I know that the Dual option is more customizable, but is there actually a substantial improvement? What is the small bump sensitivity difference? Durability difference? Maintenance hassles difference? Opinions please.
Solo Air vs Dual Air
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Negative much lower than the design value for the fork. Not the intended way of running things at all. To get any sag, you have to run positive very low also, so both pos and neg end up way below manufacturer recommendation. This is a soft spring with a lot of preload.
2) negative pressure is 85% positive pressure
Positive will still be low compared to rockshox recommendation. Can be quite confidence inspiring, but tends to be harsh off the top. If sag is reasonable, you will get full travel.
3) negative pressure is equal to positive pressure
You will start to get a plusher feel on small bumps. Still have reaosnable support mid stroke.
4) negative pressure is 10% more than positive pressure?
Negative higher than positive is only possible or sensible with small differences. 10% is quite a lot. You may see the fork sucking down in which case you are losing travel. Very plush off the top of the stroke, but mid stroke now tends to blow through. It ramps up hard at the end so you don;t get full travel.
For negative higher than positive, you are better off setting up a postive=negative setup as per 3 and then adding one/two/three pump strokes to the negative chamber. Then go back and adjust positive a bit more to get sag. This way you will definitely end up with more QUANTITY OF AIR in the negative chamber, but the neg chamber changes size as it sucks down so pressure is no longer a reliable measure. A mild negative higher than positive setup is one I prefer, but it is very subtle compared to negative equals positive. 10% is too much.
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I have a Reba dual air with Neg set to 60% of Pos after trying many different settings. That's where I feel the fork is performing at its best. It's plush, uses most of its usable travel range over my typical terrain, and most of all allows me to enjoy my rides.
The ability to fine tune a dual air fork is a huge advantage over a solo air, get dual air if you can. Do several rides with different setting over your typical terrain until it feels right. Graphs are great for understanding the mechanics and help in fine-tuning what you feel while riding.
The ability to fine tune a dual air fork is a huge advantage over a solo air, get dual air if you can. Do several rides with different setting over your typical terrain until it feels right. Graphs are great for understanding the mechanics and help in fine-tuning what you feel while riding.
There is something I never understood from the big threads out there on setting up dual air though: some people seem to believe that you adjust spring rate with the positive pressure and then set sag with neg pressure. Others however say that the correct setup is achieved by removing all air (+/-), then add positive to achieve sag and negative to make the first part of the stroke plusher.
How can both these methods be correct? Doesn't one contradicts the other?
How can both these methods be correct? Doesn't one contradicts the other?
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64 Posts
Excellent information, thank-you.
When I think of it in terms of coil spring I can understand it. I've always liked a coil spring to have only 1 or 2 turns of preload, so I often use a spring a bit too stiff compared to one that could be too soft. Does this mean I could be a candidate for slightly less negative air pressure?
When I think of it in terms of coil spring I can understand it. I've always liked a coil spring to have only 1 or 2 turns of preload, so I often use a spring a bit too stiff compared to one that could be too soft. Does this mean I could be a candidate for slightly less negative air pressure?
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64 Posts
Excellent information, thank-you.
When I think of it in terms of coil spring I can understand. I've always liked a coil spring to have only 1 or 2 turns of preload, so I often use a spring a bit too stiff compared to one that could be too soft. Does this mean I could be a candidate for slightly less negative air pressure?
When I think of it in terms of coil spring I can understand. I've always liked a coil spring to have only 1 or 2 turns of preload, so I often use a spring a bit too stiff compared to one that could be too soft. Does this mean I could be a candidate for slightly less negative air pressure?
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As with you, I used to use 60-70% of POS pressure and used up roughly 90% of travel on most trails and that extra 10% got used on the big stuff I occasionally hit or if you fugged a move etc.
There are however loads that go by the theory or set POS for SAG, then pump NEG until they start to see the stanchions start to be sucked into their travel, which is roughly going past equal pressures - for me this was too soft and the fork wallowed in it's travel, in actuality I never really set SAG, just set POS pressure from how it rode and in general I prob only had 15% SAG when just sitting on the bike.
There are however loads that go by the theory or set POS for SAG, then pump NEG until they start to see the stanchions start to be sucked into their travel, which is roughly going past equal pressures - for me this was too soft and the fork wallowed in it's travel, in actuality I never really set SAG, just set POS pressure from how it rode and in general I prob only had 15% SAG when just sitting on the bike.
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210 Posts
Ugh. This is way too complicated. Solo air for me all the way.
Don't let propellar head talk complicate your choice. I have always been a coil fork user and after a few single fill air forks I swore off air. Along came a Dual Air on a frame I purchased. I set the pressures to the listed spec's and went for a ride. Headed srtraight to the biggest drop, on my usual route, and dropped away then checking the amount of travel used. I ended up w/ slightly more + pressure. Next I did a few runs on your average agressive single track and noted how the fork reacted to small bumps, diving, trail chatter etc. The fork was behaving much like a single fill fork - quite a bit of dive. I dropped the neg.pressure until dive was acceptable w/o a loss of small bump compliance. I ended up w/ a fork that used its travel and didn't dive unlike the single fill's I used.
