You lost me there.
Preload adjustment is all about pre-compression.
ST1300 - Unstable when riding behind a semi truck?
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You lost me there.
Preload adjustment is all about pre-compression.
It's almost like an oil thread in here 
That's the point I'm debating. What mechanism stops the bike from rising when you add preload?
If you sit on the bike and someone raises the preload, the spring does not get shorter, you go up.
The rider's weight is what compresses the spring. Preload only adjusts the compressed ride height.
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Intriguing. These are all questions you've asked before and all I can offer again is go back to jfheath's diagram, the one you posted yourself, where it is all very well illustrated.
Am I sensing that after all we discussed, the literature, the physics of the suspension dynamics, the facts, the evidence, you are now recoiling to your prior assertion?
Yes. No doubt. That's what you do to adjust sag and rebound.
But don't miss the fact that under dynamic conditions, you know, like when the bike is in motion and bumping around, (that's where you might have to dive a bit into the actual physics of the mass-spring-damper suspension system to understand it) adjusting the spring preload alone will also affect rebound.
So after you change the preload to adjust your ride height, you will have also indirectly changed the rebound characteristics of the suspension, without having ever touched the rebound adjuster.
This is clearly shown by the actual measurements in the paper posted earlier (see fig 8), with different preload settings. You may want to have a look at it again.
Experimental Analysis of Passenger Comfort with Variable Preloaded Rear Springs on a Low-Cylinder Motorcycle
The present study contains an experimental analysis of the vibratory response in a low-cylinder engine motorcycle at varying suspension preloads. Three different speed bumps of varying heights were used to subject the motorcycle to different vibrations. ...
redirect.viglink.com
If you are not used to digesting this kind of material, have a look at Dave Moss (a well-known professional tuner) adjusting preload and see how his adjustment to the preload affects how the suspension rebounds. Look first at 3:30. And he does it again at 1:40.
If what he does here is not clear to you, please let me know. I would also gladly give you a call to point out exactly what to look at while you watch, if you are really interested, just send a PM.
And if all this is still not clear enough, there is always the ultimate test:
Set your bike to Max preload and go ride a loop with plenty of varied bumps and holes. Do it several times at different speeds.
Then set it to min preload and ride the same loop again, several times and at different speeds.
Feel the difference?
"While we did not measure the spring stiffness directly, we determined the compression of the spring at each preload setting: 5 mm for the smooth preload, 7.5 mm for the medium preload, and 9.7 mm for the strong preload. "
I'm still waiting for this question to be answered:
What mechanism stops the bike from rising when you add preload?
I'm still waiting for this question to be answered:
What mechanism stops the bike from rising when you add preload?
Never left it. I still say that, as long as the suspension is not topped out, like when you're sitting on the bike, the length of the spring does not change length with preset adjustment.
I don't see how, unless the shock's damping varies through its range of motion.
phew ..... after reading all 9 pages of this topic to see if my travelling weight with full panniers , full top box and a dry bag on the passenger seat over 80 mph causing the front end to ' porpoise' like the F1 cars were doing down the straights .. i can quite clearly state .... i still have no fkn clue what the hell anyone is on about ... ive had sprorts bikes since way back in the 80s , 1000 cc heavy old monsters to modern day missles with extremely scary acceleration and handling an dyet ive never touched the suspension ... all i can add to this is , i get on , i ride and if it starts behaving like a bucking bronco i just ride it through and not worry about it , its part of growing up with steel framed heavy heavy heavy bikes that didnt handle , didnt stop well and certainly had to be muscled around bends then lifted up coming out of corners ... dazed and confused totally now .. all i wanted to know really was if i have a bloody heavy rear end with full boxes and no pillion passenger what would be the best setting from zero ( anticlockwise ) and what the little screw does on the right side of bike (when sitting on the bike ) through the hole in the right side footpeg hanger ?? hahahaha ride safe all .. my bike is an ST13 .. by the way lol
I have had very good experiences with the Nivomat suspension from Wilbers. The suspension automatically adjusts to the load.
Function:
The patented Wilbers Nivomat system automatically ensures sufficient spring rate, damping and spring deflection without manual adjustments - completely independently via the hydropneumatic function and always ideal for the payload.
Look here:
www.wilbers.de
Function:
The patented Wilbers Nivomat system automatically ensures sufficient spring rate, damping and spring deflection without manual adjustments - completely independently via the hydropneumatic function and always ideal for the payload.
