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Suspension

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by chicken78, Aug 8, 2011.

  1. Ok peoples I need a real quick definition/explanation of the following;
    rebound
    sag
    and compression?


     
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  2. oh dear......so many lines
     
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  3. Oh :p.. The reason I ask, is I deal with a Mountain bike/motorbike shock and suspension company, got into a heated debate with a Mr "know all" who now has me questioning my definitions of each...
     
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  4. isnt compression when two objects are pushed together like what shockers or springs experience when weight is loaded on the forks ?
    Rebound [I thought] is the force that go the opposite to the compression?
     
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  5. sag?
    well my bum's sagged so lack of muscle tone? lol
     
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  6. My theory sag - is the amount the spring compresses from being topped out and fully loaded?
     
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  7. What did Mr All say? Did you tell him he has too much sag? :LOL:
     
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  8. He just had his definitions all ass about,
     
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  9. what did he say then?
     
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  10. One problem I see often when people talk to others about their area of expertise is that they use jargon, short versions of terms, and assume the others have knowledge of some point without confirming it. Geeks do it a lot.

    So, he may really be talking about Rebound Damping and Compression Damping, rather than just Rebound and Compression. He may also be talking about the direction of forces associated with Rebound and Compression Damping, in which case the direction of each is opposite to the direction of actual movement.

    So, while Rebound is the extension of a shock absorber or forks, Rebound Damping is the force in the damper that resists the rebound movement. It acts in the opposite direction to the movement, which is to prevent the extension of the shock absorber or fork, and is therefore in the direction of Compression.

    In a similar way, Compression is the shortening of the shock absorber or forks, while Compression Damping is the force in the damper that resists the compression movement. It acts in the opposite direction to the movement, which is to prevent the shortening of the shock absorber or fork, and is therefore in the direction of Rebound.

    So when discussing definitions with Mr All, you need to confirm if he is talking about the movement, or the force associated with it. If he is from a shock and suspension company he is probably automatically talking about the forces. Hence, the disagreement and confusion.

    Sag is just Sag, although there are different categories or subsets of it, as mentioned above.

    If all of the above sounded like blah blah blah, it is because I'm a geek as well.
     
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  11. Running or rider on sag is usually a third of the spring length.
    There is also static sag which is just the weight of the vehicle on the springs.
    If we did not have dampening it would be like riding on the moon.
    The spring would compress and extend all day and we would just boink boink boink down the road. Although I would fall or throw up after the second boink.
    Compression dampening is the slowing down of the springs compressing.
    Rebound is the slowing down of the springs extending.
     
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  12. Static sag - the amount the suspension compresses under the bike's weight (- measured by the difference between the suspensions fully extended length versus the compressed resting position.)

    1G sag or just sag or rider sag - the amount the suspension compresses under the bike + rider + gear + luggage weight.


    Rebound and compression are usually short hand for the rebound and compression damping controls - Roderick has these ones sorted, but in mega laymans terms:
    - when you ride over a bump, the suspension compresses. How fast it does this depends on the compression setting (simple suspension has a preset setting).
    - Once you're over the bump, the suspension extends. How fast it does this depends on the rebound setting (simple suspension has a preset setting).

    :)
     
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  13. ...I think there's furious agreement here. lol
     
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  14. What.....? You mean a netrider thread that everyone agrees on & doesn't dispute ??? What has happened to our forum !:D
     
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  15. Very cheeky Al. :beer: (but with coffee)
     
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  16. Damn! Was hoping for a geek fight.

    Maybe we need to ask about the physics of nodding. Or whether right gloves go on first in the Northern Hemisphere.
     
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  17. Speaking of nodding........................
     
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  18. i actually just learnt something!
     
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  19. I don't think that is what's being said at all.
     
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  20. The lesson to be learnt is never ask questions which encourages the geeks
     
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