Suspension suggestions?

[JohnL]

Hes running 18" gestalt wheels on an eg civic sedan,so its set super stiff to reduce tyre scrubbing on the inner wheel arch round corners etc.

I can see that a stiffer damper setting may reduce how often such scrubbing occurs by slowing the rate at which the body rolls, but it won't stop it from happening altgether. The damper doesn't control the ultimate amount of body roll, it can only control the rate at which it happens, so in shorter / sharper manouvres with increased damper rate there may be some benefit in this respect because there is insufficient time for a lot of roll to occur, but if you're in a long corner and going a bit hard (e.g. on a big roundabout or similar looong corner) then the scrub is still likely to occur even with a stiff damper setting, just not as soon. For this arch scrubbing problem a stiffer damper is a band aid at best.

The only way to ensure it never happens is to move something, like the metal where the scrub is occurring, or change the position of the wheel via camber adjustment, rim width / offset change / narrower tyre etc (not a good reason to change these things, unless you intended doing so already for handling / grip reasons). Second best bet to stop the arch scrubbing would be stiffer springs and / or ARBs which may prevent body roll enough so it doesn't occur in practice even if theoretically it still could. This said, if your springs and / or ARBs are already at the rates you want, then stiffening them up just to avoid arch scrubbing isn't great either. You could try longer bump stops, but again not a good solution, and possibly a very bad one!