What is a road bike bar?

It is not advised. It COULD be done, depending on your current set up. If your tri bike has tons of spacer and a riser stem, then roadie bars could work. If you are actually fit correctly on your tri bike, the drops on the bars will be so low as to be practically useless. The steering geometry of tri bikes tends to be pretty twitchy, so I wouldn't really want to use one as a roadie.

There could definitely be geometry/fitting issues. Some fitters think real problems can arise from putting aero bars on a bike with road geometry, much less the other way around.

My own bike may be one of the most sniggered-at tri bikes, the Trek Equinox 5. I bought it before my first tri because it was cheap ($800), but I believe the model has been discontinued. This may be because it has drop/road bars with Profile aero clip-ons. Trek may have been trying to bridge the gap between road and tri bikes to appeal to those who wanted elements of both.

The E5 qualifies as a tri bike according to most criteria (basic frame geometry, especially seat-tube angle), but many would mistake it at a distance for a road bike that happens to have clip-on aero bars and a "Kamm tail" downtube.

For a newbie like me, the E5 is fine. According to a Trek fitter, my position is aerodynamically sound on the aero bars, and resting my hands on the roadie brake hoods offers plenty of stability and additional grip when ascending. I doubt I'll ever sell the bike even when I upgrade to a more "pure" tri bike because of these road-bike qualities.

But because I’m fitted on the bike to be in the aero position, riding on the hoods definitely isn’t as comfortable as it would be on a road bike (or my bike set up differently). I feel distinctly “shoved forward” on the hoods, yet it’s bearable…just not ideal.

So I'm wondering: Why do you want to put drop/road handlebars on a tri bike? Stability/handling you think you'd lack on typical tri handlebars? Bigger roadie brakes to grab on to? More positional options?

If you're talking about simply replacing a base bar with a drop bar, and still using the bike as a tri bike with aerobars, then there's usually no issue, with the possible exception of the ends of the drops being too close to your knees when you're riding out of the saddle. The brake hood position will be pretty much the same as the base bar position. However, you may find that the drops are too low to be a useable position. About the only reason I can see for using drop bars instead of a base bar would be to use STI shifters instead of bar-ends, but then you'd have to break out of your aero position in order to shift.

If what you want is to dump the aerobars altogether, and use a tri bike as a standard road bike, then there are a few issues you may run into. If you leave the seat angle steep, you'll probably find that the position isn't comfortable, because your center of gravity will be too far forward and you'll have to support much of your body weight with your arms. Aerobars, when properly fit, allow your skeleton to do most of the work, but without them, it'll be your muscles doing all the support. If you move the seat back to a standard road angle (73-75 degrees), you might run into some fit problems. The reach on most tri bikes is on average 3-4cm longer than a similar sized road bike. So if you change your seat angle from 78 degrees to 73 degrees, you'll need a shorter stem (usually about 3-4cm shorter), otherwise you'll be really stretched out. So if you're starting with a 90mm stem, to get a proper fit you may need a 50mm, which if you could even find one, wouldn't do much for your bike's handling. Also, most tri bikes are designed to compensate for moving the rider's weight forward when using aerobars: shorter chainstays and longer front-center to get the rider's weight more evenly distributed over the wheels, and a slightly longer wheelbase and more trail to make the bike more stable. The result of trying to ride a bike designed that way with a 73 degree seat angle is a poor handling bike.

So, if what you're trying to do is convert a tri bike to a standard road bike, at least in my opinion, it isn't worth it. An entry level road bike will ride much better, and be much more comfortable, than a P4 fitted with drop bars...

It might be a goofy geometry, but it could work. I skimmed the other posts and I didn't catch any mention of shifters and brakes. If you have bar-end shifters and separate brake levers on your tri set-up, and you want to swtich over to road bike bars, you'll need to get integrated shifters+brakes. Probably an obvious suggestion, so never mind if you know this already. This could be a pretty big price committment: bar-end shifters and brakes in a tri-set up are considerably less than SRAM or Shimano road shifters (~$500 for SRAM Red and Shimano Dura-Ace control levers).