I have a 2018 Tarmac, carbon, 105 groupset, rim brakes, fully stock for that year. I also have a 2020 Allez, aluminum, 105 groupset, rim brakes, fully stock as well.

Ok, so they are not “stock” both bikes have been to the same bike fitter, have narrowed handlbars, a different stem. But, essentially these 2 bikes are identical, except one is aluminum and one is carbon. Same geometry, same wheelset.

I rode 5000 miles last year, most, but not all, on the Tarmac. I just took the Allez out for its first 70 mile ride. The results? Its not as stiff as the Tarmac, but other than that, the ride experience was the same. My time for the route, which I have done several times on the Tarmac, was essentially the same time.

I bought both for different reasons at different times. Both bikes were discounted from MSRP.

I love my Tarmac, and it is, and will be my primary bike. But the Allez is no slouch. Both are amazing bikes.

Yeah, 1# difference in bike weight just doesn't really matter during 70mi of recreational or enthusiast riding.

Allez is a great bike. I'd agree that a 1lb difference is insignificant for anyone not racing a bike up a mountain. I would assume the main differences here would be in terms of ride quality. The Allez is, by all accounts, a very nice riding bike that doesn't have some of the sterotypical harshness and buzz that other aluminum frames are associated with.

I have a similar comparison with two bikes I own, but they are both CX bikes. I have an older aluminum Cannondale CAADX and a newer carbon Cannondale SuperX. The biggest difference I notice between them is that the carbon bike is more dampened and feels more comfortable on rough stuff.

Allez and Tarmac share geometry’s (or at least very similar) and are designed for the same rider experience. It sounds like Specialized got it right!

Most of our decisions past the basic equipment is really because we want it, no matter what reason we tell ourselves.

Back in 2015\2016, I was looking at the Emonda SL and was ready to pull the trigger on it, and that same year, Trek came out with the Emonda ALR. I was not even looking at them as an option, that was, until I actually rode it. The ALR felt just as nice as the SL, was lighter than the SL, and cost less than the SL. Win, Win, Win. I put some carbon bars and seat post, picked up some carbon wheels and the bike rides like a dream. I have bought and sold 7 or 8 bikes since I bought that ALR, but I still have that ALR and I will never get rid of it. Within the last year, I upgraded wheels to go tubeless and in Nov, I replaced the 11 speed mechanical shifting and upgraded to AXS. This is just a bike I love to ride and generally have put more miles on it, than I put on my carbon frames, but that is ok, I don't mind have a "secondary bike" that is more like a primary bike. Some people don't understand n + 1, but that is also ok, they don't need to.

Timely topic. A couple weeks ago, I took my 2020 Canyon Grail SLX8 (with road slicks) and my freshly built Lynskey GR300 (with 42mm Pathfinder Pros) to the BMW Performance Center test track and conducted a comparison. 20 laps (10 for each bike), trying to keep my heart rate between 157-160. The results were surprisingly (for me) similar.

Interesting, I would agree with you that looking at the averages they were pretty close. I wonder if you do a x-y plot between lap time and HR for each bike separately, would the slopes of the best fit lines be different?

No idea how to do that.

Most of the weight of a bike is not in the frame. If they have similar components the total system weight will not be very different. And even then the whole bike is not a huge share of the total bike/rider system, except for very lightweight riders. And even then the weight only really matters for acceleration (including gravity). So ultimately it comes down to how the bike feels for you. And also maybe how it looks to you

Can't really argue with you here.

Plenty of people doing crits and rolling road races on Allezes. You can shed a bit of weight with carbon wheels and bars. Great bang for the buck for the gentleperson racer.