20 psi seems a little high... is that the recommended pressure on the sidewall? Usually manufacturers recommend anywhere from 4-12 psi, although it varies widely depending on the tire. If memory serves, the factory tires on my Big Red recommend 2.2 psi.
Current Trikes:
'86 350X (x2)
'86 200X (x2)
'86 250SX
'85 250SX
'85 250SX / 200X Hybrid
'87 250ES
'85 250ES
'83 ATC 70
Current Quads:
'16 Polaris Outlaw 110
'14 Polaris Ranger XP 900
'13 Polaris Sportsman XP 850
'07 Honda Recon ES
'05 Yamaha Raptor 80