Motec i2 for GSC: interpreting the data

Marco Versele

Hhmmm, yes ...
Mar 31, 2013
Can anyone confirm how the suspension position should be understood in the Motec graphs?
I made a worksheet with on one hand the suspension position (FL, FR, RL and RR) during a lap.
On the other hand I made a graph beneath it with the ride height.
I assumed that the suspension position being = 0 means the suspension is bottoming out, or completely compressed, so you should stiffen the springs ( or sometimes stiffen the damper bump).
And when the ride height =0, I assume the suspension is fully compressed.

The graphs combination of suspension position and ride height show that when the suspension = 0, then the ride height is the highest, and when the ride height is lowest, the suspension position is higher.
This would mean that the number of the suspension position represents the rate of extension and not the rate of compression.

This means that when the suspension position = 0, the suspension is not bottoming out?
So in order to see if the suspension is bottoming out you need to know the suspension travel!

Or do I see things wrong?

Rick Malm

Feb 28, 2014
I took this screen shot at the Ring ("Carousel") and plotted the sus pos.

Interesting point is, I see some clipping of the top of the waveform of ride height Notice the suspension numbers can go negative. (Front Left into the turn).

So If you make the suspension maximum soft you might see
it bottom out and clip the peaks off these position curves. Then you have the
max extension and you can stiffen them up depending on the track character.
Might be better to find a dip and get all 4 to compress but I thought the
corner would make it clear.

Also found the following GTR_2 guide with google that was interesting re suspension tuning as the LAST thing to do. I have not read all of these but they look helpful so I will read it as time permits.

Found part 1 and 2 here Guide to MoTeC Parts I & II v01_000 by

I found looking at sus pos vs ride height on one wheel at a time helpful.
Notice the long clipping area at 58 on the Ride Height FL and a few spikes that are clipped on the RL at a little larger value like 72. I would be interesting a REPLAY side view TV camera to
watch what is really happening in this corner at what time since the tires can be in very different
stress points depending on where the car is in the Carousel groove.

Marco's interpertation:
"You can see that the left hander 'Carousel' causes the right ride height to lower (even into negative in this very rare case), while the right suspension compresses. But the right suspension pos in the graph increases! It means the right suspension traveled more - from less loaded toward a more compressed situation. Hence be aware that a suspension pos of 0 does not mean the springs are bottoming out. The negative ride height means you were driving with the left wheel on the concrete side in the banked curve, and the right wheel on the bitumen side out of the banked curve of the track, so that the 0 ride height position was higher and somewhere in between the two wheels. The negative left suspension position would mean that your suspension was higher than at the normal position at rest. So I think your left suspension got lifted off the road in that corner."

Since its not clear where the tires are in this complex corner,

just to make sure of polarity I tried a simple FULL Dead stop Accelerate and FULL Dead stop
see attached to see the sus pos at rest and during braking straight forward. See attached.

Then I went to some bumpy grass to try to make it hit the end of travel. out. Could not get sus pos to go to 0 but close and the waveform starts getting distorted as the right gets large Notice when the right height is max (RL RR) the sus pos is headed for 0 but does not get to 0 or below.


  • suspension at the RING carasoul.jpg
    suspension at the RING carasoul.jpg
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  • RL.jpg
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  • RR.jpg
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  • FR.jpg
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  • FL.jpg
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  • Driving In Grass Bumps Bottoms out.jpg
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  • Skidpad Dead stop Accelerated Brake to Dead stop.jpg
    Skidpad Dead stop Accelerated Brake to Dead stop.jpg
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