Points to consider:


Carl Hutchins
Walnut Creek, California, United States
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If we’re talking about the upper, inner front XJ bushings, then all one has to
do is look at OE ones still on the car to see how they deteriorate, then look
at a new OE set and note the lube inside the central tube, thus to see that it
must rotate on the threaded mounting bar.

The manual also says to tighten these with suspension at about normal ride
position, yet there’s no mechanical reason to do so. The only aid to mounting
is having the wheel supported enough so the upper bars come off the bumper on
the spring mount. It may simply be that long ago there were reasons to do
bushings at normal suspension positions, but, at least at the top front, that
has nothing to do with rotation of their inner cylinders on their mounting shafts.

I’d guess the inner lowers are similar, since anything like 25 degrees of
rotation isn’t something a metalastic piece of their diameter is going to
handle – long. But we can have long arguments about most anything!
;]–
Alex
79xj6L SII (BRG + wires)
86xj6 SIII (Black)
61 Sprite MkII (Red)
Menlo Park, Calif.

PeterCrespin wrote:

In reply to a message from Peddlarbob sent Mon 31 Mar 2008:

Err, actually I didn’t Bob but I’m sure it’s very nice to know! :slight_smile:

I’m not personally aware that this specific point has been
discussed in the past, publicly or privately, although I daresay it
would have been because everything else has. It’s the first time
I’ve pitched in anyway.

The polybush ‘feel’ issue is true, but I could argue that merely
having a stiffer material that resists radial deflection better
would result in more precise handling at the price of a less
refined ride - regardless of how the bush actually pivots.

Since the poly bushes are not bonded to the sleeves I believe there
is a rotational action with those, rather than a ‘poly-in-shear’
equivalent to the rubber bushing scnario. But evne there the sleeve
is not rotating around the pivot bolt but hte bush rotates around
the sleeve I believe. I deliberatley kept away from poly bushes
though, in order that we clarify between us all what is, or isn’t,
happennig with the OEM stuff. I think most of the numbered points I
made are unarguable, but there may be others people can bring to
the discussion which hint at some other mechanism. I’m sceptical
but open-minded :slight_smile:

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Just an engineering correction or two here…

a) 1st para below – if new lower inners are delivered with lube on the inner
surface of their cylindrical shafts, and those shafts have no locking
mechanisms at the ends (analogous to a broached/toothed surface), then there’s
no way the cylinder can be prevented from rotating about the axial bolt. The
other comment about 25 degrees of potential rotation further supports this
reality.

b) 2nd para below – the rear-suspension’s outer shaft takes direct vertical
impact from road bumps. The inner front shafts do not, since the spring and
ball joints take the vertical shocks, while the inner lower bushings have
considerable leverage (due to their inboard position) reducing such forces.
So, they don’t have to function “in exactly the same way” in any case.–
Alex
79xj6L SII (BRG + wires)
86xj6 SIII (Black)
61 Sprite MkII (Red)
Menlo Park, Calif.

Peddlarbob wrote:
[clip]

Another thing that you did not cover was that if the Inner metal
bushing was supposed to be allowed to pivot around the shaft. It
would not make the slightest difference to the feel of the car when
poly bushings are installed in place of the original rubber. But it
does, there is a lot of difference, the ride becomes a lot harsher
and to my mind unacceptable.

In the rear suspension where the swing arm was intended to pivot
directly on the shaft. Jaguar installed roller bearings to allow
this movement to be made without undue wear taking place. They also
installed grease fittings in order to allow these bearings to be
lubricated. Why then would they change to an altogether different
design for these front pivot bearings if they were to function in
exactly the same way as those in the rear.

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The question is easily answered by someone who’s actually replaced the lower
inners – did the new ones come with lubing inside, as the upper inners do?

Not having replaced the inners, but done 2 cars of uppers, I can testify that
the uppers are indeed intended to rotate freely around the mounting bars.
Torquing the end nuts just brings the chromed end washers properly against the
bushes and the end of the rods’ threading. If the lowers are similarly
delivered & tightened, end of story.–
Alex
79xj6L SII (BRG + wires)
86xj6 SIII (Black)
61 Sprite MkII (Red)
Menlo Park, Calif.

PeterCrespin wrote:

Apologies - I meant to start new rubber bushing thread. Ignore
previous post and please repsond here with the points I’ve missed:

Doug, Alex, Bob (and possibly Alyn?)

