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

Sidekick

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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.
 
Anyone know the best way to remove /install the rear shock? I’ve got a tiny leak near the banjo bolt at the damper. I need to get a replacement hose made & replaced. How difficult is it?
 
Anyone know the best way to remove /install the rear shock? I’ve got a tiny leak near the banjo bolt at the damper. I need to get a replacement hose made & replaced. How difficult is it?
I don't think you need to remove the shock itself, removing the bracket is straightforward and maybe getting a used hose/banjo on ebay should be possible.
 
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.
Honda determined that much of the high speed instability was due to the engine mounts being that the engine is a stressed member of the frame. I read a Honda engineering study years ago about it that detailed how the engine mounts if not torqued enough would allow the frame to flex and cause the wobble. Honda did make changes to the engine mounts but I don’t know exactly what it was. It may have been tolerance changes or stiffness.
 
I don't think you need to remove the shock itself, removing the bracket is straightforward and maybe getting a used hose/banjo on ebay should be possible.
I don't think you need to remove the shock itself, removing the bracket is straightforward and maybe getting a used hose/banjo on ebay should be possible.
Looks like you’d have to remove the shock to get to the banjo bolt on the top front of it?
 
The stock rear spring is simply too soft for riders over 150 lbs or so. The relationship of static sag and rider sag stare you in the face before compression damping comes into play. A shock that is bouncing off the bump stop destabilizes the motorcycle. I am lucky to be a light rider and could live 180,000 miles with the stock spring but I did upgrade the damping qualities with a RaceTech massage that installed their upgraded damping valving in an OEM shock body. I found the upgrade more than worth the $350 cost at the time. I never found my 2005 in the Pan Weave under 115 mph or so even with the weak suspension. After the upgrade it was better but the Weave is real.
 
... 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.
There were many reports over here that at minimum stiffening the rear preload, or even install/upgrade with an aftermarket shock at least eases the issue described...

Friend of mine has upgraded his '06 ST1300A (ED) with Wilbers front and rear suspension...
While this pretty much cured what you're describing, is he still convinced about some aerodynamic issue within the front fairing/screen/end design...
It still acts sensitive to like the wake of a semi and would show tendencies to "rock up", but the Wilbers components now calm the whole ride much quicker then the previous OEM setup...
 
If you really want to fix the problem this is what you need.

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This was configured for my weight plus load, things like top box, etc. I did this back in 2007. Personally tested to 147 MPH with bags and top box.
 
If you really want to fix the problem this is what you need.

1785970323781.jpeg

1785970427629.jpeg

This was configured for my weight plus load, things like top box, etc. I did this back in 2007. Personally tested to 147 MPH with bags and top box.

"Great, that's 'The Full Monty'—$1,500, but it's worth it."
Thank you for sharing.
 
Wouldn't" The Full Monty" include a fork revamp too?
RaceTech cartridge emulators, or similar?
(In the interest of full disclosure.)
The Quest For The Holy Grail!
Fix one thing well and you start seeing the next limitation clearly. I only upgraded the springs for now, better, but doesn't prevent hydraulic locking and harshness.
Adding $700 to the budget then.

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I also agree that up to 100 mph the behavior is civil and requires all your attention over 100 mph and with an oversize trunk adds to the buffeting issue so if you plan on spending a lot of time over 100 mph loose the trunk as it really disrupts the airflow especially when running with the semi-trailers Just my 2 cents
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