[x300] An interesting comment from my mechanic, re: front suspension


(jaguarSean) #1

The VDP is headed back in to Brookline Jaguar Service
tomorrow for an oil change, a mysterious rattle from below
(cat heat shield, perhaps?), an engine rattle at start up
(tensioner wear or old oil?), and possibly new rear shocks.

John at BJS doesn’t believe that we actually need new rear
shocks, but the rear end feels loose to me especially after
the new front shocks were installed. I can bounce the rear
of the car and it will continue to bounce through 3 more
cycles when I’m done.

In any case, we started to talk about the front suspension
and why it seems to CRASH over seemingly small sharp bumps.
According to John there are no bump stops in the X300/330
front suspension; the crashing that I feel is the coil
spring completely closing and transfering it’s energy to the
vehicle’s structure! BANG!

This is a troubling predicament. There’s no way to smooth
this type of suspension action? Has anyone moved to a
stronger aftermarket spring to try and lessen the impact up
front? Of course, the worry would be that you’d ruin the
ride with a stiffer spring, correct?–
jaguarSean '97 VDP
Walpole, MA, United States
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(Linda & RTMcSherry) #2

In reply to a message from jaguarSean sent Wed 20 Apr 2005:

Sean;

Did they install new shock bushings, especially at the top, when
they did the shocks. Mine did and does the same thing after new
shocks, and I have the new top rubbers to try, with fingers
crossed.–
The original message included these comments:

According to John there are no bump stops in the X300/330
front suspension; the crashing that I feel is the coil
spring completely closing and transfering it’s energy to the
vehicle’s structure! BANG!


RTM 96 XJ6 4.0L
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(Jack C. Hollibaugh) #3

Wow, those got to be some hellatous bumps or weak springs. My car doesn’t
exhibit those symptoms. Definitely something wrong up there.

jack - '99 XJ8L
York, PA USA

< snip >
The VDP is headed back in to Brookline Jaguar Service
tomorrow for an oil change, a mysterious rattle from below
(cat heat shield, perhaps?), an engine rattle at start up
(tensioner wear or old oil?), and possibly new rear shocks.

John at BJS doesn’t believe that we actually need new rear
shocks, but the rear end feels loose to me especially after
the new front shocks were installed. I can bounce the rear
of the car and it will continue to bounce through 3 more
cycles when I’m done.

In any case, we started to talk about the front suspension
and why it seems to CRASH over seemingly small sharp bumps.
According to John there are no bump stops in the X300/330
front suspension; the crashing that I feel is the coil
spring completely closing and transfering it’s energy to the
vehicle’s structure! BANG!

This is a troubling predicament. There’s no way to smooth
this type of suspension action? Has anyone moved to a
stronger aftermarket spring to try and lessen the impact up
front? Of course, the worry would be that you’d ruin the
ride with a stiffer spring, correct?–
jaguarSean '97 VDP
Walpole, MA, United States
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< snip >


(jaguarSean) #4

In reply to a message from r t mcsherry sent Wed 20 Apr 2005:

Yes, in fact that was the first thing noticed when we
complained of a dull rattle up front over bumps; the
bushings were shot.

Are there better bushings available? I can’t even imagine
how a different bushing could calm the slam we feel.–
The original message included these comments:

Sean;
Did they install new shock bushings, especially at the top, when
they did the shocks. Mine did and does the same thing after new
shocks, and I have the new top rubbers to try, with fingers
crossed.


jaguarSean '97 VDP
Walpole, MA, United States
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(jaguarSean) #5

In reply to a message from Jack C. Hollibaugh sent Wed 20 Apr 2005:

I, too, have suspected weak springs. If the springs were
weak and allowed the VDP to settle too far it would
effectively reduce the travel of the front suspension. Then
again, the car doesn’t look terribly low (for a Jaguar) and
in fact the front end was measured for height when the
shocks were replaced.

