Front Suspension – part 1

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: 

https://www.toolstation.com/fischer-ftr-m-threaded-stud/p55597

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…

And I drilled my wishbone accordingly...

 

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. 

After the car suspensions have settled a little and it is geo set-up, I will fit some spreading back plate (I need to cut some sheet metal) and some good quality certified high tensile M8.

No, It is not a concourse car, it is a car I want to play with and if fitting metric stuff makes my life easy… And yes, I will clean up the excess duralac once it's cured and hardened.

Chassis wise, the next thing will be the rear suspensions; remove the spax telescopic shock absorber kit and refit Armstrong shocks and connecting rods. New radius arm will be needed too along with the mounting box.

When it comes to 1/4 elliptic spring, I am still undecided. I can see that people fit either:

• Standard springs
• Standard springs with a lowering wedge (reducing the height by ~1.25")
• Softer lowered spring (reducing the height by ~2.0")

A 0,5" rack angle (front lower) is what I would aim for to load the front tyres when braking and cornering.

The rear axial will be complemented with a Panhard rod kit.

In part 2, the Armstrong shocks will be upgraded/refreshed with new motorbike suspension oil (w22) and if suitable upgrade stiffer valves as fitted on MGB.