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Got some revs. Scoured the internet and read how to set them up, took them out on Saturday for a test and i don't think i had them set up right. It's the first time i've used rockshox forks - i get that the more air you have in the -ve chamber the more supple they are but they felt like they were only using the middle third travel and ramping up at the end. I weigh 11 stone and had them at 100psi in each.
I was thinking of bringing them down to about 85psi in both, or maybe 85 +ve and 70 -ve but i ran out of time to test it. Is it OK to have less in the -ve chamber? Do all rockshox air forks ramp up sharply at the end of their travel like this?
If you could share your weight and +ve & -ve settings and describe how they ride that would be great help.
Cheers!
I weigh just under 12 stone and run 80psi +ve and -ve in my Rebas. Thats was the best feeling for me after trying lots of combinations.
To post air pressures and rider weights is totally pointless.
There's waaaay to many other variables to take into account: Fork travel, specific model of fork (the air chambers vary) weight distribution, riding style, etc etc
Even the table RS used to print on its forks was way out.
Learn how to set them up yourself, and KEEP BOTH PRESSURES THE SAME (or less -ve if you like a firmer feel) and certainly don't run more negative than positive. It just sags the fork. 🙂
When setting pressures ALWAYS do it in this order or you'll end up with an imbalance and loose travel.
1) let out the negative air
2) adjust the positive
3) set negative to same as positive or 5-10 psi less. Never more!
4) check sag or test ride
5) if adjustment is needed either way, go back to number 1
That's how it's done. Believe me. 🙂
New RS stuff has solo air, with self balancing positive and negative chambers that are always at the same pressure. Because that's the best way. Fox shocks have always done the same thing too.
If you set more negative than positive the negative spring pushes against the positive to equalise the pressure. Which it does by reducing travel slightly. Check it again and both pressures will be the same. Keep pumping it up and you'll loose more travel. Try it. Then let the negative out and watch the fork extend. So it's pointless running more negative, see? So don't do it. 🙂
I have to run mine very, very hard to stop them blowing through the travel. Not ideal really as I lose all of the small bump sensitivity.
170 psi in both + & -. But I'm 120kg and ride like a hooligan.
I like the idea "Set the positive, then add negative til it moves. Works well with the old Teams at least and coincidentally ends up around 10psi under the positive with mine.
Peterpoddy, with all due respect i've done all that and i can see how the fork works. I appreciate your advice and i won't put more in the -ve as it seems like you're not the [i]only one[/i] giving that advice. The more people that post up with rider weights, fork settings and ride details the more accurate picture we can get.
Keep on posting 'em up.
11 1/2 stone. 105 psi both chambers works for me.
Definitely got some air in both chambers of my 100mm Rebas.....seriously though I do need to tune them so will keep tabs on this thread. Good advice so far
Northwind - Member
I like the idea "Set the positive, then add negative til it moves. Works well with the old Teams at least and coincidentally ends up around 10psi under the positive with mine.
This is better than any RS instructions, It's starting to make a bit more sense now. So just add the required +ve (probably less than 100psi for me going by kjrogers' post) and add -ve pressure until it reaches its balancing point.
RS advise putting up to 15psi more in the -ve chamber to increase the small bump sensitivity, and i've read somewhere (from some self proclaimed expert on bikepedia) that you have to be [i]sat[/i] on the bike when adjusting both pressures as they change when you're off the bike! Unless you've got arms like Mr Tickle i'd say that was impossible. There's so much guff out there.
11 1/2 stone. 105 psi both chambers works for me.
Headpotdog, what fork? does that setup give you quite a firm ride?
The pressures will change when you're on and off the bike but in a totally predictable and repeatable way, so you can set it off the bike then jump on (for sag) or set it off the bike then ride (for everything else). Basically your settings when not on the bike correspond exactly to a setting when on the bike
http://locotuning.co.uk/forks-sag.html, set up guide.
As said above, let all air out neg. then al air out pos. then fill pos. and then neg.
Balance pressures and set sag, reduce neg. pressure to reduce initial movement.
