CREATE TABLE table_31572 ("Place" FLOAT, "Rider" TEXT, "Country" TEXT, "Machine" TEXT, "Speed" TEXT, "Time" TEXT, "Points" FLOAT)

Which rider had a speed of 90.57mph?
SELECT "Rider" FROM table_31572 WHERE "Speed" = '90.57mph'
SELECT "Rider" FROM "table_31572" WHERE "Speed" = '90.57mph'