AIR FORK

[Hanss_Otto]

WHAT DOES THE POSITIVE AN NEGATIVE VALVE DO AND SHOULD I PUMP UP BOTH OR JUST THE ONE?

(EXCUSE MY IGNORANCE)

[Flowta]

What fork is it?

[techguy]

Pump the positive chamber first to the recomended pressure,then the negative chamber to the same pressure.

 

The negative chamber balances out the positive and helps the fork with small bump absorbsion, to test this for yourelf pump the positive and let all the air out of the -ve and bounce the fork, see how hard it is to move the fork, then pump the -ve to the same pressure as the +ve and bounce the fork - you'll fell the difference...

[Flowta]

The negative air in mine (Marzocchi All Mountain SL) adjusts the travel of the fork. and also affects the small bump sensitivity

[Iwan Kemp]

Is it a rock shok?

[TNT1]

 

negative air

 

What's that? Like a rotten fart?

 

[Flowta]

 

negative air

 

What's that? Like a rotten fart?

 

It's when you get a backdraft.

 

[Johan Bornman]

WHAT DOES THE POSITIVE AN NEGATIVE VALVE DO AND SHOULD I PUMP UP BOTH OR JUST THE ONE?

(EXCUSE MY IGNORANCE)

 

There is no such thing as an ignorant question.

 

Forks can have three types of springs: Coil (steel), air or rubber. Today we only use coil or air. Air is preferred due it its light weight. However, air springs have a problem that towards the end of their travel they become harder. We say, "the spring rate increases." A coil spring fork does have a linear spring rate. Simply put, it doesn't become harder the more you compress it and it feels the same at he beginning of its travel as it does towards the end.

 

They then invented the dual-air spring. As you push down on the fork, one part of its internals increase in pressure and the other decreases in pressure. This is referred to as the positive and negative spring (in that order).

 

This dual-spring gets rid of most of those "ramp-up" problems where the spring becomes harder as it compresses. A very nice side effect of this design was a huge reduction in stiction. Stiction (short for static friction) is that effect where something grips a lot before it slides. Car tyres are a good example. They grip like hell until they start to slide and then they don't grip at all.

 

Stiction makes a fork resist bumps. Dual air forks have less stiction.

 

A dual air fork has a third side-effect in that you can use one of the air systems to adjust the ride height, or preload, as was pointed out by Flowta.

 

Pump  both and experiment with the different feel as you work on different combinations.  By fiddling with it all you can adjust the ride height (preload), and reaction to bumps.

 

Most of us just put some air in there and go for a ride.

 

 

 

 

 

[Face Plant]

thanks for the explanation Johan could you perhaps tell me how often you should check your air pressures?

[Hanss_Otto]

thanx for the help guys.

Its a 2010 Reba race. its my first air fork, so I didnt know what the negative valve was for, but youve answered my question. thanx

 

[gummibear]

Thanks JB

I am going for a ride now and taking my newly aquired shock pump and going to play arround and see how it works out. 

[kennyg]

I check mine every 2 weeks.

I only need to add a little air every 2 months or so, or I am changing it for rougher or smoother tracks.

 

Thanks

Ken

[Face Plant]

so what you saying is you ride different pressures for different conditions Ken?

[Hanss_Otto]

Seeing that you guys are on the Airshock topic how often do you need to service the shock and replace seals ect? What should you look out for as signs that the service is due ect?

[gummibear]

So i took my bike out armed with my "skok pomp" and rode a route i have ridden a few times now.

I ended up pumping it up a lot at + end and lowering the pressure at - end and wow has it made a huge difference epecially on the fast downhill section.I thought my shok was faulty as it kept on bumping together.

So i see it helps to play arround with your settings every now and then.

 

Thanks for the advice guys