How to adjust rear travel on Motobecane 2009 Fantom Trail DS?- Mtbr.com
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  1. #1
    BWX
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    How to adjust rear travel on Motobecane 2009 Fantom Trail DS?

    How to adjust rear travel on Motobecane 2009 Fantom Trail DS?

    This is my first FS MTB, I searched around this Motobecane forum and did not see it being discussed. I am sure it was but I can't find it. When I take one bolt out of where the shock is connected to the "rocker arm" (or whatever it is called), the other bolt just spins and doesn't come out.

    I had another question as well, do the bolts pictured below have anything to do with it? If not, what are they for? I didn't see anything in the literature about it, and I hope they are not important for the safe operation of the bike as I have gone downhill faster than 37 MPH.

    EDIT- link to bike model--
    http://www.bikesdirect.com/products/...trail_ds08.htm
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  2. #2
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    OK... first off, those bolts are bosses for cantilever/ V-brakes - they thread into either your fork or your seat-stay. - not necessary if you have discs.

    Second - getting the bolt out of the shock...
    one side is a screw (male) the other side is a sleeved 'bolt' (female)
    to get that out, just before the screw becomes completely unthreaded from the sleeved-'bolt', push it back in toward the rocker as you support the weight of the bike neutrally (when you pull out the sleeved-'bolt', the suspension will want to collapse) - this will press out the sleeved-'bolt' enough to grab the head.

    As far as travel goes... the forward placement on the rocker is a 2:1 (~4"), middle 2.5:1 (~5") and rearward position is a 3:1 (~6")

    * note actual travel 'distances' I used are just guesstemates - I don't know your bike - just how it works. So, rearward=most travel

    -hope this helps
    Honestly... ahh I give up

  3. #3
    BWX
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    Quote Originally Posted by highdelll
    OK... first off, those bolts are bosses for cantilever/ V-brakes - they thread into either your fork or your seat-stay. - not necessary if you have discs.

    Second - getting the bolt out of the shock...
    one side is a screw (male) the other side is a sleeved 'bolt' (female)
    to get that out, just before the screw becomes completely unthreaded from the sleeved-'bolt', push it back in toward the rocker as you support the weight of the bike neutrally (when you pull out the sleeved-'bolt', the suspension will want to collapse) - this will press out the sleeved-'bolt' enough to grab the head.

    As far as travel goes... the forward placement on the rocker is a 2:1 (~4"), middle 2.5:1 (~5") and rearward position is a 3:1 (~6")

    * note actual travel 'distances' I used are just guesstemates - I don't know your bike - just how it works. So, rearward=most travel

    -hope this helps
    Thanks, next time I will try to do what you said. I think it is 3", 4", or 5" travel-- or something close to that.
    BTW, I did let off all the pressure on the spring before I tried it last time.. I forgot to mention that, but of course that wasn't the problem, I just didn't push the bolt through like you described.
    And yes I have discs, so that's why those bolts weren't used.

  4. #4
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    Quote Originally Posted by BWX
    ...
    BTW, I did let off all the pressure on the spring before I tried it last time.. I forgot to mention that, but of course that wasn't the problem, I just didn't push the bolt through like you described.
    ...
    yeah, I wasn't talking about backing the preload off of your spring, more that the weight of the bike itself, trying to compress the suspension via the rocker, was pressing down on the sleeved-'bolt' and holding it in place with friction.
    If you lift up the bike slightly (@ seatpost or top tube or something) you will relieve the weight / friction on the 'bolt' allowing it to slide out freely from the shock's eyelet/ bushing
    Honestly... ahh I give up

  5. #5
    BWX
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    Yeah and I am glad you said something about that because I probably would not have thought about it and the suspension would have collapsed hard.. if I even was able to get the bolts out with the weight of the bike on them.

    So I think I am ready to try out the 5" travel setting.. thanks again!

  6. #6
    ~Disc~Golf~
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    also worth noting, as you change positions, the spring will behave differently due to more or less leverage applied to it - as you move it rearward (3:1ratio), the spring will compress easier, so your suspension will feel softer w/ the same spring - - vice-versa for moving it forward.
    you may want to try it out to see if you like it, but you may need to get a new coil-spring if the feeling/ performance is unacceptable.

