Westfield Elevens

10 threads on mine that were set to -1.25 camber with me in the car, toe was set to O and the tyres at 20 psi for the IVA. Running at -1.25 camber, slightly toe in (for stability) and 16-18psi now.

Yep, pump the tyres right up to help, and in extremis if the above tips don’t work enough, helper springs can be introduced under the steering rack gaiters to help too (to be removed later as this is a 'get through the test bodge')

Thank you for all your comments, retest booked 6th Sept, so should have plenty of time to complete the mods needed.

You don't want to put anything into the steering rack. The rack should return without any assistance.
One thing to check is the bolt that tightens the mesh of the rack and pinion. Loosening this can help your caster return dramatically. Some racks are set way too tight. Don't forget to grease the rack as well.

I had a rack that arrived set way too tight. Slightly loosening the bolt made a significant difference in return and feel.

So far..... adjusted the top arms to show 10 threads, tyres at 32psi, chassis plate fitted.

Tire pressure, for your safety, should be no more than 20 psi. Remember, you car is about 2000 lbs lighter than the sedan that the tires were designed for.
At 32 psi, it will skitter all over the road and have no steering feedback. It will feel underivable.

My car works best at 18 psi cold front and rear.

The number of threads is not really useful as all the cars are a little different, depending on the ride height, bushings, and if the car has been run on a road (the metalistic bushings will shear and distort if torqued to the recommended specification, changing the camber). If you can get a camber gauge, you can set the front end properly. AND... With the driver in the car, and the ride height properly set, you may find that the left to right static camber settings are different, and that the car may be as much as 1.75" higher on the driver's side, depending on the driver's weight. Also, the thickness of the jam nut you are using will change the thread count. Of course, not everyone uses a jam nut at this location.

My car has a 3/8" thick jam nut, and shows 3 threads on the driver's side, 1 thread on the passenger side.
Camber is -1.5º left and right. It has been some time since I checked the caster but when I received the car it was at 4.7º left and right.
I only torque the metalistic bushings to 5~7 lb.ft. You can use 1 kg/m (7.3 lb.ft). I do this by hand, just tight enough so that the bushing can rotate around the bolt.

The 32psi tyre pressure is a short term solution to get the car through the self centring test required by the IVA and will be reduced to sub 20psi once the test is successfully passed.

You are correct about using the thread count to set camber, but all things being equal, it gets me in the ball park. I am looking for a local suspension expert to set the suspension correctly and hopefully dial in some self centring.

The W11 has strong caster return and feedback, so if you are having a problem with no caster return, it is not the tire pressures.
What I have found on the cars that had caster return problems was in the previous list. Most of the time, it was binding in the steering rack, rack coupler rubbing the chassis on RHD cars, and incorrect toe setting, usually excessive toe out.

Or stiff stub axle rotation (as I had) due to a likely out of tolerance lower wishbone geometry?

Or an over-tightened top trunnion nut?

Morris.

YES! This is quite common. I knew I was forgetting something...
The trunion top should be shimmed, but often isn't. This can be relieved somewhat by just reducing the tension on the nut, which will free up the steering.
Tightening this even a little too much will bind up the steering.