Look here:
Wilbers Suspension Manufaktur | Wilbers Nivomat | purchase online
Wilbers Nivomat - The "Wilbers Nivomat" shock absorber offers excellent comfort in all circumstances. It adapts to different loading situations without any effort on the riders part, automaticalle wit
www.wilbers.de
I ordered a Laminar Lip based on this review and several others on the Laminar site. I have yet to ride with it because it's 115 degrees here but am looking forward to reducing this buffeting behind semis as well. I thought maybe I was the only one, or perhaps something was wrong with my ST13.All good advice here, especially John Heath's (always) comprehensive post.
If you have the stock windshield, as I do, this is my advice based on 10+ years on my ST1300:
Buy and install the Laminar Lip:
I put this on my ST at the beginning and I wouldn't ride this bike without it.
The "lip" deflects the air up and over your head, and - most importantly - lets you ride with the windscreen nearly all the way down - at any sane speed.
You will be looking over, rather than through, the windshield. A world of difference.
With the lip, and the windshield down, the bike presents a much better aerodynamic profile to the oncoming air resulting in much less buffeting from trucks, and in all riding.
It's not totally eliminated, but is much less. You will also notice the bike feels, and handles, much better overall riding like this.
And looking OVER the windshield is much more pleasant then looking through it - and a dirty windshield really doesn't matter anymore
With the "lip", I ride with the windshield down always - and only raise it to clean, or in a heavy rain.
IMHO it's the only way to go....
I have had very good experiences with the Nivomat suspension from Wilbers. The suspension automatically adjusts to the load.
Function:
The patented Wilbers Nivomat system automatically ensures sufficient spring rate, damping and spring deflection without manual adjustments - completely independently via the hydropneumatic function and always ideal for the payload.
Look here:
Wilbers Suspension Manufaktur | Wilbers Nivomat | purchase online
Wilbers Nivomat - The "Wilbers Nivomat" shock absorber offers excellent comfort in all circumstances. It adapts to different loading situations without any effort on the riders part, automaticalle wit
Have you had a chance to try it on the ST1300?
This guy did and seems to have issues with how much it raises the rear, too high for the Center Stand to be useful anymore. Would be interested in your take on that. Thanks,
Unless the shock is topping out, that's impossible. Plus, it won't be topped when you're sitting on it.
When you move one end of the spring, what stops the other end from moving the same amount?
If you perch your bike (or a car) on a speed bump, does the spring compress or does the bike rise?
What matters, and what you're actually adjusting, is the ride height when laden with rider and gear.
@Larry Fine , wondering if you've done the suspension homework suggested by @ASPC?
And so it does on mine!
Set your rear shock(s) to Max preload and go ride a loop with plenty of varied bumps and holes. Do it several times at different speeds.
Then set it to min and ride the same loop again, several times and at different speeds.
Feel the difference?
And so it does on mine!
Set your rear shock(s) to Max preload and go ride a loop with plenty of varied bumps and holes. Do it several times at different speeds.
Then set it to min and ride the same loop again, several times and at different speeds.
Feel the difference?
This is the rebound damping adjustment.
You can start with 1.5 turn.
Then you'd have to go and test ride to fine tune from there as it all depends on the road conditions, driving style and preload settings (and unfortunately also on how close your shock is from needing servicing). It is not a "one magic number fits all" case.
If the bike "po-go sticks", add some rebound damping.
It is "packs", take some off.
Typically, on a relatively smooth HWY you can add some preload and rebound damping, and then loosen up preload and damping once on bumpier smaller roads.
It also depends on what tires you have on (and pressure), as tires have their own stiffness and damping characteristics. And those who are in tune with their suspension will also feel the difference in damping between hot summer temp or late fall CO pass temps.
Good luck.
Yes, statically, when sitting on the bike. But once you start riding, the preload setting affects damping.
Try to move on from the static consideration to what happens "dynamically". By now, we know you have a good concept of the static part of it, the Hooke's law.
To make it as easy as possible to understand, I had posted this vid for you earlier, clearly showing at 3:30 and 1:40 the effect of preload adjustments (front end in this example) on rebound.
Here it is again.
Did you spend a minute watching it?
Could you clearly see how changing the preload setting (on the front in this example) affected the rebound?
Or just not really interested in understanding suspensions anymore?
It seems to me that the wobble issue is actually caused by tires. When using Metzeler Z8 tires my bike is very stable on the interstate regardless of wind or semi’s. I can overtake lines of semi’s with just one hand on the throttle at 80 plus and the bike almost seems to fight anything but a straight line, it is very stable even in high winds and bad weather.
In comparison, I just recently took a trip on the same interstate with well broken in Dunlop Roadsmart IVs, a few thousand miles. While sitting behind some semi’s the bike was bobbing from side to side fighting the wind. On the same interstate I traveled on with the Metzelers. I think the Dunlop Roadsmart IV and III are garbage compared to the rock solid stability of the Metzelers, which where extremely stable.
