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There is a trick which some cyclists use. Instead of the regular fork, let's say 100mm, they put a fork with bigger travel (140-160mm). Then they pump pretty low pressure so the sag is huge and the new fork has about 100mm of actual travel. This gives extreme plush.

Technically, the result is a 100mm fork with huge negative air chamber. A little heavier than the original one.

Is it actually notably softer?
Will such a fork resist strong bumps as good as normal 100mm?

I'm not advertising this and never tried by myself, but I received such recommendations. What I really like to hear is your personal experience.

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    What is the intent of that trick?
    – k102
    Jun 25 '20 at 14:57
  • @k102, to get better performance on small bumps, I think.
    – kelin
    Jun 25 '20 at 15:17
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Lots of drawback for this. I think too many to list, and some of them are subjective.

First, if you want to improve the performance of the front end, you don't just change one variable (ie fork length). All bikes are specifically designed on purpose and if something doesn't work well, there are more fundemental problems than that.

My first suggestion if you want to improve the bike, would be to see a qualified person that has lots of experience on that specific type of riding. Not any mechanic or random person.

Different travel bikes have their specific amount of travel for a reason, the harder hitting, the bigger travel (to a limit), the less extreme, the less travel. If you change the amount of travel of a bike that was suited to 100mm, you will take away a lot of it's specific properties, ie it's bump vs pedalling efficiency.

2 scenarios:

  1. You add 40mm travel and set the fork how it's designed to be riden (ie correct sag etc). What you have done is drastically changed the geometry of the bike. Whether this is good or not, is subjective. The fact is the bike will desend with more stability but will pedal badly and corner much worst. Not to mention the extra stress on the frame which may break it.

  2. You add 40mm travel and set the fork so the geometry of the bike is the same (ie very under pressure). What you have done is put a poggo stick on your front end. Yes, you won't feel small bumps, but you won't be able to stop bouncing.

The take away message should be, either improve your current bike by properly fine tuning your fork or upgrade to a better, more suitable, fork which does what it's supposed to do.

On the other hand, you might actually need more travel, as your type or stype of riding dictates that, then you should get a different bike more suited for your riding. You don't take an XC bike to ride enduro or visa versa.

I learnt a lot about this watching Vorsprung Suspension on YouTube. Some of it gets pretty technical, but it's fantastic to learn.

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  • You saying that I should listen somebody experienced, well I've seen this trick on a bike of my friend who is semi-pro and have some medals. For your poggo stick argument - higher compression will solve it.
    – kelin
    Jun 26 '20 at 16:32
  • @kelin Did it work better (faster lap times) on your semi-pro friend's bike compared to a normal fork? For one, long travel forks are heavier. If you put more compression, you make the fork stiffer, therefore losing all your small bump sensitivity.
    – MaplePanda
    Jun 26 '20 at 19:22
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    @kelin Then maybe ask them, or just do it. You asked for the negatives and I have given them. You have two choices if you want to put a 140mm fork on a 100mm bike, either low compression and correct geometry = poggo. Or correct compression and bad geometry = bad cornering. I'm open to discussion if you think what I have said it wrong.
    – abdnChap
    Jun 26 '20 at 20:36
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    @abdnChap Sag is regulated by air chamber pressure, compression is a damper feature.
    – kelin
    Jun 27 '20 at 4:23
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    @kelin there is no way around the fact that running an air pressure so much too low is going to cause issues. Whilst you may be able to eliminate the 'pogo' type feeling by adjusting the rebound to be very slow, you won't be able to solve problems like brake dive, lots unwanted compression when climbing out of saddle, bottoming out too easily etc.
    – Andy P
    Jul 27 '20 at 9:36

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