for X300 owners ...

take a look at post #9 below

poly bush kits?????

it may be the cure for tramlining, except that the term being used is "camber chasing"

it involves the installation of poly bushings in the upper control arm.

 

Thanks Plums.

I *think* that posting was from one of the original members of XJR6.com (now defunct).

If so, the bushings he had made (and was selling) were offset to actually change the camber, since X300s have no camber adjustment.

XJREngineer, if he sees this thread, might remember the details and/or the source of the bushings.

Cheers
DD

 

That would be nice! I'm all for urethane bushings!

 

Poly bushes for the X300 are readily available, see here.

SuperFlex: Advanced polyurethane suspension bushes

I have these (top and bottom wishbones and ARB bushes) on mine and they work well. They do introduce some harshness but it's not a deal breaker for me.

 

Powerflex is another vendor.

In the original post, the poster refers to only replacing the bushes on the upper control arm. That makes sense if the actual thing he was doing was controlling camber change without steering input.

I would doubt that poly bushes alone could be offset because they rotate more easily in the bush bore than do rubber types. It would have to be a pressed steel sleeve that had an offset between the inner and out sleeves. And of course I could be completely wrong on that

Anyways, just the uppers would be relatively inexpensive to solve a problem and certainly easier to replace than the lowers.

The thinking on the ARB bushes is that they effectively offer a stiffer ARB with more immediate action because there is less slop to take up before coming into play. It's like getting a fatter ARB for $40.

Now ... any thoughts on bad lower control arm bushings being the root cause of steering wheel shake at highway speeds when braking for an off ramp without exhibiting pedal pulsation?

It was mentioned in one thread here. But most posts on JF will get a response pointing at rotors. Yet, in other forums for BMW, Audi will at least consider the possibility of bad lower control arm bushings when there is no pedal pulsation.

BTW, the only X308 LCA bushes offered by rockauto are URO for about $5 a piece. And they look to be worth about that much. I've seen better hockey pucks. Very disappointing that a company that is essentially a drop shipper does not at least offer better alternatives. It would cost nothing except bandwidth if they don't sell since they don't stock themselves.

 

Now ... any thoughts on bad lower control arm bushings being the root cause of steering wheel shake at highway speeds when braking for an off ramp without exhibiting pedal pulsation?


I would say yes they are a definite candidate. Any bush that could allow the front wheels to move in a horizontal plane could cause that. I would also check the front subframe rear bushes and V mounts.

 

Thanks ...

any input on how to reliably check the LCA bushes besides visual inspection? Pry bar while weight taken off the suspension with the wheel dangling? That is, by jacking under the jacking point.

The X300 and X308 have a similar LCA setup.

 

I'm not sure how the tendency to rotate was addressed but the steel sleeve was not concentric with the the OD of the bushing. Of course this mean that the bushing had to be carfully located before being pressed into place.....





That right. This also means that, if for some odd reason you didn't like the poly bushings, removal is just as easy as installation.





Makes sense to me.





URO parts are developing a poor reputation. And it appears that they've become a supplier to Jaguar for service replacement parts on older models.

LCA bushings are a big job to install. I'd hate to do it twice on the same car unless at least 100k miles had elapsed since last replacement. I'd be a little upset.

Cheers
DD

 

The pry bar technique is good, IMHO, to identify bushings that are badly enough worn that they've developed slop.

Before a bushing has worn to the point of being sloppy it can be distorted.....the rubber on one side visibly compressed....so that the control arm isn't flopping about but , rather, is simply no longer in the correct postion. Therefore I also look for concentrcity....although sometimes the shape and positioning of the parts prevents getting a good view


Cheers
DD

 

Yes, that's essentially what I meant. In order to get an offset, an additional external steel sleeve with offset is required because the rest of a conventional poly bush design could never hold an offset reliably.

Of course, even without a camber change, if the upper control arm can just hold camber more steadily, a normal design concentric poly bush might still be a benefit to all those tram riders.

BTW, on the wandering interior heat situation ... the X308 system appears to have two thermistors in the evaporator/heater core sandwich. These will behave much like the thermistors in the MAF in that a film of dust throws them off. Something to consider if the X300 has the same setup. Too much work to get at them though

 

I went through all this a year ago when I bought my 3.2

It had crappy budget tyres on the chromed 16" turbine wheels. A result of a 93 yr old owner letting the family do budget servicing...

