Shock oil vs Piston changes

This week’s tip is a question I get asked from time to time when discussing my setups with other drivers at the track. I try to keep certain aspects of my car setups pretty simply. I don’t often get as much track/tuning on my personal gear compared to the average club racer. So I maximize my time eliminating some “chase” time in my setups. One of those areas is shock piston selection.  I’ll go over how I see the difference between shock piston changes and shock oil changes. Again I never claim to be an expert these are just things I’ve found that work for me.

Shock Oil

When talking about shock pistons and oil you will often hear the term “pack.”  Pack is the term given for how the shocks react to movement. Less pack means the shocks are supple and soft. More pack is the opposite which creates a more “live” car. Less pack gives more roll, and runs through the rough bumpy sections of the track better. More pack gives less roll, and a bouncy but more responsive car.

Personally I often stick with 2 hole Avid pistons in the 1.5, 1.6 or 1.7 range.  I’ve yet to find a setup on a car that I couldn’t get speed out of with one of these 3 pistons.  That being said let me explain pack a bit more.

Imagine you have two identical cars. You have 1.5×2 pistons in all 4 shocks (for arguments sake) with 25wt oil.  You have the second car with 1.6×2 pistons in all 4 shocks and 27 ½ wt oil in that car. When you drop Car B, the chassis bottoms out harder than car A.  Both feel the same in your hand, but the larger holes will have less pack therefore is less sensitive to the velocity of the piston travel.  So how do you choose which piston/oil setup to go with?  Think of it this way; if the track you’re on has a lot of large jumps where your car is bottoming out, you may want more pack to prevent the car from slapping and bottoming out which slows you down.  On a really rough track where there are a lot of sharp edged bumps, you will want less pack which allows the suspension to cycle quicker soaking up those bumps.

In the end, more pack is slower reacting suspension but a quicker reacting car on the track. It can be “bouncy” feeling and hard to drive at times.  Less pack will be a slower reacting car, will provide a suppler ride in the rough stuff, and often be the easier of the two to drive.  A car with less pack can also be lazy feeling at times too. As with anything in regard to racing, there’s always a balance.

If I’m struggling at a track, I will often ask one of my team drivers or good friends that have a similar driving style as my own to drive my car while I watch it on the track. This helps me observe the car up close. This helps me out a ton personally, especially if I’m struggling with the track and setup.

Remember that you need to setup the car for you, your own driving style, and your track. What may work for one of the top pro drivers like Drake, Lutz, or Boots may not work for you. I know I can’t drive as good as they can, but I can use their setup to get me close at times.

So go out, get some practice, take some notes, and see what works for you.

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Shock Oil vs. Piston Change

Shock Oil vs. Piston Change

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