What is it with all these rules youcant do this or you should only buy one of those for tts. How many mtbs have seen a mountain not many plus how many fit road tyres on mtb because its only used on the road, how many of you comute 20 or less miles on a sportive/audax bike shame on you for not doing 100 miles per journey. Then there are those on here who ride full carbon racing bike wearing full team lycra and average 15 mph or less will their bike ever see a race.
Ride what you want you pay the money its your choice. I will add allways have a good test ride make sure you are comfortable that is a good pricemy lbs are asking the full £1500 for those at the min
TT bikes are designed to do a very specific thing and to do so under certain circumstances.
As has been said several times, a TT bike is designed to go as fast as possible in a straight line.
They do not corner like other bikes and can be quite dangerous, most TT courses have very few corners and many of them are not sharp. Any which do feature sharp corners and you will notice a few crashes.
TT races often take place on close roads/circuits or on roads which have little traffic on them. This makes using them easier under races circumstances but using them on a road where there are many hazards and lots of stopping and starting it is dangerous.
Factor in where the controls are, the brakes and gear systems are separated on the handle bars, unlike other bicycles which have brakes and gear controls in similar positions so you can use them at the same time. A big problem with TT bikes is the lack of braking whilst you are on the aero bars, to get to the brakes you have to shift your whole body weight to get back up and move your hands a good distance. Changing gear whilst not on the aero bars also requires you to remove your hand(s) from the brakes.
They really are not designed to be used in situations where there is lots of braking and turning.