Shocks: pistons and oil
 

Hello, I have a big doubt with the pistons and oil:

Which is the difference between making the shock with less holes or a heavier oil?
Also which is the difference making more holes or bigger holesor lighter oil?

Thank you

The weight of the oil will either slow down (thicker viscosity) or speed up (thinner viscosity) the rebound of your shock. The hole size and number of holes can be used to fine-tune the rebound.

shock oil and shock piston holes have same effect.

light shock oil/more/bigger piston holes
more turn in,quicker reaction,better on bumps

heavey shock oil/less/smaller holes
less turn in,slower reacting,better on smooth tracks

I have been told that for high grip flat tracks is better bigger holes and heaver oil than lighter oil and smaller holes, and this is something I really don't understand.

The heavier oil will slow down the reaction into the corners and keep the car flatter due to more "pack" in the shock. Pack is when the piston tries to push through the oil. Light oil doesn't have much "pack" because the oil will push through the piston oils a lot quicker. The car tends to roll over and feel dumpy in high grip with this setup.

Jeff

I think you are asking does the followings combination give the same result.

For example:

1. 30-degree oil with 1 1.5mm hole.
2. 60-degree oil with 1 3mm hole.

IMO, the answer is no.

They are not the same. But the different is depends. I have read a article which talking about the different on the oil/hole combination on a buggy car. In the article, it talking about the landing of a jump and running on a bumply track. The main different is the change of resistance/damping force on such different combination. Whenever an oil passing through a hole, turbulence will occure. The strength of this turbulence and when will it setup is depending on how fast the oil passing through the hole. This turbulence of course will happen inside a damper no matter when it is being push in or pull out. This turbulence also highly contribute the resisting force inside the damper. Now telling the different:

When Light oil passing through a small hole, the speed is very high. Hence turbulence will happen in the very begining of compression. While with thicker oil but passing through a corresponding larger hole, turbulence will setup later and hence the resisting force will happen late.

In the article, because of the thing mentioned. It suggest when running on bumpy trace using a thick oil but large hole. But because the resisting force come out later, it will make the car response shower but more stable. In a flat trace, light oil/smaller hole would be better. It will give shaper and faster response.

The article is only talking about buggy. I don't know how much does it apply on touring. But I would say it does.

Thank you for your answers, I don't really understand how does the "pack" affect to an on road car, what I knew before and have learn here (thank you Jeff and mr4) was that pack affect on jumping landing :confused:
Thank you again

On a bumpy track with big jumps you want a more turbulent flow (i.e. lighter oil with smaller pistons) to smooth out the taking off / landings.

check Team Orion's setup guide about shocksHERE everything is well explained.

Your damping depends also on the speed at which you piston is moving. At low speed (laminar flow) you will feel no great differenz between small holes with light oil or greater holes with heavier Öl, but if your speed increases you flow will go from laminar to turbolent and you'll have more damping. But the point where it changes (speed) is different for both combinations.

Funny thing, i've learned about laminar and turbolent behaviour of fluids on university, but never thought that knoaledge could actually be usefull to something...

i dont this is old thread but im not making a new one.

so what a good setup to do? 60wt front and 40wt in rear with 3 hole all around?

Its best to just ask what the fast guys at your track are running (same chassis) and copy. Then consider what YOU want and tune from there. Most fast guys run very similar setups everywhere anyway so check out a few online setups and you will probably be sorted.

i dont goto track yet. still beginner.

this will help you understand what car setups do
http://users.telenet.be/elvo/