Let’s get to the bottom of this one. We are 4-5 good people with a
lot of knowledge who are split into two camps on this and we can��t
both be right but we can all learn and enjoy doing so.

Sorting this kind of thing out is exactly what the forum is about
IMHO. I��ll start the ball rolling with my (non Mech Eng) view. I��m
vaguely familiar with this technology from its use 50+ years ago by
Greeves and BSA et al.

The idea of rubber in torsion suspension pivots is that you get a
waterproof and maintenance-free joint in an exposed part of the
vehicle. Bike suspension bushes often last the life of the vehicle
and quite a few cars too I guess? The main downside is that unlike
precision bearings or bushes, rubber can��t give totally precise
location and there tends to be a little ‘give’ in other planes
besides the one around which the lever is meant to rotate. They do
reduce vibration and harshness which we know Jag were trying to
eliminate. Greeves even used the rubber in torsion as the main
springing medium, let alone pivot, but that��s rare.

Points to consider:

  1. Why would a manual ever mention the strong caution of not
    tightening until mid-laden, if the sleeve can rotate on the shaft
    through has many degrees as required with no ill effects? There is
    no mention of this kind of caution for any IRS pivot, for example.
    The XJ, XJ-S and E-type manuals all say final tightening of the
    pivot bolt must not occur until the car is resting on its wheels.
    This is so that the bonded steel sleeves are clamped tight at mid-
    position and therefore the rubber does NOT need to deflect, say, 30
    degrees �V only 15-ish degrees in each direction. This is doable.
    Even the upper wishbone bushes, which have a push-fit sleeve, are
    not supposed to be tightened until the car is resting on its
    wheels, although these are not rubber-in-shear bushes AFAIK.
  2. Where else, on any assembly, is a thin plain steel sleeve
    asked to perform heavy duty, un-lubricated bearing duty around a
    plain steel pin, with no provision whatsoever for maintenance? Even
    door hinges are supposed to get a squirt of oil, but not wishbones.
    Steel on steel is not a viable bearing surface in an un-lubricated
    setting. A spring steel slipper bearing against a chain running in
    an oil bath is one thing. A steel suspension bush wearing on a pin
    with no surface treatment or lube is quite another.
  3. There is obviously zero movement once seized/rusted. If
    the sleeve was the designed pivot, then when seized all the
    suspension movement has to be taken up unexpectedly by the rubber
    bush or the pin rotating in the subframe (which it doesn��t). I��d
    expect rubber to crumble fairly quickly if it was being asked to do
    something it was never designed for. However, many bushes with
    seized sleeves are still intact.
  4. The bushes DO get shredded if people tighten the pivots
    while the car is up on stands with its wheels dangling down (hence
    the cautions in the manual to tighten only when the weight of the
    car is on them). This highlights the fact the rubber is supposed to
    be twisting, not the sleeve rotating, but it is only designed to
    twist through half the arc, not the total range of movement. If the
    sleeve were rotating on the pin it wouldn��t make any difference
    tightening up the pivots with the car on stands.
  5. The only way parts seize with rust is through prolonged
    immobility. Yet suspension bushes seize on the pivot pin even in
    cars in constant use. Un-lubricated or poorly-lubed steel on steel
    which is in constant motion typically wears rapidly �V giving clear
    wear grooves like on door hinge pins or door lock mechanisms etc.
    Has anyone ever seen a grooved pin or a sleeve worn thin from
    rotating against the pin? They either come apart as normal or are
    seized. They are never sloppy or worn. Do we check pins and sleeves
    for wear, or is there any spec for the pin OD or sleeve ID in the
    manuals? Not AFAIK.
  6. How come no Jaguar manual mentions lubricating the
    sleeves or the pin before reassembly if this is supposed to be a
    bearing? You and I may put anti-seize on but no Jaguar publication
    mentions lubrication of the sleeve or pin.
  7. If the steel sleeves rotate around the pivot pins and are
    free to spin, how come 45-50 lb/ft on the nuts doesn��t clamp them?
    Where do the nuts are tighten against if not the sleeve? If the
    sleeve is free to turn, how come there is no end float spec like
    there is for the hub carrier fulcrums at the back?

