Air forks

[blueflag]

Hi all,
more questions I'm afraid!
What exactly does the air do in the forks? Do I need it? If I fit different fork tops as I know people do, then am I right in thinking that I would lose the air "assistance" and gain adjustable preload?
I've not long bought the bike (Tri arm), it's a race bike with standard fork tops and I was wondering if there is anything I can look for to find out if the forks are already uprated. (spring lengths, spacers etc.)
Thanks again!
Mike

[Wozza]

What is the sag like?

[blueflag]

Sag's 20mm, I have no idea what standard is, probably a bit more?

[Wozza]

Sag sounds about right, standard would be more unless you're about 7 stone! Also as it's a race bike I'd definitely imagine the forks have been upgraded, and the springs will have been matched to the previous rider's weight. The matched springs negate the need for any air pressure in the forks - yes you can fit NC29 or NC30 fork tops to give you preload adjustment (sounds like you might want slightly more but I'm no suspension expert). Do you know if the previous rider is about your weight / bit heavier / bit lighter?

[blueflag]

Reckon about half a stone heavier than me but this Christmas I've been trying to catch up! (sadly)