[gabbard]

I have an 06 Reba Race, and the lock-out has never really been rigid, even with the Floodgate fully closed. I don't expect a rigid fork, but my old Fox fork was much more "locked-out". I rebuilt the fork a few days ago, put the right amount and viscosity of oil in it (per the rebuild instructions), and it is better, but still not totally locked. Are there any tweaks that need to be made to the instructions for a 29er fork - more oil, different viscosity, etc., or do the RockShox forks tend to have a squishier lockout?

Steve

 

[xrmattaz]

My '06 doesn't totally "lock out" either, but I'm learning to accept that. Much better than the Marz Marathon I used a few years ago!

Really doesn't bug me at all now, and I hate "bob".

If you're running the correct oil height, that's the best it gets, from my understanding.

 

[Curtezyflush]

Make sure your setting the floodgate to fully closed with the fork locked out as opposed to the lever being in the unlocked position when setting the floodgate. As long as your doing that, thats as locked as its easily gonna get.

 

[anden]

It is designed to have a little travel even when "locked out". I think it's mentioned in the manual too. This is the damping unit, where the red plastic can always be compressed:

 

[TigerRider]

Mine feels solid when locked out ('06). Remember to adjust the floodgate with the lockout ON. When I did that it feels as solid as my headshock lockout.

 

[xl_cheese]

Unless you guys are riding your bikes like you're jumping on a pogo stick you don't need a 100% lockout.

 

[mrsalty]

Well.............

CHEESE,
With all due respect...........................
You are NOT qualified to judge what somebody else 'NEEDS'.
Regardless of how/what they ride.
Maybe people ride SS, and have to stand............anyway.

I also am annoyed that the 'Lockout' feature on my REBA seems half hearted.
If I wanted a partailly locked out REBA, I would dial it using the compression knob.
LOCKED OUT is exactly how this 'pogo stick pilot' would like the fork to be.
I have no use for movement, climbing a steep service road or packed ST slog.
My Zoke MX Pro has the same lockout feature (with 1in of stiff travel).
I like my Z1 MCR because the 'lockout' is just that..........no movement once engaged.
Not sure who decided it was a good idea to make a 'soft lockout', but I personally think it was a mistake.
Especially in light of the fact that you can dial in the compression on a REBA anyway.
You can adjust the 'bob' by using less pressure in the negative chamber, but you lose the small input sensitivity.

My .02

C.

Unless you guys are riding your bikes like you're jumping on a pogo stick you don't need a 100% lockout.

 

[anden]

You can adjust the 'bob' by using less pressure in the negative chamber, but you lose the small input sensitivity.

Actually, with less negative pressure you get a softer spring (just like with less positive pressure). Which means more small-input sensitivity and more bob.

The RockShox instructions are wrong on that, unfortunately.

 

[mrsalty]

you sure?

a,
The negative pressure is directly competing against the positive pressure.
The more 'assist' the negative pressure gives to the bump input, the more bob.
The less negative pressure, the less input. More positive pressure to resist the bob.
That was my understanding and experience.

Please explain, because I am now REALLY confused.

C.

Actually, with less negative pressure you get a softer spring (just like with less positive pressure). Which means more small-input sensitivity and more bob.

The RockShox instructions are wrong on that, unfortunately.

 

[MtotheF]

no.

Actually, with less negative pressure you get a softer spring (just like with less positive pressure). Which means more small-input sensitivity and more bob.

The RockShox instructions are wrong on that, unfortunately.

with rockshox, less negative pressure means stiffer initial spring rate and less bob. the negative spring is there to create a gentler initial spring rate and reduce the usual stiction associated with high pressure main chamber air springs. pump more pressure into the negative chamber and the fork sags more, and is softer at the top of its trave. deruce the negative air pressure and the fork rides higher in its stroke, is firmer off the top, and in extreme cases begins to top-out audibly.

perhaps you are confusing RS dual air with the manitou and 5th element SPV/IFP systems, where more air pressure in the small chamber creates a higher platform threshold. this is exactly the opposite of that.

