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

(PeterCrespin) #21

In reply to a message from Kevin Campbell sent Sun 24 Apr 2005:

There’s no question that the Jag-spec P4000 is different from
normal - I just can’t recall exactly why, and what the suffix is
which denotes the correct spec. Might be a J or an E or something.
I’m almost 100% certain the difference is in the number of plies
but whether it’s the sidewall or the tread belt plies I also can’t
recall. I ‘think’ but am not 100% certain, that the Jag-spec P6000
is also different from that for other cars.

Which is not to say that a box-stock P4000 or P6000 won’t work fine
most of the time and many people wouldn’t notice the difference.
But for anyone looking for the ultimate level of achievable
refinement over bumps, then it pays to go with what the factory
testers developed for the car. Apart from anything, as has been
pointed out, it’s a whole lot easier and cheaper than replacing all
the suspension hardware in sequence… Once you have the right
tyre, drop the pressure to the low end of the recommended range to
suit your requirements and you’re well on the way to that elusive
magic carpet ride. For any hard / fast trips put a bit more air in
and drive safely on the firmer ride until it’s cruising time again
at the lower pressures.–
Peter Crespin 94 X300 Daimler / 66 2+2 ‘E’
Buxton, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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(Dave and Patsy Lokensgard) #22

Kevin wrote:

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

and Peter wrote:

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

The OEM tire was the P4000E. It is about twice as expensive that the P4000
Super Sport, which Jaguar recommended for a time in the early '90s as a
replacement for the discontinued P5 on the XJ40. The P4000E is a suitable
tire for the XJ40 or the X300, while the P4000 Super Sport is pretty
universally disparaged as being not suitable.

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

(uncle) #23

In reply to a message from Peter Crespin sent Sun 24 Apr 2005:

The Pirelli P4000e and the P6000J both have two ply sidewalls. The
non J have one ply.
My opinion is that this was specified so that lower pressures could
be run and still maintain high speed performance.
Finding this category of tire (high speed all season touring) with
two ply sidewalls is very difficult. Some of the Dunlop SP5000’s
have them, but most in the 60 series do not.–
The original message included these comments:

There’s no question that the Jag-spec P4000 is different from
normal - I just can’t recall exactly why, and what the suffix is
which denotes the correct spec. Might be a J or an E or something.
I’m almost 100% certain the difference is in the number of plies
but whether it’s the sidewall or the tread belt plies I also can’t
recall. I ‘think’ but am not 100% certain, that the Jag-spec P6000
is also different from that for other cars.

–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

(Geekay) #24

I’d like to get some follow up on this very old post. I have previously complained about the ride on SWMBO’s '97 VDP compared with my silky smooth XJ40 - I’m talking about crashes, bottoming, whatever you want to call it on the X300. Both cars are 200k drivers.

Some years ago I did a “FULL MONTY” on the front end - sub frame bushings, vee mounts, Bilstein HD shocks, all bushings, steering rack, tires, ball joints - you name it I replaced it. The ride improved but I never solved the issue. It does seem as tires age the issue gets worse. I’ve played with psi settings and on SC roads it seems better to stick with 34psi.

I just got through replacing my diff and restoring the prop (UJs, center bearing and re-balancing).

My wife drove my XJ40 (same HD shocks) while I worked on the X300 and while she is thrilled that the diff no longer whines (thanks DM!), she said she was spoiled driving my XJ40.

So…I’m seeking any new feedback from X300 owners. I’ve considered springs but that seems like a possible sideshow.

I intend to put the car on the lift this weekend and re-visit all components.:

  1. Tires -? Currently both have Pirelli P7 Plus all Season Plus
  2. Both have Bilstein HD shocks.
  3. Shock Upper bushings - X300 has Bilstein yellow OEM looking bushings. XJ40 has aftermarket rubber and has for many years. What torque is best for the factory soft yellow bushings? I don’t recall the factory spec but it seems they are very compressed. I’m planning on switching to rubber to compare then OEM.

Thanks for any feedback.

(Art Ford) #25

Any chance you are using the popular fork lift tires and afro wheels? My '02 308 never hits bumps hard. It runs 16" wheels. Larger wheels will not work as well.

(Geekay) #26

Standard 16" factory rims. Just the same complaints on this model that a significant number of owners have reported over the years.It just seems complaints are more prevalent on the std (non sport) 94-97 X300.

(PeterCrespin) #27

34 psi is high if you want comfort.

The foam bushes don’t respond to torque as they should go over a sleeve that allows compression of the foam a fixed distance and no more.

(Geekay) #28

Peter - If I understand you correctly you can just ratchet down the nut until it stops - compressing the foam bushes as far as they will go? I heard that once before from a Jag mechanic but questioned it in my mind because there is a quoted psi on the X300 CD - 15.5 - 20.5 NM. I’m not clear what you mean related to “34psi is high if you want comfort” if the foam bushes don’t respond well to torque. Are you suggesting that using 34psi will result in an uncomfortable ride? Sorry for confusion.

