Jeremy Forlong, owner of the Off The Chain Cycles shop, said he received a call from police about 6.30am today about what looked like a smash and grab at the Cumberland St premises in the central city.
A Cannondale Topstone Carbon gravel bike that had been on display by the window was gone.
It had a retail value of about $8300, Mr Forlong said.
Glass from the broken window had travelled 15 to 20 metres, he said.
"They've hit it with a lot of force."
Police said they had noticed the broken window early this morning and inquiries were ongoing.