I got new tyres, Toyo 16 x 225/60 - a lot better

then I got all front suspension bushes replaced with genuine Jaguar rubber ones. Even better, but not as much as I hoped. The mechanic said the old ones weren't as bad as they might have been - perhaps 'code' for this wasn't necessary??

Then a month went by - I was busy at work - still a bit disappointed with a touch of tramlining on certain bits of road.

Then I finally got the alignment done - yes, I know, but I was busy - what a revelation. And it was only out by half a degree.

Then I went from Chrome Turbines (16" x 225/60) to Asteroids off an XJR 308 (18" x 245/45) and I went from no tramlining to a little. But not much.

Winter is coming and I may flick back to the Turbines with their new tyres for a while... if I do, I will let you all know if ride/tramlining improved.

 

Originally Posted by plums View Post

any input on how to reliably check the LCA bushes besides visual inspection? Pry bar while weight taken off the suspension with the wheel dangling? That is, by jacking under the jacking point.

I always try and test suspension bushes with the weight of the car on the wheels. Having wheels dangling puts the whole suspension in an unnatural position and can hide issues.

I lower the front wheels on to some sturdy supports and get underneath to observe and feel movement while an assistant (read wife) rocks the steering wheel.

I've also seen a tool recently made by Sykes Pickavant that looks like a great idea. I don't have one but I may try making my own with a piece of scaffold tube and a metal bar. See here Suspension Wear Indicator (in Tools And Equipment section) @ Prosol UK

 

I noticed improvements on my 95 XJR by fitting pollybushes and profiled washers to the upper arms to better control for and aft movement. I also benefited a lot by using locktite on the stub axle to locate the inner bearing shell. These tend to spin on the stub axle wearing it to a slack fit. If it is not too badly worn locktite can take up the play and stop it getting worse.
John

 

I made my own sealed phosphor bronze plain bearings to replace the front top wishbone bushes. This massively improved the car's handling though has made the ride less compliant, but it is a compromise with which I am very happy. I plan to do the same for the lower control arms. I have also developed a set of rose-jointed front anti-roll bar drop links to remove all of the compliance present in the std metallastic bushes. As suggested elsewhere in this thread, this effectively increases the roll stiffness of the car, and is very effective. I couldn't detect any difference in ride quality from just fitting these new drop links.

 

One more place to take up play is the steering rack.

At both Bernard Emden's site and jag-lovers, it is pointed out that the steering rack mounting allows axial movement. The steering rack is able to move independently along the same axis as the control axis.

Imagine that the steering rack is displace 1/16 of an inch in one direction by a road disturbance or steering input. Imagine further that it does not return but stays there. Instant steering without input from the driver. One way to test might be to take a curve in one direction and then straighten out. If over compensation in the opposite lock is required immediately after returning the wheel, but the compensation requirement fades, then this might point at the steering rack moving and binding.

The fix for some people has been to put shims on both sides of the steering rack mount rubbers to take up the slack.

One member in the X308 section designed and built some nice stainless steel interlocking shims and taled about making them available to other members. Unfortunately, he only produced one set to my knowledge before departing for parts unknown.

BTW, if anyone is equipped to make them, I'll cough up the design in return for a set


Poly rack bushings are available for the X300 .. not sure about the X308.

 

Really? Where can we find 'em?

The rack bushings on the older Jags (like Bernie's XJS) are a notorious trouble spot. They'd often disentegrate to the point that the car was outright dangerous.

Cheer
DD

 

My bad.

I had another look around and it seems availability is for the older models.

However, I believe either polybush.co.uk or energy suspension sell poly rod. Someone with the right tools for light machining could make their own. Or start with a universal bushing and cut down as required.

 

People used to fit the spacers from the Jaguarsport XJ40 XJR (SPC1059) to eliminate the play between the rack and its mounts. Unfortunately these appear to no longer be available from Jaguar.

 

there is a pair on ebay right now

XJR XJ40 X300 Jaguar OE Steering Rack Bush Repair Kit SPC1059 | eBay

 

looking at JEPC, the X300 diagrams do not show the mounting arrangment for the steering rack.

the X308 diagram shows a bushing that has dimples on the internal circumference. if the X300 is the same, maybe those dimples could be an upgrade.