He's not using 1.8/1.9D Xantia spheres though, he's using CX turbo spheres, so while the pressure and centre bypass holes might be similar the threshold valves may not have the same calibration. (I don't know of any easy way to determine this other than empirically by evaluating the ride/handling...)DickieG wrote: Bear in mind that these sphere's are standard specification for a non Hydractive Xantia using a 1.8 engine and as stated earlier in the thread using standard TD/2.0 sphere's with a 1.5 damper will apparently give a firmer ride than a non Hydractive Xantia so I can't help thinking that 1.65 damper hole sphere's will suit your purpose perfectly.
If the threshold valves are too soft and open too easily then no amount of adjustment of the centre bypass hole will give proper damping control and ride. When the combination of gas pressure, threshold valve strength and bypass hole is optimal the rebound isn't quite strong enough to open the threshold valve and the entire rebound flows through the bypass hole in the middle, so the bypass hole critically tunes the rebound characteristic. (Bumps on the other hand do open the threshold valves, allowing them to be absorbed well)
If the threshold valve is too weak the rebound will just open the valve and flow through that way meaning rebound will always be poorly controlled no matter the bypass hole. On the other hand if the threshold valve is too stiff the ride will tend to be fidgety (think Hydractive 2 in hard mode) unless the bypass hole is overly large, but then the damping would be poor.
Only if the valve has an opening threshold that matches the car (gas pressure, body weight, mechanical advantage of the hydraulic system etc) can you get good ride and damping at the same time.
At the end of the day we really don't know what if any difference there is in the threshold valve between a CX and Xantia sphere, which is why I generally don't advise mixing spheres from completely different models... You might get lucky but you probably won't. Tweaking the centre hole may or may not help. Since its easy to try its worth a shot though, especially somewhere where it's hard/expensive to obtain replacement spheres.