Why Is a Motorcycle More Aerodynamically Affected Than a Truck?

[khalid00]

can't figure this one out!

does anybody know why a motorcycle is more aerodynamically affected than a truck??
really thought hard about it but just can't figure it out!
is it because of the two tyres??

Thanx
khalid..

 

[kamerling]

Air resistance depends on the cross section. Rolling resistance depends on mass