How to speed down two-fingers trackpad scrolling?
Solution 1:
I have a MacBook Pro 11.1 running Kubuntu 14.04. Synaptic is installed, but the X11 and Synaptic config files aren't in quite the same location as listed in mdoran3844's answer.
However, based on this KDE forum post post here, I ran the following command, which worked on my hardware/software environment:
synclient VertScrollDelta=20 HorizScrollDelta=20
If that change works but isn't permanent, you may need to place it in something like your .xinitrc
or another start-up script (or hunt down the config files listed by mdoran3844's answer).
Solution 2:
This depends greatly on how your touchpad is working. Many touchpad gestures actually don't use any of the Ubuntu gesture or touch events and instead once a gesture is recognized such as two finger scrolling a macro or keycombination is performed.
In your case when the two finger scrolling is recognized then a mouse scroll event is propagated into the event device generic hardware driver, evdev.
You can use the Synaptics Touch input driver to configure your most touch pads and touch screens. When using Synaptics, you can alter the scroll speed by changing the VertScrollDelta and HorizScrollDelta located in the config file.
sudo gedit /etc/X11/xorg.conf.d/50-synaptics.conf
And then edit these two lines
Option "VertScrollDelta" "10"
Option "HorizScrollDelta" "10"
Note: The higher the value the slower and more accurate the scrolling will be. This may seem counter intuitive to the standard mental model of sensitivity.