Hi Fella,
This response was posted by Cy on another thread – useful infor:
@hh45 – Just because the can take 140mm forks, doesn't mean you have to use 140mm forks. It's all about where you're riding, and your preferences. 140mm forks do feel a little floppy in fast singletrack, but when you're out blasting rocks most of the time it's completely mint. The inverse is true of 100mm forks. 120mm is a nice compromise, and F120's are a very nice fork. Make sure you get the QR15 one and it'll be sweet.
The key thing with all these differences in fork length is that you have to think about adjusting your contacts points on the bike to compensate for the geometry changes. If you go from 100mm forks to 140mm and don't change anything, you'll be way too far back on the bike to make it climb. But, shove your saddle forward 10mm, roll the bars forward back to where they were with the shorter forks, and maybe drop the stem 10mm (if there's room), and you'll be back in a similar position on the bike to the shorter forks and it'll all work a lot better. Going the other way, dropping the travel when you've set the bike up nicely for longer forks will mean you'll have very low bars and loads of weight on your wrists, which is less than ideal too.
Obviously adjustable forks mean you need to run your setup good for your most used fork length, but when switching between fixed length forks, this is well worth thinking about.