Just put my old air forks (reba dual air) on my bike having used coils for the last 18 months.

Please could you remind me what the negative spring does? Should it be the same as the positive?

I guess I can play around with different pressures but have no idea what difference it'll make. A bit of knowledge will be helpful rather than the hit & miss playing about business

From what I gather the negative spring adjusts the plushness feel of the fork so more negative air and the fork will push down nice and smoothly. Too much negative air and you will begin to lose travel. I find the best way to set them up is to run slightly less negative air that positive air to retain all the travel but some people prefer to sacrifice 5mm and run extra smooth forks.

A) remove most or all of the negative pressure
B) adjust the positive pressure until you have the desired amount of sag (20%-25% of travel ?)
C) top up the negative chamber and stop just before the fork begins to lose travel. – you may have to do this carefully and a couple of times to get it just right.

ps… PeterPoddy knows much more about these forks than I do so he might have a better way of doing it.

Kev

The negative spring is used to adjust the initial response of the fork to bumps.

Word of caution – make sure the fork is inverted before inflating, otherwise the oil inside the negative chamber is forced out.

Adding more negative pressure(!?) smooths out the bump response at the expense of losing a tiny amount of travel. Unless you're really anal about every last millimetre it's not worth worrying about.

if you loose the oil out of the -ve side .how do you replace it.
does it come from the normal oil volumes.

No it doesn't.

The only way to replace the oil is to depressurise the fork and remove the lower legs, before following the relube and reassembly procedures on the Rockshox website.

Is the oil coming from the valve,or shaft nut/interface with the lowers.

Oil lost via the -ve valve itself comes from within the air chamber not the lower legs.Oil in the air chamber is to lubricate and maintain the air chamber o rings.To top up,depressurise forks,remove air chamber top cap on ns of forks with 24mm socket,and add up to 5ml of 15wt oil.
Alternative method is to remove valve core and inject some in with a syringe.If adding a little into -ve,make sure bike/fork is inverted……!