[WTGPhoben]

I'm in the process if upgrading my superlight, and I want to replace the float RC shock that I'm currently using. from the reading I've done, the idea of the floating piston has gotten more complicated... it used to be that the FP just separated the air and the oil, decreasing cavitation, but now the FP (on 5th elem. air, for example) is separating two different air chambers, creating some magical effect that I don't understand, and in typical form, they don't provide tech docs with schematics worth sh*t so I can't figure it out for myself....

So if any of you out there are engineers (I'm one too, so feel free to get technical) I would love to hear an explanation of the physics of this dual air FP thingy. (I guess 5th element is the one I'm most interested in hearing about because I know someone who owns one already)

and while you're at it convince me which of these I want:

-5th element air
-Manitou swinger (how many ways?)
-fox propedal

 

[Kornphlake]

A 5th element somehow connects the air in the chamber to a valve in the compression damping cirucit. The air holds a valve closed so that a sizeable hit has to come along to open it allowing oil to flow through the circuit, the size of the hit required to open the valve is determined by the air pressure holding the valve shut so more pressure=less small bump compliance, more bob resistance, less pressure=more small bump compliance, less bob resistance. I'm not sure how that all occurs inside the shock but that's the theory. The air shock works under the same principle but there's an air chamber where the spring is on a coil shock, I believe there are two air valves, one for the air spring and one for the platform air pressure. The manitou swinger is the same as a 5th element with some different castings and labels, they consider preload to be an adjustment so they claim 6 way, 3 way shocks give you air pressure, compression and rebound, IIRC, no high speed compression or air volume adjustments, Progressive recently released some lower end shocks that are 3 and 4 way adjustable. Fox propedal is something unfamiliar to me. I believe that they use a spring to hold the blowoff valve shut rather than air pressure so the platform is not adjustable, or maybe it is by changing the preload on the spring. I've never seen a propedal shock in person so I'm not too sure about them, I think they operate on the same principle as the romic shocks only with an external reservoir rather than the twin tube design.

 

[Repack]

Every r shock needs an IFP. It is what seperates the oil from the nitrogen or air. R shocks cannot be open bath. They are a sealed unit. As the shaft goes into the body, oil is forced up into the res. The piston is in the res and is forced back ast oil pushes against it. As the shock rebounds, the pressure pushes the oil back into the main body of the shock.

 

[Toshi]

i'll sell you my 9.5x3" swinger 6-way, keith hehe. i'm sure it'd fit on your superlight with, er, a few "modifications" to the frame

 

[MtnbikeMike]

and while you're at it convince me which of these I want:

-5th element air
-Manitou swinger (how many ways?)
-fox propedal

When I was racing at Sea Otter, I was behind a guy w/ a Superlight and 5th Element shock had some major side to side play, thanks to the swivel hardware mounts. It probably mived about a 1/4" to each side . Now, the Fow w/ Propedal doesn't have an adjustable pedal platform, it's also a different technology. So your best bet is the Swinger. It'll keep some lateral rigidity of the frame and you can adjust the pedal platform/small bump compliance.

 

[Kornphlake]

Actually if your frame flexes as much as this guy's superlight you do want the swivel hardware (spherical bearings) They'll keep the shock from being side loaded which makes shocks blow up. The shock isn't meant to be a structural member, it should not stiffen the frame in any way, if it does then I wouldn't expect the shock, especially an air shock, to last long. I'd reccomend the 5th air over the swinger simply because it does have the spherical bearing hardware which in theory will make it last longer and require less mantinance.

 

[MtnbikeMike]

However, the eyelets on the shock are some sort of plastic and can crack of bottomed harshly. I've heard of some Blur's blowing the 5th Element Shock because of the number of pivots flex under pedaling power, causing a side load. The swivel eyelets didn't help. Also, the shocks on some frames do help in keeping later flex down. Richard Cunningham(Mr. MBA) pointed out that the 5th E can make bikes with a lightly built rear feel flexier. Although he ism biased at giving bike purchase advice, he spent time designing bikes so he knoiws what he's talking about.

 

[MtnbikeMike]

Oh, and another thing. The 5th is a VERY light shock, so maybe Progressive designed it with swivel eyelets because it wouldn't otherwise last? I think the Swinger is about 50-100 grams heavier, depending on whether it's the 4-(w/ piggyback) or 3-way(w/o).

 

[Kornphlake]

eh, I've never ridden a frame with that much flex. Mr. Cunningham must be into frames that are notorious for blowing up shocks if he actually expects a shock to stiffen the frame laterally (personally I've quit reading his column with any intention of broadening my understanding.) Sure it could be true but why would it need to be? The 5th air was designed to be the lightest shock possible. They had to push the limits in certain places to get that weight, which probabally means the shock can't take a side load, which is why they give the spherical bearings. The frame manufacturer shouldn't expect the shock to be a structural member, the frame should be inherently stiff in my mind, or it should have some linkage to reduce flex at the shock like the Yeti ASR.

 

[binary visions]

However, the eyelets on the shock are some sort of plastic and can crack of bottomed harshly. I've heard of some Blur's blowing the 5th Element Shock because of the number of pivots flex under pedaling power, causing a side load. The swivel eyelets didn't help. Also, the shocks on some frames do help in keeping later flex down. Richard Cunningham(Mr. MBA) pointed out that the 5th E can make bikes with a lightly built rear feel flexier. Although he ism biased at giving bike purchase advice, he spent time designing bikes so he knoiws what he's talking about.

Kornphlake is right - if the frame is so lightly built that the shock causes the rear end to be stiffer (which is possible), the shock will blow very, very quickly. Shocks that get side loaded are little time bombs - it's not a matter of IF they will blow, it's a matter of WHEN.

Any frame manufacturer that actually believes the shock should be a structural member of the frame is not designing frames well.

The eyelet problem on the 5ths is supposedly fixed, according to the guy from Progressive that hangs out on here and on MTBR.

Oh, and I was reading an article on the 5th air shock, and they mentioned that the only reason they could get it so light was through the use of the spherical bearings to prevent the shock from taking side loads. Straight from the proverbial horse's mouth.