[El Caballo]

I know SSV is a damping rod, and ECC is a cartridge with an actual washer stack that blows off on hard hits.

I know SSV-F is also a damping rod, but is there something else in the system? I've read the maintenance manuals and searched threads, but I still can't tell what the actual, physical difference is between it and regular SSV.

The question is: what makes a Z150 Dropoff with SSV-F better than a 150mm Dirt Jumper with SSV (which you can get for cheap because everyone hates them and pulls them off their Big Hits)?

And if you're feeling extremely helpful, you can compare and contrast how the Manitou Sherman SPV dampers work. I know motorcycle suspension, but I don't know bicycle suspension well.

 

[binary visions]

At one point I knew exactly what the difference was, but regardless of the difference, the net result is that the SSV and SSVF dampers feel exactly the same.

The difference was a niggling one, and the SSVF damper is still a simple ported damper that suffers from all the same hydraulic lockout as SSV.

 

[binary visions]

RE: SPV system...

Normally, oil passes through shims - fork compresses, shims flex, allow oil to pass. In the case of SPV, instead of shims, they use aluminum cups (that do not flex) that are held in place by the air pressure in the SPV chamber. Once the pressure of the oil against the cups overcomes the air pressure in the SPV chamber, the cups move out of the way and allow oil to flow through.

Bottom out resistance is provided by a knob that adjusts the size of the SPV chamber, thereby changing how fast the pressure increases inside the chamber (obviously, a bigger chamber means the fork doesn't ramp up as quickly).

To correct a small error in your post, ECC isn't actually a compression damper - HSCV is the compression damper. ECC is a rebound lockout.

The only functional difference between the Z.150 Dropoff and 150mm DJ fork is that the DJ lineup has steel stanctions and a burlier steerer tube.

 

[El Caballo]

Thanks, BV. That was exactly the information I needed.

So SPV is basically a way to do two things:
1) control the breakpoint between low-speed and high-speed compression damping
2) add progressiveness to the spring rate

So the whole "stable pedaling platform" thing is kind of a side effect for suspension control you want anyway -- the difference being that full stability under pedaling requires lots more SPV pressure than you'd want for ideal suspension performance. But you can choose either one.

Am I understanding this correctly?

 

[binary visions]

So SPV is basically a way to do two things:
1) control the breakpoint between low-speed and high-speed compression damping
2) add progressiveness to the spring rate

So the whole "stable pedaling platform" thing is kind of a side effect for suspension control you want anyway -- the difference being that full stability under pedaling requires lots more SPV pressure than you'd want for ideal suspension performance. But you can choose either one.

Am I understanding this correctly?

Not exactly.

The air pressure actually keeps the compression circuit closed. That is, you basically have a locked out shock - it's not "low speed compression damping" up until the point that the cups move. The shock allows no oil to circulate until the pressure on the shock overcomes the pressure in the SPV chamber and the oil starts to flow.

Obviously, I'm not in the designer's head, but it would appear to me that SPV was designed from the ground up to have the stable platform - it's just just a "fringe benefit".

 

[El Caballo]

OK, got it.

I managed to find this in an old Bike article tonight:

"Compression damping, the control of oil as suspension is compressed through its travel, is traditionally handled by oil flowing through a valve. The flow of that oil is usually governed by a stack of thin shims, the fluctuation and deflection of which determine (in addition to the size of the valve and the viscosity of the oil) the level of damping in a given component. Thicker shims are harder to displace, and tend to make for stiffer damping, thinner do the opposite. Now, with the introduction of SPV (the genesis of which can be found in Chuck Curnutt's work with three-foot travel desert race trucks), that compression shim stack has been replaced with a pair of overlapping aluminum cups. About the size of a 10-mm tall stack of nickels, they fit into one another, and the resultant atmospheric pressure trapped in between causes them to naturally push apart, no springs, no shims. They are mounted on the compression side of the damper valve. In static state, at the top of a suspension's travel, the cups are held closed against the valve by air pressure on the oil in the damper, preventing oil flow. Depending on the level of air pressure, it's possible to tune out low amplitude forces, like pedal-induced bob, and create a breakaway threshold from which the shaft begins moving through its travel. More air pressure on the oil will make for a higher breakaway threshold, less air will make for a plusher initial state, but with more resultant pedal bob.

OK, now, in the instance of higher amplitude forces, like rock impacts, the static pressure holding the SPV closed is offset, and it pops open and allows oil to dump unimpeded through the valve, which makes for plush, bump eating mid-stroke performance. But then, as the shaft progresses through its travel, oil is displaced and the pressure exerted on the SPV tries to push it closed again, which creates a progressive hydraulic ramp up against bottoming out."

Manitou propaganda aside, this is a pretty good explanation.

 

[JRogers]

The "F" in SSV-F is for floating piston, I believe. I think it is just a slightly upgraded version of SSV w/a floating piston that came out around 2000-1. As Binary said, same bad habits.