ST1300 High speed buffeting/wobble: rear shock is the likely culprit

Sidekick

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Location
Rhinebeck, NY
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ST1300A '05
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.
 
What you have said reinforces what I discovered. When i first bought my 1300, the bike was fine except for some controlled wobble* when I hit the turbulence behind and passing semis. I learned to live with it, and the bike showed no other instabilities. By and by I decided to improve the ride and reduce the damping via the adjustment screw in the rear shock. Big mistake, the bike was now very sensitive to buffeting and turbulent air. I returned the damping back to the stock setting per the manual and my ride returned to 'normal'.

*by this I mean the bike reacted to being pushed from side to side by the wind but not in a frightening fashion.
 
So, is the rear shock due for refurbishment or do you feel this is a feature of the shock? What do you plan to do about this?
After literally chasing a ghost for years, I can finally put a name to it. This isn't about shock fatigue or a rebuild candidate, the OEM Showa unit simply lacks compression damping adjustment, and no amount of refurbishment changes that. It's a design ceiling, not a wear issue.
The only real fix is an aftermarket unit, Öhlins STX46, Hyperpro, Wilbers, but putting $1K+ into a 21-year-old platform is a hard sell when that shock may outlast other components on the bike. The improvement treadmill is real: fix one thing well and you start seeing the next limitation clearly.
So where I've landed is this: the ST handles very well within its design envelope. I know where the ceiling is now, and that's actually useful information. I just got back from a 3000-mile trip through Canada, highways shared with trucks running hard and generating serious buffeting. The ST managed it, but it demanded attention and respect above 100mph rather than inspiring confidence. That's the honest assessment.
Knowing your bike's limits isn't defeat, it's just riding with accurate information instead of chasing ghosts, and god I love this bike!
 
Running over 100mph, passing trucks looks like some of those Facebook posts I see and shake my head at. There was a high-speed wobble that early 1300's were subject to, which led to at least one police fatality. Not sure when the fix came in.
 
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