Between Spring weights? fox forks

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  • Between Spring weights? fox forks
  • jamiesilo

    i have some old vanillas which are great but i seem to be between a soft (purple) and a standard (blue) spring.
    with minimum preload i get a maximum of 25mm sag. recommended range 20-33mm and i’d like to be further towards the 33 end as i find them a bit firm. i’ve tried a purple soft spring but bottomed out far too often, even with max pre-load. don’t remeber where i was in terms of sag but i think about 28mm, sounded ideal, but wasn’t

    could it be that the pre-load knob doesn’t ‘create’ overlap between the spring weights?
    is there another fix i can use? eg take a spring from some other fork?


    I had a similar problem with the Van 36s on my old SubZero, but I was on the “cusp” of standard and firm springs – the firm was too stiff with no preload and the standard was too soft with max preload…

    So I tried an old motorbike trick – I knocked up a small spacer 30mm diameter (so it would fit loosely inside the stanchion) by about 6mm wall thickness by 10mm deep.

    Sit this on top of the spring and refit the preload adjuster cap. It takes a bit of doing, because essentially you’re “pre-preloading” the spring. That said it worked perfectly in that I could set a reasonable amount of sag.

    The guy I sold the bike too is still running it like this AFAIK.


    Another motorbike trick is one of each to give an average of the two.

    Premier Icon johnikgriff

    Eat more/less cake 🙂 ^^^ their answers are better…


    coil springs are linear, preload only alters the sag it does nothing to the force needed to compress the spring.


    thanks johnellison, i’ll give that a go. wish i hadn’t sold on the soft spring

    and thanks b45her, but i don’t agree.
    they are linear but that line is not horizontal on a graph so to speak.
    it still takes more force to compress eg 10mm near the end of the stroke (when the spring is more compressed) than near the beginning.
    from another forum:

    the red line is a linear shock, the blue a progressive.
    ‘X axis would be how far into the stroke you are and Y axis being how much force needs to be applied. All shocks, no matter if they are progressive or linear, need more force to compress them the farther they go into their travel’

    that means johnellison’s trick with a spacer would work because the spring is already more compressed at any given point in the travel than it would have been otherwise, requiring more relatively more force than before to move the same part of fork travel.

    [and that is why preload affects sag.
    the spring can be made more or less compressed at a given point in the forks travel or conversely, with a given force acting on the system, it can be made to move more or less depending how far through it’s compression the spring is.]
    anyway blah blah blah. that’s my understanding of it.

    but it’s got me wandering how far you can space before the spring becomes fully stacked before full travel. not much danger of that i’d guess…


    could i just put in a purple spring from a set of 140mm vanillas?

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