"Skittish" back end

[jwlshort]

Hi,

Whenever I go over even a small bump or slightly protruding manhole cover with the back wheels of my '98 4.0 XJ8 the back end of the car does a little sideways skip. This is quite disconcerting and something I would like to cure.

My previous Jaguar was a 1988 3.6L XJ40 Sovereign which had exactly the same problem until some bright spark spotted that the tyres were the wrong size for the wheels. This was not until after a Jaguar main dealer had sopect a lot of my money shaving bits off my ball joints! The tyres were replaced and the car then handled perfectly.

I have checked and checked the tyres on my current model and they do appear to be the correct size.

I was wondering if anyone else has had a similar problem and can suggest a cure? A perfect ride is one of the joys of owning a Jaguar I think. I'd just like to have it with my current Jaguar.

[daveji]

Suggest you E-mail David Marks on this one.

[MrChrome]

I have a 98 and have the same problem. Changing the A-frame and the anti roll bar bushes helped but did not cure. I'm hoping that by changing the tyres (pirelli) the ride will improve.

[Blackadder]

I have exactly the same "skittish" problem.

I also have a high frequency vibration coming through the front wheels which is particularly bad at around 60mph, although is noticeable upwards of 40mph. It decays at 70+, but is still noticeable at this and higher speeds.

Have tried replacing bushes, re-balancing wheels, etc but no change.

My local Jag specialist can't suggest a solution, so any advice gratefully received...

[joejag308]

Blackadder......i have the vibration for a short distance and only every now and then.....the sideways jumping with mine was overinflation of the tyres .......not much but it is critical the pressures are kept up to.
but the overall logical explenation seemed connected with the cats suspension......if you have the car stood for a few days its the suspension that is resetting itself .......possibly not your exact probs but thats what mine was........also at the last service i forgot to tell the garage not to interchange the wheels as i had two tyres that had done more miles on the front than the two on the back,so there is a mismatch there too.
I have 4 new Pirrelli isometricos to put on for the season that should even it all out..........joe

[Blackadder]

Hi Joejag - did it work for you?!

[joejag308]

My prob turned out to be funny enough, the tyres,they had just started to wear on the inside edge on both front ones which were the two more worn ones (actually they were the original tyres) so i went to my local tyre guys who said don't put the new Isometricos on just yet. So we put the more worn two on the back and the better two on the front.
Then we checked the tracking (evidently quite an issue on the 308s) and found it to be slightly out of line.......so it was adjusted and off to Southern Day we went. It actually ran a lot better with no vibration and the steering was more positive so that was only with a minor adjustment. Anyway I dern't turn up there with Admin going as well, hes very keen on the standard of any forum vehicles that turn up....so be warned...........Joe