On the check-down run, I found the car was lacking of front grip and was behaving like a boat… The steering was a little hard (which could have been explained by the larger tyres) and somewhat approximate.
Reading the suspension section of the book “MG Midget & Austin Healey Sprite high performance manual”, I decided to aim for a “hard
road” set up; something a little stiffer than classic fast road and much softer
than full race setup… basically, a comfortable hillclimb set up:
- 360Lbs x 8.5” springs from magic midget - @ the limit of “hard road” and “competition” in the manual cited above
- 11/16” anti-roll bar kit for frogeye spares - “hard road” in the manual cited above
- 1.7° negative camber trunnions from moto-build.
After further investigations around the steering area, I
noticed that the passenger side gaiter was split and a bit dry 😟. A bit of
lithium grease was injected and the steering became much smoother to operate. A
new “gaiter/trackrod end” kit was ordered… from ANG.
Steering Rack
The steering arms were marked to ease resetting the geometry
and things were put apart. Once the old cracked gaiters were removed, the
steering rod joints were lubricated and covered with the new gaiters. Once the gaiter
small end was sealed, the gaiter was partially filled with some 75w90 LSD gearbox
oil and then closed. Further gearbox oil was added to the steering rack.
Kingpin Trunnions
The original trunnions with the cracked bushes were removed
and the moto-build were not fitted…😣
- The inner bore of the trunnion was too small, 50 micron undersized causing a press-fit condition rather than a clearance fit. 😤
- The bush area on the trunnion also interfered with the brake disc shield backplate.
The disc backplate was trimmed, 20mm was removed to clear
the trunnion arm.
The bore was polished but it was not enough… in order to
achieve adequate kingpin rotation, 2 bronze thrust bearings had to be stacked up
shifting the trunnion up by 3.75mm. In doing so, the camber angle is increased roughly
by 0.5 to 0.75°.
Note that the 2nd thrust bearings and fulcrum pins were supplied by frogeye spares.
Spring swap
I basically followed the method showed in this video : https://www.youtube.com/watch?v=L82Y8s9Hcp8
However, I did not use some threaded bar, I brought a M8 stud
kit from Toolstation:
I could use ratchets and I did not need to mess around with mole
grips etc. as showed in the youtube video.
Instead of reusing the spring support plate fasteners, certified
high tensile (8.8) M8 fasteners were fitted.
Note: as the car gets
lowered, the camber angle decrease going to towards greater negative camber.
For the performance manual, every lowered inch reduces the camber by 1°.
With the new springs
of a car with a steel bonnet, the lowering is ¾”. The camber alteration from
the lowering is cancelled by the trunnion shift cited above.
The final static
negative camber should be about 1.5 to 1.7°. This will be fully looked at when
the car goes for a geo set-up.
Antiroll bar (ARB)
This Frosch is still fitted with the original bottom
wishbone that does not include the ARB mount holes. Adding holes is not
difficult but knowing where they are supposed to be is critical as it will
affect the tension properties between the ARB and the rest of the suspension. This
was critical on the lotus Elise so I thought some researches were needed and I
found the following on a spridget forum…
When putting together dissimilar material on the Elise
(steel to aluminium for example), it is good practice to paint in between a tacky
compound called “Duralac”. As I still
have a can, I put some between the freshly drilled wishbone and the ARB mount.
Due to time constraints, I used the fastening hardware
supplied with the kit but I was not impressed with the bolts.
