Front end alignment matter, an update

XJ-S
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Folks:

I last posted here regarding the potential impact of worn ball joints on a severe pulling problem that my 1990 has developed.

I have been investigating this, and have discovered significant wear on both front tires, but much worse for the driver’s side. The wear is biased to the edge and is down to smooth rubber, while significant tread is left elsewhere. I examined the tie rods while moving the wheels, and I do not see any visible slop in either tie rod connection. This is with the front lifted onto stands behind the front wheels. The steering response is sharp, one-to-one: control input, wheel movement. Of course, there is no friction force that the tires must overcome (with respect to ground contact) to move.

I have to test the ball joints, but visual inspection shows the boot integrity to be solid, and there is no external evidence of lubricant leakage from any of the joints at either wheel.

Some history, and particulars: first, this car has around 97K on it. I have replaced the rack, having done this about 10-11 years ago. I put around 1 to 2K miles on this car per season, it is a fair weather car. When I installed this, I took care to note the old rack’s fixing locations, and the tie rod positions (number of exposed threads on each), and refitted the tie rods and the rack to the same positions as I found the originals.

I did not have the front end aligned after the new rack was installed. It appears that I should have, as when I carefully looked at the front tire position with the steering wheel centered up, neither front tire was pointing squarely ahead- could note deviations by eye, with the passenger side being toed out rather markedly, once I looked carefully at it. I did not recall this when the rack had been changed out; I looked carefully, then, too, at that time. But I did not have the worn tires and handling behavior evidence to suggest a problem, then!

In any case, the direction and degree of wheel direction seems to correlate with the position and severity of wear on the tires.

Also: I had installed poly bushes on the car in the original rack- loved the response- VERY precise, with good road feel. I went through H*ll getting the old bushes out, having chosen to do the job when I had the engine and trans out of the car to do the 5 speed switchover. This enabled good access to the rack, and boy, did I ever need it- getting those bushes out was quite a monstrous exercise. I got the new bushes in, and rebolted the rack, and proceeded to finish the 5 speed switchover- circa 2008 or so, as I recall.

Eventually, the rack tower seal started leaking, and I ordered a rebuilt unit…which came with OEM bushes preinstalled. In my rush to get the car back on the road, I installed it as it came. Big mistake- while the rack was fine (no leaks, that is), the sloppy steering and lack of road feel returned. I really missed the behavior from when poly bushes had been fitted. Oh well. I drove it this way for several seasons, as I just did not have the desire to repeat my experience of getting those bushes out again.

So, I am leading up to a question, now: the Jag manuals, on the procedure for R/R the steering rack, advise to use special tools: one to locate the precise steer center point, JD-117, ‘Steering Rack Centralizing Pin’, and another to locate the rack with respect to the lower A-arms prior to tightening the mounting bolts, JD-36A, ‘Steering Rack Checking Fixture’. I had/have neither tool. I am guessing that the tool that centers the steer point could be substituted for an awl or something similar. But the tool I am interested in is the one that locates the rack with respect to the lower A-arms.

This tool is not mentioned in any significant way in The Book. Have any of you who’ve messed around with the steering rack devised a similar tool? I am looking to do some work on this rack, to ensure it is properly centralized, R/R the bushes (gonna use a commercial tool this time- the one I made according to The Book did not work out well for me the first time I R/R’d the bushes on the old rack), and then centralize the rack/pinion/steering wheel, to get a proper center point, and THEN work to adjust initial wheel pointing and toe settings.

A final note: as an experiment, I put a pair of tires on the front, tires with even wear and good tread (an extra set of 245-50-17’s), and ran the car- no pulling at all. But the steering was terrible- sloppy and awful feel. Matched with multiple posts I found in this list of what the car behaves like when the steering rack bushes are mush. These observations are leading me to believe the problem I have been experiencing is due to two things: 1) improper toe setup of the front wheels (I missed the mark when I installed that rebuilt rack, and the long term wear effects on the tires led to the pulling phenomenon) and 2) the rack bushes are now old enough that they have gone super soft, and need replacing.

I could still have a ball joint problem, and I have to do more checking on that, but I KNOW the rack related issues (toe and bushes) need to be addressed for sure.

One more bit of history on the car: I rebushed the front end completely around 15K miles ago- poly upper/lower A-arm, poly sway bar and end links, and replaced the front and rear suspension cradle mounts as well. New shocks and fresh mounts as well. I do not think the issues I have been experiencing are due to any of these areas, at least at this time.

Interested to hear what folks do, in place of the JD-117 and JD-36A tools!

Thanks in advance!

-M

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A lot to digest.

Is the worn part of the tire on the outter edge or the inner?

Two issues are possible. One is incorrect toe and the other incorrect camber. for rapid wear, toe is the prime suspect.

A couple of DIY means are avaible to check it.

  1. A string from te center of fthe rear wheel hub to the front hub Deflection??? A riny maount s roper. \\I set toe on my 4 x4’s by this method.

Car.

