Flutter stacks - where to begin?

[slawson2000]

The question: What are you running in a similar configuration or what do you think I should run for a flutter stack?

The information: My Bronco has 4" Skyjackers with 10" SAWs up front and F53's, 6" shackles, pivot relocation, and 12" SAWs in the rear. I am getting ready to rebuild the shocks. None of the valving currently matches on the shocks. They must have come from different vehicles. While I do not have a micrometer (yet) I do know the quantity and diameters differ. After much searching and reading I really think I want to go with a flutter stack for the reason that my truck spends most of its life as a DD and I often travel many a highway mile before turning off road.

Driving style: At times "spirited", but not as fast as I used to be. I do not race or even pre-run, but most of my friends say I should. (I have no idea honestly).

Terrain: When I can get off the black top, mostly fire roads and some questionably maintained roads, maybe up to 100mi into where I want to be. Washboard / cobblestone type stuff. From there, a little bit of everything. Rocks. dunes, whoops, air, anything is possible.

Disclaimer: I know shock valving is subjective, but I hope I can get pretty close to start with your help. If you do not want to share your "secret" valving with the rest of the world, I hope you would PM me your setup.

If you need any more info on my setup, I would be more than happy to share, but I think it is pretty average.

Thanks in advance…

[hobbyturnedobsession]

Front is difficult because i run coilovers and a soft spring rate but the rear you may try somewhere in the neighborhood of 8 comp. 10 or 12 rebound.

[slawson2000]

Front Compression
_ .012
__ .012
___ .012
____ .012
_____ .012
______ .010
___ .010
______ .010

Front Rebound, probably all .010's or .012's

Rear compression - same as above but with .008s and .010s

Rear Rebound - same as above.

This is where I am thinking of starting, any ideas or experience with a similar setup?

[slawson2000]

What about any standard valving? Anyone?

[shockseals.com]

1.625-.750X.188 chromoly washer(compression retainer)
____ 1.35.012
_____ 1.500x .012
______ 2x 1.750x.012(largest shim for given shock you are using)
___ 1x.008
______ 1.750x .008(largest shim for given shock you are using)
_______________Piston with 1 bleed open

charge to 250psi min. If it doesnt ride nice on road and dirt roads/small stuff go to 1 of the .012 thats doubled. If it rides nice everywhere but bottoms out to on square charge to 300psi and make sure its not because cavitation. If still bottoms on square edge change the fulcrum shim to .008 and run at 300psi

Front Rebound stack of .012 shims to start.

Piston Nut 30ft-lbs

[philofab]

The fulcrum shim I see on your diagram is already .008?

[shockseals.com]

The fulcrum shim I see on your diagram is already .008?

thats a flutter shim but I guess could be argued its also a fulcrum since the first shim bends over it.

Fulcrum shim is the first piece off the compression retainer in standard shock talk though and its a 1.35x.012 in that diagram.

[shockseals.com]

1.625-.750X.188 chromoly washer(compression retainer)
____ 1.35.012
_____ 1.500x .012
______ 2x 1.750x.012(largest shim for given shock you are using)
___ 1x.008
______ 1.750x .008(largest shim for given shock you are using)
_______________Piston with 1 bleed open

charge to 250psi min. If it doesnt ride nice on road and dirt roads/small stuff go to 1 of the .012 thats doubled. If it rides nice everywhere but bottoms out to on square charge to 300psi and make sure its not because cavitation. If still bottoms on square edge change the fulcrum shim to .008 and run at 300psi

Front Rebound stack of .012 shims to start.

Piston Nut 30ft-lbs

If too soft in the small stuff bump the flutter shim diameter up.

[slawson2000]

Thanks for the input. To help me understand a little more maybe I need some help with the terminology.

My understanding (I do not know if it is right) is that in shockseals stack going from top to bottom would be the stack, followed by a 1x.008 fulcrum shim, folloew by the 1.750 x .008 flutter shim.

Is that correct?

[shockseals.com]

Thanks for the input. To help me understand a little more maybe I need some help with the terminology.

My understanding (I do not know if it is right) is that in shockseals stack going from top to bottom would be the stack, followed by a 1x.008 fulcrum shim, folloew by the 1.750 x .008 flutter shim.

Is that correct?

If you held the piston up to the sceen with the compression face, facing the ceiling you would stack the shims on just like its listed. The compression retainer is the first part to go on the shaft and each part goes in order from there.

[slawson2000]

Maybe I should have been more clear in my question. I understood the orientation of the configuration, just a little confused about the terminology of the other two shims (in this case the lowest two). Is the bottom shim referred to as the flutter, and the next one up the fulcrum?

[shockseals.com]

Maybe I should have been more clear in my question. I understood the orientation of the configuration, just a little confused about the terminology of the other two shims (in this case the lowest two). Is the bottom shim referred to as the flutter, and the next one up the fulcrum?

The fulcrum shim is always the last shim (relative to the piston) that all the shims bend over.

The flutter shim is the 2nd shim from the piston in your layout but one could argue it too could be called a "fulcrum" since the first shim is "fulcruming" over it but its not common diction to call the flutter shim the fulcrum. The fulcrum is the fulcrum, the flutter is the flutter.

Post a picture of your piston assembly before assembling the shock if you arent sure what you are doing. Included everything from the shaft to the nut in the photo.

[slawson2000]

I appreciate the offer and might take you up on it. I am curious as to the doubled .012's intent. Is it to make the shock initally stiff at higher speeds?