Tracking, What is the correct tracking for an XM?

Toe-out is, to a certain extent, logical with front wheel drive as the driving force of the wheels exerts a turning moment around the king pin axis which, should there be any play or compliance in the steering linkage, will lead to parallel or toe- in tracking. If you start with toe-in this effect will lead to excessive toe-in and consequent tyre wear. I have heard of toe-out on other FWD cars.

Hi Peter,

Did you dismantle the tops to oil them, or did you just squirt some in behind the rubber cone? I always thought oil etc would be bad for that kind of rubber, but I know nothing about this and you know where assumptions can get you!

Hi All

I have been looking into strut top corrosion for a while now. So far I have concluded that there are 2 distinct failure modes.
1. Corrosion of the metal to which the rubber is bonded. This starts from the top of the metal under the thin layer of covering rubber. This can be seen from the top of the strut head as rusting or bubbling. I am satisfied that this is the result of a design or manufacturing flaw.
2. The main body of the rubber support for the strut can be ruptured. This can be seen by examining the underside of the strut head as tears in the rubber support. This is mechanical damage that results from excessive force on the strut head. Driving with shot spheres can cause this damage but so can a excessively rusted strut head where the residual steel cannot retain the rubber correctly.

There is no major design differences between Mk1 and MK2 strut heads so Mk2's are going to start popping up through bonnets any day now if they havent already started. I took some photos the day before yesterday of the strut heads in a scrap 98R reg 2.5TD, one was heavily rusted and I reconed that the other was a miracle that it had not popped.
Before you all get too worried that car had 264k on the clock and the clutch and gearbox had died. I think that outside parking (condensation), accumalated mileage and sphere condition are the major factors in sphere head life.

A while ago I had a look at the Scandinavian system which comprise a pair of half shells that bolt over the top of the rusted the gap to the rusted head filled with windscreen adhesive then the half shells welded to each other. Cost for a pair of these was less than one single new head. As they only came as a pair and at the time I wanted 3 all one hand so decided it was not the best solution for me. I did not fancy sending a car into an MOT with an obvious repair to one strut head using components that did not have UK provanance.

Regards

XMexc

Cheers XMexc, that's quite helpful. Will be having a thorough look at mine later.

When you mention the underside of the strut head, do you mean around the bottom of the big rubber dome thats visible just below the sphere?
I'd appreciate seeing those photos sometime if you get a chance.

I don't suppose anyone has an exploded diagram of the inside of a strut top? Never having taken one apart, I find it hard to visualise what's in there and what you should be checking for.

Cheers.

Ciarán

Hi Ciaran

I have been collecting the odd rusty strut head when I can get them and meaning to section one or two to be sure of the construction and degradation processess. When I do I will upload the photos as I now take and use the digital camera on virtually every bit of XM work.
The torn rubber on the strut head can be seen from in the wheel arch not from above. You should not need to disturb the strut rubber bellows as this only clips over the centre part of the underside of the strut head rubber mount and the tearing and damage shows clearly in the rubber moulding outside this if there is any.
It will be much easier to describe when I can again put up photos. Sorry.

Regards

XMexc

Aha I see what you mean now, will investigate with head in wheel arch later. Many thanks for that. I'm sure everyone will be looking forward to seeing the photos, I bet this keeps many an XM owner awake at night!

Cassmo - King pins? you must be nearly as old as me! If you look at the suspension pivot point of a Mcpherson strut it is inboard of the wheel, so any backward force will tend to make the wheels tow out, hence the normal 'tow in' adjustment. That was the beauty of the CX, it had the steering knuckle assy right in the centre of the wheel, so any backwards pressure didn't upset the steering. In fact when the M5 first opened a drove some distance with a flat o/s front tyre before I realised it. I thought the road surface was a bit rough....

Ciran - Yes I agree that the oil will have a detrimental effect on the rubber but that will be a slow process and is infinitey preferable to a strut through the bonnet! I just rans some oil around the top of the strut and let it soak in.

Peter.N.

Apparently one of the signs of impending failure on Xantias is that the rubber bellows that surrounds the leg becomes detached at the top so that it sags like Nora Batty's stockings. The ring at the top of the strut in the wheel arch distorts and can no longer hold the bellows in place.

The New Zealander "Mandrake" who I have recently mentioned has done a lot of work on this subject and has produced some real horror photos of failure modes. The theory is that UK and NZ cars fail through corrosion of the steel caused by moisture ingress plus road salting, whereas Oz and similar places (Spain? Portugal?) suffer failure of the rubber through heat.

Ciaran, the page from the workshop manual that Noz published (see this subject) shows a cross section of the strut top. It's a Series 2 head but CitroenXM says there's no difference between Series 1 and 2. Funny, I heard that they redesigned the Series 2 to solve the problem. Now I've got something else to worry about.

Peter, if the leg pivot is inboard of the wheel contact, then the driving force from the wheel will producing a forward force at the hub, which will produce a moment about the leg axis (does the same job as a kingpin) that will tend to produce toe in.

Derek

So, coasting will produce toe-out and pulling toe-in. Most driving is under some level of pull even if only to keep a steady speed which would suggest a level of toe-out best to compensate.

But, presumably different cars give different levels of each part of this effect depending on design - hence the different reccomended tracking settings for different models.

Am I right?

If that is the case, then presumably changing something like the tyre width could change this ballance and therefore require a different setting. I guess anything of that sort that is done as an option on the car would be within the tollerances given though.

Hi DerekW

I did have a look through some NZ work on strut failures fairly early on but was not happy that salt corrosion would rust the strut head from the top down as seems to happen. There is a large amount of metal in the engine bay even more exposed that should but does not corrode.
If you can provide a link I would like to check on the NZ work you mentioned.
Thanks for the interest, hope the drivers widow is still working.

Regards

XMexc

Rowanmoor - I would have thought the opposite would have been the case. If you are coasting there is little or no load on the wheels, so they will stay pretty well as tracked. When you are accelerating the wheels are being pulled back, which if you look at the pivot point inboard of the wheels will tend to make the front of the wheels turn outward = tow out.

Peter.N.

Hi guys,

Many thanks for the informative replies as usual, will take a look at the workshop manual shortly.

Just a suggestion, but what does everyone think about making a dedicated thread on strut tops, even a how to post of what to check them etc? A coallation of the helpful posts in this thread perhaps?

This is obviously an issue that troubles us all, but it's often one that there isn't clear information available on, and I fear that many 'everyday' cars get binned when they develop a bonnet blister, which a quick bit of checking would have saved them from...

Just a thought

Hi Guys.

Aren't you all missing something here -- ? In any given position, the relationship of the two wheels in terms of track is fixed by the track rods, which , assuming no defects, should have no lateral play. Therefore, even if some force is being exerted dependent on the wheel / kingpin relationship, if the tracking is set at a given figure, the rods will maintain that ??

Mike.

Theorectically yes, but the track rod ends, inner balljoints, lower suspension joints and wheel bearings will all have a little movement, especially when you consider the force applied to the wheels under acceleration, so some movement is inevitable.

Peter.N.

Surely, under acceleration, the front wheels are pulling the car and not the car pulling the wheels. that would make the pull in relation to the car a forwards pull making them toe-in.

That is ignoring any forces cause by the driveshafts etc. Will they be significant?

I am waiting expectantly to be proved wrong here...