Tyre wear!! - uneven wear unexplained

Pilkie

Pilkie

Active Member
Hi all,

what causes have members found for uneven front tyre wear that are unusual ???
My castor,camber,toe in/out on all 4 wheels according to my local liner uppers laser gadget,and using settings from the proper workshop manuals "the red ring binder ones" is as close to spot on as could be expected!! Wheels and tyres also balanced and true!! yet I am still getting excessive inner edge front tyre wear!! is this the same type of thing that jag xj6's suffered from!! ie "its normal??"
Any suggestions ?? ?? ?? ??
 
Cars with PAS can knock the edges off the tyres if you wind from lock to lock a lot. Wear on the inner edges suggests too much toe out so I would set the FWA to the maximum recommended toe in setting.
I would also check all the ball joints for wear, they will cause tyre wear if worn, and a lot of people/garages don't know how to check them. I've had cars pass the MOT with 4 knackered joints because the tester hasn't known how to check for wear.
 
As the tester said they were spot on -0+,I will toe them in another 1-2mm then swap with the rears,I will also get my crowbar out and have a good lever on the front joints once ive relieved the loading on them! I should of rotated the tyres more often,but it crept up on me!!
ps Ive got 2 job interviews next week :p xxxx all my fingers,toes,etc!!
 
Did the tester jack the car up before checking the alignment?

It's recommended you push or drive the car around a bit afterwards to settle the suspension

Did you watch him do the test ? I've known mechnanics go under the car and "pretend" to adjust the toe in and then tell you it's OK .You can't argue unless you've seen the readings
 
He certainly won't have adjusted the FWA on a P6 if he went under the car to do it!
When the cars were common most tyre shops and garages just wouldn't do P6 FWA, they all used to think it was far too difficult, luckily for me!!! :D I used to love doing them, always a chance of finding a ball joint to do as well.
 
Well , if he did go under a P6 to do the FWA you'd know you've been ripped off

My 3500s always seems to be high up at the front after being jacked up and any measurements should be done with the suspension settled

It's not hard to do the tracking , you just need to realise a very small adjustment makes a large difference to the wheels and you need to get your head round which way to turn the adjuster

I've forgotten but no doubt Harvey can tell us - is it lengthen the adjusting link to increase toe in or vice versa ?
 
It works exactly the opposite to all other cars in that if you have the track adjustor behind the front axle line you would expect to shorten it to increase toe-out, on the P6 the adjuster is behind the axle line and you shorten it to increase toe-in.
 
What if the rear wheel alignment is out as in my case? Not anything terrible but not what you should expect either.
Is there any means of adjustment or it just means that it has a bent de-Dion tube?
 
I would think if the actual de dion tube itself was bent it would seize, other than that the only rear suspension adjustment I can think of is ride height. All I can think of to alter the alignment of the rear wheels is some kind of damage, and I'd look first at where the rear hub bolts to the de dion elbow, I would think that would bend before the bottom arm in the event of say, hitting a kerb
 
Mine to suffers a little from wearing the inside edge of the front tyres. I done a full laser four wheel alignment on it a couple of years ago, and every thing came up within tolerances. Trying to do the rear wheel run out was interesting though, with the rear wings in the way! I've put my tyre wear down to the fact that I have power steering, and 195/65 R15 tyres.
I know what you mean about ball joints. I've had one of the bottom ball joints fail in less than a year, and after only about five thousand miles ??? Some of the speed bumps around here are viscious to say the least :angry:
 
harveyp6 said:
All I can think of to alter the alignment of the rear wheels is some kind of damage, and I'd look first at where the rear hub bolts to the de dion elbow, I would think that would bend before the bottom arm in the event of say, hitting a kerb
Click to expand...
Damage from kerbing sounds the obvious thing to me too...

Although it must have taken quite a bit of effort to bent those parts! I also think that the damage will be measurable with the special equipment but not something obvious that you can see with your own eyes. In the end perhaps i will have to replace one or both of the rear elbows, and not because of rust...

Ah, used cars...
 
Erik The Viking said:
I know what you mean about ball joints. I've had one of the bottom ball joints fail in less than a year, and after only about five thousand miles ??? Some of the speed bumps around here are viscious to say the least :angry:
Click to expand...
How fast are you trying to take Erik off over them :D :D :p
We have some BIG speed humps,but I have found a route home that avoids them and only increases the distance by 1/2 mile :;):
Harvey,
am I right in that turning the big adjuster by -1 flat+ = about
-1mm+ at the wheels??
 
pilkie 0 said:
Harvey,
am I right in that turning the big adjuster by -1 flat+ = about
-1mm+ at the wheels??
Click to expand...
I have to say I wouldn't have a clue, I still work in imperial! I just used to see how far out it was and vary the amount I turned the adjuster accordingly, although however far out it was I wouldn't go more than one turn at a time, then move the car backwards and forwards (in that order) and then re-check.
I have to say if what you say about 1 flat giving 1mm alteration at the wheels, that would be 6mm (1/4"ish?) for every turn, and that seems a bit much. But I don't know, I've never thought about it that way (and certainly not in metric.)
 