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Doing so simply gets you to a “close enough” point so the car be been driven to an alignment shop… where the toe-in can be accurately measured and adjusted

Never used it on any of my oldie Jags…or even seen one with my own two eyes. Since I’ve never had a tire-wear problem my conclusion is that your tire wear problem is not specifically related to lack of using the location tool.

Cheers
DD

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Jd36 is nothing like an awl. JCNA lists having one as a loaner if you feel it necessary.

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I just use the end of a drill bit the appropriate size to center the rack instead of JD-117.

It sounds like you just need a good alignment. The will also tell you if you have parts worn out, so that it cannot be brought into spec .

Jon

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When i removed/reattached my rack, the steering gear didn’t budge, so I just put it back as is.

Also, my toe in was definitely off with new bushings. I tried eyeballing it, looked pretty straight. I drove only 500 miles before bringing into alignment, that was enough to feather the tire edges, they said i was 1" out!

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As Carl asked, inner or outer side?
I think you have more then one issue here and it’s neither the ball-joints nor the rack (except the slopy bushings).
Incorect Toe will wear both tires at the same edge and at the same amount.
Excessive Camber will wear the inside edge of that side and meybe the outside edge of the opposite side.
When only one side wears, a very probable cause, that many disregard, is that the rear alignment is off and thus you have a non parallel Thrust Line.

It never works…

You can’t eye ball… need to measure properly.

A drill bit, screwdriver or whatever fits snugly on the rack hole will do.

Did not use it either. Just make sure the rack is parallel to the bottom edge of the subframe.

They may very well do need replacement, but it’s definitely not the cause of your tires wearing.

After you change your rack bushings (if you intentd to do tthis) you, or an alignment shop, need to measure both front and rear ends and report back.

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Hello to the many of you who responded to this thread:

I have been away on travel for many days and have arrived back home yesterday, in time for the 4th holiday weekend.

First, let me say a hearty Thank You to each of you- a great many things were brought to my attention and they have been extremely helpful to inform my understanding of things.

To all who have pointed to toe being out: I checked the tires I removed from the car, and both are worn on the inside edges, one more so than the other. The wear is very asymmetrical in terms of tread depth, too, in that the tread on the outside edges of the tires is almost newish in depth- hardly any wear there. So, it looks like a toe problem.

To those who have pointed out that any changes like this (rack change, rebush of front suspension, etc.) requires an alignment, THANK YOU. I do not trust this car to just any mechanic, and I REALLY fear places like alignment shops. This car is strictly a hobby car, and I do not care to drop excessive amounts of cash on it, in the hands of a shop of unknown ability/experience with what are now aging models.

Turned out, though, that in this case, the mechanic I should be fearing is the one in the mirror (!).

Good advice to bring to a shop. I can direct such a shop to ONLY perform toe adjustment, and advise as to the as-founds for caster and camber, as well as wear of the ball joints and tie rod ends. In fact, I think I will be replacing the tie rod ends with new parts, and also replacing the rack mount bushings with poly (again, but for this second rack). THEN I will bring it in for toe adjustment. I will acquire the tooling to measure this myself, though, as I do want to maintain some degree of closeness to the whats and hows of procedures I have not done before.

Aristides: excellent comments and points. I have had the rear cage off this car twice, to do the rear brakes and to change the diff out (2.88 replaced by 3.54). I did not measure the caster/camber after doing this, only moving my output shafts and shims from the 2.88 unit to the 3.54 unit, and bolting it up.
I have never had any unusual handling or tire wear problems with R/R of the IRS as a unit, but I am careful in how this is removed and especially, how it is replaced, to be sure it is as free as possible to settle itself before torquing the cage mounts in particular. Anyway, I have not measured the results in terms of alignment, but I will, now- must acquire the tooling for this job, but that is OK- I want to know what it is. Also, I know the rack bushings are not the cause of the alignment/front tire wear issue, but are responsible for the poor ‘sailboat tiller in calm waters’ response that I have on the steering. Still, there may be more than one issue contributing to the front tire wear problem/front end alignment.

I will be checking the ball joints next, in any case.

Thanks again to all!

-M

2 Likes
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Keep us posted.
Some more characters.

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If you’re swapping out the ball joints, might as well do the upper control arm bushings. Use OEM

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Veekay:

Thanks for this suggestion- I fully rebushed the front suspension about 20K miles ago, with poly. Of all the bushes and mounts, the upper A-arms were in the best overall as-found condition. The lower A-arm bushes, on the other hand, were largely gone, and the front suspension assembly mounts were not great, either.

I will certainly look at all the bushes as I get into this, but am not anticipating having to change the poly bushes already in place.

-M

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There are some really good home-alignment tools available, a lot of track guys use them to make repeatable changes for weather, differing surfaces, etc, etc. Certainly not a computerized rack accurate, but with patience and a good understanding and technique my experience has been that one can get it plenty good enough to not wear the tires if all is in good order otherwise. At a minimum I keep a pair of toe plates around, I don’t know about a Jaguar but most more pedestrian vehicles of the era have pretty liberal toe setting requirements, easy with a couple of tape measures and a sharp eye.

I feel your pain about finding the right alignment shop. You might see if your area has a Porsche Club Of America chapter and see who they recommend.

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I gave up long time ago…