 

[anden]

a,
The negative pressure is directly competing against the positive pressure.
The more 'assist' the negative pressure gives to the bump input, the more bob.
The less negative pressure, the less input. More positive pressure to resist the bob.
That was my understanding and experience.

Please explain, because I am now REALLY confused.

C.

That is a very common misunderstanding.

What you are missing, is that when you increase the negative pressure, then you increase the positive pressure equally much - as measured when the fork is sagged.

When you are sitting still on your bike, the difference between the two air forces to the piston (and thus to the wheel) will always be zero. And the bigger those two forces are, the firmer the spring and vice versa. Imagine yourself taking the position of the piston and being stuck between two firmer springs versus between two softer springs - when would it be easier to move.

So no matter where you pump in air, the fork becomes firmer. However, pumping up the positive decreases sag and pumping up the negative increases sag. The total amount of air determines spring firmness. The air distribution between the chambers determines sag.

Less air -> more responsive in every aspect, more bob, more dive
More air -> less responsive in every aspect, less bob, less dive

So when tuning, first ask yourself if you want it firmer or softer. That decides whether you need to release or pump in air. Then ask yourself if you want more or less sag. That decides which chamber to do it at. If you want to only adjust firmness or sag without affecting the other, then you need to adjust both pressures. For example, for only increasing firmness you need to increase both pressures, and for only increasing sag you need to increase negative pressure and decrease positive pressure.

 

[mrsalty]

Ok

a,
What I found, was that using a matching (+) and (-) pressure setup, the fork was very ACTIVE.
When decreasing the (-) pressure, the forks is stiffer, and more static to small input.
I did not really notice much difference in the sag (but it may be there) on either setup.
I will give it a try on my next ride to test the theory.

C.

That is a very common misunderstanding.

What you are missing, is that when you increase the negative pressure, then you increase the positive pressure equally much - as measured when the fork is sagged.

When you are sitting still on your bike, the difference between the two air forces to the piston (and thus to the wheel) will always be zero. And the bigger those two forces are, the firmer the spring and vice versa. Imagine yourself taking the position of the piston and being stuck between two firmer springs versus between two softer springs - when would it be easier to move.

So no matter where you pump in air, the fork becomes firmer. However, pumping up the positive decreases sag and pumping up the negative increases sag. The total amount of air determines spring firmness. The air distribution between the chambers determines sag.

Less air -> more responsive in every aspect, more bob, more dive
More air -> less responsive in every aspect, less bob, less dive

So when tuning, first ask yourself if you want it firmer or softer. That decides whether you need to release or pump in air. Then ask yourself if you want more or less sag. That decides which chamber to do it at. If you want to only adjust firmness or sag without affecting the other, then you need to adjust both pressures. For example, for only increasing firmness you need to increase both pressures, and for only increasing sag you need to increase negative pressure and decrease positive pressure.

 

[anden]

with rockshox, less negative pressure means stiffer initial spring rate and less bob. the negative spring is there to create a gentler initial spring rate and reduce the usual stiction associated with high pressure main chamber air springs. pump more pressure into the negative chamber and the fork sags more, and is softer at the top of its trave. deruce the negative air pressure and the fork rides higher in its stroke, is firmer off the top, and in extreme cases begins to top-out audibly.

perhaps you are confusing RS dual air with the manitou and 5th element SPV/IFP systems, where more air pressure in the small chamber creates a higher platform threshold. this is exactly the opposite of that.

Stiction is mechanical friction between pistons, seals, and tubes, and does not depend on air pressure.

As for the rest, about the spring, I just addressed it in another reply.

 

[wolfy]

Which is negative/positive with respect to top/bottom?

-M

 

[MtotheF]

stiction, friction...

Stiction is mechanical friction between pistons, seals, and tubes, and does not depend on air pressure.

