If you install clip-on aero bars and get a seatpost that can push your seat forward for the aero position, you will obtain a huge percentage of a dedicated time trial bike advantages. It is totally fine to ride in your normal road configuration too. Many mega triathletes rode and ran amazing times before tri bike geometry was widespread. You will mostly just give up a couple MPH on the ride.

The only benefit of a tri bike for someone like yourself who is on a budget and does not want a TT bike in the apartment or garage is that it will put some extra coin in the bike shop owner's pocket.

Sure, could you drop a couple grand on a new bike and finish the bike leg a couple minutes faster? Yes. On the other hand, assuming you already have clip on aero bars, you can drop $100 on an aero helmet and make up much of that. (If you don't have aero bars, get some). Spend a couple hours really working on your transitions and you can make up much of the rest.

A tri bike matters at some point because they can be more aero and all the other gains have already been made. But 75% of triathletes still have free or nearly free ways to make up a ton of time time somewhere else during the day.

I'm glad to hear this. ^^ I too have wondered, when I see triathletes all kitted out on the latest and greatest bike with a super pointy (err...aero) helmet, but clearly struggling otherwise and moving pretty slowly, if they've made wise investments, or if they should focus their attention elsewhere. But, to each their own.

I've raced a number of 70.3's on my road bike and had a blast. As the other posters have suggested, get some clip-on aero bars and get comfortable riding in that position. You may have to adjust your position on the bike a bit to get comfortable in them, but it's worth it. The only other thing I did was get a wheel cover (I used the AeroJacket from Wheelbuilder:

http://www.wheelbuilder.com/aero-disc-covers.html

Snaps right over your current wheel - and helps reduce a little bit more drag. Just make sure to test ride that a bit as well - you may have to get creative with duct tape on the inside of it to keep it from rubbing on your frame.

A lot of folks seem to post as if these things are somehow mutually exclusive. They are not. You can work on fitness while you also improve position and optimize gear. The answer is both and.

There are a few great tables out there that list the most impactful investments you can make to improve time trial performance. In parallel to this, you can also improve fitness, transition times, comfort in position, whatever.

1. Position - You can achieve a tremendous benefit of improved position with clip-on bars and a forward seat on your road bike. Then a true tri bike would take you incrementally from there to 100% optimized.
2. Tri Suit - A tri suit is your next best investment. They will make you faster in the water (in a non-wetsuit race) and faster on the bike.
3. Helmet - The pointy helmet will add some real speed to your universe.
4. BTA Hydration - This saves watts and gives you water
5. Tires & Tubes - Get some low rolling resistance tires and latex tubes. Not sure exactly where to rank these, but this is probably about right.
6. Wheels - These are the first big investment (if you do not get a bike for #1). The benefit is real, but due to cost, the watts per dollar is the smallest so far.

I road my road bike in a 70.3 last year. I did have aero bars installed, but I did not use them enough to make it worth while.

Go for it on the road bike. If down the road you want a tri bike, then do it. There are ways you can find to store an extra bike, like hanging it on a wall while not using it.

Int summary, definitely do not need a tri bike.

FWIW, my tri bike was damaged (cracked frame) and i did ironman texas on a road bike.

I went with the redshift switch aero system and was pretty happy.

https://redshiftsports.com/switch-aero-system


I rode 5:20 and according to bestbikesplit.com, I probably gave up about 10-12 minutes versus my tri bike -- it correctly predicted my day within a few minutes on my target of 200w with road bike setup

good luck!