Two offenders were seen running off with the bikes just after midnight on Saturday, June 4. They are described as male, of similar height and wearing dark coloured clothing. One of them had a white JD drawstring bag.
One of the bikes was a specialised XC in grey and the other was a Trek 3500 in black and green.
Two photos have been released of similar bikes to the ones that were stolen.
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Anyone with information can contact Northamptonshire police on 101. Alternatively, they can call the independent charity Crimestoppers anonymously on 0800 555 111