Originally Posted by PDKL45

Is yours the 105 disc version? If so there's a chance to fit 26" wheels and tires, as 26x2.3 has about the same diameter as 700x23. Lateral tire clearance may be an issue, though.

Otherwise look for 700x30-32C gravel tires, a flat handlebar, flat bar brake levers with road pull (Shimano Tiagra are economical and look just fine as well as shifters). 105 is probably 10 or 11 speed, so check out Microshift thumb shifters with the correct indexing. Reverting to a road bike would also be fairly easy if you retained the STI brake-shift levers and drop bars.