Two specialised bikes, worth a combined £4,000, have been stolen from a garden shed on Altham Terrace in Lincoln.
Jason Hill, who regularly uses the bikes for both street use and cross-country trail riding, discovered the theft on February 4 when he returned from work.
The bikes were taken after thieves forced entry through a seven foot gate and smashed a padlocked shed door.
It is thought that the incident took place between 10am and 1pm.
One bike is a large specialised Camber Comp with industry stickers, Maxis tyres and atom lab pedals worth £1500.
The other is a blue and black complete custom trails bike by Echo and Hope with Alfaowner stickers. This bike is worth around £2500.
Anyone with information is being urged to contact Lincolnshire Police on the 101 number, quoting incident number 299/4/2/14.