    A spring calculator is handy to use in determining what spring rate you should get (ie. 450 lbs) - I'll try to find the link to the calc I used when changing my rocker position

    **Edit - ahh found it! here ya go - just enter all of your data and voila!
    http://forums.mtbr.com/showthread.php?t=47726

    The Calc wont work in firefox and the link to the fix is broken in that thread, so you may have to use a different browser if you use FF (IE or Opera etc)
    Honestly... ahh I give up

  7. #7
    ~Disc~Golf~
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    Here's another calc which works in FireFox, but I kinda like the way the other one (above) works better, because you can compare all three rocker positions side-by-side
    http://www.igorion.com/_coilspring/
    Honestly... ahh I give up

  8. #8
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    i have the same bike and was also wondering about the travel. i knew the setting furthest back had the most travel, but couldn't wrap my head around why. sounds like you know highdelll. so what do the ratios (3:1) you are talking about refer to?

  9. #9
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    Quote Originally Posted by willie-d
    i have the same bike and was also wondering about the travel. i knew the setting furthest back had the most travel, but couldn't wrap my head around why. sounds like you know highdelll. so what do the ratios (3:1) you are talking about refer to?
    simple leverage principals man...
    as you move the shock closer to the fulcrum (pivot), the leverage changes
    you can see this using a pen (or similar) pivoting on your finger; as you move one end (the rear axle), you can see that as you get closer to your finger on the opposite side the 'axle' side has to move more for the 'shock' side to move a given amount.

    OK, so...
    The shock has a fixed amount of travel or 'stroke' that it has the capacity for; say 2"
    The '3:1' means that the axle has to travel 6" to use the full stroke (2") of the shock - as the axle moves 3 units, the shock mount moves 1 unit.
    Likewise, with a 2:1 ratio, the axle only has to move 4" to use the full 2" stroke.

    see my sh!tty drawing
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    Honestly... ahh I give up

  10. #10
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    thanks a ton for taking the time to explain that, with pics no less. crystal clear.

  11. #11
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    cool,, I'm pretty horrible at explaining things sometimes - I already know I shouldn't be a teacher for my profession
    -glad ya got my rambling
    Honestly... ahh I give up

  12. #12
    BWX
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    Sorry to resurrect this old thread-- but had a question..
    maybe someone can help.

    When I was adjusting that shock last year the bike
    was higher with the shock mounted all the way to
    the front so I left it there last season. It felt like it
    had more travel, and it was definitely higher- I had
    to put my seat down and the top tube was higher.
    Is there a way that the bike was higher but had
    less travel?

    I'd like to know for sure, here's the bike:
    http://www.bikesdirect.com/products/...trail_ds08.htm

    better pic so the entire rear suspension it in view...



    There's four hinged points and a pivot point (five
    if including shock mount), so just making sure
    here before I adjust it again.

    I am trying to get the full 5" travel. The adjustments
    are 3", 4", and 5".. I realize it's been answered
    already but not sure if he had enough info
    on the setup. It seemed opposite when adjusting
    it.. confusing.....

    I'm staring at the pic and in real life but cannot
    seem to get it.. I can usually just "see" things
    like that. I don't know.
    Last edited by BWX; 03-18-2011 at 11:20 PM.

  13. #13
    DynoDon
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    put it in the rear most possition on the rocker for the most travel, here is a pic of mine in the rear.. Happy Trails

    <a href="https://photobucket.com" target="_blank"><img src="https://i892.photobucket.com/albums/ac122/manabiker/P1200001.jpg" border="0" alt="Photobucket"></a>

  14. #14
    AZ
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    Quote Originally Posted by BWX
    Sorry to resurrect this old thread-- but had a question..
    maybe someone can help.

    When I was adjusting that shock last year the bike
    was higher with the shock mounted all the way to
    the front so I left it there last season. It felt like it
    had more travel, and it was definitely higher- I had
    to put my seat down and the top tube was higher.
    Is there a way that the bike was higher but had
    less travel?

    I'd like to know for sure, here's the bike:
    https://www.bikesdirect.com/products...trail_ds08.htm

    better pic so the entire rear suspension it in view...





    There's four hinged points and a pivot point (five
    if including shock mount), so just making sure
    here before I adjust it again.

