Worth Upgrading to carbon bike?

GCNs video yesterday was looking at aluminium bikes and talking some caomparisons to carbon.

I did a short ride on the missus' alu bike. Didn't do the same 20 mile ride as I wasn't enjoying it. Novelty wore off after a few miles. Won't say much because it's not a fair comparison. Posh carbon frame to cheap alu frame (Infinton CV to Nirone 7). Also the size of her bike is too small for me. Massive difference, more than I expected. Really felt everything from the road, just didn't feel nice to ride. Fine for cruising around at low speeds but my God, no. Going to get her something much better after I finish my bike, doing upgrades on it atm. Feel guilty now!

That said, they say the new high end alu frames are amazing, and I'd believe it. Especially with carbon forks and finishing kit.

There is so much more to the bike than material and weight. Generally I'd say you would say that the carbon would be laterally stiffer allowing better power transfer and cornering ability but this obviously depends upon the alloy and carbon frames you compare.
Reducing wheel weights makes a huge difference and even if 2 bikes are the same 'static' weight it's the 'dynamic' weights that can make a difference. Again this depends upon where you ride. If you live somewhere pancake flat the extra wheel weight will only be noticeable in changing speed and direction and you may benefit from deeper section wheels that give an aero benefit. If you live in the mountains then perhaps not. As for most of us it's about finding a balance.
I've got a light (7.3kg curb weight) carbon road bike and a mid weight (8.2kg) alloy fixed (and most of that weight is in the wheels). They are very different bikes and to be honest the difference in speeds is small judging by strava times. I've set equal amounts of KoMs on both but then the alloy frame is one of the stiffest I've ever had.
Conclusion; take the time to work out what is best for your riding regardless of material and focus on bike fit.

I've done the reverse, bought a carbon Ridley Fenix and then got the alloy version for winter . Yes I can tell the difference, the carbon feels much better to ride, faster, easier etc.

Or it could be a placebo effect that I've spent so much on the carbon frame that it has to be better. Therefore I'm actually riding harder to justify the spend.

My bike's out of commission at the moment. Thinking to take the missus' alu frame out later today on the same 20 miler I did yesterday on my carbon bike to see the difference. If I do it I'll report back later with the experience and numbers etc from Strava.

I have a TCR and it's a great bike, stiff and light. arguably you might notice a little improvement on climbs and might find the geometry encourages you to 'push on' more in general.  It's a smooth bike too. But your Defy is also a quality bike and plenty capable of riding uphill quickly and going fast. The limiting factor is likely to be the rider not the bike in any scenario!

In terms of generally 'should I upgrade to carbon'.  I wouldn't say carbon is inherently a better material than Aluminium or Titanium or Steel. They can all be made to do certain things very well depending on the brief and ability of the manufacturer and designer

Anyone ridden to power on their new and old bikes to see if there really is a difference? I'd like to see if holding 400W or whatever up a hill makes much difference when bike and rider is 77kg or 80kg with heavier bike.

I know he's a codpiece in general but the once piece of advice I did take off Durianrider, the youtube  motormouth, is get a power meter not a new bike. I've only had it about 2 months but I've got another year older and beaten a lot of my PRs using it to gauge myself better.

I can't do a comparision myself as my other bikes are totally different beasts to my road bike.

Nice review, Griff. Great to see a few numbers being thrown in there to help justify your first impressions. The difference between 10kg and 7kg must feel brilliant when you get out of the saddle.

Good point about less weight not helping your speed on the flats (unless it's stop, start, stop, start type riding) so I'd say it's the more aero position that's making a sizeable difference to your time. Aerodynamic drag is almost all the resistance we encounter on a flat (mechanical inefficiencies being around 2-3% and rolling resistance slightly higher (but with a broader range due to pressures, side wall material and overall section). The drag on your body itself is approx 70-80% of the total drag, the rest being the bike (this balance obviously depends on the body, clothing, position and the bike of course!) so getting a bit lower can make a huge difference, easily accounting for the 4% you estimate, probably more!

Re: your point about potholes, I've noticed in my time that the stiffness of your wheelset is a large factor in how harsh the bike can feel. But there are so many factors here (not to mention tyre pressure) particularly the fact that you can get more forgiving aluminium frames than carbon frames, so its hard to say by how much.

Hi roadgenius4,

I can't comment on either of the Giant bikes, but having upgraded over the weekend from a £600 Al bike with carbon forks (similar in price and construction to a Defy4), to a £2.5k carbon bike (not unlike a TCR), then maybe  I can give you first impressions, hot from the press.