As for the rest, about the spring, I just addressed it in another reply.

yeah, probably the wrong word to describe ways people use to reduce the "bump" threshold of an air spring. but then again, since we are talking about seals and tubes and pistons, it is probably the right word, too...

as to your other reply, i don't entirely agree. i see what you are saying about increasing the total pressure of a system by adding air to either half - that adding air to the negative chamber effectively increases the air pressure in the positive chamber at a given sag point.

but, in practice, running a hypothetical 120psi in the main chamber with about 80psi in the neg will make for a stiff at the top, high in the travel riding fork. bumping the neg pressure up to about 120 will significantly soften up the initial travel and will make the fork run lower in its stroke. it will also probably make the overall spring rate much less linear, and will make for a higher positive air pressure at the lower sag point, but that will be because the fork is effectively further compressed at that sag point, and is therefore utilizing an effectively smaller air chamber, no?

 

[Padre]

you guys having fun with this technical discussion?

 

[anden]

yeah, probably the wrong word to describe ways people use to reduce the "bump" threshold of an air spring. but then again, since we are talking about seals and tubes and pistons, it is probably the right word, too...

as to your other reply, i don't entirely agree. i see what you are saying about increasing the total pressure of a system by adding air to either half - that adding air to the negative chamber effectively increases the air pressure in the positive chamber at a given sag point.

but, in practice, running a hypothetical 120psi in the main chamber with about 80psi in the neg will make for a stiff at the top, high in the travel riding fork. bumping the neg pressure up to about 120 will significantly soften up the initial travel and will make the fork run lower in its stroke. it will also probably make the overall spring rate much less linear, and will make for a higher positive air pressure at the lower sag point, but that will be because the fork is effectively further compressed at that sag point, and is therefore utilizing an effectively smaller air chamber, no?

Remember that those pos/neg 120/80 and 120/120 are just pressures when the fork is resting towards the top-out bumper.

At sag, when you sit on the bike, those pressures may be something like 130/70 and 140/80, with the differences in forces being the same. The negative pressure is indeed bigger in the latter case, but so is the positive pressure. With two stiffer springs, the resulting spring will be overall firmer, everywhere in the travel.

Don't mix up more sag with a softer spring. If you are familiar with spring curves, the left, first part will be significantly lowered while the right, upper part will be very little lowered. So the whole curve is being steepend, and the sag point moved to the right.

 

[gabbard]

Which one is you?

Padre,

Nice picture from your middle school days. Which one of them is you?


Steve

 

[anden]

you guys having fun with this technical discussion?

Hey there, everyone is welcome.

 

[MtotheF]

not mixing up

At sag, when you sit on the bike, those pressures may be something like 130/70 and 140/80, with the differences in forces being the same. The negative pressure is indeed bigger in the latter case, but so is the positive pressure. With two stiffer springs, the resulting spring will be overall firmer, everywhere in the travel.

Don't mix up more sag with a softer spring. If you are familiar with spring curves, the left, first part will be significantly lowered while the right, upper part will be very little lowered. So the whole curve is being steepend, and the sag point moved to the right.

yup, aware of the curve shapes and where the sag point hits. but i think that the negative pressure would DECREASE as you sat on the big, while the positive pressure would INCREASE. you seem to be implying that the pressure in both chambers would be increasing as the fork moves deeper into its travel, which is not the case.

as a real cheap and dirty experiment, just try using the negative spring, with no positive air pressure at all. pump about 150psi into the neg chamber. your fork would basically be bottomed out. do the same at the other end, with the positive chamber pumped up and the negative spring deflated, and your fork would be topped out and stiff. more linear spring rate perhaps, but still pretty stiff.

the main spring curve on these forks is a function of the volume of the main chamber, is it not? the negative spring only serves to suck the piston down into the stroke, moving it to an admittedly steeper part of the spring rate curve, but it is still part of the same basic chamber size. the amount of positive pressure is still what determines the bottom-out point of the fork. at least, that's what the last 8 years of dicking around with these things has seemed to show me.

but hell, if i'm wrong, it wouldn't be the first time...