I am relatively new to the world of cycling/ triathlons, so my apologies if these are silly questions. I’m getting a fitting for my road bike (Giant Defy Composite 3 compact) and am considering clip-on aerobars. My question is whether it is worth getting aerobars on a road bike. Do they really make a difference or are aerobars really only effective on a Tri/TT bike? Also, if I installed the aerobars and then had the bike fitted for the aerobars, would I be in a less efficient position when I use the regular handlebars?
If your position in the new bars reduces drag then yes, assuming you are doing a triathlon and reducing drag is beneficial.
They are effective in both types of bike (see above), more so if the bike is fitted for you to be in a position to use them effectively.
Depends what you mean by efficient. Road bikes will generally climb better and have you in a position to climb better, a TT position will have the saddle further forward and raised, reducing efficiency from climbing muscles.
All three of those are an opinion and I am not 100% sure about the last one 
but I am sitting on a ferry with time to kill so happy to type nonsense for a while.
My question is whether it is worth getting aerobars on a road bike. Do they really make a difference or are aerobars really only effective on a Tri/TT bike
If it’s the bike you’re racing, and you spend the bulk of the time in the aero position in a non-drafting race, then it’ll make a big difference.
Also, if I installed the aerobars and then had the bike fitted for the aerobars, would I be in a less efficient position when I use the regular handlebars?
That depends on a lot of things. Generally speaking people who get clip-ons for road bikes choose to keep their known-good road position and do the best they can with the aero position given those constraints. You can tell your fitter to do that.
Or you could try to turn the road bike into an all-out tri bike. But that’s often problematic for a variety of reasons.
Thanks for your comment. Sorry, I should have included more details. First, I do triathlons-Olympic and half iron distances. Second, I live in Chicago, which is pretty flat. Some of the races around here have some hills, but it’s mostly flat. My main goal is to get faster in races. I average a little over 20 mph for the Olympic distance and am wondering how much of a difference aerobars (and the fitting) might make. However, I’m also worried that if I get fitted for the aerobars that I will be out of position for the drops. Given the traffic and quality of Chicago’s roads, I’m assuming that much of my practice time will not involve aerobars, and I’m worried that I’ll be uncomfortable on the bike if I’m fitted for aerobars but using drops.
Aerobars are the single best speed upgrade you can make to a bike.
A tri position on a road bike will put too much weight up front (poor handling, and arm fatigue when supporting your weight on the hoods/drops).
Road position with tri bars (better alternative IMO) will either be a more choked-up “big slam” position, or have you sitting out on the saddle nose (ok for short periods, but not very comfortable).
Slam
Nose riding
My own experience with clipons bars on my road bike has been very good.
My changes were:
Added redshift aerobars
Switched to fast forward seatpost and a tri specific saddle
Dropped my stem and flipped it to -17*
Overall the new position has taken some getting used to, and I’m sure I could dial it in a lot better, but my results were obvious: I immediately (first ride out) took 30 seconds off my PR for my normal 3.3 mile loop. Have consistently seen faster times in my workouts.
Granted my old position was very upright even by road bike standards, and I’m not a strong rider in the drops so the bar was set low, but I couldn’t believe the difference. Also definitely felt different in terms of my legs and where I was feeling the burn.
Handling took a bit of getting used to but it’s nothing a decent rider can’t handle.
For reference, I’m very much MOP for my AG the bike. On a reasonably flat Sprint distance course I used to ride about 20 MPH in my old settup. Haven’t tried it with the new.
Also I can take the clip on bars off and put my road post back in and have my old settup back for group rides/more casual riding.
Just my experience…
Full disclosure - I’m one of the owners of Redshift Sports, and we make products (aerobars & seatposts) that are specifically designed to address the issue of riding a proper aero position on a road bike (without sacrificing your normal road setup, I’ll add). So I’m obviously biased, but I’ve also spent a lot of time thinking about this issue, so I thought I’d weigh in.
Adding aerobars to a road bike is the single biggest thing you can do to increase speed at the same power output on a road bike. It’s also generally the most cost-effective upgrade from a dollars-per-watt standpoint. However, it’s important not to put aerobars on a road bike without thinking about your riding position as a whole.
A lot of people slap aerobars on a road bike and don’t change their saddle position at all. Since you have to rotate your torso forward to reach the aerobars, this leads to two problems.
Your hip angle (angle between torso and thigh at the top of the pedal stroke) gets too tight, meaning you’re fighting against your own range of motion. This frequently causes hip and back discomfort, especially for olympic distance races and up, and can actually cause a decrease in power output, since you’re essentially using one leg to push the other leg over the top of the pedal stroke.The distance from the saddle to the armpads is usually too far, meaning you have to stretch your arms out to reach the pads. Again, this is uncomfortable and tiring, because you end up using your muscles to support your upper body, rather than having your weight transfer straight down through your skeleton.
The key to riding comfortably in aero on a road bike is saddle position. As others here have mentioned, the saddle needs to move forward and up slightly (relative to the ground), effectively rotating your whole body forward about the bottom bracket. This will naturally bring your upper body down toward the aerobars, maintaining an open hip angle and squaring your shoulders over the armpads. This leaves you in a **much **more comfortable aero riding position where you can also generate power effectively.
The obvious downside to this saddle position change (which you hit on already) is that your road riding position is, well… awful. You have too much weight on your hands when you’re riding on the hoods, and it feels like you’re always about to flip over the handlebars. I’ve experienced this first-hand after I set up my bike with a static forward post. So, here goes the shameless plug - Redshift’s dual-position seatpost lets you ride a proper forward aero saddle position, but it also preserves your normal road saddle position, and you can switch back and forth between the two positions on-the-fly while you’re riding.
Based on some of your comments, I think our quick-release aerobars and dual-position seatpost might be a really good fit for the type of riding and training you do. But regardless of whose aerobars you end up with, definitely look at saddle position. More than the aerobars themselves, saddle position is the key to riding comfortably in aero on a road bike.
I hope that was helpful - let me know if you have any questions.
Stephen