This is my first write up for 2019, and I have been hesitant to go into the theme of 'dampers' as I am still learning and experimenting things myself. Damper setup is one of the more advanced tuning techniques, but very crucial to the chassis performance.
Many refer to dampers as 'shocks' ... but I prefer to use the word 'dampers' for its function.
I would like to start out with one of the basic topic of PISTON and OIL, and move on to other topics when I am prepared to do so.
Similar to the discussion of FDR, where FDR and motor type both comes hand in hand to understand the impact of FDR. Many question and share information about their damper setup based on the 'oil weight' only. If you are using 10wt oil, but someone else has a different piston setup, then the discussion is completely irrelevant.
OIL TYPE ?
There are two major oils used in RWD RC drifting scene. I will note the basic differences, but what you use is purely your preference.
Advantages Easier to find, lower cost, and more options available.
Less affected by temperature.
Disadvantages Attacks and swells O-rings (Use of 'green slime' will minmize swelling)
Advantages Does NOT attack O-rings, dampers operates smoother.
Disadvantages Higher cost, and harder to find.
Can be affected by extreme heat conditions.
I see many discussions on oil type. One is not significantly better than the other, and this is purely preference and also based on what type of dampers you own and availability of oil.
My assumption is that majority of the people use silicone oil, simply due to availability. I personally use Team Associated for silicone oil, because of the availability and the excellent variations of oil weight.
Overdose HG damper is specifically designed to be used with mineral oil, due to the tight fit of the pistons against the damper cylinder, and obviously designed to be used with the Overdose mineral oil.
WHY IS O-RINGS SO IMPORTANT?
O-ring selection is key to assuring that the oil is sealed tight, but does not create friction with the damper shafts. Silicone oil is known to attack O-rings and make it swell, which will restrict the damper shaft motion.
Yokomo blue O-rings are well known to perform well. Topline green O-rings, and also Kose O-rings in different durometer is also known to perform well, but harder to find. X-rings is also an option, which is available from Tamiya TRF, Kyosho and Overdose, however you need to understand how to use these and being able to apply proper preload.
Good O-rings and knowing how to assmeble the dampers properly will not only make the dampers perform well, but also will extend the rebuild cycle of the dampers.
OIL WEIGHT ?
Each brand has their scale of oil weight. Technically this should be based on a 'standard', but due to the difference in the chemical mix or something, the same weight may not necessarily be identical between two brands. Some brands show the weight (wt), and some show centistokes (cSt). Team Associated shows both, which makes it simple.
I would strongly recommend staying with one brand to tune the dampers, so the oil weight is consistent, and not go to 10wt on one brand and 15wt on another brand. You will see many references on the internet, but just safe to stay with one brand to have several weights of oil on hand.
Silicone and Mineral Oil also has a different feel to the weight compared to mineral so 10wt in silicone is NOT the same as 10wt in mineral. Mineral oil will typically be less in viscosity.
WHAT DOES OIL WEIGHT DO?
In simple terms, lower the number, the dampers will be faster/softer. The higher the number, the dampers will be slower/stiffer. But again, this is closely related to the piston which I will mention later in this writeup, but also does not mean faster/softer is always better. Again, this is purely preference and a tuning technique.
We often see many people jumping on to the 10wt oil, or even 5wt, just to make it a soft as you can possibly make it...Yes, now you achieved your dream super soft and bouncy suspension....but is that really the best??
You could be losing a lot of traction in certain tracks, as every imperfection in the running surface will make your tire bounce, and because the dampers are so soft, it is not actually 'dampening' anything, and allowing the tire to bounce around. Or your chassis may have an awesome pitch and roll action, but if your dampers are too soft or bouncy, the pitch/roll weightshift action can easily be lost as the chassis will bounce right back.
Traction and roll/pictch action may be controlled better going to a heavier oil, so this is where each tuner needs to be careful in oil selection.
Pistons is what dictates how much oil goes through the piston. More holes will make it faster, and larger the holes will also make it faster. As noted above...softer/faster is not always the best tuning in different circumstances, this is why many brands and aftermarket brands offer variety of piston options. Different variations of hole sizes and number of holes, and some offer tapered pistons, or even ones with lexan film to provide tuning options for directional speed. Some people will modify their own with a drill bit, but this may result in a inconsistent piston due to the hole size or angle being slightly off between the pistons.
Oil goes through the holes, as well as the outside perimeter of the pistons. Some may not realize this, however as there is a gap between the piston and the cylinder of the damper, the tighter the gap, less oil will pass through the perimeter, but to have a tighter fit, will increase the cost of the pistons to manufacture them more precisely. This is why the pistons in the kit, are usually less in accuracy, compared to the pistons offered by aftermarket companies.
Please be careful to chose the correct piston for your dampers, as the diameter of the cylinder is different between Yokomo BD, BB and Tamiya TRF, or any other brand of dampers you may have.
Overdose offers precision pistons for the Yokomo and Tamiya dampers, as well as variations for the Overdoes HG dampers.
HOW DO YOU TUNE??
The table below is actually where I wanted to get to in this writeup and this is something that many don't consider, or at least from what I have seen. This is a simple excel table calculating the surface area of the piston hole. Number of holes in the horizontal axis, and the size of the hole in the vertical axis.
The orange highlighted area, and this is my 'personal opinion' on what is a 'practical' usable range for general damper setup using silicone oil. Yokomo BD, BB or Tamiya TRF, or any other generic dampers. The blue highlighted range, is added for the Overdose HG dampers using mineral oil. As the OD HG dampers are designed and manufactured to the highest quality, it will allow to expand the usable range to fine tune the dampers.
Difference may be subtle, but with the same surface area but different number of holes and hole sizes, the larger hole size will tend to make the dampers 'react' quicker.
Between the oil weight and piston size, you should be able to find the right combination you like. Softer/faster, may look good on the bench, but may not necessarily perform as well as you think. Some of the pro-drivers, even Yokomo drivers uses oils up to 50wt. If you are able to control the motions of the dampers with your driving, slower dampers may be more controllable as softer/faster setup can make the chassis too loose and unpredictable.
January 11, 2019 / Charlotte NC