My Aluminium bike is a Trek series 1, Claris 16 speed (like an original Defy 4), but race geometry whereas the Defy is Endurance. I don't have the advantage of your wheel and gear upgrades. The bike weighs in at around 10Kg.

New bike, Scott Addict 20, Ultegra gears and rim brakes. 7.1Kg without pedals. 

Although both are race geometry, the Addict is marginally more aggressive than Trek, having a stack/reach ratio of 1.44 as opposed to 1.49 in my size. The store also set the Scott up with the bars quite low, and with the two bikes standing side by side, seats are the same height, bars on the Scott about 5cm lower. It remains to be seen whether I stick with this setup, or depending on how the vertebrae fare after a few rides, I need raise the bars.

The Scott came with 52/36 chainset as opposed to 50/34 on the Trek, so the Scott is geared higher by 4% and 6% in high and low ranges respectively.

Application of a bit of basic Physics suggested that on hills where weight is the limiting factor, the 3Kg drop in weight on 80Kg all up, would give me an extra 4.5% in speed, or about an extra half a gear. I didn't expect to notice much difference on the flat.

Out on the road, Physics theory went out the window, and the carbon Scott was faster right from the off. It is difficult to conclude too much from one ride due to many variables (wind, traffic etc), but on a regular route which I must have done 30 times on the Trek, on  my first outing on the Scott I covered the 26 miles marginally quicker than my previous PB, despite still getting used to the bike. Oddly though, while I found the hills to be a complete breeze, I did not beat my previous hill segment PBs, but did arrive at the top less fatigued. Clearly I took advantage of the new bike to take it easy instead of mashing the pedals as hard as before. Must try harder next time.

So if I didn't get that extra speed climbing, clearly the bike is faster everywhere else, and that was the impression while riding. The highest gear was used about the same amount of time on the Scott, despite being 4% higher ratio, which I guess means 4% quicker. Ease off and it doesn't slow as much, no need to change down as much, and the acceleration is phenomenal. Why? I guess lots of little things. I didn't give too much credibility to the semi-aero frame argument, but maybe it, plus the more head down position, gave me something. The Trek's standard Bontrager wheels never ran totally true, those on the Scott do (at least to my eye), so  I guess that would also help. Maybe even the stiffer frame means more power to the wheels and less twisting the BB. Hard to explain, but it is just a faster bike.

But a bike is about more than sheer speed. Downhill, the handling on the Scott is extremely confidence building. Think about where you want to go, and it goes there, where with the Trek, it sometimes feels as if  I am manhandling the bike round the corner. This might sound odd, but it feels like a smaller bike, due the agility it has.

Now we all hear a lot about less "road buzz" on a carbon frame. To be honest, through the bars, I didn't notice a difference (but then my Trek does have a carbon fork). Through the seat, there was certainly less vibration on a rough road surface, but road level changes due to potholes or joints in the road surface, I felt it more with the Scott, and a couple of times it seemed to skip.  I put this down to the carbon absorbing higher frequencies, but the stiffer frame not handling lower frequencies like those from potholes quite as well.

Final point on brakes: A month ago  I was looking at disks, due to the poor performance of my Trek's unbranded rim brakes, no doubt in the name of keeping the price low, compared to mt MTB disk brakes. All I can say is that the Ultegra brakes on syncros rims would stop a freight train. I have now changed sides in the disk brake argument. All those ex MTB'ers like myself, would maybe be as well off upgrading their rim brakes rather than buying disks.

Back to your original question "Is it worth upgrading to carbon". Absolutely no doubt in my mind, but as I hope I've explained, it's not all about weight.  Don't however expect a new bike to knock 10% of your route times. At the end of the day the limiting factor is your own legs. In my case I now need to think about whether or not to keep the alloy bike. I had originally intended to keep it for bad weather, but I will need to be seriously motivated to get back on it!

Carbon won't make you any faster unless there's some other factor involved. Saving a bit of weight or getting into a more aggressive aero position will help, but probably not by a huge amount.

I went the opposite way to you, and changed my boardman team carbon for a canyon ultimate aluminium. I haven't ridden the boardman in a while, but I swear it does have a slightly smoother ride. I will prefer the canyon overall, it fits me better and has a nice groupset. If you're not happy with the geometry of your current bike, and you've tried changing the bits you can, then I'd sell it and get a bike that fits you the way you want. You don't give a budget, but in the 1k-1.5k price range, I'd take better kit and aluminium over carbon every time.