1st Gen Icon 2.5 IFP Revalve/Piston Modification

A set of Icon 2.5 IFP coilovers will be going on my 1st Gen double cab shortly. Other brands aren't a consideration, these cost next to nothing so that was the reason for going with the Icons. These are the extended travel version with the smaller spacer. They're already due for a rebuild so that needs to happen anyways.
The truck is pretty light overall. Bumpers and sliders will be aluminum and it will have a winch. Most of its use is hunting trips. Long trips on the freeway/highway from state to state followed by long runs on dirt roads from main roads to fairly awful trails.
In the past I've had shocks on 1st gens (Bilsteins) with digressive valving and wasn't crazy about how they acted on small bumps/rocks. Linear valving was more comfortable at all speeds when switching to Fox shocks.
Has anyone modified Icon's valving and piston to produce a more linear damping curve? Options seem to include additional/enlarging bleed holes, modifying the piston to remove the digressive geometry, or just revalving. Experience on 1st gen trucks or 2nd/3rd would be great.

 

Update: These have been in the truck for a couple of trips now. Low speed valving feels great, but it seems to blow through the travel and bottom out way too easily. I thought maybe it was the 550lb coils or maybe that they were low on oil as they were leaking a lot. Upon pulling them apart for a rebuild it appears that someone was attempting to do exactly what I wanted to try with them. Both compression and rebound have spacer shims to negate the digressive piston geometry. The compression stack is set up as a flutter stack. There are also three ~.060 free bleed holes in the piston, one of which is plugged with a screw.
My plan is to plug all of the free bleed holes at least, and maybe play with the valving a bit. The high speed valving is really inadequate. Pics to come.

 

Think @Bandido was messing around with his to remove some of the digressive qualities of the dished piston

 

If the low speed feels the worst I kind of doubt blocking the free bleeds will make a large difference, it'll just muck up your static and low speed valving. What's your full stack look like, can you provide the compression shim diameters and thicknesses and actually the rebound would be good too, sometimes what you think is one can easily be a fault of the other as well

 

Plugging the bleed holes with affect more low speed feel than high speed damping. If the shocks need to be rebuilt already, I personally wouldn't mess with the valving because your baseline feel is skewed by the shocks not performing as they should be, especially if they were leaking that much, that's probably a big part of why it was blowing through travel. I would rebuild them and run it for a couple weeks and see what you think, then begin to mess with valving once your 'baseline' is off of a properly performing shock.

It sounds to me like that's the factory Icon valving but not 100% sure. You can call Icon and get the factory specs from them.

 

Icon pistons have a 0.02 dish in the center for the digressive valving, I bet your valving stack is stock Icon spec. If your shock was not at 250 psi then then it will feel soft, I would rebuild and run it to get a baseline. FYI those shocks come standard with 13"x 650 lb springs. If you have 550lb on there now then they have been swapped in. I would go up to a 14x600lb for your truck, I have some eibach's in stock. PM for more info.

 

https://www.tacomaworld.com/threads/icon-2-5-revalve.567758/

yup.

and as mentioned, if the pressure was really low, the high speed comp gets messed up the most as the fluid can cavitate very easily.

 

Gotcha. These have a very small diameter shim against the piston to negate the dish for the digressive valving. I didn't measure pressure on the first one but will on the second one before bleeding it off. I put the 550lb coils on, the guy I bought them from had 14" 700lb springs on them. I may need some 600s, I'll let you know.
@Bandido @TMFF what pressure would be low enough to cause serious issues?

 

Even 25-50psi low will change the feel but below 175 I'd think cavitation could start to become a real issue on high speed hits with these

 

Personally I am a fan of lower spring rates, as long as its providing the ride height you want, and the spring isn't compressing to the block height in compression!

I rebuilt my Coilovers again this spring and changed one thing from the stack I posted...but don't remember what it was, I think I took out the pre-load reduction shim completely and opened all 3 freebleed holes.

 

Damn, wat dia are the free bleeds on an Icon, I have two open and I think I'm borderline too soft on lowspeed.

 

they are super small, but I forget
Correction... I opened 3 of 4 on my piston

I'm really soft on low speed but don't feel too soft. Definitely noticeable in corners.

 

Here are what my piston and compression valve stack look like. I'll be putting it all back together this weekend, currently all three free bleed holes are plugged. I'm thinking that will help with the high speed issue. Any input? I didn't realize those were there from the factory.
I think the free bleed holes were a #2-56, so about .070. Had the wrong screws so they're #4-40 now but all plugged.

 

Free bleed will affect low speed more than the high speed as it is just allowing oil to bypass the valve stack (in both directions). So plugging them will result in a firmer ride (tighter handling feel), but not really affect high speed events as much, because the volume of oil able to pass through the hole is limited to the hole size. So as the shaft speed increases, the volume of oil able to flow through the hole is maxed out which causes the oil to be forced to flow through the valve stack.

 

Do not do that, you won't be able to bleed that piston and it will ride extremely harsh. Go back to what it was which should have been 1 bleed screw and run it to get a baseline with a properly working shock before you make drastic changes.

 

This

 

Thanks for the sanity check! I'll take two back out.
One major detail I left out is that there was only 40 psi in that coilover. Didn't check the other one. I'll post results after they're back in and charged properly.

 

Make sure to set IFP depth according to Icon's spec during assembly as well. IFP's are sensitive to oil/nitrogen volume differences due to it being a smaller volume of each.

 

Where do they publish that spec? Right now I have them set 1/4" deeper than the top of the shaft can reach.

 

They don’t publish it that I know of, but if you call them and tell them you’re looking for technical help for that specific first gen extended travel coilover, they should transfer you to someone that can help. They’ll look up the print for that shock and tell you the IFP depth.
I’ve found Icon has been pretty good to work with in getting those kinds of specs relatively easily.