[wilf leek]

Tom - I have been thinking about your puzzle, and have come up with a possible scenario:

If the disc run out at the front is such that it is forcing the caliper pistons backwards significantly, it could be that you cannot achieve enough fluid displacement to get the fronts to grab the disc before the rear master goes "solid", and prevents any further pedal travel. Would the linkage system allow that to happen? Really scratching my head here.

If you disconnect (hydraulically) the rears, do the fronts work then?
Is the disc run out OK? Any pulsing through the pedal on the road?