Your X308 may have a different suspension geometry or make
up; I have no idea.–
The original message included these comments:

Wow, those got to be some hellatous bumps or weak springs. My car doesn’t
exhibit those symptoms. Definitely something wrong up there.
jack - '99 XJ8L


jaguarSean '97 VDP
Walpole, MA, United States
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(Ant '95 3.2) #6

In reply to a message from jaguarSean sent Wed 20 Apr 2005:

My start up engine rattle disappeared with new upper tensioner
piston fitted. �50.00 for the part. Jag oil filter important too
for silent start. I also have the crashing over small bumps. Have
changed shocks, their bushes, and many other bushes including the
antiroll bar link bushes -but still some crashing and rumbling is
there. Let me know if the weak spring diagnosis is proven.
Ant, 136k–
The original message included these comments:

tomorrow for an oil change, a mysterious rattle from below
(cat heat shield, perhaps?), an engine rattle at start up
(tensioner wear or old oil?), and possibly new rear shocks.
front suspension; the crashing that I feel is the coil
spring completely closing and transfering it’s energy to the
vehicle’s structure! BANG!


Ant
Kent, UK, United Kingdom
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(Dave and Patsy Lokensgard) #7

Sean wrote:

John at BJS doesn’t believe that we actually need new rear
shocks, but the rear end feels loose to me especially after
the new front shocks were installed. I can bounce the rear
of the car and it will continue to bounce through 3 more
cycles when I’m done.

In any case, we started to talk about the front suspension
and why it seems to CRASH over seemingly small sharp bumps.
According to John there are no bump stops in the X300/330
front suspension; the crashing that I feel is the coil
spring completely closing and transfering it’s energy to the
vehicle’s structure! BANG!

Your mechanic is incorrect, the shock performs the bump stop action, if you
have the correct shocks. If your springs show evidence of coil-to-coil
contact, something is seriously wrong. Ask if the OEM shocks were fitted,
and if new bushings were used.

Definitely sounds like you need rear shocks as well, to me.

Dave Lokensgard
'96 XJR (DAVZCAT)
'90 Sovereign (MELZKAT)
'90 Vanden Plas Majestic (PATZCAT)
'55 XK140 OTS
Poway, California


(jaguarSean) #8

In reply to a message from Lokensgard sent Thu 21 Apr 2005:

The SHOCK is the bump stop?? That sounds horrendous.
Wouldn’t the shock be destroyed?

We bounced the rear end of the car and it went through a
couple of cycles. We bounced the rear end of a 140K mile XJ6
(swb) and it instantly got control of itself. We bounced the
rear end of an '01 VDP with 50k miles on it cycled
identically to our '97 VDP. The consensus is, the VDP is
THAT soft in the rear.–
The original message included these comments:

Your mechanic is incorrect, the shock performs the bump stop action, if you
have the correct shocks. If your springs show evidence of coil-to-coil
contact, something is seriously wrong. Ask if the OEM shocks were fitted,
and if new bushings were used.
Definitely sounds like you need rear shocks as well, to me.


jaguarSean '97 VDP
Walpole, MA, United States
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(Dave and Patsy Lokensgard) #9

Jaguar Sean wrote:

The SHOCK is the bump stop?? That sounds horrendous.
Wouldn’t the shock be destroyed?

No, not if it’s designed to do the job. ALL Macpherson strut suspensions,
for example, have this feature (not that your car has a Macpherson strut,
but you get the idea). Look at your prings to see it they show evidence of
coil-to-coil contact - it should be obvious is they do. Most times when a
Jag front suspension makes noise, it’s due to the upper shock mount bushings
being tired or incorrectly installed. Less often the lower shock bushings.

We bounced the rear end of the car and it went through a
couple of cycles. We bounced the rear end of a 140K mile XJ6
(swb) and it instantly got control of itself. We bounced the
rear end of an '01 VDP with 50k miles on it cycled
identically to our '97 VDP. The consensus is, the VDP is
THAT soft in the rear.

The spring and shock rates may differ between the X308 XJ8 and the XJ8 VDP,
I don’t have access to the parts fiche for those cars, (although that would
be a departure from the XJ40 and the X300, where all sedans except V12s and
XJRs used the same suspension parts), but any car that bounces more than
once in response to an downward impulse needs new shocks - just my opinion,
of course, but also conventional wisdom. The fact that you found a similar
car (with 70,000 miles!) that behaves the same as yours only proves that
your shocks are consistent with those on a car with 70K miles (very possibly
worn out). On the other hand, the XJ6 with 140K miles certainly must have
had its shocks replaced, perhaps recently…

Use logic here, the car once rode well and should be able to do so again. If
the ride height is O.K., the springs are fine.