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Exactly how I came to my preferred setup on the Reba when I owned and rode one.
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i find it quite simple... more air in the - means a softer initial stroke while less air means the opposite. At least, that's how it translate on the trail with my revelation XX. I use the + only to set sag and the overall feel of the fork (hard vs soft...).
My preferred set up is ~5 extra psi in the - chamber for all around trail riding, which I think is where dual air systems really shine.
On bigger bikes, I find Solo air type stuff to be plenty...
But anyways, nothing beats open bath coil forks !
My preferred set up is ~5 extra psi in the - chamber for all around trail riding, which I think is where dual air systems really shine.
On bigger bikes, I find Solo air type stuff to be plenty...
But anyways, nothing beats open bath coil forks !
More Negative, forces you to have more sag, forcing the fork into the travel making it firmer in brief.
If won't really change end stroke much at all.
You don't get the claimed small bump, infact it works the other way, less Neg makes the fork more active.
If won't really change end stroke much at all.
You don't get the claimed small bump, infact it works the other way, less Neg makes the fork more active.
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202 Posts
Dosen't feel like this at all on my revelation...
The problem is you've read the RS sales pitch so the placebo effect takes over.
First ride I went -10 and loved the fork, next ride I put the pressure to +5 and hated it total lack of small bump especially on stutter bumps, kept riding and hating it believing the BS until I dropped it then all happy again.
I tested it on a mate aswell, he's not read the RS stuff or had a clue what neg pressure I put in my fork he was borrowing and confirmed what I think / feel / theorize.
06 RS Reba SL 29er.
07 RS Rev 130 426's.
10 RS Reba SL 120mm.
Higher Neg also creates a cushion slowing the rebound down towards the end of the stroke, wrecks stuter bump hits totally unless you run your rebound to fast then you end up with a pogo stick on big hits.
Most people including Pro racers run Neg -10psi under at all times take a hint from them.
Way to go on the fear, uncertainty, doubt.
The different pressures set different spring rates and preloads; that is all. If the negative pressure is set for a different value, a different positive pressure is required to keep sag the same.
In my model (remember the graphs a few pages back), for the same sag, for the same rider:
80+ 46.27-
90+ 67.51-
100+ 88.74-
110+ 109.98-
120+ 131.21-
That set of combinations give you the same sag (and therefore very similar ramp up at the bottom of the stroke with just different spring rates.
Negative air pressure is a very useful tuning tool, just you have to approach it from having two interrelated settings rather than two independent settings. If you just swing the negative pressure and not the positive, the sag changes. Bet you a quid, most of the effects you feel are related to the new sag setting. If you change negative and then spend a bit of time fine tuning positive to keep your sag consistent, you have now fine tuned your spring rate and preload.
I don't see why you're het up about people running negs higher than positive. Chill. Quit with the FUD and give up on the "10psi less is the only way to be because Turveyd says so" line. If the answer was 10psi less in all circumstances then dual air would be a terrible concept because it is making something simple complicated.
Myself, I designed a rig to set both chambers equally and then allow a fine adjust. I've probably got the most repeatable way of setting up these forks of anyone on the planet. I did a 24hr solo back in 2008 on a dual air fork running neg 10 less than pos and it absolutely hammered my wrists. I'm now running a neg slightly higher than pos setup and I get small bump sensitivity, grip and controllable mid stroke to my liking.
I also had a Push Factory tune on on one of my dual air forks. When I ran that with negative 10psi less than positive, it was dreadful, felt completely dead in response because it didn't have enough spring rate to push open the rebound stack I couldn't steer in a straight line through technical descents. Changing the positive/negative balance fixed this. Dual flow (Blackbox damping) rebound is a lot like the Push Tune but less aggressive. In the same way, I like matching the Blackbox damper in my reba with a fairly stiff spring with the negative creeping above the positive.
My preferences. YMMV.
Yes the Sag will be similar most likely with those values but you'll get a totally different amount of travel.
Why I set the + by travel used aiming for 90% under general use, then use the - to set the sag, I like slacker angles so running +125 / -100 on the RS Reba 2010 120's.
It's quite active at that I run some compression damping most of the time to tame that, but it's nice to be able to have very active fork at times.
Watch how much they bob on climbs with lower -'s.
Im a 150lb rider, I do some trail runs and also use my bike to commute to work. So what you guys think which is better for so trail and commuting (with street bumps and a bit of rocky pavements).. As of now I have the stock RST Deuce Coil and wanted to upgrade.
I'm leaning toward a Reba, but they said recon is almost as like Reba in performance. Just wanna make sure of what should I get that will work best both on trail and mostly to my commuting.
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