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I have a rockshock air fork on my bike and it feels too firm. The compression is on the softest setting I believe so opposite to the lock symbol (see photo) so I think this means that it will compress the most it can but I am not 100%. So I am 45kg (14 years old). So I am asking if it feels too firm do I need to let some air out of it and if so do I need to get a specific shock pump? Thanks enter image description here

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  • The answers have good points on how to proceed. I run on Fox forks and will always run lower air pressure than what is charted by Fox for my weight. Manipulate the air pressure based on achieving your desired sag, which is 25-30% of full travel. Rebound sould be adjusted a few clicks with a change in pressure. Reducing pressure requires an increase in rebound speed. Running a slightly thinner viscosity oil in the damper is another way to change it's characteristics. This is not complicated but likely something that should be tried after air pressure changes.
    – Jeff
    Oct 22 at 12:27
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Yes, you will need a shock pump. They have a screw on head that you don't get with a track pump. They also have a narrower barrel which allows you to deal with the high pressures often found in rear suspension.

It's very likely at 45kg you will need to reduce the pressure in your fork. I find that even at 60kg it can be tricky to get suspension setup well as it is typically designed around a more 'normal' 75-80kg rider.

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You can indeed somewhat affect the "firmness" feeling of an air fork by changing the air pressure inside it. However, this is not a primary mechanism for controlling compression damping, as it has side effects. Reducing air pressure will also increase static sag of your fork, meaning that you will end up with less usable travel. The fork will simply become shorter when you rolling on a flat.

The compression damping is primarily controlled by a separate hydraulic circuit in the fork. In simple terms, it is sticky oil that flows back and forth through a hole. A larger hole or less viscous oil will mean that the fork legs can move faster. Closing the hole (with the control knob you see) makes the hole smaller, thus increasing the firmness feeling.

Range of achievable variation in compression for given damper construction is always limited. You cannot make it compress infinitely fast. If you want to set it outside the available range, it can only be achieved by modification to the damper unit. That is quite advanced and expensive fork modification.

A few recommendations.

  1. Make sure you set up the air pressure so that the sag is within manufacturer's recommendations. Aim for larger sag (say, 30%) and check if it fits your needs. There are many tutorials on the web on how to do that.
  2. Yes, you need a special high pressure pump for that. Regular tire pumps are not designed to operate on suspension forks. Attempting to ignore it is like to try towing with a car where a tractor should be used.
  3. The front tire also plays role in how firm the ride feels. Try reducing the front tire pressure a bit.
  4. Make notes to see what adjustments you tried (what pressures in fork, tires and etc. settings) and how they felt. It will take a few iterations to figure out the best settings, or find yourself at the end of the adjustability ranges.

Good luck!

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  • Yep, there's definitely only so much can be achieved with the stock factory dampers. Ideally i'd have them swapped both front and rear in my trail bike, but it doesn't get used enough to justify the expense. Although as a light rider an air fork which i can run 'under-pressured' is still a giant step forward from a coil which are always WAY too stiff for me
    – Andy P
    Oct 21 at 10:55
  • @AndyP The other side of the weight spectrum has similar problems. Allow yourself a bit too many sweet donuts and land on the right side of 80 kg — and the stock dampers will likely feel too soft. Especially in rear air shocks. Oct 21 at 11:30

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