Although the damping will have a bearing on how you set them as there are quite a few different systems that have been fitted to the dual forks over the years, oil weight will also affect this (manufacturers specs and performances vary) but we're getting picky with this 😉
Not that it's really that relevant but my 2012 RCT£ dual air revs reduced to 120mm run 110 pos. 100 neg. @13 1/2 stone, but I do run stuff quite stiff.
11 1/2 stone Rev RCT3 100 psi +ve and -ve. Might be a hair less -ve as I tend to use the "pump up -ve until it just moves" method, which seems to make the -ve pretty much the same as the +ve on mine.
Iirc its 135 psi in both, I'm 90kg on a good day
Its a soft setting but I find it encourages them to move up and down rather than twanging backwards and forwards as they do if I use higher pressures
Not that it's really that relevant but my 2012 RCT£ dual air revs reduced to 120mm run 110 pos. 100 neg. @13 1/2 stone, but I do run stuff quite stiff.
Not at all that's exactly what i'm after. The more people that share setup and ride character the better reference this thread is for me and others. Learnt a lot already!
+ve whatever gives 20-25% sag
-ve set after the +ve to just when it starts to "suck down". Fnar fnar.
No idea what these pressures actually are.
+ve whatever gives 20-25% sag
-ve set after the +ve to just when it starts to "suck down". Fnar fnar.No idea what these pressures actually are.
How do you set the sag without filling the -ve chamber? On mine, if I don't have anything in the -ve chamber I don't think the forks will compress at all (or at least not as far as they would with the -ve chamber at its operating pressure).
12.5 stone
100 in each.
Revs
2011 Rev RLT Ti's at 140mm here.
68kg, 85psi +ve, a smidge under 90psi -ve
I think they're brilliant set up that way (as Rockshox suggest) but some above would say I'm doing it wrong.
I agree with
How do you set the sag without filling the -ve chamber? On mine, if I don't have anything in the -ve chamber I don't think the forks will compress at all (or at least not as far as they would with the -ve chamber at its operating pressure).
If I put nothing in the -ve, got 25% (or whatever%) sag, then put air in the -ve to match the +ve the forks would suck down and I'd end up with 60% sag!
How do you set the sag without filling the -ve chamber?
You can't, not accurately anyway.
The negative chamber is so small it's a complete lottery how much air ends up in it as you can lose anything from 20-60psi (non repeatable) every time you disconnect the shock pump. I generally run the same or a little less. 12stone, 80-100psi depending on where the forks are in their service regime (more earlier on, less as they start to become sticky.
My Revs have never felt quite right but I openly admit to never really mucking about with them much. Will follow the advice above later and let you know how I get on with what settings feel best.
I set my Reba's up differently to suit the bike / riding.
Solo air (100mm travel HT 29er) get 90psi.
My dual air (120mm FS 26er) get 80psi in both chambers.
Weigh approx 68kg.
I let the air out of everything and make sure the compression is open.
I pump up the + until I get around 20% sag when I'm stood up on the bike (on the basis that I want it working best when I'm stood up).
I pump up the negative until it moves down a bit then let a bit out then a bit more or it's too soft for me.
No idea about pressures but that works not much "small bump sensitivity" but I have a big front tyre for that. I want "not blowing through all travel all the bloody time"
Don't get me started on the best setting for the compression.
I used
100psi +ve
nose more, 105psi, in the -ve
2009 140mm revs, 100kg rider
The negative chamber is so small it's a complete lottery how much air ends up in it as you can lose anything from 20-60psi (non repeatable) every time you disconnect the shock pump.
you lose pressure when you [i]connect[/i] the pump
that hiss you hear when disconnecting, is the air [i]in the pump itself[/i]
not the air in the shock, which stays nicely put
let the air out of everything and make sure the compression is open.I pump up the + until I get around 20% sag when I'm stood up on the bike (on the basis that I want it working best when I'm stood up).
I'm pretty sure that wont work with my Rev RCT3 forks, which makes me wonder whether one of us has a problem with our forks.
