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Help Setting Up Front Forks

iLukeKendalliLukeKendall Posts: 160
edited May 2013 in MTB workshop & tech
Hi all,

So I'm kinda new to MTB, and bought a 2013 Trek Mamba about 4 months ago. It came with a RockShox XC32 (Coil Spring), and since owning it I've not been completely satisfied with the fork - it seems very stiff and doesn't seem to absorb much at all.

The fork allows for two adjustments;
1) Rebound - Adjusted by turning a dial under the right fork towards either a tortoise or a hare.
2) Preload - Can be loosened or tightened.

I have tried adjusting these but I don't really now what I'm doing and haven't seen a massive difference (not that I've extensively tested different settings).

I mainly ride across open moorland which can be quite rocky. At the moment it feels almost as if its locked out all the time, even when it's not (although it will budge if I stand up and start bouncing the fork).

I was wondering if anyone could please offer me some advice on how I should best set this up for my weight/body size, as I have no idea! Should I have the rebound set to the hare or tortoise? Should the preload be loose or tight?

I'm 18, around 6ft tall and weigh around 10st 11lbs, or 69kg (slim build) in case that helps at all!

Thanks a lot for reading and for any suggestions!
Whyte 29-CS • Canyon Ultimate • #CCWMTB • Strava Profile

Posts

  • nicklousenicklouse Posts: 50,675 Lives Here
    preload sets the SAG. you want about 20%
    rebound controls the speed that the fork extends. you should just be able to pick the bike off the ground before the fork fully extends from compressed.

    that is all you have to play with.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • iLukeKendalliLukeKendall Posts: 160
    nicklouse wrote:
    preload sets the SAG. you want about 20%
    rebound controls the speed that the fork extends. you should just be able to pick the bike off the ground before the fork fully extends from compressed.

    that is all you have to play with.

    Thanks for the reply. With regard to the SAG, should this be 20% from when it's fully loose or fully tight?
    Whyte 29-CS • Canyon Ultimate • #CCWMTB • Strava Profile
  • supersonicsupersonic Posts: 82,708 Lives Here
    Whatever it takes to achieve that amount of fork sag when stood on the bike.
  • iLukeKendalliLukeKendall Posts: 160
    supersonic wrote:
    Whatever it takes to achieve that amount of fork sag when stood on the bike.

    Sorry, I'm being completely dumb here - does this mean how much it compresses when I'm stood on the bike? So it should compress by about 20% when standing?
    Whyte 29-CS • Canyon Ultimate • #CCWMTB • Strava Profile
  • cooldadcooldad Posts: 32,599
    Yes.
    I don't do smileys.

    There is no secret ingredient - Kung Fu Panda

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    Parktools
  • plasma_manplasma_man Posts: 129
    When sitting on it in a normal riding posture.
    - 2013 Cube LTD, SL 29, grey / black.
  • supersonicsupersonic Posts: 82,708 Lives Here
    No, standing in attack position!
  • iLukeKendalliLukeKendall Posts: 160
    Thanks for all the advice - I'll try some different settings tomorrow.

    I have been doing a bit more research and came across this: http://cdn.sram.com/cdn/farfuture/w-Vgi ... _rev_c.pdf

    According to that guide, for my weight I should have a 'yellow' soft coil - the fork came with a 'blue' firm coil. Would this make much difference?
    Whyte 29-CS • Canyon Ultimate • #CCWMTB • Strava Profile
  • supersonicsupersonic Posts: 82,708 Lives Here
    Possibly, see what measurement you get.
  • iLukeKendalliLukeKendall Posts: 160
    supersonic wrote:
    Possibly, see what measurement you get.

    Sorry, by this do you mean the sag measurement? What would I be looking for to decide whether the coil is too stiff?

    I'm sorry for my stupidity - I've fallen in love with riding but I'm slowly trying to get my head around all the mechanical stuff.
    Whyte 29-CS • Canyon Ultimate • #CCWMTB • Strava Profile
  • cooldadcooldad Posts: 32,599
    If you can get enough sag the spring will be ok. If not you need a softer one.
    I don't do smileys.

    There is no secret ingredient - Kung Fu Panda

    London Calling on Facebook

    Parktools
  • The RookieThe Rookie Posts: 27,804
    Measure sag as follows....
    Measure exposed length of upper stanchion with no weight on bike.
    Measure exposed length of upper stanchion with you on the bike in the 'attack position' get someone else to do it, you can't do it yourself.
    Correct nominal travel by nominal sag (so 100mm travel, 20% sag is 20mm) and see if that is the reduction in stanchion length you got, if it sagged too much add preload, not enough, take it off.
    Current steed - Whyte T129, 2013 frame, mongrel Revelations, Giant dropper, Stans S1 wheelset. 12, Magura Trail Sport brakes, 1x11. 12.8Kg
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