Setting dual air forks up

bennett_346

I've had my dual air revs for a few months now and it's struck me that while i can tune the dual air, i don't really understand what i'm doing to the fork and just shooting in the dark setup wise.

Without asking too much of anyone, roughly what direction should i be heading in for a firm initial feel and setup that keeps the fork fairly INactive, ie i want to use my travel properly, but i dont like the fork being overactive and want to keep the front end fairly upright without having it so firm that it doesnt use its travel.

Thanks to anyone who can offer some tips!

ricardo_smooth

add 5-10psi into the negative chamber. Beware too much pressure imbalance in the -ve chamber can force the fork to suck down into it's travel

bennett_346

ricardo_smooth wrote:

add 5-10psi into the negative chamber. Beware too much pressure imbalance in the -ve chamber can force the fork to suck down into it's travel

This may be where ive been falling down, the manual seemed to suggest that less pressure in the negative than the positive would make the fork feel less active.

bails87

The manual is right. If you want it firmer at the start then less negative pressure is needed.

Essentially, the negative chamber sucks the forks down, so if negative pressure is higher than positive the fork will sit in it's travel, but be plusher. Other way round (neg<pos) and it will 'sit up' and be a bit firmer. Which is what you want.

angry_bird

bails87 wrote:

The manual is right. If you want it firmer at the start then less negative pressure is needed.

Essentially, the negative chamber sucks the forks down, so if negative pressure is higher than positive the fork will sit in it's travel, but be plusher. Other way round (neg<pos) and it will 'sit up' and be a bit firmer. Which is what you want.

This

ricardo_smooth

bails87 wrote:

The manual is right. If you want it firmer at the start then less negative pressure is needed.

Essentially, the negative chamber sucks the forks down, so if negative pressure is higher than positive the fork will sit in it's travel, but be plusher. Other way round (neg<pos) and it will 'sit up' and be a bit firmer. Which is what you want.

http://www.bikeradar.com/forums/viewtopic.php?f=40043&t=12629675

FFS that's twice in two days i've written the opposite thing to what I know is right......It must be the man flu

bennett_346

Ah, in that case maybe i need even less pressure in the neg air. I've been previously reluctant to go more than 7-8psi under the positive pressure but ill drop it a wee bit more.

Thanks all that helped.

bails87

Maybe bump them both up by 5psi?

bennett_346

bails87 wrote:

Maybe bump them both up by 5psi?

Hmm, i was already struggling to bottom out, which is what was confusing me. Fork was overactive but was never bottoming.

supersonic

Remember you have a compression damping adjuster too.

bennett_346

supersonic wrote:

Remember you have a compression damping adjuster too.

Yeah. It's just finding a setup i like. 30 mi ride tomorrow so with any luck i'll come to a good setup by then end.

plugp7

Does anyone have any tips using the fork pump?
What I mean that is when I put air into a chamber then unscrew the adaptor I loose pressure. Now I know this is unavoidable to some extent but I can't get away without loosing up to 35lb when unscrewing from the bottom valve.
Fork is Revelation 426 dual air.

angry_bird

plugp7 wrote:

Does anyone have any tips using the fork pump?
What I mean that is when I put air into a chamber then unscrew the adaptor I loose pressure. Now I know this is unavoidable to some extent but I can't get away without loosing up to 35lb when unscrewing from the bottom valve.
Fork is Revelation 426 dual air.

How do you know you're losing that much?

When you unscrew the pump 2 things happen, as you start to unscrew it the pump releases the valve, closing it, but leaving the seal intact between the pump and fork. Then as you unscrew it further the seal is broken and air escapes the pump which is the air you hear leaving it.

The negative chamber is a small chamber comapred to the positve, when you reconnect the pump to the fork it uses the air in the negative chamber to equalise the pressure in the pump... as it's such a small chamber in the first place it appears that you've lost a lot of pressure from the negative chamber, but that's perfectly normal.

supersonic

Yep, is usually air leaving the pump. When you reattatch the pump, air is released into it from the fork - so appears has lost air, but it hasn't until that instant. When you disconnect, the reading on the pump is true.

Ouija

+1

The air pressure reading is only correct when the pump is initially connected to the fork. When you take the pump off and then reattach it at a later date, air floods out of the fork and into the pumps tube and chamber until pressure in the fork and the pump equalize. This gives the false impression that you've lost pressure in the forks..... which you hadn't until you reconnected the pump and let all that air out. This is also true of tyres too and gets worse the bigger the pump you connect to it

So always go by the initial reading of the pump when you first inflate fork/tyre. Subsequent readings after reattaching pump will be way off.

plugp7

I get it. When you stop and think about it's pretty bloody obvious. Trouble is, I didn't. Thanx.

nicklouse

Sould have a read through the FAQs some time as topics like these are all covered in there.

But yes the air thing messes with many peoples minds.

plugp7

Was it covered?

Ouija

Yeah. Another catch of all this is the 'hiss'. Typically, when disconnecting a pump there is a noticeable 'hissing' sound for a moment as you rip the pump off. Most people think this is air escaping from the tyre/fork when it's actually the high pressure air inside the pump escaping until it levels out with the ambient air pressure of wherever you are. But of course, they think they've lost air in the tyre/fork and immediately reattach the pump to see if that's the case..... at which point their fear is realized the second they look at the dial (but of course there was nothing wrong for the reasons described in previous posts). Lol. It's a vicious circle until you realize whats going on.

plugp7

Thanks again Ouija. Your explanation comprehensive and well received.