Rim to disc feels sluggish

I went from an aluminium Triban 3 rim-brake road bike to a carbon CX bike (about 2kgs lighter) and noticed the same thing. Put it down to geometry/position differences as rubber was more or less the same (28 on the CX, 25 on the Triban). The only place the carbon bike was faster was on climbs - to the point that most of my Strava times for local climbs stand 2 years on from selling the bike. 

Now I'm back on an aluminium CX bike and that bike is also slower than the Triban despite being a similar weight. I'm putting that down to much wider tyres - 32mm Gators vs 25mm 4Seasons.

On my relatively flat commute the Triban was around 1mph faster than the two CX bikes. Feel like I'm bedded in on the new bike now as I've done over 300 miles and its certainly much more comfortable than the Triban so its not a position/comfort thing.

Bit of disc rub slowing you down?

I presume the wheels spin freely with no rubbing?

Wheels/frame flexing causing a bit of brake rub when youre riding, but not when when you spinning the wheels when you're off the bike?

How much do you weigh?

How are your times comparing?

Buyer's remorse? You bought it because it was cheap, not because you loved it?

tyres?

edit : the answer will be yes I know that

Sounds like the title should be 'Titanium to carbon feels sluggish' 

I initially thought the same when I went to carbon fiber two years ago . However now I am at one with the material and have recently bought a second cf frameset and tbh would not now go back to anything else.  Cf IMO is unbelievably comfortable once you get used to the feel. It reacts differently to  aluminum or steel and your riding style has to adapt. My old ally winter hack bike is unlikely to be ever ridden again and also the other beauty about cf is that it is unlikely to be affected by winter salt on the road.

Feels sluggish is different to is sluggish. Checked your times for various known stretches?

I went from a mid range aluminium bike to a Canyon Ultimate CF and for a few weeks was somewhat underwhelmed. In time though it's clear it's a faster bike, I think it just took time to adjust to riding it. Like a pair of new shoes. Now I'm delighted with it.

I can relate to this, my first and so far only good carbon road bike after years on a steel frame machine felt distinctly sluggish in comparison, especially for climbing. I sort of expected this as the carbon frame is ever so slightly endurance oriented to accomodate my aging carcass and it is certainly far more comfortable after a few hours in the saddle. It also has the additional weight of electronic gears and disc brakes (which are both fabulous btw)

I had fortunately factored in the purchase of some fancy wheels (Reynolds Assualt tubular) and these changed the bike significantly. It is still not as 'excited'about hill sprints but it certainly holds momentum. We maintained a decent section of our ride this morning at 26mph + and it was absolutely in it's element.

Absolutely love riding it.