Do what you like, and good luck!

Dave Lokensgard
'96 XJR (DAVZCAT)
'90 Sovereign (MELZKAT)
'90 Vanden Plas Majestic (PATZCAT)
'55 XK140 OTS
Poway, California


(jaguarSean) #10

In reply to a message from Lokensgard sent Thu 21 Apr 2005:

In all honesty, I’m hesitant to question the opinion of a
mechanic who has specialized in Jaguars for the last 25+
years and who drives a series III as his personal car (he
uses a C4 Audi as his winter car running my wheels and
Vredestein Wintrac tires).

My problem is, I continue to compare the Jaguar to my Audi.
I spent the day driving the VDP and I luxuriated in the
smooth response and handling feel that is Jaguar. Honestly,
Audi drivers would not BELIEVE the smooth responses of a
Jaguar unless they spent an entire day with one. That being
said, the Audi is a nice ‘‘athletic’’ feeling change from the
Jag.

Nevertheless, my wife is happy with feel of the Jaguar VDP
other than the overly sensitive front suspension on sharp
bumps. If it were my daily driver, the VDP would become a
test bed of new suspension parts in search of the perfect
long wheel base suspension. My first shot across the VDP bow
would be a set of Bilsteins for swb XJ6s. I’d also like to
know if the springs for X300s and X330s are running the same
rates… if not, I’d probably push for the X300 springs.

You know, it’s funny… Jaguars are supreme vehicles on the
road. They’re smooth, relatively quick, handle beautifully,
but there doesn’t seem to be an aftermarket targeted at
improving the performance of these fantastic cars. That’s a
shame. I spend way too many hours and $$$ improving my Audi
and I’m such a sucker that I’d do the same for the VDP if
given half the chance.

On a final note. I’ll call the mechanic and ask if he sees
coil-on-coil contact evidence. After that, it’ll be a
brainstorm session on this shock-as-bumpstop idea.–
The original message included these comments:

No, not if it’s designed to do the job. ALL Macpherson strut suspensions,
for example, have this feature (not that your car has a Macpherson strut,
but you get the idea). Look at your prings to see it they show evidence of
coil-to-coil contact - it should be obvious is they do. Most times when a
Jag front suspension makes noise, it’s due to the upper shock mount bushings
being tired or incorrectly installed. Less often the lower shock bushings.


jaguarSean '97 VDP
Walpole, MA, United States
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(Brian Caro) #11

In reply to a message from jaguarSean sent Wed 20 Apr 2005:

There may be more than one thing causing the crashing sensation,
one is design-based… the rubber mounted front subframe. This
subframe is heavy and when its mass is set in motion suddenly by a
sharp bump on both front wheels at the same time, its inertia and
sudden stop will lend a definite jolt to the body. Next, just about
every X300 will have no effective upper or lower bushings
supporting the radiator or AC condenser, based upon what I saw when
changing mine a couple weeks ago. The mass of these two things
loose in their mounts will lend a definite ‘‘thud’’ to the
proceedings. It did in my car, which is now more docile after
replacement of these bushings. It is possible that your tech is
right on the bump stop, I see none in there, and it is possible
that the spring closes up in heavy hits, but the crashing can
happen on small bumps, way too small to bottom the springs.–
Brian Caro
Newport News, VA, United States
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(uncle) #12

In reply to a message from jaguarSean sent Thu 21 Apr 2005:

I have 148K on my 95, replacement Bilsteins all around, new
radiator/condensor bushings, and for the most part good supsension
components. I am also in a location where rust is not a problem,
and everything under may car is still in paint.
I get no vibration, no tire wear, no pulling, etc. The alignment
is the original from the factory. I am on my 5th set of tires, and
have never had one wear unevenly. Driving my car at speeds in the
80-90 range is also quite smooth.
That said, when I drive the car on roads with sharp obstructions,
pot holes, ridges, etc. I get a thud of some sort also. I have not
been able to isolate, but think it may be the sway bar bushings, as
regardless of which wheel hits the obstruction, I get a sensation
across the front. This is a very muted sensation, and is tough to
describe. It happens only on lousy streets.
I could drive on decent roadways and never feel it.
Because I live in a old city with poor streets, I have thought
about using V12 shocks on the front. I did have a set at one time
and they are dimensionally identical to the XJ6 shocks. They are
valved differently to handle the additional 200+ lbs of weight on
the front , so In my opinion they would help.
If this was not adequate, you could change the front springs for
the V12 springs also. This should help out quite a bit.
I run 34LBS all around so perhaps lower pressure would help absorb
the bumps.–
uncle
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(uncle) #13