    I am trying to get the full 5" travel. The adjustments
    are 3", 4", and 5".. I realize it's been answered
    already but not sure if he had enough info
    on the setup. It seemed opposite when adjusting
    it.. confusing.....

    I'm staring at the pic and in real life but cannot
    seem to get it.. I can usually just "see" things
    like that. I don't know.


    Chris (highdelll) nailed it. In short, less ratio = more travel.

  15. #15
    ~Disc~Golf~
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    Quote Originally Posted by BWX
    Sorry to resurrect this old thread-- but had a question..
    maybe someone can help.

    When I was adjusting that shock last year the bike
    was higher with the shock mounted all the way to
    the front so I left it there last season. It felt like it
    had more travel, and it was definitely higher- I had
    to put my seat down and the top tube was higher.
    Is there a way that the bike was higher but had
    less travel?
    ....
    I'm not sure what you mean by "higher"?
    moving the rocker position wont change the height of the bike (except fractions of an inch~1/8" maybe?)
    But, for the same weight of rider and same rate spring, the bike will sag more in the aft position (also longest wheel travel position) due to more leverage and conversely, will sag less in the fore position (less leverage)
    Honestly... ahh I give up

  16. #16
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    Quote Originally Posted by AZ.MTNS
    Chris (highdelll) nailed it. In short, less ratio = more travel.
    which way are you looking at the ratio?
    I always think more ratio = more travel i.e. the bigger the gap between the #'s
    3:1 more
    3:2 less
    Honestly... ahh I give up

  17. #17
    BWX
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    Quote Originally Posted by highdelll
    I'm not sure what you mean by "higher"?
    moving the rocker position wont change the height of the bike (except fractions of an inch~1/8" maybe?)
    But, for the same weight of rider and same rate spring, the bike will sag more in the aft position (also longest wheel travel position) due to more leverage and conversely, will sag less in the fore position (less leverage)
    That's probably what happened.. not sure why it felt higher but it did.

    Ok, thanks for all the input.. I will enjoy the extra travel after I fix it.

  18. #18
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    That other bolt isn't a bolt at all. It's a female threaded sleeve that accepts the bolt you took out of the rocker. Push a small screw driver into the hole on the other side and push that "bolt" out
    >>"Every chance I get!"

  19. #19
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    Quote Originally Posted by BWX
    That's probably what happened.. not sure why it felt higher but it did.

    Ok, thanks for all the input.. I will enjoy the extra travel after I fix it.
    You'll be best served to match the spring rate with your weight and your "ratio position"
    Try this spring calc to get you in the right direction
    http://www.bearandwife.com/bear/cycling/springcalc.html
    Honestly... ahh I give up

  20. #20
    DynoDon
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    I let the air out of my rear shock and measured the distance from the floor to the top of the seat, it was awhile ago, so I don't remember the readings, I do remember the longest travel was in the rear setting, and it wasn't 5 inches, but it wasn't 4 either, somewhere inbetween. I'll take all I can get.

  21. #21
    BWX
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    Quote Originally Posted by damnitzhym
    That other bolt isn't a bolt at all. It's a female threaded sleeve that accepts the bolt you took out of the rocker. Push a small screw driver into the hole on the other side and push that "bolt" out
    Right, yup I got it adjusted last year.. I just went the wrong way.

  22. #22
    BWX
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    Quote Originally Posted by manabiker
    I let the air out of my rear shock and measured the distance from the floor to the top of the seat, it was awhile ago, so I don't remember the readings, I do remember the longest travel was in the rear setting, and it wasn't 5 inches, but it wasn't 4 either, somewhere inbetween. I'll take all I can get.
    like maybe 120mm? 4.7244 inches? That's what I was thinking.

    BTW i tried 4 times to edit above post and mtbr is so slow now it times out most of the time. I doubt this will even get posted.

  23. #23
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    did that spring calc tell ya anything?
    Honestly... ahh I give up

  24. #24
    BWX
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    Quote Originally Posted by highdelll
    did that spring calc tell ya anything?
    Tried to respond yesterday.. I couldn't open MTBR on my PS3 browser for some reason.. weird.. still can't.

    Anyway, I looked at that page and it is interesting.. I think that's a 750lb spring on there IIRC
    Last edited by BWX; 06-17-2013 at 04:41 PM.

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