Mountain bike forks

Shibooty
Shibooty Posts: 7
edited November 2013 in MTB buying advice
Hi I'm new to mountain biking just got a cannondale sl5 and it as been upgraded with rockshox tora 318 u-turn fork but the guy said he haven't put the right amount of oil in the forks so lost about 30 to 40mm it's that right or are the forks broke thanks

Comments

  • mattv
    mattv Posts: 992
    If it's not got enough oil in a fork, it generally just affects the lockout and damping. Is it that it won't compress to full travel? All the way down? Thats a common failure on rockshox of that era, a seal goes inside the fork. Part is like £13. And a lowers service as well, expect a local shop to charge around £50-55 to fix and lowers service.
  • cooldad
    cooldad Posts: 32,599
    Or maybe they're U turned down.
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  • bartimaeus
    bartimaeus Posts: 1,812
    But you could try replacing the oil in the damper - measuring the right amount. It does make a big difference - the tolerance is pretty tight on the volume needed (to a ML or two).
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  • Thanks for replys sounds like it the oil as when I'm on the bike the forks drop 30mm straight away thanks will try new oil in damper and bottom legs
  • The Rookie
    The Rookie Posts: 27,812
    That's not a lack of oil.....when you are on the bike in the normal riding position (not seated) the forks should drop by about 25% of the travel! you adjust the spring not the damper (where the oil goes) to adjust this sag.
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • That's all adjust right m8 got to be oil
  • 97th choice
    97th choice Posts: 2,222
    Sorry, can you clarify that? when the bike is unweighted the forks are fully extended, and when you get on they sag by 30 - 40mm, right?
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  • rockmonkeysc
    rockmonkeysc Posts: 14,774
    Thats not oil. Either the spring is too soft or something internal is broken or the u turn is wound down.
    The damper just controls how fast the fork compresses, not how much it sags. Thats controlled by the spring.
  • CitizenLee
    CitizenLee Posts: 2,227
    If they are adjusted correctly then they should drop 25-30% of their travel when you get on the bike. It's called sag, and you need it for the forks to function correctly on the trail. I'd be more worried if they didn't drop when you got on it.
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  • Yer they do sag but to much it's like half of the 130mm travel just had all new seals but not enough oil I think
  • The Rookie
    The Rookie Posts: 27,812
    NO no no.....oil goes in the damper, it is not part of the spring that holds your weight up, the spring (air or coil) is too soft, it has NOTHING to do with oil.
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • It do have something to do with oil coz I've just came back from my local bike shop he topped the oils up in the damper and bottom legs and wot do u no back too normal now it only sags abit not half way thanks for all your replys great help lmao
  • cooldad
    cooldad Posts: 32,599
    Unless they were air and he pumped them up.
    Kaching.
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  • The Rookie
    The Rookie Posts: 27,812
    Suggest you learn the difference between a spring and a damper.....oil did not make any difference at all.....

    I rebuild car suspensions as well as bike forks, all they did was add air or change the preload to fix your sag, they may have added oil and charged you for that as well....'lmao'
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • No I think u need to learn m8 preload adjuster was tuned right out and the same when I had them back so think u need to learn more don't you lmfao and there is no air on this ones m8
  • cooldad
    cooldad Posts: 32,599
    Please stop with the text speak. Apart from being against the rules, it's annoying and makes you sound like an idiot.

    But as you are an expert, why ask in the first place?
    I don't do smileys.

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  • The Rookie
    The Rookie Posts: 27,812
    Preload needs to be wound in to reduce sag......

    But I'm sure you can explain in simple terms how damper oil changes the sag.........
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • rockmonkeysc
    rockmonkeysc Posts: 14,774
    Oil is used for damping. Damping controls the SPEED that the fork moves in either direction it does not stiffen or soften the fork.
    The is some oil in the lowers but that is purely for lubrication.
    Have a read about how suspension works.
  • bartimaeus
    bartimaeus Posts: 1,812
    A lack of oil in the damper can limit the amount of available travel - though the manual actually suggests "Oil volume is critical. Too much oil reduces
    available travel, too little oil decreases damping performance". Either way, it doesn't sound like that is the problem here.
    Vitus Sentier VR+ (2018) GT Grade AL 105 (2016)
    Giant Anthem X4 (2010) GT Avalanche 1.0 (2010)
    Kingley Vale and QECP Trail Collective - QECP Trail Building