To set the ride height on a 2CV you really need two things: a flat and level surface and a 9-22mm tie rod adapter. When changing the chassis we had the former but not the latter and when I subsequently acquired the latter I didn’t have the former. Now I have both…
To make measurement easier I cut two bits of wood to the lengths of the required chassis height as measured between the axle bolts, 195mm at the front and 280mm at the rear (±2.5mm).
To adjust the ride height the tie rods need to be screwed into, or out of, the eyes that connect to the suspension arms via the knife edges. To facilitate this, the tie rods have 9mm flats on them. Whilst you can use a 9mm spanner you need the shock absorbers off in order to address the flat – which is what we did when we were putting it back together after changing the chassis. The right tool for the job is a 22m hex that has a 9mm slot cut in it.
Whilst access to the tie rods is still a bit restricted, with the adapter on the tie rods the 22m spanner can address it in 12 possible ways which, whilst a bit fiddly, is adequate for the job.
Ensure the tire pressures are correct and the car is unladen (except 5l of fuel if you’re being precise). Using the appropriate wooden measuring stick you can see how far off the ride height is. Then, with one side of the car jacked up to take the weight off the suspension and hence the tie rods, you can screw the tie rods in to raise the car or out to lower the car – a rule of thumb is one turn of the tie rods is about 5mm. After making an adjustment, let the car sit back down on the suspension, give it a bounce to settle it, and re-measure. Then, if needed, jack up and re-adjust. As I needed to raise Judith I put a bit of WD40 on the tie rods where they entered the eyes as that made them a bit easier to turn.
When you’re done the wooden sticks should just fit under the chassis between the axle bolts.