Berg Trailrock 100x

What's the max amount of travel you guys think i could install on this kind of frame geometry? I have the same bike as the image. It comes with a suntour 100mm fork and a really stiff rear shock coil. The bike is designed for XC, but i would like to hit some bigger jumps on it. Aluminium frame. The bike model is Berg Trailrock 100x

  • 1
    That's a really short head tube. I wouldn't increase the fork length at all personally. Sell it as-is and buy something more like what you want. If you do embiggen your forks, don't go more than one size up. See bicycles.stackexchange.com/questions/30872/… for more.
    – Criggie
    Sep 29, 2015 at 0:20
  • So i could possibly fit 120mm of travel safely?
    – RSMAuZ
    Sep 29, 2015 at 0:46
  • "I wouldn't increase the fork length at all personally." So no, I would not install a longer fork.
    – Criggie
    Sep 29, 2015 at 1:21
  • Why? Unless your particularly attached to that bike, check carefully on prices - You cannot usually buy 'cheap' after market forks - a new fork will be much higher quality than the rest of the bike and wasted. Better to buy a used bike with more travel.
    – mattnz
    Sep 29, 2015 at 2:57
  • The bike is brand new, i just wanted a better fork because i find this one to be bad. So yea. I'm kinda attached to this bike for now. Maybe a decent 100mm fork would help?
    – RSMAuZ
    Sep 29, 2015 at 11:34

2 Answers 2


I wouldn't consider anything over 140mm. beyond that, you're really messing up your geometry and endangering your frame.

Keep in mind that your frame's limits are really determined by how much you weigh. If you're 140 pounds, the frame will take much bigger jumps than if you're 240.

You say that the rear shock is really stiff. It seems there is an imbalance in stiffness between the front and rear suspensions. If you don't have the preload on your Suntour cranked all the way up, you should try doing so before upgrading.

  • Im around 5,7" and weight 150 pounds. The rear coil is designed for 850LBS from what i saw on the website
    – RSMAuZ
    Sep 29, 2015 at 0:35
  • Springs are rated using lb per inch, where the distance is the difference between the spring's free length and compressed length. The linkage of your rear suspension will convert a large wheel movement into a smaller compression at the shock, but with a proportional increase in force. The ratio varies throughout the range of travel. You can fit a longer spring to increase the travel, but the suspension linkage behaviour may not be desirable at extensions beyond standard.
    – Emyr
    Dec 9, 2015 at 14:47

You could fit 120mm, but you really shouldn't. You shouldn't even really be jumping on that bike shaped object.

Hitting bigger jumps does not require more suspension unless you are doing it on the kind of terrain which that bike is not capable of handling. Hitting bigger jumps only requires more technique.

If you are serious about getting into dirt jumping I would try to sell that bike, add some money, and get a 2nd hand dirt jump bike without any suspension and work on technique.

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