It appears to me as though the Roadsmarts have no directional bias. When the Metzelers most certainly do, even in the wet. If someone has never ridden an ST1300 with tires that work well with the bike they may never know how amazingly stable these bikes really are, regardless of wind, weather or speed.
I am 60 years old, I have ridden motorcycles on and off since I was 12, I have worked in motorsports with both cars and motorcycles and I think the Dunlop Roadsmart tires are dangerous.
In comparison, I just recently took a trip on the same interstate with well broken in Dunlop Roadsmart IVs, a few thousand miles. While sitting behind some semi’s the bike was bobbing from side to side fighting the wind. On the same interstate I traveled on with the Metzelers. I think the Dunlop Roadsmart IV and III are garbage compared to the rock solid stability of the Metzelers, which where extremely stable.
It appears to me as though the Roadsmarts have no directional bias. When the Metzelers most certainly do, even in the wet. If someone has never ridden an ST1300 with tires that work well with the bike they may never know how amazingly stable these bikes really are, regardless of wind, weather or speed.
I am 60 years old, I have ridden motorcycles on and off since I was 12, I have worked in motorsports with both cars and motorcycles and I think the Dunlop Roadsmart tires are dangerous.
Good info, Danke!
This is on a ST1300, right? Not sure from your avatar what you ride.
So now you can happily go from riding by yourself to fully loaded without ever adjusting anything and the suspension always being exactly like you would like it to be?
No. I use required steering effort to adjust rear suspension.
I'm sure I would, but I would still revert to the setting that delivers best steering response.
I still don't see how, unless shocks have damping that changes as it travels through its stroke.
I did watch some of it, but I didn't see how it applies to an ST1100 with OEM suspension.
No, I still don't get it. Does any of that video explain more than just watching him make adjustments?
I very much am. I'm trying to get it, but I didn't see an explanation as I skimmed through the video. I see the spring and the shock as two separate mechanisms that each do different things.
The spring supports weight and compresses with applied weight. As long as neither end of the motion is restricted by outside forces, its laden length doesn't change, even with "preload" adjustments.
A given spring will be a given length with a given load compressing it. That overall length will not change just because you have repositioned one end; the other end (and the bike) will move the same distance.
To the spring, the shock is merely a positioning device, holding it in place by its ends being attached to the fixed (frame) and moving (swingarm) attachment points. We can have springs without shocks.
We want the static laden position of the bike to be where we have the most travel in both directions without it being stopped by hitting end-of-travel limitations, usually 1/3 to 1/2 of travel.
The shock controls, or damps, free motion so the bike isn't constantly bouncing as it goes over road imperfections. If the fluid is too heavy or light, the movement will bee too stiff or too loose, respectively.
I get that the compression and rebound damping settings must be set so neither is so high that it prevents the suspension from returning to that ideal static laden position between multiple bumps.
I also understand that the suspension gets temporarily compressed extra while in turns, due to the lateral G forces being added (vectorally) to vertical forces on the bike from the rider, passenger, gear, etc.
What I don't get is how the position along the (not limited by topping or bottoming) shock travel has any effect on damping. I'm ignoring unladen topping because a bike can't be ridden unladen.
Can you please try explain what I am missing, using the same wording I used? Once the bike is loaded, ready to pull away, how does changing ride height change damping, and not just ride height?
Are bike shocks non-linear? Does the damping change along a curve as it moved through its travel? If so, then I can understand how damping can be altered with changing the spring position.
Help me, Obi-Wan Kenobe.
To add, what I mean is I aim for the ride height that gives me the lightest, most neutral, responsive, and predictable steering. I ride 99% by counter-steering, and I look for the setting that requires equal effort to lean over and come back up again.
If the rear suspension is too low for me, which it was when I got the '01, it fights being leaned over, and requires so much gross steering input pressure that it's difficult to hold it while making fine steering input adjustments as I'm leaned way over.
If the suspension is set too high, it becomes twitchy and over-sensitive, making it flop over easily, but more difficult to bring back upright. Also, it becomes harder to hold steady at high speeds. I look for the middle ground, easy steering both ways.
The previous owner of my '01 is much lighter than I am, and it handled like a pig for me. I raised the rear about 1/2" on the shock, which translates to about 3/4" at the axle, and the steering immediately improved greatly. I then had new tires put on.
When I picked it up, it was so twitchy and hard to ride that I was sure I'd have to lower the rear, but by the time I got home, I was used to it, and I haven't adjusted it since. It handles delightfully, and it's a blast on the twisties once I'm warmed up.
My point is that I would not adjust the suspension differently if it reduced the sharpness of the handling.