Just something somewone told me ??? wasnt sure if it was true or not.
my neighbour has the old fashioned level floor mounted,look down the tube type alignment tool,I will use that and turn them in to toe in max,swap the front/rears around, and see how that goes.
 
pilkie 0 said:
my neighbour has the old fashioned level floor mounted,look down the tube type alignment tool,I will use that
Click to expand...
If you mean the Dunlop gauges, they may have been around for a while, but you won't find anything that will do the job better. I've got a set, and always found them great to use. Not for the amateur though, at £500plus for a set. (Come up on ebay sometimes, and seem to make £200plus on there)
 
Thats the ones!!! I used to use have a go with them when I ran a petrol garage in the 80's.They had a large w/shop, and tyre/exhaust centre round the back,and I was always round there helping out!! loved it!!! I think once ive had a look at it,I will remember how it works,its only basic geometery!! :p
 
Check the basic alignment of the gauge before you start by putting the 2 pieces together and checking you get a Zero reading

I made a tracking gauge out of a few pieces of wood and my front tyres have hardly worn at all in 10K + miles

I would describe it but purists would laugh
 
With regard to the wear on the inside of the front tyres I was recalling the discussion I had with my Australian freinds about their car with more steering lock in one direction than the other. One of the scenarios we came up with was a grossly out of line drop arm or quadrant on either the steering box or the idler box (or both!). You would be able to compensate for this by adjusting the toe in for the straight ahead but when the steering was on lock there would be a further error because of the quadrant angles not being correct. In essence you'd get the wrong ackerman angles. This would be a real pain to check, involving releasing the drop arms / quadrants from both boxes and setting up from scratch. Best first try, has the car had a replacement for either of the steering boxes to your knowledge?

Set up procedure to check:

1 park car with steering set straight ahead (easier said than done for the precision required - watch how your laser equipped tyre dealer achieves this)
2 release the drop arms / quadrants from both steering boxes and detach the cross link/adjuster
3 find the centre point of the steering box
4 recouple the steering box drop arm / quadrant so that the fixed linkage on the drivers side matches precisely to the centre point / straight ahead position.
5 find the mid point of the idler box
6 recouple the idler box drop arm / quadrant so that with the passenger side wheel in the straight ahead position the fixed likage on that side matches with the mid point of the idler box
7 recouple the cross shaft / adjuster adjusting to suit.

The manual has no comment on this process other than to say that the angular alignment of the drop arm on the idler box is critical and the idler box should therefore be replaced with a factory item if there is any defect. Curiously the overhaul procedure for the manual steering box specifies removing the drop arm / quadrant but makes no comment at all about refitting it. For the power steering box the manual goes into some detail on the vertical clearance between the drop arm / quadrant but does not mention angular adjustment (although there is considerable discussion on getting the null point of the power assistance to coincide with the lock to lock centre point of the box).

The body alignment section of the manual (pages 76.10.57 to 76.10.62 for the V8 manual) doesn't really help either - though I'd recommend anyone setting out to weld a base unit to have a careful read - there are quite a few gold standard nuggets in there!

Never having removed a drop arm / quadrant I am assuming that they are simply spline located as shown in the manual and therefore they can be installed in any location rotationally. Reading between the lines of the manual it sounds like this is definitely true for the idler box but it could be that the steering boxes have some other method of location as well.

Then of course, if the car has been kerbed heavily at any time I guess it's always possible that the drop arms / quadrants have been bent. Whilst the side rods are obvious to change the drop arms / quadrants might have been overlooked.

Where the manual does get fairly excited is in the vertical alignment of the steering boxes to the base unit and in particular to the location of the upper suspension arm pivots on the front bulklhead. I have to say I don't follow the significance of this.

Regards

Chris
 
Phew! second strand of reply re the back suspension!

There is one area where damage or wear can influence rear suspension alignment. The entire rear alignment is taken off the differential via the fixed length drive shafts. If there is anything awry with the diff location this will be transmitted out to the wheels. There's a surprisingly large range of options here. Most likely is loose diff location bolts into the base unit. This is quite common and can cause surging and vibration in the drive line as well. Then there is damage or deterioration to the metalastic bushes in the base unit. Not forgetting fatigue damage causing the base unit to break up in the vicinity of the mountings (also surprisingly common). Finally the diff is located sideways by a panhard rod bolted up to the diff carrier at one end and to the rear vertical wall of the boot at the other. And we all know how solid P6 boots are after a few decades rust!

Of course there will actually be a small amount of variation of toe in / out as the rear suspension rises and falls. The whole point of a de dion is to allow the track to change in response to changes in drive shaft angle. Since the trailing arms have a fixed front pivot point it follows that their angle relative to the centre line of the car must vary thus altering toe in / out. Thus if your rear springs have sagged you could expect this to have influenced alignment slightly.

Finally there is the possibility of machining error of the rear hub housings. On my SD3 216 VDP I have one hub housing machined to give a noticeable toe out to that wheel (this on a fixed axle). The alignment operator's view was that this is very common and they actually carry angled shims to correct it on the more common cars (they don't see many SD3's for full laser wheel alignment!! - their main stock in trade is competition cars).

Regards

Chris
 
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