poly bushes on an XJR

[Zippyworld]

I am interested in peoples opinions in fitting poly bushes to a 1998 XJR.

I read in Jag World "Do not fit poly bushes" in an article on modifying the X308. But they failed to say why.

I have a mechanic who has fixed Jags for 30 odd years, the sort who drinks engine oil and eats plastic tensioners and he reckoned that the suspension is so sophisticated and effective that its not necessary unless the car is used on track days, which its not and it will rarely be so.

Now I'm gonna be totally honest and say I have fitted them and I am seriously considering replacing them with originals.

The car just doesn't feel confident on potholes, grids etc....

Thoughts

[a8hex]

Mike Cross is pretty good
Unless you want to do something radically different they he thought you would then tinkering with the chassis is not likely to improve things for a general road car.

[NormanD]

I have full poly bushes on my 1999 XKR

I haven't found any dislikes about then, they is not even more road noise

[DickLotus]

I too have fitted poly bushes back and front to a 36,000 mile XKR convertible with 20" wheels + SS suspension. I did this when I was chasing the usual wheel vbration. Apart from one upper inner front wishbone bush the originals were fine. I am about to throw out the out of round Pirelli's. I have no problem with Poly bushes especially fitted to a heavy and hard sprung car, and have known them transform other modern sports cars. I can't say I feel any worsening say of stability under relatively hard braking or turn-in. I guess incorrect geometry settings would have more drastic effect. Transmitted road noise seems to be about the same (SWMBO accuses me of being a little deaf), but I would think this is the real area adversely effected. I might be kidding myself, but I feel turn-in and a general direct connection with the car has improved slightly. So the real benefit may just be long life.

[RW774]

There are changes to be made to the steering geometry to get the most out of Poly bushing.Camber and caster have been factory set to cope with the compliance of rubber bushes, that is why it is now so twitchy on standard settings. Polys take away the compliance.
Tyre pressures also need attention as do dampers and springs.
You have only some of the ingredients for improvement, take the whole package man, not just a bite of the cake.
EG, as much caster as possible with an element of negative camber on the front and neg on the rear aswell.Decent dampers and progressive rate springs.
Drop the car and away you go. Sounds easy, but its` not. If you change the wheels to a different offset the weight loading changes on the top/ bottom balljoints adding to camber/ tyre slip angle changes, hence the need for progressive springs.Its` a science you need to understand first

[Straight6DOHC]

These appear to be available for X308 and there's plenty of advice on them here: http://xjr6.com/forum/index.php?topic=32.0

[designXKR]

We have supplied and fitted numerous sets of Poly bushes to XKs all with very good results. Unfortunately due to a recent fire at the Powerflex factory they are unable to supply any new bushes until sometime in January. Please be aware of buying any poly bushes from UK ebay at the moment. Check to see if the seller actually has them in stock and is not reliant on the factory supplying them.

[Zippyworld]

Thanks for the input guys, I am starting to think that I am not gonna benefit from the poly bushes. I have no intention of doing track days in this car and it will very very rarely be stretched to its handling limits ( not intentionally anyway ). I am opting to put original spec bushes back on the car. Britishparts are doing a full set (8) for aboout £60. Anyone used these or are they that criticalthat I should be taking my pants down at the dealership ?