Correct tube size for which rims and tyres

[FirstV8]

 Just a heads up for those who ride slick tyres . I use a hard tail 29 for my daily training ride doing a urban stroll ( mixture of tar ,grass , gravel and pavements ) with slick tyres 29 x 1.40 . I used a 29 x 2.25 tube which would bunch up in spots and give a bumpy ride . I have now replaced those tubes with 700.x 40 tube . I was concerned that it would not be wide enough for a 1.40 tyre but it fits perfectly no bunching and pumps up to 4 bar seating the tyre bead .