I think it's an evolving policy...and the changes move slowly through the TSA, depending on your location and/or when this was.

Two weeks ago my wife's multitool in her carry-on bag set off a major freak-out at the Tucson AZ airport...took 3 TSA agents to stare at it through 3 different machines before they finally took it out, showed it to my wife, & asked "What is this?" When she told them it was for making emergency repairs on her bicycle -- and when they had confirmed that none of the implements on the tool were longer than 3" -- they let her keep it.

Contrast this with the first business trip I took after 9/11, when I had a little greenie (the Xcelite miniature screwdriver or "tweaker" used for adjusting tiny trim pots on electronics, with a business end that's all of about 1.75" long) in my briefcase. There was no way in hell they were gonna let me take that on the plane.

They did however say I could leave it with them & pick it up on my return. Which I did..so upon returning to the airport of origin, they lead me to a room where they have three large cardboard cartons filled with all manner of confiscated tools. They said "find your tool and take it" and then left. If I had been an unscrupulous individual I could have pocketed half a dozen Leatherman tools, along with some seriously Toby Hooper-esque garden sheers. I found my little greenie & left.

BTW, I can think of NOTHING more uncomfortable than walking through an airport in cycling shoes (MTB *or* road). Plus, they make you take your shoes off at every US airport security checkpoint anyway, might as well carry them & wear flipflops or bedroom slippers or mocassins or sneakers or...ANYTHING else!