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Fork Pressure and rebound

tobamorytobamory Posts: 101
edited November 2013 in MTB workshop & tech
When I got my bike it had been setup whilst I was there, but I wasn't fully kitted out. Ive been using it for a few weeks now without issue, so I thought id check out Foxs recommended pressure for a 220lb bloke. It was around the 175PSI, I checked my pressure and it was lower so I pumped it 175 and that was that.

When I went to my brothers this weekend and did some of the routes around hebden bridge, soon as I got on the bike I noticed the rebound clunk, not a massive clunk but something I hadn't noticed before. I actually thought the stem was loose. Anyway after a day out in hebden ( man them hills LOL ) we made it back.

I came home and lowered the pressure to around the 130 mark, and the rebound clunk wasn't there, IE like it was when I got it from the shop. When u pulled wheelies it didn't clunk at full extension. Obviously the clunk is the fork rebounded to its unsat on state, but as ive never heard these before I had to ask

So a noob questions really, is that rebound clunk IE the fork stopping at the end of its travel something you should feel or should I let some air out and lower it a tad.

the forks in questions are Fox Factory Kashima 140mm 32s..650B

thanks guys

Rob

Posts

  • POAHPOAH Posts: 3,369
    have you adjusted the rebound for the increased pressure
  • mcnultycopmcnultycop Posts: 2,143
    Ignore the manufacturers suggested pressures, just set the sag properly.
  • tobamorytobamory Posts: 101
    I did play with the rebound at the bottom but this didn't seem to take out the Clunk... lowering the pressure did

    I set the rebound the the slowest
  • mcnultycopmcnultycop Posts: 2,143
    Set the sag properly first.

    Then play with the adjusters.
  • POAHPOAH Posts: 3,369
    turning the rebound knob fully round should slow the fork down significantly - if its not doing that then there is an issue with the damping.

    like other people have said ignore the PSI and set sag to what ever you want 20% say then adjust the rebound.

    http://www.youtube.com/watch?v=j9vgrNqjwOA
  • Kowalski675Kowalski675 Posts: 4,412
    POAH wrote:
    have you adjusted the rebound for the increased pressure

    Damping and preload (sag) adjustment are completely independant of each other. Rebound damping controls the speed of the rebound stroke, altering sag doesn't change that.
  • Kowalski675Kowalski675 Posts: 4,412
    POAH wrote:
    like other people have said ignore the PSI and set sag to what ever you want 20% say then adjust the rebound.

    +1
  • Dirtydog11Dirtydog11 Posts: 1,621
    I checked my pressure and it was lower so I pumped it 175 and that was that.
    :shock:



    Guidelines for a 220lb rider is 100psi, I'll be suprised if you need any more than 80-90 psi, no wonder they where topping out.

    http://www.ridefox.com/fox_tech_center/ ... 26_32.html


    Your lucky you haven't damaged them!

    P.S.
    The noise will have been the top out and negative springs being crushed under the pressure.
  • tobamorytobamory Posts: 101
    Dirtydog11 wrote:
    I checked my pressure and it was lower so I pumped it 175 and that was that.
    :shock:



    Guidelines for a 220lb rider is 100psi, I'll be suprised if you need any more than 80-90 psi, no wonder they where topping out.

    http://www.ridefox.com/fox_tech_center/ ... 26_32.html


    Your lucky you haven't damaged them!

    P.S.
    The noise will have been the top out and negative springs being crushed under the pressure.

    Dirty am I reading this wrong then,

    Mine are the 2014 Kashima 140 32s

    http://www.ridefox.com/help.php?m=bike&id=31

    Appreciate yours says 100 but this one says 175 ? or am I being a noob

    Suggested Starting Points for Setting Sag




    Rider Weight lbs/kgs 130mm 140mm 150mm
    ≤125 ≤57 95psi 85psi 80psi
    125 - 135 57 - 61 105psi 95psi 90psi
    135 - 145 61 - 66 120psi 105psi 95psi
    145 - 155 66 - 70 130psi 120psi 110psi
    155 - 170 70 - 77 135psi 130psi 120psi
    170 - 185 77 - 84 145psi 135psi 130psi
    185 - 200 84 - 91 160psi 145psi 145psi
    200 - 215 91 - 98 175psi 160psi 160psi
    215 - 230 98 - 104 190psi 175psi 175psi
    230 - ≥250 104 - ≥113 200psi 190psi 190psi
  • tobamorytobamory Posts: 101
    Im taking it for a service soon so I,ll have them look, I should really go with Sag and not the guides. The forks in Dirtys most be the old model correct ?
  • Dirtydog11Dirtydog11 Posts: 1,621
    Indeed those pressures are for a 2013 model and 175 appears to be correct for your model, 175 still sounds a lot thats approaching shock pressures!
  • RockmonkeySCRockmonkeySC Posts: 14,770
    I used to run my Fox Float 32's at around 110psi when I was the same weight as you. Set the sag and then wind up the rebound damping to suit.
    There is a factory recall on 32 forks at the moment. Could be worth checking with Mojo to see if yours are affected.
  • DCR00DCR00 Posts: 2,160
    Regardless of what the links say, set the sag manually
  • Tobamory wrote:
    Dirtydog11 wrote:
    I checked my pressure and it was lower so I pumped it 175 and that was that.
    :shock:



    Guidelines for a 220lb rider is 100psi, I'll be suprised if you need any more than 80-90 psi, no wonder they where topping out.

    http://www.ridefox.com/fox_tech_center/ ... 26_32.html


    Your lucky you haven't damaged them!

    P.S.
    The noise will have been the top out and negative springs being crushed under the pressure.

    Dirty am I reading this wrong then,

    Mine are the 2014 Kashima 140 32s

    http://www.ridefox.com/help.php?m=bike&id=31

    Appreciate yours says 100 but this one says 175 ? or am I being a noob

    Suggested Starting Points for Setting Sag




    Rider Weight lbs/kgs 130mm 140mm 150mm
    ≤125 ≤57 95psi 85psi 80psi
    125 - 135 57 - 61 105psi 95psi 90psi
    135 - 145 61 - 66 120psi 105psi 95psi
    145 - 155 66 - 70 130psi 120psi 110psi
    155 - 170 70 - 77 135psi 130psi 120psi
    170 - 185 77 - 84 145psi 135psi 130psi
    185 - 200 84 - 91 160psi 145psi 145psi
    200 - 215 91 - 98 175psi 160psi 160psi
    215 - 230 98 - 104 190psi 175psi 175psi
    230 - ≥250 104 - ≥113 200psi 190psi 190psi

    That link is for Talas equipped forks.
  • tobamorytobamory Posts: 101
    I'll ask shop when I take her next week to check recall.

    What's mojo?
  • Kowalski675Kowalski675 Posts: 4,412
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