A teenage boy was on his bike on Old Church Road at around 4.10pm on Saturday (16 May) when he is reported to have been approached by a group of boys.
Shortly afterwards, the victim was pulled from his bike and punched to the face before he had his mobile phone, bike and keys taken.
The group are understood to have left the area towards Minworth and Castle Vale.
The victim suffered facial injuries, which are not believed to be life-threatening at this time.
A 14-year-old boy from Sutton Coldfield, two 16-year-old boys from Birmingham and a 14-year-old from Birmingham were arrested on suspicion of robbery.
They have been bailed until 13 June pending further enquiries.
PC Reece Smith-Tyler said: “This was understandably a nasty incident for the victim but fortunately he is not believed to have suffered serious injuries.
“We continue to investigate and would ask anyone who was in the area at the time or who witnessed any suspicious activity to get it touch with us.
“Any information no matter how small could help with our ongoing investigation.”
Anyone with information should call 101 or Crimestoppers anonymously on 0800 555 111 quoting incident 320 of 16 May.