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Fox 34 Rhythm Bottoming out

fierygasolinefierygasoline Posts: 2
edited 7 April in MTB general
Have recently upgraded to the world of full suspension bikes with a 2021 Giant Trance 2 after owning a 2012 Carrera Fury for many years. I love the bike but I'm having trouble setting up the forks correctly.

On first purchase I set the forks for my weight (66kg) and had a few moments on nose heavy landings or g-outs where I bottomed the forks out hard, enough to make a horrible *clang* sound and shock through the hands. I've upped the pressure slightly but it still just blows straight through its stroke. Adjusting the compression damping seems to go from soft to too hard for rough tecky decents.

What settings are folk running for these forks? Are they supposed to have some sort of bottoming resistance? I expected a bump stop at the bottom or something rather than a hard bottom!

Any help would be much appreciated!

Posts

  • JBAJBA Posts: 2,749
    Are you setting the sag correctly?
    Wear what you would for a normal ride, including back pack if you use one, and adjust the air pressure to give 20% sag. Ride with that and adjust the pressure up or down until it feels right.
    Also check how many, if any volume reducers are fitted to the fork and add or remove to get the response you want.
    “Life has been unfaithful
    And it all promised so so much”

    Giant Trance 2 27.5 2016 ¦ Sonder Broken Road 2021¦ Giant Revolt Advanced 2 2019 ¦ Giant Anthem 3 2015 ¦ Specialized Myka Comp FSR 2009
  • When I first set the pressure I measured the sag at around 18%, which is why I'm surprised it goes through the travel so easily. This might be a bit of a beginner question but, is it normal to be able to use almost all the travel just by bouncing on the suspension whilst riding?

    Will open up the forks tomorrow and have a look at the spacers, hopefully I've got a socket that fits :)
  • mully79mully79 Posts: 261
    First thing to check is your shock pump. Are you fully engaging the valve when you screw it on. (ie keep screwing on till its tight) Ive pumped the hose to the correct pressure by mistake a few times.

    If you increase the pressure check it feels like the fork is stiffer before you throw yourself off something !
  • steve_sordysteve_sordy Posts: 2,194
    Take a look at this Bike Radar video on setting up your suspension in ten mins.


    Other things.

    #Most relatively new air forks (and I believe that yours is one of them) need inflating from zero in stages, ie add 50psi then cycle the fork to at least 50% compression half a dozen times, then add another and so on. But check the fork manual or check Ridefox.com

    Assuming that you have inflated the fork correctly and set the sag correctly and you are still bottoming out the fork, then what do you do?

    Modern air forks now have the ability to tune the air spring. That means that you can make it ramp up more towards the end of the travel. An air spring is different to a coil spring. A coil needs the same amount to compress it by one inch at the start of its travel as it does at the end of its travel. The shape of the force/travel graph is a straight line.
    An air spring has a shape like a flat S, ie its curved. And you can change the shape of the curve by changing the volume of air. This is done by adding or removing spacers into the air side of the fork (left as you sit on the bike). You have to let all the air out before removing the top cap. There will be a limit on how many spacers you can fit so check with Fox for your fork. If you add more than the stated maximum you will break your fork.

    How to do this can be found on YouTube.

    If you want to get into suspension set up and really understand it then I can recommend this from Bike Rumour. It will tell you all you need to know in easy stages and with lots of pictures.

    https://bikerumor.com/2014/10/30/bikerumor-suspension-setup-series-full-series-pdf-free-download/
  • steve_sordysteve_sordy Posts: 2,194

    ...............

    Will open up the forks tomorrow and have a look at the spacers, hopefully I've got a socket that fits :)

    The fork will either need the same sort of tool as you use to remove your cassette or your centreline discs. Alternatively, it may need a large hex socket. You may even have a hex or double hex socket that fits. But be careful! The top cap is TIGHT and it is only aluminium and the edges of the hex are low. It is very easy to round off the top cap. Make sure it is a good fit.

    To ensure success, grind down the end of the socket so that the internal chamfer disappears. This will increase contact between the socket and the top cap. You can buy sockets made for the job but they can vary from a Fox one for £30, to ones from obscure websites that will take some finding for less than £3.
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