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  1. #1
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    Coil fork question: light spring with max preload or heavier spring with none?

    I have a fox 36 van rc3/fit yada yada yada.

    I feel I am in between spring weights (Soft/Med) so I gotta ask if there are any negative effects to preloading the spring compared to a heavier spring with no preload.

    Dre

    I searched for this but all threads were from 2005 & before.

    thx in advance

  2. #2
    Bicyclochondriac.
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    Have you actually tried both?

    FWIW, what was true before 2005 is still true today regarding this.

    I always found that if I need to use a whole lot of preload on a coil, it is going to be undersprung (regardless of the preload you actually use). The Rock Shox U-Turn Coils don't even have a preload adjustment, you just find the one that works best with none (well, almost none).
    15mm is a second-best solution to a problem that was already solved.

  3. #3
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    I prefer to run as little preload as possible. Preload is used to adjust the sag point it does not increase the spring rate.

  4. #4
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    I'll give the MED spring a good thrashing this weekend before passing judgement. Just thrashing around it felt too firm with the compression H/L opened up.
    The soft spring felt plush but sat a little low.

    Any opinions on undersprung/overdamped VS oversprung/underdamped ?

  5. #5
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    Maybe lighten the damping then

    With the spring, good way to test is on steep turn, fast with good chunk. Usually Fox will not return fast enough on that if the spring is too light.

  6. #6
    Bicyclochondriac.
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    Quote Originally Posted by sanjosedre View Post
    I'll give the MED spring a good thrashing this weekend before passing judgement. Just thrashing around it felt too firm with the compression H/L opened up.
    The soft spring felt plush but sat a little low.
    When you say the soft sat too low, are you talking about it diving too much, and using travel too easily? If so, you want a firmer spring or more compression damping. If it just feels like the front end is too low, you can dial that out with your cockpit setup.

    Any opinions on undersprung/overdamped VS oversprung/underdamped ?
    Personally, I find that a firmer spring with less compression damping is preferable.
    15mm is a second-best solution to a problem that was already solved.

  7. #7
    Vorsprung Suspension
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    Preload adjusters are really only there to take up the slack in the fork assembly tolerances, which is primarily the length of the spring. They should be wound in as far as necessary to remove all play from the fork, but beyond that they are of little use other than to adjust the ride height in tiny increments. On motorised vehicles, particularly cars, ride height is of critical importance (2mm difference in ride height has an enormous effect on the handling of a racecar), however this is really not the case on mountain bikes. If a spring is too soft for you, you need a stiffer spring. Sometimes, particularly for lighter weight riders, you may feel like you're "between" spring rates - the only real solution for this is an air spring, as it will let you tune the rate more finely. Adding preload can cause the fork to ride harshly at the very start of the travel, and in extreme cases can cause harsh top-outs as well. It affects the amount of force required to bottom the fork out by very little compared to changing the spring, and should not be used as a substitute for a stiffer spring. Basically, it is an adjustment best set to minimum and left alone.

    Generally speaking, with forks it is better to err on the stiff side, and with rear shocks better to err on the soft side, because going the other direction (soft front/stiff rear) can create dangerous imbalances in the bike. Because of this need for balance, you may find that what feels like a slightly-too-soft spring feels better if you soften the rear of the bike to match, or that a slightly-too-stiff spring feels better if you stiffen the rear of the bike to match.
    VorsprungSuspension.com - fully engineered suspension retuning & servicing in Whistler, BC.

  8. #8
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    How much travel are you getting out of each? If you are getting max travel out of the stiffer spring, then go with that one.

    Cranking up your preload doesn't change your spring rate on a coil fork. All it does is increase your rebound speed for any given rebound setting.

    Compression damping can keep you up in your travel and out of your travel but it can also keep you from using all of your travel.

    It really depends on how much travel you are getting and your riding style. The pro boys run less sag and heavier springs than us mortals. They bounce off of stuff and hit stuff REALLY hard when running full on.

    Find someone who knows suspension and ride with them. I spent all last year doing this for people and you'd be amazed how good it feels when you get it right.

    Good luck.

    mk

  9. #9
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    as a general rule..

    with everything else remaining the same
    the longer a spring is at the same rate the more linear it will be
    the shorter a spring is (using a spacer or preload to take up the extra space) the more progressive it will be
    so.. a softer spring with more preload will be more progressive then a heavier spring with less preload

  10. #10
    Vorsprung Suspension
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    Quote Originally Posted by flyinmike View Post
    as a general rule..

    with everything else remaining the same
    the longer a spring is at the same rate the more linear it will be
    the shorter a spring is (using a spacer or preload to take up the extra space) the more progressive it will be
    so.. a softer spring with more preload will be more progressive then a heavier spring with less preload
    Sorry but this is not true with coil springs until you reach the point at which the spring binds. In the case of fork springs, they are dead linear even when fully preloaded. Preload DOES NOT affect the spring rate at any point in the travel, it only (very slightly) shifts the force values up by a constant offset.
    VorsprungSuspension.com - fully engineered suspension retuning & servicing in Whistler, BC.

  11. #11
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    how about slowing the compression down or heavier weight oil with the soft spring or visa versa...