In reply to a message from jaguarSean sent Thu 21 Apr 2005:

Sean:
Somethimg else you may want to ask them about. My understanding is
that there are multiple thickness spring shim/spacers for the front
and the rear springs on these cars. Fronts show as 1.5mm or 4.5mm,
there may be other sizes as well. If I recall, there were differnt
sizes for the rears.
I have not found any reason for these different thickness shims.
Maybe the dealer can shed some light on the reason.
By the way, my early 95 was always a bit down at the rear. There
had been a TSB which I missed that if the customer complained about
rear vibration when the car was fully laden, to change the rear
springs. My car did this. Wnen I changed the shocks, I installed
new spring islolator bushings, (the old ones were compressed a
little) and the car now sits at an improved height. The old
isloators wre compressed no more than (1/8’’) 3mmm so that amount
can make a diffrence.
I think they could change the front spacers easily.–
uncle
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(TSL) #14

In reply to a message from jaguarSean sent Wed 20 Apr 2005:

Having spent multiple thousands to try to rectify the ‘‘crash’’ up
front on my previous 97 L - which included brand spanking new front
Bilstiens AND brand new springs AND almost all entirely new front
suspension soft parts - and a few hard parts. All still not fixing
the crash (softening it progressively, but not fixing it). I am of
the firm belief that the tires are a big part of the cause of
those ‘‘crashes’’. If perchance you happen to have a set of P4000e’s
on the front, may I suggest that you go get a new set of 2 P6000’s
and have them mounted up front. Then go try your bumps and see what
happens.

Now this is not to say that you are not in need of new front
shocks/dampers, but TRUST ME, it is much cheaper to start with the
tires.

TSL–
96 VDP ’ I’ll be in in a minute dear . . . ’
Maple Valley, WA, United States
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(JaguarXJ6) #15

In reply to a message from TSL sent Thu 21 Apr 2005:

Bingo!

You could even swap wheels with another owner to test the problem
by investing in jack stands (that you get to keep) and see if the
suspension reacts the same without having to buy new tires and hope
its fixed.

Mine P4000’s are stiff. Once or twice a week they flat spot (the
infamous Pirelli flat spotting) and have definitely contributed to
the transmission of smaller bumps into the frame/cabin.

FWIW, if I put my foot on the rear bumper (thats missing a bumper
cover), and give it a strong push with my leg using my weight (150
ish lbs, don’t laugh) and release, my rear end takes one cycle and
change. Change means, 1 cycle and a 2nd cycle half the size or
less than the first before its calm. Dave’s got the XJR
suspension, don’t listen to him. :wink:

Sunny–
The original message included these comments:

the crash (softening it progressively, but not fixing it). I am of
the firm belief that the tires are a big part of the cause of
those ‘‘crashes’’. If perchance you happen to have a set of P4000e’s
on the front, may I suggest that you go get a new set of 2 P6000’s
and have them mounted up front. Then go try your bumps and see what
happens.
Now this is not to say that you are not in need of new front
shocks/dampers, but TRUST ME, it is much cheaper to start with the
tires.
TSL


Sunny Garofalo, '97 XJ6 Anthracite/Charcoal, 121k miles
Burbank, CA, United States
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(burmaz) #16

In reply to a message from TSL sent Thu 21 Apr 2005:

Does your VDP crash over bumps like your XJ6L did? How does the VDP
ride compared to the XJ6L? How does the handling compare?–
The original message included these comments:

Having spent multiple thousands to try to rectify the ‘‘crash’’ up
front on my previous 97 L - which included brand spanking new front
Bilstiens AND brand new springs AND almost all entirely new front
suspension soft parts - and a few hard parts. All still not fixing
the crash (softening it progressively, but not fixing it). I am of


burmaz
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(Jagnrights) #17

In reply to a message from uncle sent Thu 21 Apr 2005:

Count me among the ‘‘Crash’’ victims. 1997 XJ6L 150k miles.