If I have nothing in the -ve chamber and even a tiny amount in the +ve then the forks are going to be reluctant to move. That makes sense, I think. If the seals are working properly and the -ve chamber is at low pressure then it should resist any movement of the fork, since you are (kind of) trying to create a vacuum in the -ve chamber. In order to set the sag accurately I need +ve and -ve chambers to be at their operating level.
So, my rather long winder procedure is:
1. Let air out of both chambers
2. Pump up +ve chamber to some pressure X
3. Pump up -ve chamber until forks just start to suck down
4. Check sag
5. If sag not correct then go back to step 1 and adjust X accordingly
I'm not seeing why you need to do the -ve before checking the sag? Can someone explain.
I set mine as above^^^^^^^^ to get 25% sag
Finished up with 135+ve 130-ve, I'm 100kg currently and it seem plush with a progressive end stroke.
The negative spring is trying to pull the fork into it's travel and the positive trying to extend it, so if filled it'll affect the initial travel and the sag to a certain extent although not alot.
The pressures people are using arn't really much use as every bodys setup, body shape and how they're on the bike when they set the sag is different also as mentioned the damper systems are different so will work differently along with people mentioning different models of RS forks again will need different pressures.
The loss of air when unscrewing a shock pump is the air pressure in the hose of the pump not from the fork chambers, unless you pmp is knackered.
If your fork is sucking more than a 5 or 6 mm hen pressures are balanced there are probably issues with the seals.
Think that covers most questions 😉
joolsburger - Member
I'm not seeing why you need to do the -ve before checking the sag? Can someone explain.
Because it acts against the positive spring in much the same way your weight does. It softens the initial part of the travel. So if you set sag without it, then full the negative chamber, the forks will be too soft.
The pressures people are using arn't really much use as every bodys setup, body shape and how they're on the bike when they set the sag is different also as mentioned the damper systems are different so will work differently along with people mentioning different models of RS forks again will need different pressures.
:applauds:
Thank you. I know this, you know this. But apparently people still want random, pointless figures to gaze at. 🙂
Learn how your forks work. Numbers mean nowt, basically. If you know how they work, you don't need numbers. 🙂
The loss of air when unscrewing a shock pump is the air pressure in the hose of the pump not from the fork chambers, unless you pmp is knackered.
Yes. You only loose pressure when you attach the pump (into the pump) not when you detach it.
I am surprised the OP finds that the Dual Air forks ramp up; most people find that they blow through their travel too readily which makes things like steep drops to flat really scary. Most people compensate by running them hard. I run 120 psi in 140mm Revs and am a fat git at 10 1/2 Stone.
I run a bit more neg air to suck the fork down reducing travel from 150 to 120. The bike handles better with less travel and a plusher but more supportive feel than having lower but equal pos and neg which felt saggy and divy. The counteract the firmer feel I run compression damping at the minimum.
I realise this is way off manual and universally condemned,but after much dicking about it seems to work best for the bike. All I'm suggesting is that after trying the conventional, follow the crowd approach, other approaches might work for you. Worth a go since it's so easy to adjust.
+ve whatever gives 20-25% sag
-ve set after the +ve to just when it starts to "suck down". Fnar fnar.No idea what these pressures actually are.
Obviously typed + and - the wrong way round earlier.
I am surprised the OP finds that the Dual Air forks ramp up; most people find that they blow through their travel too readily which makes things like steep drops to flat really scary
i'm just comparing them to fox Talas that i had before, they never ramped up as much but maybe that was because of the LAS (linear air spring).
Peterpoddy, you already p*ssed on the thread earlier, no need to p*ss on it again. I'm finding the info on here pretty useful.
Set sag with no -air then push the O ring so it's a couple of mm above seal. Pump -air till you see seal move to the O ring. Done courtesy of Tftuned
Off the top of my head +110 -100. I'm pretty sure that when I had the pressures the same, the fork dived a bit too much under braking. 12.5 stone.
I've never got my rev's perfect, but I'd always go for a tad too firm than too soft.
