Ignatius has 8 tires because 2 x 4 = <<2*4=8>>8
His friend has 24 tires because 3 x 8 = <<3*8=24>>24
There are 20 bicycle wheels because 24-1-3 = <<24-1-3=20>>20
He has 10 bicycles because 20 / 2 = <<20/2=10>>10
#### 10