Happy to hear the opposite side of course, so I learn more stuff
myself. Over to the ��spinner�� camp ��

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In reply to a message from Cannara sent Mon 31 Mar 2008:

The upper bushes are Glacier DX a plastic bearing that is
designed to work with some lubrication if you look at it. it
looks like a colander with holes in the bush thickness to
retain lubricating grease.the bush has a steel outer to
strengthen it The bush is not clamped ‘solid’ when
assembled.
The centre tube on rubber in torsion bushes is definitely
clamped by the fixing bolt & can’t rotate.They often rust
solid to the fixing bolt without adverse effect on the
rubber bush. These have been used for years-the rear wheel
of my Messerschmitt bubble car & Moulton Bicycle were
reliant on this type of bush as the actual ‘spring’ & pivot
of the suspension. I did replace the rubber bushes on one of
my Lancias front suspension lower wishbones with Nylatron
Moly filled Nylon which did pivot round the centre bush as a
bearing. Worked fine & did not badly increase the harshness
of the suspension there was enough flex in the nylon to damp
the road thumps–
The original message included these comments:

If we’re talking about the upper, inner front XJ bushings, then all one has to
do is look at OE ones still on the car to see how they deteriorate, then look
at a new OE set and note the lube inside the central tube, thus to see that it
must rotate on the threaded mounting bar.
I’d guess the inner lowers are similar, since anything like 25 degrees of
rotation isn’t something a metalastic piece of their diameter is going to
handle – long. But we can have long arguments about most anything!


Keith Turner '79 XJ6 based Aristocat,
Swansea, United Kingdom
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In reply to a message from Doug Dwyer sent Mon 31 Mar 2008:

Hi Doug, I know of one application of the shear bushings in GM
cars [I’m sure there are many] The Corvair bushing on the cross-
shaft [tie rod] When tightening this bushing, the wheels must be
straight, as the bushing helps self-centre the steering. It goes
through a huge twist and lasts about a year.
Hal Klassen, 1985 V12 VdP, 1966 Glenn Pray Cord [Corvair powered]–
2cords
Coquitlam B.C., Canada
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In reply to a message from Keith Turner sent Mon 31 Mar 2008:

When I replaced the front uppers on mine I had a long session
of ‘‘hows this supposed to work then?’’. The inner sleeve looked very
much like the bushes we fit to the drive end of CAV commercial
vehicle starter motors, so I surmised the pivot bolt needed
greasing and the bush would rotate on the bolt, the rubber just
acting as a support for the pivot/bush, giving a degree of
flexibility and isolation from vibration. The washers on the ends
appeared to need to just hold it all in place, rather than clamp
anything. But then when I did a trial tightening with just the
wishbone arms I could feel them definitely twisting the rubber when
deflected. Given that all the instruction say ‘‘don’t tighten until’’
I assumed I’d done the job correctly, but was obviously not on the
ball about how it’s supposed to work.
One side pivot bolt had seized to the bush, the bush had just
started to wear the upper wishbone arm. Obviously once the pivot
gets seized and the bush gets a bit loose on the wishbone arm it
can rotate in the arm, with disastrous results. I was lucky I
caught it before it got to be a problem.
It didn’t seem right to me that there were no grease nipples
fitted, I considered fitting some but was a bit dubious about
drilling such an important piece of kit.

Dave–
The original message included these comments:

The upper bushes are Glacier DX a plastic bearing that is
designed to work with some lubrication if you look at it. it
looks like a colander with holes in the bush thickness to
retain lubricating grease.the bush has a steel outer to
strengthen it The bush is not clamped ‘solid’ when
assembled.
The centre tube on rubber in torsion bushes is definitely
clamped by the fixing bolt & can’t rotate.They often rust
solid to the fixing bolt without adverse effect on the
rubber bush. These have been used for years-the rear wheel


Dave Collishaw '79 S2 Daimler Sov '92 xj40
Peterborough, United Kingdom
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In reply to a message from sparx sent Mon 31 Mar 2008:

