It's a while since I've come across an aircraft where I've had to do this and I'm afraid I've forgotten the specifics.

However, the numbers to play with are in the aircraft.cfg and are under the [Contact Points] section.

Here's a list of which numbers refer to what, as described by Microsoft:

[contact_points]
//0  Class
//1  Longitudinal Position        (feet)
//2  Lateral Position             (feet)
//3  Vertical Position            (feet)
//4  Impact Damage Threshold      (Feet Per Minute)
//5  Brake Map                    (0=None, 1=Left, 2=Right)
//6  Wheel Radius                 (feet)
//7  Steer Angle                  (degrees)
//8  Static Compression           (feet)  (0 if rigid)
//9  Max/Static Compression Ratio
//10 Damping Ratio                (0=Undamped, 1=Critically Damped)
//11 Extension Time               (seconds)
//12 Retraction Time              (seconds)
//13 Sound Type
//14 Airspeed limit for retraction     (KIAS)
//15 Airspeed that gear gets damage at (KIAS)
//GEAR

From memory, you need to adjust the 3rd number along in each contact point list for each of your landing gear, but don't take that as gospel.