What soap said. I think people are over complicating it.
Peterpoddy, you already p*ssed on the thread earlier, no need to p*ss on it again. I'm finding the info on here pretty useful.
What? Because you know I'm right? 🙂 Chill dude. 🙂
I'll keep saying it, random figures are no use to anyone. I could have 2 bikes that are identical apart from the forks. Both with the same travel RS fork on them. But if one was dual air and one was dual air u-turn, they'd run different pressures because the u-turn air cartridge is smaller.
If I told you one of those pressures without qualifying it, I'd just confuse you.
I could have a fork, say my Revelation, running say 120mm travel (as it's set now) and 120psi. If I then remove a couple of spacers and let it out to 140mm I'd have to adjust the pressures. I know this because I've done it. Have you? 🙂
Rider weight and air pressure alone simply s not anywhere near enough info to make any use of.
You need those plus type of fork (u-turn, 26/27.5/29, age, model) , travel of fork, intended use (race/XC/AM etc) type of bike, weight distribution front-rear, all that and more. Even RS have stopped printing the suggested pressures on the inside leg of the fork, because it was way out, mostly.
I'll put my money where my mouth is, so heres an offer - if you're within striking distance of Farnborough, Hants or the bike shop where I'm mechanic in Isleworth, come round and I'll happily help you set them up properly, and we can get into servicing, and damping setup as well if you like. How about it? 🙂
Yeah, i get what you're saying but i am trying to get a good OVERALL picture based on real rider setups - a ballpark setup from which i can tweak. The resources on Rockshox fork setup are abysmal.
The point of this thread is not to have a lengthy discussion on fork setup, you're clouding the thread with minor detail and turning it into a who-knows-best. I hear what you're saying but you're missing the point. Please just let it run and stop fudging it.
What soap said. I think people are over complicating it.
Maybe there is something wrong with my forks, but as I understand it, when you compress the forks you compress the +ve air chamber (decreasing its volume) and expand the -ve air chamber (increasing its volume). If there is no air (or just atmospheric pressure) in the -ve chamber to start with and all the seals are intact then it's going to be very resistant to expanding in volume. Certainly a lot more resistant than it will be with 100 psi in there.
So, if you measure the sag with (say) 100 psi in the +ve chamber and nothing in the -ve then pump up the -ve until it just moves (around the same pressure as the +ve) the sag increase by quite a bit. Making your original measurement incorrect.
Well that's how mine seem to work, but happy to be proved wrong.
Stupid question: 454 dual air uturns here - should you set the travel first then air pressures or does it not matter? I run my forks at 120 pretty much all the time, should I wind them out to 140 when setting the air pressures?
Ta!
mulacs, i would set them up at 120, since you run them like that anyway.
75/70ish I am 71 kg
My thoughts on the matter. Seem to match up with real-world experince for me. YMMV
http://singletrackmag.com/forum/topic/dual-air-revs-my-thoughts
Long story short: Don't overdo the neg pressure or you'll lose travel. Even if it's reading the same as the +ve you may have overdone it. Car park smoothness is not the same as good on the trail.
75/70ish I am 71 kg
i weighed myself today and i'm a shade over 71kg Was probably running way too high a pressure at 100 then!
It's hard to set up forks when the trails are so damn muddy, what i need is some dry dusty Calafornian trails….one can dream.
Running them that soft will make them plush but if your riding involves steep drops onto fireroads etc you may find yourself flat on your face, spitting out teeth....
Only saying, like..
Right, i've had a chance to get out on them now and reckon i've got them set up pretty well, So i can now add my own setup to the list.
72kg/11.3 stone
85 +ve
65 -ve
rebound half way and then a couple of clicks towards the rabbit
I've set them up so they use all the travel and don't dive too easily under braking, mainly by running 20psi less in the -ve chamber (they "equalised" as per Northwind's post at 80+/ 70-) and messing with the compression.
They're plush! I might put a bit more air in the positive chamber yet, maybe go to 90+/ 70- but i haven't had any problems with fork dive or bottoming out so far. Very pleased.