Personally I like the poly bushes that rotate. However if Jaguar
were truly trying to manufacture a quality car ( as viewed from the
enthusiasts point of view - never mind the pinic tables or the
genuine sheep skin throw rugs - these are known in the car biz
as ‘‘candy’’ for the shi shi folks ) they should have disregarded
the beancounters and put more effort/engineering into these
bushings. So what are bushings? Rubber bushings are a poor solution
to a weather tight bearing - which costs a lot more. To say that
the rubber is supposed to isolate and prevent harshness from road
shock,… that is what the shock (damper) and spring are for. That
location is supposed to be the pivot point for the lower A arm.
No,… Jaguar took the MGB way out. Put on some cheap rubber
bushings instead of a good sealed lubricated bearing system in the
interest of PROFIT and to hell with the knowledgeable enthusiast
who might be the owner of the car. My MGB has the same trash
bushings on it pure junk and you still have to hammer the hell out
of them to get them off the pivot bolt. A very cheap way of doing
things and then foisting the problem of replacement onto the car
owner. To be fair there are a lot of car companies that do this
little trick. The newer poly bushings are a compromise between the
rubber bushings and a fully lubricated A arm bearing as opposed to
a ‘‘rubber’’ bearing that eventually bonds itself to the pivot bolt
with rust. Have I seen any rubber bushings that have sheared after
the inner ‘‘tube’’ has rusted itself to the pivot bolt? NO. Do I
think that the lower A arm pivots freely after the spring and
damper have been removed? No it doesn’t It is stiff and a lot of
force has to be exerted to even move the lower A arm by iself. I
will take the poly bush and rely on the damper and spring to handle
the road shock as they are supposed to.–
Alyn
Seattle WA, United States
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In reply to a message from sparx sent Mon 31 Mar 2008:

Peter perhaps you are reading too much into the Jaguar manual? As
Doug has pointed out there are plenty of flaws, and this is the
book that lists a torque setting for every nut and bolt on the
chassis/suspension, but only the bare essentials for the engine? I
guess the manuals are not written by the same engineers who
designed the components?

The front lower inner bushes are clearly designed to be lubricated,
as Keith has stated, but no provision is made for same except
through dissasembly. Same applies to the top inner’s after
replacement with Nolothane. Dissasembly and re-lubing every couple
of years is a pre requisiste to getting any life out of the bushes.

I understand that even the rear setup is not without flaws.
Allegedly the range of movement is insuficient for each bearing
roller to move into the space occupied by it’s neighbour, so wear
is accelerated as each roller moves on it’s same piece of track
through only a part of it’s circumference.

If the OEM front bushes are designed to flex through the rubber,
with the centre bush clamped by the washer, prudent assembly would
still dictate copper slip or similar on the shaft merely in the
interests of subsequent dissasembly. This of course begs the
question why are the shafts stepped, and aren’t we lucky to be able
to turn that shaft into a pivot when we fit the poly bushes that do
rotate about the shaft.–
Neville S1 XJ12
Christchurch, New Zealand
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I don’t think that’s the “shear” effect that we are discussing. I think
that’s merely some small friction between the ends of the bushings and the
face of the mountings…be it the washers on the upper bushings or the
mounting lugs (for lack of a better word) on the lowers.

Doug Dwyer
Longview Washington USA
1995 XJR
1990 T-Bird SCFrom: “sparx” dave@dcelectrics.plus.com

But then when I did a trial tightening with just the
wishbone arms I could feel them definitely twisting the rubber when
deflected.

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Oh boy. I don’t remember, to be quite honest. Anyone have some new ones in
the box to look at ?

Doug Dwyer
Longview Washington USA
1995 XJR
1990 T-Bird SCFrom: “Cannara” cannara@sbcglobal.net

The question is easily answered by someone who’s actually replaced the
lower inners – did the new ones come with lubing inside, as the upper
inners do?

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They don’t have a method of locking, and that’s one of the things that makes
me think they are supposed to rotate…because I don’t think the clamping
pressure alone could keep them stationary.

Straying a bit, what would be the design intent of having these bushing work
“in shear” ? What is accomplished that isn’t already accomplished by the
springs and shocks? None, that I can fathom…but I’ll try to stay open
minded :-).

No, I think the bushings are there to provide insulation from noise and
vibration and not play a roll in the “action” of the suspension other than
of course, to keep everything properly located…

Doug Dwyer
Longview Washington USA
1995 XJR
1990 T-Bird SCFrom: “Cannara” cannara@sbcglobal.net

Just an engineering correction or two here…

a) 1st para below – if new lower inners are delivered with lube on the
inner surface of their cylindrical shafts, and those shafts have no
locking mechanisms at the ends (analogous to a broached/toothed surface),
then there’s no way the cylinder can be prevented from rotating about the
axial bolt. The other comment about 25 degrees of potential rotation
further supports this reality.