When I first got the car, about 13K miles ago, it would
jarringly crash over the smallest of potholes or expansion
joints. At the time it had P4000 tires that still had about
half-tread on them.

I have now at least mitigated the crash by doing the following:

-Added Bilsteins and new bushings all-around.
-New Michelin MXV4Plus V-rated tires all-around.
-(I considered replacing the springs, but as someone said
previously, the bumps that cause the crash aren’t large
enough to cause full spring compression so I decided to hold
off.)

At that point, I still had the crash, but it was less
severe. I was running 34lbs front and rear. Since then, I
lowered the pressure to the ‘‘comfort’’ setting listed in the
chart under my console lid. (I think it was 26lbs front and
28lbs rear for my car.)

Dropping the pressure has taken care of the crash, although
I still wince in anticipation when crossing onto one
particular bridge in town. I’m sure it was a combination of
all three things I had done. I plan to raise the pressure
gradually to find the ‘‘thresehold’’ for the crash, and settle
on a pressure just below it. At the 26/28 tire pressures,
poor road surfaces – like grooved pavement in a
construction area – cause the handling to become a bit
exciting. By which I mean dangerous.

One thing I’m curious about is, do those of you who
experience the ‘‘CRASH’’ also suffer from the affliction known
as the ‘‘SHIMMY.’’ I have often wondered if the two are
related, but while my Crash is gone, my Shimmy rolls on.

Hope this helps.–
Jay Huggins, 1997 XJ6L
Charlotte, NC, United States
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(TSL) #18

In reply to a message from burmaz sent Fri 22 Apr 2005:

No Sir. No crashes. SMOOOOOOOOOOTH!

@ 42+ K w/P6000s on 'er, she is a HUGE improvement over the L.

I finally got my fat cat ride.

TSL–
The original message included these comments:

Does your VDP crash over bumps like your XJ6L did? How does the VDP
ride compared to the XJ6L? How does the handling compare?


96 VDP ’ I’ll be in in a minute dear . . . ’
Maple Valley, WA, United States
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(PeterCrespin) #19

In reply to a message from TSL sent Fri 22 Apr 2005:

For small bumps the tyre is important. F1 cars have ahrdly any
suspension movement and rely on the tyre hugely.

Pressure, type and construction are important. My understanding is
that the P4000 (for example) specified by Jaguar is NOT the same as
the p4000 you buy down the local tyre dealer. It has a different
number of plies and this could well account for a difference in
sensitivity to small bumps. If Jaguar went to the trouble of
developing a unique tyre spec to ensure their flagship rode like a
Jaguar should, then it’s not surprising that deviating from the
spec causes issues. The right tyre, suspension in good condition
and the pressure set at ‘comfort’ settings is the way to go for the
best ride. Anything else is less, as Harley Davidson used to say.
Having said that, I go for compromise pressures nowadays, around
the 30-32psi mark.–
Peter Crespin 94 X300 Daimler / 66 2+2 ‘E’
Buxton, United Kingdom
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(Kevin Campbell) #20

In reply to a message from Peter Crespin sent Sat 23 Apr 2005:

This rings a bell from my days of XJ40 ownership, I recall
some discussion back then that the US retail P4000 was not
the same thing as the OEM fitment. It might be worth
trawling the old ‘‘Modern list’’ archive, as tires have been
discussed and re-discussed to an incredible degree. Tread
design and sidewall construction both have an impact on the
noise transmitted to the cabin and the management of smaller
bumps.

Kevin–
The original message included these comments:

In reply to a message from TSL sent Fri 22 Apr 2005:
For small bumps the tyre is important. F1 cars have ahrdly any
suspension movement and rely on the tyre hugely.
Pressure, type and construction are important. My understanding is
that the P4000 (for example) specified by Jaguar is NOT the same as
the p4000 you buy down the local tyre dealer. It has a different
number of plies and this could well account for a difference in
sensitivity to small bumps. If Jaguar went to the trouble of


Jagless in Seattle
Bothell, WA, United States
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