Here is a tutorial on how to measure ride height on our radio control cars when doing a proper setup.
Measuring RC Car Ride Height
How do you measure ride height on RC cars?
Each manufacturer recommends a chassis height in its "standard" setup; from there it is up to us to adapt it to our driving style or personal setup.
In Dioni Santana's case, for the MGT7 he usually runs 9 mm front and 10 mm rear, although as he explains in the video, on a very smooth bump-free track that could drop 1 mm on both axles—always keeping the rear slightly higher than the front.
Remember ride height must always be measured with everything mounted—at full running weight as the car will go to track. Here Dioni shows it stripped down so we can see more clearly where height is measured.
MSB0534 
Dioni uses the dedicated Mugen tool, which is the most convenient, but you can also use a setup gauge or even calipers, subtracting chassis thickness. On the rear it is much easier to measure with a setup gauge or calipers.
Another important point—do not confuse this: RC car ride height is always set with shock preload, never with downstops!!!! Many people miss this, but downstops limit suspension travel—they do not set ride height.
Here is Dioni's tutorial on measuring ride height:
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