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Collapsing the bladder on purpose!?!

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I met a suspension tuner that explained to me he uses a vacuum pump to measure how much collapsed he wants the bladder (he didn't wan't to tell me how much psi.) before the final step of bleeding and installing the comp. adjuster. He says it's for a more progressive bottom out resistance, the resistance would ramp up quicker. Honestly, this is plain dangerous is it? I think this the perfect receipe for a shock explosion :worthy:

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asking for trouble for sure.

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I met a suspension tuner that explained to me he uses a vacuum pump to measure how much collapsed he wants the bladder (he didn't wan't to tell me how much psi.) before the final step of bleeding and installing the comp. adjuster. He says it's for a more progressive bottom out resistance, the resistance would ramp up quicker. Honestly, this is plain dangerous is it? I think this the perfect receipe for a shock explosion :worthy:

I don't understand the need, but I do understand his effort.

He would be better off running a spacer in the bladder, or just running a smaller bladder.

It's not a good idea to run the bladder collapsed too far down on itself.

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Just thinking out loud here, but could you have the same effect by partially filling the bladder with oil????

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Just thinking out loud here, but could you have the same effect by partially filling the bladder with oil????

Ah good point...and yes you could. :worthy:

Anyone have any concerns with this?

For some of my rebuilds I put one of those brass jingle bells in there. :lol:

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Just thinking out loud here, but could you have the same effect by partially filling the bladder with oil????
Ah, I just remembered, he said that as a side benefit, you get a measurable amount of extra oil in the shock. I figure by putting oil in the bladder instead it would be easier to be consistent in the volume reduction, but the down side is this oil in the bladder would not be circulating in the system.

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Depends on the bike :worthy:

Honda seemingly is of the philosophy that they want the progression...

Yamaha certainly is the opposite.

Suzuki is maybe middle of the road...

Kawi about the same as suzuki

I tend to run stiffer than avg valving in shocks. In doing so, I like as little progression as I can get....

For those long moto's, heat build up is serious issue for ground pounders. In that instance I feel the more nitro volume the better.

For most of us mortals who cant pound a 30 min moto, usually the heat issue isn't too bad.

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Suspension tuners have long tried to extend the capabilities of shock absorbers..... especially where fade is concerned. There have been many so called innovations and breakthroughs that have come and gone. I feel these innovations have had more of a sales benefit than a practical one. This is simply another example. The greatest improvements in consistancy have come from the manufacturers of higher quality oils. If you want more progression, change the linkage. You will get a much better result.

Terry

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Suspension tuners have long tried to extend the capabilities of shock absorbers..... especially where fade is concerned. There have been many so called innovations and breakthroughs that have come and gone. I feel these innovations have had more of a sales benefit than a practical one. This is simply another example. The greatest improvements in consistancy have come from the manufacturers of higher quality oils. If you want more progression, change the linkage. You will get a much better result.

Terry

AMEN

And keep the damper at a constant safe working temp, especially the N2 portion

PK

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OK, if I get it right, reducing the N2 portion increases the heat more than anything, and is just a bad way of tuning for bottom out resistance, right??

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it is.

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OK, if I get it right, reducing the N2 portion increases the heat more than anything, and is just a bad way of tuning for bottom out resistance, right??
it is.

Ah wait just a minute here.

The nitrogen chamber does not cool the shock, so more or less should not matter with regards to the operating temperature of the unit. That said, nitrogen in a shock will run cooler than that of regular air as it takes more energy to heat nitrogen. I guess my point is that a greater nitrogen volume does not mean a cooler running shock, (at a macro level). The reservoir (bladder) is not a radiator.

Aside from that would be the matter of if more or less pressure within a shock generates more or less heat, but I would think not, given that heat generation is a function of resistance and the molecular structure of the fluid. Someone check me on that.

The size and volume of the balder means everything to the rate of progression and resistance pushing back on the rod (F=P*A). So bladder size and pressure does have an effect on bottoming resistance.

