After chasing a front-end handling issue on my 2005 ST1300 for a while (91K), I want to share what I found in case it helps others dealing with the same frustration.
My bike had a persistent sensitivity to buffeting and instability above 100mph. Like many owners I suspected aerodynamics, tire pressure, or front-end geometry. I had done extensive front-end work , fork alignment, bearings, springs, without fully resolving it.
On the front end I replaced the OEM springs with Racetech units, which noticeably improved feedback and damping feel. I also removed an aftermarket fork stabilizer clamp that was introducing its own issues. Then I fitted Bridgestone T33. The T33's stiffer sidewall construction made an immediate and significant difference to stability and handling precision. The bike tracks naturally, holds its line with confidence, and the front end feedback is in a completely different league from the previous tires. If you haven't tried the T33 on the ST1300, do it.
But above 100mph the buffeting sensitivity remained, and with the front-end variables now largely eliminated, I could finally feel what was actually happening: the rear shock hitting its damping limit under high-speed inputs and rebounding faster than it should. That energy propagates forward through the frame and you feel it as a front-end response to a rear-originated event "like an echo". The front isn't causing the instability, it's answering it.
The OEM rear unit has no compression damping adjustment. At speed, under sustained buffeting loads, it simply runs out of authority. Preload and rebound alone can't solve it . The compromise between low-speed comfort and high-speed stability is a real ceiling with this shock.
Worth noting: a steering damper addresses the symptom at the front end but not the source at the rear, that may explain why results with dampers are so mixed.
For those who've been chasing this issue, I believe the ST1300 wobble is essentially a consequence of the limitation of the OEM shock.