What do you propose on the aftermarket rubber ones?

I have aftermarket ones arriving Wednesday and am going to compare the Bilstein/Aftermarket ones.

Separately Technical Bulletin 19.7-0.3 6/96 does not instill confidence:

Some 1995-96 MY Sedan Range vehicles may experience knocking noises from
the front shock absorbers.
To overcome concerns of knocking noises from the lower shock absorber
mounting, the torque specification for the mounting nut has been raised to 51.6 lb.
ft. (70 Nm) from VIN 777889”

Appreciate your insight.


(PeterCrespin) #29

It was a long time ago and I may be mixing up X300/XJ40/Series 2 but I believe the principle is the same for petrol tank or radiator mounts, top damper mounts etc where you need a solid mount but cushioned. The rubbers go over a rod or tube or shouldered bolt where the nut or bolt is turned fully tight but this does not totally squash the foam or rubber. This assumes the spacer/sleeve or shouldered bolt is present.

I prefer the foam bushes as original.

34psi is what you said you run the tires at. If you want comfort you can run at lower pressures like 28 psi if you keep below 100 and don’t expect quite such good steering turn-in or responsiveness.

(Geekay) #30

Ah! I understand. I don’t believe that’s the setup on the XJ40/X300. If you tighten the top nut fully it will compress the top foam bushing down to perhaps as little as 1/4". Btw the Bulletin states 35nm not 15.5-20.5nm as I quoted above from the CD.

One of my preferred suppliers says to tighten the top nut down until the foam starts compressing and stop.


(j limongelli) #31

A lovely car as I have 6 of them , most since new…
The car is now 21 plus years old…
If you like it, the following will get rid of it all.
As others have said…
1.Change ALL the bushes, front/back upper and lower.
2. Change the tranny mount!, you wont believe what it does.
3. Change the shocks.
4. If yours is a 4.0 check the ball joints but they are sealed and pretty much bullet proof.
The bushings and shocks will transform the car…GET MICHELIN ALL WEATHER PILOTS!
The car will now run brand new.
If you have the 12 which I don’t think so…the heavy front killed the entire suspension, every 50,000 miles all has to be replaced.
Good luck!

(Geekay) #32

Joey …Hmm…I did the FULL MONTY but it’s been 100k of hwy miles. Surprised needed as frequently as 50k intervals. I did ALL including all bushings, shocks, vee mounts, engine mounts, steering rack and sub frame - EXCEPT Transmission mounts. New shocks have only 10k or so on them.

Mine is the 6 not the 12. Interesting comment on Michelin. I once put XV4s on my XJ40 and took them off after a week and put Kumhos on until recently when I put Pirelli P7 on. XJ40 runs smooth as silk at 210k. Same tires on X300. Never had a single bushing changed on XJ40.

What impact did changing the transmission mount have?
What shocks are you using and to what extent are you tightening the upper shock retaining nut?

I am getting it on the lift this week after I change shock bushings and will be pry barring everything. I’m not in a hurry to drop those springs again.


(j limongelli) #33

50,000 for the v12, not the xj6.
I went stock all the way around but the tranny mount is set in a way that if worn or ripped ,you hear a thud or the shields vibrate along the tunnel if it moves.
100,000 miles is about the max.
Again the car is now 20+ years old.
They were built right.
If you use the Michelin Pilots , it will transform the car.
Your old xj40 had different size wheels and the front camber and geometry was different.
Early xj40/6 had the horrible metric tires. Throw on the Michelins, it will be in ROLLS ROYCE territory
Good luck.

(Geekay) #34

You must be referring to earlier XJ40s. The '94 I have has same 16" wheel tires and shares mostly the same parts on the steering/suspension with the '97 VDP. Only thing that I believe were speccd different were the springs on the X300.

Comment noted on Michelon Pilots.


(j limongelli) #35

Yes I didn’t know what year xj40

(Geekay) #36

Special thanks to GTJoey1314 for being insistent on the transmission mount. Having changed the diff, center bearing, Prop UJs, re-balanced the propshaft, changed transmission fluid and filter, starter motor, Idler pulley and belts, I decided to look at the transmission mount. At first blush it looked fine. Even off the car it looked fine. But I decided to change it. Holy smokes. My old one was intact - no visible deterioration in the rubber but the rubber “legs” appeared to have shrunk!. I’ve attached a picture of old and new side by side.

Car is smooth especially on hard acceleration.

Now - can I get this puppy to 500k? Its at 235k right now. Off to change the bottom shock bushings to poly.

Thanks again Joey - I may have overlooked that but for your insistence!

Gary :grinning:

(j limongelli) #37

Happy it worked out!
It was a lucky guess:)
Those cars were built like tanks!
Simple and last DIY.
I had the same issue 15 years ago and thought a u joint broke, but it was the flex over a bump or turn, like a buck board Model T.
The lesson here is that everything old shrinks a little…Gentlemen, do we agree?
Old Seinfeld show…
P.S. run 20 /50 in summer, 10/40 in the winter, its a lot less stress on the old aj motor.