For example, on a YZ 18mm rod, 100PSI is 39 pounds of force to the rod. At 150 it's 59 and at 200 it's 78.

What we need now is the mathematical comparison between rod displacement to that of bladder volume shift and pressure.

:worthy:

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interesting stuff dave.

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FC has on their site the progression of stock honda showa shock. It's not much. For kyb it's much less too.

large bladder ressy's and more nitro volume are purely to minimize the effect of heat build up and it's effect on the nitro pressure rise.

A thread was posted a long while back about this...and the change in pressure is dramatic from large temperature change.

On one guy I tested with, his bladder temps were VERY high...well in the 250's(F) and on long motos above that quite a bit. Stems from a lot of damping putting a lot of heat into the system!

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Ah wait just a minute here.

The nitrogen chamber does not cool the shock, so more or less should not matter with regards to the operating temperature of the unit. That said, nitrogen in a shock will run cooler than that of regular air as it takes more energy to heat nitrogen. I guess my point is that a greater nitrogen volume does not mean a cooler running shock, (at a macro level). The reservoir (bladder) is not a radiator.

Aside from that would be the matter of if more or less pressure within a shock generates more or less heat, but I would think not, given that heat generation is a function of resistance and the molecular structure of the fluid. Someone check me on that.

The size and volume of the balder means everything to the rate of progression and resistance pushing back on the rod (F=P*A). So bladder size and pressure does have an effect on bottoming resistance.

For example, on a YZ 18mm rod, 100PSI is 39 pounds of force to the rod. At 150 it's 59 and at 200 it's 78.

What we need now is the mathematical comparison between rod displacement to that of bladder volume shift and pressure.

:worthy:

You are the first person other than Paul Thede, that I have heard, who has ever said that nitrogen does NOT cool the shock.

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Dave you could mathematically come up with the added resistance.

When you do, I'd be curious to see how much % change you add to the main spring counting in the rising rate of the linkage.

My guess is the amount is not much percentage wise.

Zerodog over in PumpkinLand is using this technique. He has seen it used on MTB's, which it is, but they also use a rubber cushion as opposed to the MCU like a dirtbike.

They comment about the as keeping the shock cooler...true story, long ago, if anyone remembers the S&W shocks that had little freon bags inside the, I as a newbie to suspension, thought freon / air conditioning / cooler running. Had to learn somehow.

PK

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You are the first person other than Paul Thede, that I have heard, who has ever said that nitrogen does NOT cool the shock.

In the grand scheme...I don't think it a significant element of cooling (that's what dave was saying by using the term macro...)

Though if it's temperature were less than that of the oils...it would act as a cooling element.

I think the main thing here as stated is pressure change due to temp...and a nice thread was posted I beleive by JC on the issue.

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interesting stuff dave.
You are the first person other than Paul Thede, that I have heard, who has ever said that nitrogen does NOT cool the shock.

Well…let’s talk about this a bit more as it’s an interesting subject, and as I’m not quite sure why someone would say that nitrogen “cools” the shock, other than the stigma that “nitrogen is cold”, which I don’t believe is true.

I mean, when a shock is at rest, it is not any cooler than anything else in the room, right?

In addition to this, my tank of nitrogen out in the shop is not any cooler than anything else, nor are any contents stored inside a nitrogen chamber. And if I release that nitrogen and it blows against something, it does not cool that object anymore than helium or argon would. Obviously a very different story if it were Freon.

So nitrogen, in a gas state, is not cooling anything. Liquid nitrogen, on the other hand, is a very different story, but we don’t need to talk about that.

Now…that said, nitrogen does take more energy to heat up than other gases. So in that sense, you could say that a nitrogen filled shock will run cooler than one that is filled with regular air. But I can’t see how it would be correct to say that the nitrogen is “cooling the unit”.

To me, “cooling” is an exchange of energy. Like aluminum fins could be a cooling device as they allow heat (which is a type of energy) to be moved or shifted.

But I don’t see how encapsulated nitrogen would contribute.

Agree…disagree?

Anyone?

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