It happened in Warings Green Road, Solihull shortly before 4.30pm on Saturday 7 May.
A small white car deliberately collided with the 81-year-old and sent him flying into a ditch.
Three men emerged from the car with one riding off on the blue Trek FS4 Firefly which he’d only bought a week earlier.
The victim suffered severe bruising to his legs, face and a broken wrist and needed hospital treatment.
Police are conducting CCTV enquiries in the hope it will show the offenders.
Officers appealing for anyone who’s been offered the bike for sale or knows someone who’s recently got a bike like the one pictured to get in touch.
They are also asking any motorists or cyclists who were in the area at the time and may have caught the small white car on dash-cam or helmet cam to contact us.
Detective Constable David Spencer, said: “The victim initially overtook the white car but shortly afterwards it pulled up in front of him and three men wearing masks got out.
“He tried to cycle off but the car approached and he was rammed into a ditch.
“He suffered nasty injuries but clearly it could have been much worse.
“This is a despicable offence and I would urge anyone who suspects the people involved to get in touch. They don’t deserve any protection: the victim could have been one of your elderly relatives so do the right thing and drop us a line.
“You can contact us anonymously, we don’t need your name, just who’s responsible.”
People can contact the charity Crimestoppers anonymously on 0800 555111 or message West Midlands Police on Live Chat through their website, or call on 101 quoting crime ref 20/394313/22.