Front forks not using full travel?

Rushmore
Rushmore Posts: 674
edited October 2012 in MTB workshop & tech
Ello.. i'm no expert on forks but I was wondering if anyone could help me out?

The forks i'm talking about are my Fox Float 32 with FIT with 120mm travel damping..

No matter how hard I try the forks will "bottom out" at 100mm only.. and will not use the extra 20mm...

can anyone advise me on what this problem can be? i've tried letting some air out the shock aswell so it runs a bit softer and there is still no change..

can anyone advise??

Thanks..
Always remember.... Wherever you go, there you are.

Ghost AMR 7500 2012
De Rosa R838

Comments

  • nicklouse
    nicklouse Posts: 50,675
    when you say bottom out is it a hard stop?

    if air springs let all the air out and see if you can fully compress them.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • its not a hard stop, but it definitely stops... but its an air sprung fork..

    I let SOME air out.. And it still stops in the same place... I don't have a shock pump so didn't want to make it unrideable...
    Always remember.... Wherever you go, there you are.

    Ghost AMR 7500 2012
    De Rosa R838
  • supersonic
    supersonic Posts: 82,708
    What is the sag? It is impossible to set the fork up properly without a shock pump!
  • nicklouse
    nicklouse Posts: 50,675
    buy a shock pump.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • the sag now is about 20%

    But that is 20% of the stantion, not available travel...

    feels comfy though haha... not too sure how it will fair up to bugger knocks..

    SS I'm quite close to my LBS and relitivly friendly with them.. so I can use their tools and kit...

    But yes.. I should buy a shock pump..
    Always remember.... Wherever you go, there you are.

    Ghost AMR 7500 2012
    De Rosa R838
  • benpinnick
    benpinnick Posts: 4,148
    Sounds like too much oil to me.
    A Flock of Birds
    + some other bikes.
  • supersonic
    supersonic Posts: 82,708
    But you don't know what the available travel is, as you have not let all the air out. it could be the full stanchion length...
  • supersonic wrote:
    But you don't know what the available travel is, as you have not let all the air out. it could be the full stanchion length...

    ah ok...

    Well i'll try that tomorrow and get back to you :)

    thanks for you help so far guys i'll keep ya posted..
    Always remember.... Wherever you go, there you are.

    Ghost AMR 7500 2012
    De Rosa R838
  • DCR00
    DCR00 Posts: 2,160
    how are you testing the bottom out ? if you are just testing by leaning on it, then its unlikely you will achieve that much pressure on the fork to get it to bottom out anyway

    as suggested, sounds like too much oil
  • Rushmore
    Rushmore Posts: 674
    edited September 2012
    DCR00 wrote:
    how are you testing the bottom out ? if you are just testing by leaning on it, then its unlikely you will achieve that much pressure on the fork to get it to bottom out anyway

    as suggested, sounds like too much oil

    Every thing.. Jumping on it ( on the bike obv.... )

    I even did a 3 foot drop off.... nothing.. various trail centre poundings aswell....

    ( but today i was just bouncing on it... )
    Always remember.... Wherever you go, there you are.

    Ghost AMR 7500 2012
    De Rosa R838
  • Rushmore wrote:
    I even did a 4 foot drop off.... nothing..
    I'm going to just put that down to MBUK measuring techniques :wink::lol:

    Every (decent) fork has a bump stop, which prevents metal against metal contact during bottoming out. This means that you're going to need a pretty serious impact to fully compress the forks.
    Some Fox cartridges also have a bottom out resistance built into the damper. In the last part of compression, a valve forces oil through a kind of "last ditch effort" to really slow down the fork's motion.
  • Rushmore wrote:
    I even did a 4 foot drop off.... nothing..
    I'm going to just put that down to MBUK measuring techniques :wink::lol:

    Every (decent) fork has a bump stop, which prevents metal against metal contact during bottoming out. This means that you're going to need a pretty serious impact to fully compress the forks.
    Some Fox cartridges also have a bottom out resistance built into the damper. In the last part of compression, a valve forces oil through a kind of "last ditch effort" to really slow down the fork's motion.

    By 4 I meant 3.. sorry that was a typo..
    Always remember.... Wherever you go, there you are.

    Ghost AMR 7500 2012
    De Rosa R838
  • Rushmore wrote:
    Rushmore wrote:
    I even did a 4 foot drop off.... nothing..
    I'm going to just put that down to MBUK measuring techniques :wink::lol:

    Every (decent) fork has a bump stop, which prevents metal against metal contact during bottoming out. This means that you're going to need a pretty serious impact to fully compress the forks.
    Some Fox cartridges also have a bottom out resistance built into the damper. In the last part of compression, a valve forces oil through a kind of "last ditch effort" to really slow down the fork's motion.

    By 4 I meant 3.. sorry that was a typo..
    It's ok, I was referring to the MTB equivalent of when fishermen say they "caught one THIIIIIIIS big!!" :lol:
  • peter413
    peter413 Posts: 5,120
    If they're anything like my Float RL's then it can be because of the air cartridge. If you attach a shock pump and empty the chamber then compress the forks with the pump still attached, you will see that the pressure suddenly goes from nothing up to say 50psi or so in the last bit of travel which is why you can never use full travel even when you drop the pressure a bit. And that's with two different air cartridges so it almost definitely isn't a fault with my forks.
  • grenw
    grenw Posts: 803
    I have similar/the same forks on my Canyon - FIT performance 120 models. Very rarely do I get into the last 20mm of the travel and that's with only around 60psi or so in them. Below the recommended 75psi for my weight.

    Compared to my open bath 100s they seem a lot less likely to move although they are just as smooth. It's almost as if they had a higher pressure in them but they are the same if a little less.

    I can though get them very near the top of the travel, usually when hitting a sharp compression (or whatever you call a short sharp drop followed by a short sharp hill) but it doesn't happen that often and I usually don't notice until I get home and see where the o ring is.