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Thread: Suspension

  1. #21
    RiderCoach 4000 Posts! AZridered's Avatar
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    Quote Originally Posted by Sorg67 View Post
    Would there be any merit to setting up the suspension of a bike for beginners with very soft suspension? Provide the opportunity to see the impact of acceleration, deceleration, body position, etc. as noticeably as possible. Then gradually stiffen it up to get a feel for the difference?
    Firmer is not necessarily better. There is value in riding a bit, making a change, riding again, etc., in order to begin to understand how changes affect performance and feedback. There really are correct settings for a given machine under normal circumstances. The springs need to be strong enough, and properly preloaded, so that in most circumstances the suspension operates in its middle third of travel. As the suspension extends into its upper third, rebound damping increases to slow the suspension's movement as it nears full extension, so that topping out can be avoided. In the lower third of suspension travel, compression damping increases in order to slow suspension movement and avoid bottoming out. In the middle third of suspension travel, where we are supposed to spend most of our time, damping is optimized to keep our tires in contact with the ground and deliver minimal harshness back to us.

    Damping controls the movement of our suspension's springs, so the springs need to be set in a reasonably correct manner for the damping to be effectively adjusted.

    Once suspension is in the ballpark, testing and adjusting may be done with reasonable expectation of success.

  2. #22
    Flirting With The Redline 2000 Posts! Sorg67's Avatar
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    Interesting and useful as always AZ. Thanks.

  3. #23
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    When my older son was racing (road racing) we would spend one of the practice sessions working on suspension settings. When he finally reported that the bike felt perfect I would back off to his last "It's still a bit loose" setting. He was always faster that way.

    Once we had the correct springs in the bike they were never changed. Pre-load, occasionally, minimally. Only for an exceptionally bumpy or exceptionally smooth track. Damping always changed, even from morning to afternoon, just to compensate for temperature change.

  4. #24
    Flirting With The Redline 2000 Posts! Sorg67's Avatar
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    It makes sense to me the many of the principles of suspension adjustment optimization would apply to both track and street and to both experienced and novice riders. But it also makes sense that there would also be differences based on differing objectives and differing riding styles. Perhaps the differences would be more matters of degree than type.

    The concept of keeping the suspension operating in the middle third of the range of travel makes sense and seems that it would apply to anyone since that is where the suspension would operate best and most consistently. And it would seem that in straight line consistent travel that would be mostly a function of rider weight. Although I suppose hitting a bump in a straight line at 100 mph would be different than at 50 mph. But I am guessing that does not make much functional difference.

    The part that interests me as a novice street rider is cornering and braking in emergencies, through bungled swerves or turns and through bumps and debris. I would want my bike set up to maximize its ability to maintain traction and minimize risk of loss of control of the bike.

    For cornering at slower novice speeds, it would seem that a little softer setting (more sag) would be better for a novice compared to an experienced track rider cornering at higher speeds who might want a little stiffer (less sag) setting. For cornering, my objective as a novice would be to maximize the ability to regain traction through bumps and dips. I do not really understand rebound, but by the word, it seems that could relate to this objective as well.

    But I could imagine that too much sag would make the suspension react slowly, possibly bottom out and regain traction less quickly. I could also imagine that too much sag could result in the bike becoming unstable and potentially result in loss of control. I suspect these conditions existed in both of our dual sport bikes when we got them. The suspension is set up with less sag now and the feeling on the road is more solid. For both the feeling was dramatic and very noticeable, especially the DRZ. I think the KLX probably could have a bit less sag yet, but it is much better than it was.

    I do not have a sense as to whether the Versys is set up right or not. It feels fine to me. But I really do not have a good basis of comparison. I have not even looked at it closely to have any idea of how it is set. I think that will be my next investigation. Get the owner's manual out and try to figure out where it is set relative to the range of possible settings. I am guessing that as a 170 lb novice rider, riding one-up without luggage a good place to start would be slightly looser than the middle of the adjustment range.

  5. #25
    RiderCoach 4000 Posts! AZridered's Avatar
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    The amount of sag at which the suspension is set does not affect how quickly it will react to change. Sag is merely an expression of how high or low the suspension's 'neutral' point is set. As noted, if the amount of sag is too great, the suspension will bottom out more readily and this could lead to traction issues under heavy braking, particularly at the front wheel. i.e. Once the front suspension has hit the bottom of its travel, the only suspension left is the front tire. If the tire is being used to brake and is also all that is left to respond to surface irregularities, the tire is easier to lock up. If the amount of sag is insufficient, the suspension will tend to top out. This can be a problem on irregular surfaces when the suspension is unable to extend enough to allow the tire to maintain firm contact with the ground and results in a harsh ride.

  6. #26
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  7. #27
    Flirting With The Redline 2000 Posts! Sorg67's Avatar
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    Quote Originally Posted by AZridered View Post
    The amount of sag at which the suspension is set does not affect how quickly it will react to change.
    From you earlier comment about keeping the suspension operating mostly in the middle of its range of motion, I inferred that the suspension would operate less efficiently in the top and bottom range. This makes intuitive sense to me that if a spring is not loaded at all or completely compressed it would be less efficient than if it is in the middle. Would that not allow it to react to change more effectively / quickly?

