Are aero bikes really getting faster for non racers?

Aero bikes do look more pro which makes you feel faster!

Unfortunately, the answer is, it depends.

First things first, the rider accounts for 65-80% of the aerodynamic drag when cycling. If the rider is not aero (i.e. is sat very upright and is not an aero body shape), then it doesn't matter what the bike is - they'll still have a high aerodynamic drag.

After that, the clothes a cyclist is wearing and their helmet are going to make a significant difference. Also, aero bars are going to make a very big difference too.

Wheels and frame both have an equal impact, but still not as important as the rider position and the clothes being worn.

Quantifying the real-world difference is difficult. However, the difference between my Whyte Wessex (with 47mm wheels) and my Canyon Ultimate (racey, aggressive setup and 62mm wheels) is easily 0.5 mph for the same power, same 10 miles course, same day - the Canyon Ultimate being faster, this was an easily repeatable result.

For context, my £400 tt bike is 1.5 mph faster again than my Canyon on the same course under the same conditions - that's the difference aero bars make.

So yes, there is a difference, but it's pretty small. The difference becomes noticeable at anything above about 18mph, it's very noticeable at 25mph+.

To get faster (in order of priority); get fitter, get low/aero, get slippy (skinsuit), get an aero bike/wheels.

All the aero claims are done in wind tunnels - as mentioned usually at 40kph / 25mph as a benchmark speed (you'll see claims like "saves you x watts at 40kph compared with..." or "saves you 8 seconds at 40kph compared to...")

Then you factor in that, on virtually all rides, the average club rider:
is not doing anything like 25mph constantly
has to cope with traffic, junctions, riding to the highway code, imperfect road surfaces...
has wind angles and speeds that are not constant or steady
has kit that is far from aerodynamically perfect (inc saddlebags/top tube feed bags, is carrying tubes/pump/food in jersey pockets)

So in the real world, not a huge amount. From a mental point of view though it can be quite significant (I'm on a fast bike so I feel fast!)
 

Mentally you'll be a lot faster.

There may be a measureable difference but in the real world it's worthless.

Firstly, the big very non-aero shape sat on top of the saddle makes up 70-80% of the total drag. Wheels are the next significant factor influencing drag (though much less, of course) and frame design is at the bottom of the pile.

How long would you keep an optimised position? When the rider moves around - sits up, takes a hand off the bar to have a drink or look around etc - drag goes up significantly. Unzip your jersey, more drag. Vented helmet, more drag. Wrinkled clothing, more drag. External cables or round frame tubes? Insignificant.

When riding in a group only the rider(s) on the front are getting clean air (presuming it's a 0 degree headwind), the rest are having an easier ride, 25% less effort or even more for the same speed, so aero matters less to them. And that turbulent, 'dirty' air won't hit those components the same as when they were optimised in a wind tunnel.

Also, the amount of drag at 18-20 mph is much lower than the commonly used speed of 30 mph so you'll save significantly fewer watts than is often claimed.

All these things are an order of magnitude higher than differences between frames but manufacturers want people to keep buying new kit. IMHO if you like your bike, whatever shape it is, then relax and enjoy riding it.

Tbh you get out what you put in. Riding hard(ish) solo rides on these things and yeah, you will notice a difference (compared to standard non aero bikes, in my experience). If you are more of an easy cruiser then maybe not. For group rides only if your on the front a lot I reckon.

Old vs new aero? Not sure you'd notice a radical difference in speed tbh unless you're really pushing it...and then it could just be as much a placebo effect?

Make sure you have aero wheels with your aero frame though - that will make a difference. 60mm for me is very noticeable or less if you're on the lighter side

I dont think that aero bikes make that much difference as the big aerodynamic problem is sat on top of the bike.