What is suspension 'pack'?

[simon]

As Title,.....is it the same as rebound??

[mattr]

No. ;)

http://www.oople.com/forums/showthread.php?t=114463

Should be an explanation in there.

Matt

[RogerM]

Pack is a term used to describe the point at which the damping becomes stiffer as the damper piston shaft speed increases. If you push your car down slowly it will feel nice and soft, plush even. If you push it down really fast (as in hit it hard) it will feel much stiffer.

For the next bit think of the damper fluid as people queuing to get into a spots ground or similar ... trust me.

Base (sometimes quoted as static) damping is the softer / plush option from above, this is what the car sees when running over normal lumps and bumps and when rolling around in corners.
In 'base' mode the damper fluid is moving through the piston holes in a laminar flow.

'Packed' damping is when that fluid flow becomes turbulent when the damper piston is made to move VERY quickly, for example when landing from a jump or running over a sharp edge / step up.

So going back to the people trying to get into the sports venue ...

If the people a re queuing in 10 rows and there are only 2 turnstyles but they are in no hurry, the match doesn't start for 2 hours, they will move smoothly through with little resistance as they don't need to force their way through as they can go slower... they are base damped.
If they only have 10 minutes before the match starts they will all be in a hurry, will try to get through the turn styles quicker and start tripping over each other etc. ... they will "pack" up and the overall flow of people into the ground will be slower!

So how could we avoid this packing?

One way would be to open more turn styles (the same as putting in more holes on the damper piston the same size as the original holes).
Another way would be to use bigger turnstyles so the people could go through side by side (the same as keeping the same number of holes but making them bigger).

So when would you want more / less pack? Well that comes down to driver preference, track layout / jumps etc.

As a rule of thumb less pack is best on really rutty tracks with few / no big jumps where you need the suspension to deal with the surface and prevent the car being kicked around so you can drive your lines. Something like a worn out and rutted grass track maybe.

You'd want lots of pack on a super smooth, twisty indoor / carpet track with BIG jumps so that the car remained composed on the BIG landings and reacted quickly to steering inputs etc. No need to worry about small bump performance as there aren't any!

I prefer to tune my static/base damping to pack ratio purely with pistons as described in the thread below.

http://www.oople.com/forums/showpost.php?p=713651&postcount=19

Hope that helps, any questions ask :)

[simon]

Hi,
Thank you for the great replies...........the reason i ask is that my buggy is slapping down after jumps,so someone said about more 'pack'..my standard front pistons are two hole,so shall go to three hole....

[andy-aj]

You need to go to smaller holes or less holes to generate more pack, or you could try slightly thicker oil. May help if you tell us which car you have, or look/ask for a setup in the area for your car.

[eyeayen]

@ Roger M, absolutely fantastic explanation putting into terminology any layman could understand.

On behalf of all laymen, thank you :thumbsup:

[V6Jim]

The way I always understood it from my days racing Motocross was that the bike (car) would behave in such a way over consecutive bumps that the suspension wasn't able to recover (rebound) from one bump compression in time for the next bump compression. The effect was that the bike (car) would 'Pack Down' over consecutive bumps.

This would cause the bike (car) to bounce out of control. The cause was simply over damping or under springing.

The previous posts are actually, probably, describing the same thing....

Jimmy