    Or is setting the sag in the middle only for the purpose of avoiding topping or bottoming out?

    The explanation in the video posted by Trials is also interesting, particularly the comment about setting the suspension soft and not worrying about bottoming out. Although, I would assume that the optimal setting for Trials riding would a lot different than street riding due to the slow speed and extreme handling and traction requirements.

  8. #28
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    The springs do not affect the speed at which the suspension can respond, that function is fulfilled by the dampers (shocks). The purpose of the springs are simply to support the weight of the bike and rider at an appropriate height. Whether the springing is very stiff, or very soft, the speed of response will really not be much different. With soft springing, and a lot of sag, it will be easy to bottom out. If the springs are quite stiff, topping out will happen. On the road, both are undesirable because both conditions compromise your tires' ability to deliver traction.

    The dampers, shocks, control how rapidly the suspension is able to move. Compression damping controls how rapidly a wheel can rise to respond to a bump in the road. If the compression damping is too high, the wheel will not be able to move rapidly enough and too much of the bump's force will be transmitted into the motorcycle (and rider). This damping state is referred to as 'slow', the suspension does not allow rapid compression to absorb the bump. If the compression damping is too low, the wheel will not only readily rise up for the bump but will continue upward due to its momentum. Traction will be reduced due to the low tire loading, the tire could even momentarily break contact with the ground. This state of damping is referred to as 'fast', suspension will allow the tire to move very rapidly. Ideally, compression damping is fast enough to allow the wheel to readily cross over a bump without transmitting too much of the bump's energy into the motorcycle, but slow enough so that the tire will maintain sufficient contact with the ground.

    Rebound damping (sometimes Tension) controls movement in the opposite direction. Rebound controls how rapidly the springs are allowed to extend the suspension. On the aforementioned bump, if rebound is too slow (too much damping force), the suspension will not extend rapidly enough to allow the tire to maintain contact with the road as the wheel travels on the downhill side of the bump. In this case the motorcycle actually falls a little bit as the tire rolls downhill. Once across the bump, the springs now have to move the motorcycle back up to its designed riding height and compression damping comes back into the picture. A rough ride. If rebound damping is too fast (insufficient damping force), the suspension will try to extend too suddenly as the wheel rolls over the bump and you can end up with the tire rolling down the back of the bump while the motorcycle's momentum is still upward (a little) ending up with the suspension actually over extending. Now the bike has to settle down onto the springs, more than necessary. A rubbery ride. Ideal rebound damping force will allow the springs to keep the tire in contact with the ground, matching the rate at which the motorcycle settles.

    When you bounce on the seat of your bike, or hold the front brake as you push forward, it is compression damping that slows how rapidly the springs compress. Normally, compression damping is fairly minimal. After you have pressed, the bike returns to its normal riding height. The speed at which this happens is controlled by rebound damping. Normally rebound damping is considerably slower than compression damping.

  9. #29
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    The least complex suspensions on motorcycles will normally have only spring preload at the rear suspension. This is because when you add stuff to your motorcycle, the front end is only minimally affected, almost all of the weight has to be supported by the rear suspension. Ideally, when fully loaded, you have the rear spring preload set high enough that the motorcycle will maintain the same ride height as it would when you ride alone.

    The next step in complexity adds rear rebound damping adjustment. When you stiffen the rear spring by adding preload it is nice to be able to add rebound damping to balance the added spring force.

    The next step adds external front preload adjustment. The front suspension's preload can always be adjusted by adding or removing spacers from the inside of the fork. Including an external preload adjustment just makes the process simpler. Once set, it is pretty rare to need to change front preload.

    The next step is to add a front rebound adjuster. Just like the rear suspension, adjusting front rebound allows you to match the spring's force.

    Last, front compression adjusters allow you to fine tune the front suspension's response to bumpy surfaces.

    You may also hear of high-speed and low-speed damping adjustments. The speed term refers to how rapidly the suspension needs to move, not how rapidly you are travelling down the road. Common damping is high-speed damping. This is what suspension needs to absorb sudden changes caused by bumps and ruts. Low-speed damping is not common and is for tuning at the highest level. When you accelerate rapidly and weight shifts to the rear suspension, that is dealt with by low-speed damping. It is not a rapid change. When you ride into a banked turn and extra force is transferred into the suspension, that is smoothed by low speed damping. When you are riding rapidly on a rolling road and get that roller coaster feeling as you crest rises, that can be tuned with low-speed damping.

  10. #30
    Flirting With The Redline 8000 Posts! Trials's Avatar
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    Trials riding isn't near as slow as you think it is at least not where we ride.
    https://youtu.be/V6DBSn7FFB0
    Last edited by Trials; 11-16-2018 at 06:51 PM.

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