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Joaquin 04

How Enzo Fork subtanks work, and how suspension works.

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I messaged Enzo on how their fork subtank system works and they responded with how 1. Suspension works, 2.How the subtanks work relating to suspension.  I copy pasted what they messaged me  so this info is coming from the professionals. Pt1. Suspension Pt2. Subtank mechanics and how to adjust them.

1. The sub tank system provides what I call a "speed sensitive spring characteristic".  The two elements of suspension are SPRING element, which is load or position sensitive, and DAMPING element, which is speed sensitive. Each element does one thing, but cannot do the other. For example, a spring is load sensitive but it is not speed sensitive. If you take a spring that is 5 kg rate, if you put 5 kg on it, the spring will compress one mm. If you put 15 kg on it it will compress 3 mm.  But if you drop 15 kg on the spring it will bounce up and down more than 3mm, but it will eventually settle at 3mm of compression. So it is load sensitive, but not speed sensitive. Damping is the opposite, it is speed sensitive, but not load sensitive. Damping is like water. If you stroke your hand thru water, the faster you push you hand thru, the more restriction there is. So it is speed sensitive. But if you put a rock in the water and let it go, it will sink to the bottom because it has no load sensitivity. So both of these elements work together to create a shock absorber. KTM PDS is a rear suspension system that does not use a rising rate linkage, instead it relies on a "position sensitive DAMPER". I believe that the rising rate system manipulates the SPRING element, but they are trying to cover the lack of a linkage with a speed sensitive element: the DAMPING. So I do not believe in that system. When Jeremy McGrath signed with KTM, they were still using the PDS system and he was struggling with it, so his technician (Larry Brooks) asked me to help them.  I told them that I didn't believe in the PDS system, so rather than working with a position sensitive DAMPER, I said maybe a SPEED SENSITIVE SPRING might be better.  So I had already developed the system for the front fork so I applied it to the rear shock by manipulating the gas spring in the reservoir.

 

2. So with my system, you run a small volume in the fork, plus the extra volume in the sub tank. The total of both is the same as a big air volume.  There is a restrictive adjuster on the sub tank separating the two volumes. When the fork is compressing slowly, BOTH volume compress so it feels like a big volume and is soft.  But as the fork compression gains speed, the restriction between the two volumes prevents the volume in the sub tank from compressing so it feels like the small volume only. So the faster you compress the fork, the stronger the progressive spring force. Adjusting the screw on the sub tanks should make the fork get stiffer as the speed picks up. If it still bottoms, then you should add oil to the fork.  If it gets too stiff too quickly, you should remove oil from the fork. So it is SPEED SENSITIVE. The tighter you adjust the adjuster, the sooner the small volume comes into play. 

(* This was copy pasted from what they messaged me directly from the chat) Hope this helps anyone wondering 🙏

 

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I didn't know they tried it on a PD's shock 

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15 hours ago, mog said:

I didn't know they tried it on a PD's shock 

Yes, they did it before I ever saw FC's remote reservoir tanks. The difference in application, I believe, was FC's uses an unrestricted line to add total volume and less pressure rise but Enzo restricted it to have an adjustable pressure rise. 

Edited by homo erectus
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Do you know where I can get a Spec. Sheet or Manual on how to set these up?  I just found a pair on a 05 CRF250R.  Everything I read so far say they work on a single chamber fork.

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You can use them on a TC fork ,you have to raise the oil level to at least the max level 

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34 minutes ago, mog said:

You can use them on a TC fork ,you have to raise the oil level to at least the max level 

I have an old cr125 coming through,  and I think I may kick down a set to my bud. I like the idea of sub tanks much more on oc forks. I believe Enzo still sells the mounting bracket as well. 

Of course I would choose an air fork on the light cr125 first, but keeping with the stock platform, this is a "works" mod.

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You need to increase your fork oil by the volume of the sub tank so you need to measure it first.  Start with you fork oil somewhere around the middle (maximum recommended volume if you like to go big) of the recommended settings then add the tank volume to that for a starting point . Turn the adjusting screw in until it bottoms then back out one full turn to start. The effective tuning range is one turn to one quarter of a turn out from bottomed. On TC 47mm Showa forks the ics piston can block the relief hole to the outer chamber rendering the sub tank almost useless. If you're serious about using them you can drill a hole thru the outer chamber higher up....this in turn has the possibility of affecting the effect if the ics spring, The only way to find out is to try...

Edited by Budlite
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