Here is a good example:
In Southern California we race off-road 8 scale outdoors in very desert like conditions. When we arrive at the track and begin our practice runs, the temperature may be at a cool and pleasant 68 degrees Fahrenheit. The car feels a little stiff but not enough to justify any changes to shock oils. We then begin our first qualifier around 10 or 11am and the temperature may have increased to 80 degrees and the car feels great. By the time the second qualifying race comes around its around 1pm to 2pm and now the temps may be around 100 degrees. You now do your second round of qualifying and your car is very soft and the rear end is bottoming on the jumps, "YEP" you forgot to account for the temperature change and the effect on the shocks.
So now you are waiting for the main event sheets to be posted but you are not sure if you will be one of the first races at 4pm or one of the last races between 9 to 10pm at night. So again, not thinking it totally through in your mind, you remember you are bottoming out on the jumps and bumps, so you change your shock oil to a thicker oil by 50cst to 100cst more. THIS IS A BIG MISTAKE, as you have to plan better and anticipate when your MAIN race will be (meaning approximately what time are you going to be on the track) and what might the temperatures be then? With today's smart phones, you have no excuse to not looking-up the hourly temp changes for your area on your favorite weather website.
In the example above, if you changed your shock oils to a thicker CST/Viscosity, say by going up 100cst to maybe a 600cst in front and now 500cst in the rear, in hopes of stopping the bottoming out of the RC on the jumps and bumps. You probably hit the track at lets say 8pm and the temperature is now 80 degrees. This oil change now just made your main event a lot tougher.
You will remember, your original setup was perfect at 80 degrees in the first qualifier but now you just went up 100cst (front and back shocks) on your RC. So guess what, your Main Event is going to be bumpy ride!!!!!
So to help you understand how much the temperature can effect your shock oil viscosity, we have included a nice chart that shows the test results of the effects of increasing or decreasing temperatures on the CST (viscosity) of the silicone shock oils from two major shock oil manufactures. The 40wt oils are usually around 500CST at room temps of around 75 degrees. So assuming you have 40wt or 500cst Oil in your shocks to start with, the chart shows the viscosity rate in CTS increase or gets thicker as it gets colder and CTS decreases or gets thinner as it gets hotter.
On the right hand-side of the chart is what we recommend you do based upon the temperature changing up or down by at least 10 degrees or more.
by 2.5wt or 50cst for every 10 degrees in temperature change....
Good luck and we hope you find this information useful.
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