Checking in with the brains-trust here - I have a brake shudder that is proving tricky to diagnose.
Light shuddering under brakes ONLY when at high speed (~100km/h) AND downhill.
Braking from high speed on the flat or uphill - smooth as silk.
Braking from low speeds (~50km/h) on flat or downhill - smooth as silk, no discernable shudder.
not much (if any) shudder felt through brake pedal - only through steering wheel and ears (very audible!).
Front control arm (tension strut) bushes are good, so I'm thinking it could be the lower control arms or the tension strut ball joints? Tempted to replace rotors to eliminate them but that is the priming of the parts cannon...
At 270,000kms, the (original) lower control arms and tension strut ball joints are likley done anyway but there are no other symptoms that indicate these components need replacing. They are VERY expensive here so I'm not going to simply replace them "on spec".
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edit* tldr; turned out to be rotors - replaced with new Brembo rotors and all good again.