  12. #12
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    you could have just said we are dealing with straight rate springs in that fork
    then talk about dampening and oil height etc..
    (which is what surprises me)

    but, if sanjosedre is trying to choose between the two springs he mentioned
    He should at least try using some preload and the softer spring and see if that works for him
    Maybe you could PM him and explain how to get the most out of what he has
    Or, I guess he could send the fork to you for dampening mods and maybe a "custom" spring
    You really should qualify who your talking to before you start twisting physics


    and yes having a fork setup the way that takes advantage of everything you mention with no preload would be ideal
    but that is not really helping him.. is it.







    Quote Originally Posted by Steve VS View Post
    Sorry but this is not true with coil springs until you reach the point at which the spring binds. In the case of fork springs, they are dead linear even when fully preloaded. Preload DOES NOT affect the spring rate at any point in the travel, it only (very slightly) shifts the force values up by a constant offset.

  13. #13
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    Damn, dood. You got two of the biggest mistakes about suspension in one post! Chapeau!

    All coil springs are linear (in mtn biking). And dampening means to make something wet. Suspension deals with damping.

    You need the right spring first. Damping adjusts ride quality whereas the spring affects how much travel you get over a given hit.

    Check your travel usage and sag. Get it dialed then deal with your damping.

    You need someone to walk you through this in person, with your bike, on the trail.

    mk

  14. #14
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    2 posts..
    My spelling does suck.. so does my spell check
    And, your right I didn't know that that spring was a linear curve vs progressive curve


    none of this really helps sanjosedre
    You are..
    so is RipRoar..

    "Check your travel usage and sag"
    "then deal with Damping"

    pretty good advice

    if he is between the two springs he has.. then as RipRoar says

    "how about slowing the compression down or heavier weight oil with the soft spring.. or visa versa..."
    Last edited by flyinmike; 02-08-2013 at 07:08 AM.

  15. #15
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    Only the rider can know whether a firmer or softer coil works better for their weight and riding interests. It is worth the added $30 to $40 to try a different coil weight to know for sure.

    If you have externally adjustable compression damping, and the suspension rides best with compression damping turned to the softest end of the range, then try a softer spring (coil) with more preload to have the same sag, to be able to turn in compression damping. Compression damping a few or more clicks in from soft allows adjustment to go softer for very rocky conditions which ride better with softer suspension than what is better for hardpack.

    There is nothing wrong with adding preload, up to the point there is harsh top out that firmer rebound damping adjustment cannot eliminate without being too firm for downhill speeds.

  16. #16
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    Everyone that replies to a post qualifies as "help" it stimulates conversation that leads to learning. The OP question was a little general he did not mention his weight, riding conditions, current sag, travel use or dampning adjustments. "I am in between two springs" when coil forks were prominent I read that statement quite a bit. It wasn't really the springs fault but more a lack of progression on coil l forks where you couldn't adjust the air / oil volume. A common issue was "if I run one coil my forks offers great compliance but bottoms out, a stiffer spring might control bottoming but compliance suffers. I am not a fan of the modern closed damper coil fork, if they built a proper fork full of oil it would probably weigh too much for most mtn bikers.

  17. #17
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    They built plenty of open-bath forks but the damping was wholly inconsistent as the oil would regularly cavitate, causing the damping to go away (air doesn't flow like oil).

    Again preloading a COIL SPRING will not change the spring rate, it will only make it rebound faster. Coils (in mtn biking) are linear so that means that 10 pounds of force equals 1 centimeter of travel, 20 pounds equals 2 centimeters, etc. It's a line on a graph. Air springs on xc forks and xc rear shocks are progressive meaning 10 for 1, 20 for 2 but 40 for 3, 80 for 4. It's a progressive curve if you plot it on a graph.

    I can tell you based on sag if the spring is right (or close). You make changes based on terrain and rider preference AFTER you check sag.

    And it's not true that you want more compression for smoother areas and less for rockier. On smaller hits (smoother areas), your bike will feel harsh if you don't back off the compression. You'll use the travel for those small hits. For bigger hits (drops, etc), the compression should be turned up a few clicks so that you don't fall into the travel when you are compressing into a jump or carving a turn at speed.

    In general, all compression adjustments are low speed unless otherwise specified. When you hit something really hard, you send the oil through a different port just below the shim stack, depending on the fork design.

    The slower you go, the less compression you need. The faster you are going, the more compression you need. Same goes for springs rate. You need a firmer spring to go faster over more nasty terrain.

    mk

  18. #18
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    I had a Van36R, which came with the Blue spring (I'm ~150lb) and it felt a bit harsh, but occasionally bottomed out on big hits.
    I put in the Purple spring, and the fork felt much more supple, tracked fast corners better, and still occasionally bottomed on big hits.
    So, in my case it softened the ride but didn't seem to bottom out any worse. Like has been said, you need to try both and find your best setup.

  19. #19
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    Sanjosedre, if you are in San Jose, head over to Trail Head Cyclery and ask for Lars. Or anybody, actually. They'll get you dialed in. Lars is a good buddy of mine and really knows his stuff, as do most of his employees. They'll get you dialed for sure.

    mk

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