Make a backup of the a320.TMD just in case. Master Obi Jan may not approve and may correct what I say but this is my understanding.
The nose sounds are controlled in this TMD file, towards the very end of the TMD line 56727
Here you can see the nose volume, it has 2 components, input0 gets multiplied by input1
<[soundmultiply][GroundRollVolumeNose][]
<[string8][Input0][GroundRollFactorNose.Output]>
<[string8][Input1][GroundRollFactorNose1.Output]>
>
you could try to adjust the GroundRollFactorNose, this entry is above the one above, line 56691
<[soundmapping][GroundRollFactorNose][]
<[string8][Input][GroundRollLoadNose.Output]>
<[tmvector2d][Map][ (0.0 0.1) (1000.0 1.0) ]>
>
I would guess this is the load factor on the wheel mapped to the GroundRollFactorNose.Output, so maybe raising it above 1.0 may help. Same for the 2 mains
Adjusting GroundRollFactorNose1 is speed to output, as it's the wheel I suspect radian/sec though it could be aircraft speed in m/sec . The 5 entries for GroundRollFactorNose1 are similar to a U shaped graph.
Any updates to FS2 will overwrite what you have changed, Steam may also do this during it's checks too.
Steve