29er Forks (+ve/-ve)

[Helpmytrap]

So I've got a set of RockShox SID RL 100mm dual air forks, and I'm not sure how the +ve and -ve chambers work. Anyone that can explain? (Question 1)

 

Considering that the explanation will probably help me with determining how to pump them up and I know personal preference also plays a role but I'm not sure what to pump the chambers to (Question 2.) I weigh 58 kilos and the guide on the forks says that for <63kg inflate 70-90psi for both +ve and -ve... I find them extremely stiff and currently have them at 70psi.

[jannosmit]

Try 60psi both sides. You can play with it, that table is only a guide line. The positive and negative don't have to be the same aswell. Like try 60psi for + and 50psi for -.

[IronTree]

Try this thread, http://forums.mtbr.com/shocks-suspension/reba-fine-tuning-183213.html , some interesting views...

[Iwan Kemp]

Try 60psi both sides. You can play with it, that table is only a guide line. The positive and negative don't have to be the same aswell. Like try 60psi for + and 50psi for -.

http://i0.kym-cdn.com/entries/icons/original/000/000/554/facepalm.jpg

[Iwan Kemp]

Have a read here:

 

https://community.bikehub.co.za/topic/116493-forks-all-the-jargon-you-need-to-know/page__fromsearch__1

[Iwan Kemp]

Negative Spring

A small spring that tries to compress the shock. Mostly seen in air shocks but also in some coil shocks. The seals in a shock, especially the air seals have a lot of starting friction (stiction) which makes it difficult for the shock to react to small bumps. The negative spring pushes against the main (positive) spring and helps get the shock in motion. An air shock without a negative spring typically has a very harsh feel as it takes a medium to large size bump to get the fork moving. Some manufacturers use a separate air chamber for the negative spring while others use a coil.

 

The negative spring rate (pressure) should never be higher than the positive rate [DEBATABLE] or it will overcome the positive spring, compress the shock until they become even, prevent the shock from fully extending, and limit the amount of travel. Setting the negative spring rate even with the positive rate will allow the shock to start moving on small bumps and give the most sensitive or plush performance. As the negative rate decreases relative to the positive, it will become increasingly difficult to activate the shock and give an increasingly harsh ride.

 

To set up a shock with a negative air spring, always deflate the negative chamber, set the positive pressure to achieve the desired amount of sag, and then set the negative pressure to match the positive pressure. If you feel the fork is too bouncy or too plush, try decreasing the negative pressure in 10 psi increments until you achieve the desired feel. If you set the negative pressure first, the fork will not get full travel.