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Whew ! You’ve given me an awful lot to mull over, Pete !! I’ll give it
some thought and report back :slight_smile:

Doug Dwyer
Longview Washington USA
1995 XJR
1990 T-Bird SC

Fair comment. However, the E-type manual says the exact same thing
for a different suspension set up (torsion bars) using the same
system of rubber in shear bushings. The XJS manual has the caution
too. I think the X300 one does too and the X308 and all the Haynes
ones which do not use the exact Jag wording in these assembly
sections. That’s an awful lot of mistakes for something that to me
seems an obvious caution of tightening up the sleeves with
suspension at around mid-travel.

snip
snip
snipFrom: “PeterCrespin” jag@thewritersbureau.com

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Just for youse guys, while I had the SIII up to change trans oil, I made some
observations, with pictures, of how the front, lower, inner bushes behave when
the wheel rises & falls. I also took a pic of the Parts Guide, which shows
the bushes and their fitting into the lower arm’s pivot holes. I’ll post the
pics.

But, just so nobody loses sleep tonight, on April Fool’s eve, angsting over
this deep subject, let me hint that Neville, Doug, etc., are right – the
bushes rotate rather than deform.

PS the Manual also has a wrongly titled picture or two in the EFI sensor
section – who can find the errors first!?–
Alex
79xj6L SII (BRG + wires)
86xj6 SIII (Black)
61 Sprite MkII (Red)
Menlo Park, Calif.

Nev.W wrote:

In reply to a message from sparx sent Mon 31 Mar 2008:

Peter perhaps you are reading too much into the Jaguar manual? As
Doug has pointed out there are plenty of flaws, and this is the
book that lists a torque setting for every nut and bolt on the
chassis/suspension, but only the bare essentials for the engine? I
guess the manuals are not written by the same engineers who
designed the components?

The front lower inner bushes are clearly designed to be lubricated,
as Keith has stated, but no provision is made for same except
through dissasembly. Same applies to the top inner’s after
replacement with Nolothane. Dissasembly and re-lubing every couple
of years is a pre requisiste to getting any life out of the bushes.

I understand that even the rear setup is not without flaws.
Allegedly the range of movement is insuficient for each bearing
roller to move into the space occupied by it’s neighbour, so wear
is accelerated as each roller moves on it’s same piece of track
through only a part of it’s circumference.

If the OEM front bushes are designed to flex through the rubber,
with the centre bush clamped by the washer, prudent assembly would
still dictate copper slip or similar on the shaft merely in the
interests of subsequent dissasembly. This of course begs the
question why are the shafts stepped, and aren’t we lucky to be able
to turn that shaft into a pivot when we fit the poly bushes that do
rotate about the shaft.

===================================================
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Alyn, when this thread appeared some years back, it was indeed brought up that
real racing machines use roller bearings in the suspension pivots, because
they want to exactly calibrate suspension damping via quality shocks, without
having spurious damping loads from pivots etc. that might change during a race.–
Alex
79xj6L SII (BRG + wires)
86xj6 SIII (Black)
61 Sprite MkII (Red)
Menlo Park, Calif.

Alyn wrote:

In reply to a message from sparx sent Mon 31 Mar 2008:

Personally I like the poly bushes that rotate. However if Jaguar
were truly trying to manufacture a quality car ( as viewed from the
enthusiasts point of view - never mind the pinic tables or the
genuine sheep skin throw rugs - these are known in the car biz
as ‘‘candy’’ for the shi shi folks ) they should have disregarded
the beancounters and put more effort/engineering into these
bushings. So what are bushings? Rubber bushings are a poor solution
to a weather tight bearing - which costs a lot more. To say that
the rubber is supposed to isolate and prevent harshness from road
shock,… that is what the shock (damper) and spring are for. That
location is supposed to be the pivot point for the lower A arm.
No,… Jaguar took the MGB way out. Put on some cheap rubber
bushings instead of a good sealed lubricated bearing system in the
interest of PROFIT and to hell with the knowledgeable enthusiast
who might be the owner of the car. My MGB has the same trash
bushings on it pure junk and you still have to hammer the hell out
of them to get them off the pivot bolt. A very cheap way of doing
things and then foisting the problem of replacement onto the car
owner. To be fair there are a lot of car companies that do this
little trick. The newer poly bushings are a compromise between the
rubber bushings and a fully lubricated A arm bearing as opposed to
a ‘‘rubber’’ bearing that eventually bonds itself to the pivot bolt
with rust. Have I seen any rubber bushings that have sheared after
the inner ‘‘tube’’ has rusted itself to the pivot bolt? NO. Do I
think that the lower A arm pivots freely after the spring and
damper have been removed? No it doesn’t It is stiff and a lot of
force has to be exerted to even move the lower A arm by iself. I
will take the poly bush and rely on the damper and spring to handle
the road shock as they are supposed to.

===================================================
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