[richardbradford]

Hi,
Had 4-wheel tracking done on 164 today and they couldn't correctly adjust the rear tracking as limit reached on the adjustment. Assuming this is down to me not completely balancing the tie rod ends so one has 'bottomed out'; in my defence was trying to keep good clearance of adjustment bolts at subframe end.
Anyway, I can get round this by unbolting both M10 nuts and removing the whole arm, to turn just the offending end - question is, by how much?
The left rear toe is +0,16' (originally +0,13') and the right -0,06' (originally -0,05')
Am bit confused as to why they didn't just try to get everything closer to standard parameters and was told they tried to get the rears to closer match the fronts so it drives straight - yet the front tracking is now totally within normal tolerance (-0,01' and - 0,02').
Does anyone know what degree change in tracking at the rear results from one turn of the track control arm (when operating on both ends)? If I know this I can calculate how many turns needed to correct it on mine.

 

[Michael Smith]

We would call this alignment. The shop could have adjusted the tie rods on the track rods to correct any issues you may have created. The shop would detach one end of the track rod and then either screw out the shorter end or screw in the longer end. Once the track rod had been re-centered between the tie rod ends they would reconnect it and proceed as usual. Also, the 164 has toe out at the front and toe in at the rear so your shop's description makes no sense whatever. If you have the skills and tools to DIY any of this you didn't need the shop in the first place. I suspect the shop is incompetent and you should demand your money back. You can't fix it. Rear alignment is safety critical so don't mess about. Find a competent shop who knows how to setup these cars. Zero toe to slight toe out at the front and toe in at the rear. I like the rear set about midway between the tolerances specified by the factory. That gives best tire wear and good grip at the rear axle.

 

[richardbradford]

Interesting, Michael, thanks.
Agree tie rod removal to recentre them would have resolved the lack of adjustment issue.
The factory spec they quoted is -0,04' to 0,00' for the front and +0,09' to +0,14' for the rears.

 

[Michael Smith]

Yes, when I have my 164 aligned I ask for as close to zero toe as feasible at the front, without going positive. I ask for toe in at the rear as close to the middle of the spec as is feasible.

It is strange your shop claims they ran out of adjustment range. That should not be possible. We're talking a very small range of thread here to go from max to min in the permitted range.

The most usual cause of this issue is bent control arms (the transverse non adjustable arms, very fragile).

 

[richardbradford]

Thanks but nothing bent. All brand new under there. Oh well.
Cheers, Michael.

 

[Michael Smith]

There is another possibility, unsettling though it may be. The subframe, front or rear, might not be square to the body. The left and right rear toe needs to be the same number. The numbers you relate are incorrect. If your steering wheel is straight as you drive down uncambered road then your alignment has been done incorrectly unless the axles are not at 90 degrees to the centreline of the body. I generally test the quality of an alignment by driving down the middle of an untravelled road so that road camber steering effects are equal left to right. If the car tracks straight, steering wheel centred AND the rear toe is exactly the same left and right then the bodywork, subframes and suspension have to be correct. On the other hand if it tracks straight with different rear toe left and right then something is very wrong with the car.

Incidentally this is why the process us called tracking adjustment in the UK because that is the objective of the work. We call it an alignment because that is the process used to achieve correct tracking. The suspension is adjustable so as to allow the mechanic to compensate for minor misalignments inevitable in complex assemblies. If the adjustment range "bottoms out" then something is wrong with the complex assembly that is the suspension system holding up your car.

McPherson (Chapman if at the rear) struts have a number of advantages not least of which is very reliable alignment. Generally speaking no camber adjustment is required or provided for in a strut design because the tolerances can be quite large before any effect results at the tire contact with the road. Remarkably, caster angle is also fixed. This results from the very widely spread upper pivot point for the virtual upper control arm provided by the fixed point of the top of each strut. That point has to become way off before much change occurs at the tire. Frustrating for wannabe racers with strut suspension because providing for enough adjustment range to make any difference requires massive camber plates on top of the strut towers or resorting to highly questionable methods of cam bolts or even undersized bolts at the hub end of the strut where the adjustment has greatest effect.

My 164 with very worn suspension (high mileage) has not required an alignment for many years. My SAABs were all the same, hardly ever needing an alignment although the rear axle was non adjustable being a dead beam design, very rugged.

Unlike the front axle which always splits the toe equally because of the steering rack being free to move the rear toe has to be set individually for each axle. If toe is uneven across the front axle then the the steering wherl goes off centre. If the rear toe differs between wheels then a thrust angle results. The symptom of that is again the steering wheel will go off centre as the driver compensates for the thrust forces from incorrect alignment. It is possible for an incompetent shop to get the alignment wrong at both ends in an incorrect attempt to centre the steering wheel.

The explanation given by your shop just cannot be correct.

 

[richardbradford]

Guess I'll find out more when get underneath. The car isn't quite driving straight, wheel turned slightly to the right to get it to. Corning really well though.
Had complete rebuild at rear, including 'new' subframe, struts/springs and lateral arms - front A-arms were changed too so was expecting things to be out of alignment.
Will post the findings when have them. Cheers.

 

[Michael Smith]

The thrust angle the alignment produces is to push the rear of the car to the right (toe in left, toe out right). You steer to the right to drive the car straight. It's called dog tracking here because a running dog offsets his hind legs to one side of his forelegs to keep his feet from contacting when his stride is in compression.

To visualize this draw a plan diagram of a four wheeled vehicle and sketch the rear wheels at the angles your alignment shop has performed. Then sketch in the angles the front tires have to be in order for the four wheels to track in a straight line.

IMHO, your alignment shop owes you a refund. The car is undoubtably worse than before you took it to them.

 

[richardbradford]

Thanks, Michael.

 

[Michael Smith]

This explains it well:

https://www.knowyourparts.com/technical-resources/suspension/understanding-thrust-angle/

 

[richardbradford]

Update, with reference to previous tracking data mentioned:
I got under the car, with the old rear track control arm, and discovered the left track was effectively unchanged. Given the laser readout was of negative toe on the right side I adjusted the right rod out half a turn - moving top and bottom so one whole turn combined. Took it for a drive and seemed more stable but still tracked to left.
Jacked up the front and adjusted front track rods one turn each, both towards the right, as had previously been having to steer towards the right to get it to run straight. The front tracking had been set bang on but not in relation to the position of the steering wheel and this corrected it.
Result is great. Car now drives with beautiful stability and corners brilliantly.
As for the garage that set the tracking, I think the mechanic was working on the most basic of levels and didn't actually adjust a thing on the rear, as 164 rear ends are a bit more complicated than basic front track rod ends. And think he didn't get the front of the car running straight as assumed one track rod was at the end of its travel, when it wasn't.
The lesson to be learnt? Find an Alfa specialist that does tracking. My local Alfa garage does not, hence this mayhem.