Project Morris Minor Assessment
The spanners are out as we begin our overhaul of the front suspension on this 1967 two-door Morris Minor
Ihave never been completely happy with the Stag steering, as it feels nervous and tends to wander more that the E-Type or modern cars due to small caster angles – 0.8° on the left and 1.4° on the right, whereas the specification is 2.5°. There is no simple provision to adjust the front suspension geometry. Small changes to camber can be achieved by placing shims between the bottom of the strut and the hub upright, but changes to caster are more involved. The lower radius arm’s fore-and-aft position is controlled by a fixed length drag strut, and the top of the strut is fixed in the strut tower. My calculations indicated that a 10.5mm increase in drag link length would increase the caster by around 1°.
After removing the drag link and strut from one side, it appeared the maximum increase in the length of the drag link was about 10mm without major changes to the construction of the link, so a twofold approach was required to get the caster to the specified value: increase the length of the drag links and move the position of the top mounting. Suspension Concepts, a local company to me in Australia, advertise adjustable top strut mounts for a Stag that, according to their literature, allow up to 10mm positive or negative adjustment to caster and 20mm negative to 10mm positive for camber which, together with increasing the drag link lengths, should allow an increase in caster to original specification and equalise camber. A set was ordered, and whilst waiting for its arrival I machined a 10mm spacer for one drag strut and an 8mm spacer for other to equalise caster prior to top strut adjustment.
When the kit arrived, as the strut was off the car I could immediately replace the top bearing using a couple of coil spring compressors to remove tension on the spring. The best way to remove the retaining nut on the original Triumph top bearing is with an impact wrench, and my battery powered wrench was up to the task so there was no need to resort to the increased output of the pneumatic wrench. However, when offering up the new top mount, a major design problem became immediately obvious as there was insufficient thread exposed to attach the retaining nut.
I phoned Suspension Concepts and sent them a picture of the problem. They requested I refit the original top bearing and return the complete strut together with the kit (at their cost), and they would fit the correct top plate and return together with correct parts for other side.
I received the rebuilt strut and modified kit in a couple of days, so fitted the strut to the Stag and promptly found a second design issue – the width of the new strut plate was only slightly less than the width of the strut tower, and consequently I could get very little adjustment for caster, but plenty for camber which was not what I required.
The easiest fix seemed to be to remove the strut and top plate, then cut a 10mm slice from the rear side of the plate that would allow 10mm of movement for the top bearing, thus increasing positive caster. A line was marked on the plate that went from 10mm and tapered to zero so it would still be completely gripped by the retaining plates, and after cutting off the excess material, the top bearing was reassembled and trial fitted to the suspension tower to check the range of adjustment. The results indicated caster adjustment was now from 0 to 10mm positive, and plenty of camber movement which was not measured as it was more than required. After painting the cut section of the plate, the strut was reassembled and fitted to the car.
Prior to replacing the drag link, the flexible bushes at the chassis end needed modification to compensate for the spacer and allow sufficient thread to be exposed for the retaining nut. I had purchased a set of polyurethane bushes to replace the rubber ones on the car, so thought I would initially reduce the length of an old rubber bush to confirm the drag link operation. The rubber bush was reshaped on a sanding belt, reducing the length by 10mm whilst keeping the same hemisphere shape, then the link was fitted to the car without any problem. The other side was treated to the same modifications and after tightening all drag link fastenings, the top strut bearings were adjusted to give maximum caster and mid-point camber. The polyurethane bushes will be similarly reshaped and fitted in place of the rubber ones later.
The car was then taken off the hoist and driven round the block to settle the suspension prior to measuring the camber and caster angles. I use a magnetic camber gauge for measuring both camber and caster, but attaching it to nonmagnetic alloy wheels poses a problem. The solution was to remove the centre caps from the front wheels and fit a steel plate over the wheel centre, retained by a countersunk screw attached to a specially machined nut on the inside of the wheel.
First the camber was checked and adjusted to 0.2° negative on both sides, then caster checked. Caster measurement involves rotating the steering 20° in one direction, zeroing the gauge and then rotating the wheel to 20° in the opposite direction (40° total) and reading the result. Ideally the front wheels should be on turntables, but two pieces of mild steel plate under each wheel with lubricant between them enables the wheels to be easily rotated. With some slight adjustment of the top bearing, caster was confirmed as just under 2.5° positive on each side. The top bearing adjustment plate was tightened and a test drive resulted in much improved steering response – a good result.
As to why the Stag’s caster could not be adjusted properly in the first place, I have no idea. During the restoration I discovered that there had been a hit in the LH rear wing with poorly repaired damage, and a new LH front wing had been fitted. This probably happened early in the car’s life as the paint was well weathered. The front LH bumper mounting was bent so the chassis leg could have been pushed back slightly, which may explain the 0.2° less caster on the left. However, there was no distortion on the inner front panels, so I can’t think that the chassis legs would have moved enough to make that difference to caster. Other possible causes of error are the cup that is welded into the chassis leg where the rear of the drag strut fixes could have been incorrectly located, or an error in the positioning of the front crossmember. One other possibility is that the drag struts are too short.
As there is no caster adjustment, I have presumed that this Stag was built at a time when standards had dropped and cars just came off the line with no camber or caster checks. The specification is 2.5° plus or minus 0.5°, so my 1° may have been seen as OK at the time. I had friends in the motor trade in the 1960s and ’70s working in major dealers, and they told horror stories about the amount of work that the dealer had to complete on cars delivered from the British Leyland factories before they could be supplied to the customer. My car was shipped direct to Australia, and probably never had the front geometry checked.