I mentioned this. Yes, you can, but a 6.8 SL7/8 isn’t a bargain. In fact, it’s quite expensive, and everyone seems happy with the weight penalty for being aero. To get on the 7kg mark on today’s bike the pocket will suffer.
I can’t wrap my head around that calculation. 1kg going 7% uphill only increases 3w of resistance? Not sure we’re talking about resistance. I want to know the time penalty for this 1kg.
Use any watts/cda/slope calculator and run your simulations.
I did this calculation years ago for myself. My bike club goes up the same 20 minute climb every Saturday. I wanted to know how much faster I’d be if I lost ten pounds. The answer was a pathetic ten seconds over 20 minutes.
Then I ran more calculations. To shave like 2 minutes off my time, I’d have to lose a lot more weight but more importantly pack on some serious watts - both being in the next to impossible category for me.
Yeah, it really depends on the gradient and the w/kg you are doing on the climb. We have local hammerfest ride, where the ‘crux’ climb is only 4.5 minutes or so at a hard effort. The climb is only 5.5%, and at my weight and power, I calculated that it’s around 1 pound per second. Meaning, if I dropped 5 pounds, it would be around 5 seconds saved. I was surprised the time savings were that low
All bike calculators I am aware of state the opposite, aero >>> weight, even at more moderate speeds. @mcneese.chad’s nice post gives a few concrete links that play with numbers. I think this is a case of feeling faster ≠ being faster.
On the latest Performance Process podcast episode with Dylan Johnson they gave a nice example (in the context of wider tires): a Ferrari driving over a bad fire road at 50 km/h probably feels faster than a Jeep doing 50 km/h, in no small part because the ride is harsher.
That has little to do with disc brakes and more to do with e. g. more intricate frames with integrated cable routing, electronic groupsets, integrated stem/handlebar combos and a dash of greed. A few years ago, Canyon was offering a 6 kg disc brake bike for not too much money. These days the price would likely be considered “affordable, mid-range”. Also the Aethos was and is UCI-illegal for the same reason.
Since most manufacturers want all, or at least the vast majority of their frames UCI-legal (i. e. above the 6.8 kg weight limit), they put the added weight to good use for aero features and the like.
And even then you’d likely still be significantly faster across the entire ride since you’ll eventually have to go downhill at some point.
35 Watts of aero/rolling resistance savings, savings at high speeds. These will make you a little bit faster on flat courses but not a lot. On climbs these savings don’t matter (for us mortals anyway) because we are too slow.
Nobody seems to talk about going downhill. Aero bikes go way faster downhill. This is an area where it’s really noticeable.
I was riding with a couple friends, we were coming down a mountain, fully tucked, going like 50mph. I was the only one in the bunch with aero wheels. At the bottom of the hill, I was a solid 300 yards ahead just on coasting.
Thanks for all the replies, and it seems (again hehehe) that I’m wrong.
Maybe my style and group ride are more prone to be decided on climbs, so I’d be inclined to go with a lighter bike.
Again, I’m not an idiot, a 7kg aero bike is a dream, but I can’t afford it. I have to play with the tools I have available. The rest, well… this needs to come from my legs. And, I’m not doing too bad.
The rough math is that on steep climbs (say 7% or higher), every % saved in on-bike weight will save you the same % in climbing time.
If you weight 70kg, your bike weighs 15kg, and you have 2kg of stuff (water, clothes), your on-bike weight is 87kg.
If you switch to a 1kg lighter bike, that takes your total down by 1.1% to 86kg.
If you were climbing the Alpe dHuez and were going to finish in 60min before, this new 1kg lighter bike will allow you to finish about 25 seconds faster.
That’s actually not true that a headwind is the same as riding faster.
This post explains it:
Oh not this again lol.
Aero drag is in fact the same whether you’re travelling 40kph on a calm day, or 20kph into a 20kph headwind. So yes, quoted aero savings at 40kph are the same as what you get from going 20kph into a 20kph headwind.
Otherwise wind tunnel testing wouldn’t work, and we would not have modern commercial or military aircraft.
The reason why it takes more watts to go 40kph on a calm day than 20kph into a 20kph headwind is due to rolling resistance being a function of ground speed (and drivetrain losses potentially being higher). Crr is larger when going 40kph than when going 20kph into a 20kph headwind.
Since I posted this, and sure Google, my phone and all sorts of electronic devices are silently capturing my thoughts, I’ve been flooded with: “Lighter x aero, which one is faster” heheheh
After watching some videos, reading some articles, and doing some calculations on those websites, I’m prone to think, therefore changing my mind a bit, that a pure aero bike is faster in almost all scenarios.
That’s my reason talking. My heart, on the other hand, keeps reluctant that a lighter, even a 10-year-old model, is better. Why? Well, I recently changed my 2021 TCR for a 2015 SuperSix. The latter, despite being older, is incredibly agile and a bit lighter. My times on flat did not get any worse. My climbing times are the same, somethings a touch better. Same power, same weight, same places, same wind.
So… despite the reason, calculators, data, and all information available, the reality IN MY CASE, doesn’t seem to align.
But is the 2021 TCR all that aero? It could be quite similar to the 2015 supersix - I really don’t know, but could be the case…
Which is my line of thought. So, even though they are 8 years apart, one being disc and the other rim brakes, they seem to perform similarly in regards of “aero gains”. I like to think I have a good position, which is 80% or more of the aero gains.
The SuperSix being a bit lighter is my reason for stating that a light bike helps you get over the mountain. I’ll invest in some good wheels next year and bring it to 7.3kgs. We’ll see then.
Yeah, your experience is what I’d expect - that they would be pretty similar in terms of aero. Any small aero tweaks made to the TCR would probably be lost adding disc brakes compared to the rim brake supersix - so kind of a wash.
I’m still running a 2008 cervelo SLC-SL and it seems plenty fast compared to a modern bike, other than the new crop of aero road bikes I suppose.
Aero drag is the same sure, but the pedaling power required is not the same. The ole deal that the watts to increase from 20 to 21 kph are less than 40 to 41 kph. My post was poorly worded.
What special powers do you have that the laws of physics don’t apply to you? 
Seriously, sarcasm aside, there is nothing unique about your situation that would make your results different than science. If power, weight, wind were all the same then some other variable was different to account for the time changes. Tire choices, wheels, position, clothing, etc.
Hehehe
Well, I thought the TCR would be faster. A few years of evolution, better wheels (way better). And it’s not.
So if all variables remains the same, and results are being the same, I supposed there’s no relevant difference between those models.
A few years of evolution is basically nothing for bikes. You are comparing two all-arounder type bikes. There is no magic in just a few years. There is really no aero magic in 10 years. Everything has gotten a bit more evolved but not dramatically so.
Despite the marketing, there isn’t a huge difference between various aero wheels. If you look at various charts there is hardly any difference between 0 and 10 degrees of yaw between most wheels which is what we encounter 95% of the time. Sure the person racing IronMan in Hawaii may encounter that consistent 15deg of yaw and for them the fastest wheels will rule the day.
Now if you are going from Mavic Open Pros with 32 spokes to a modern aero wheel, ok you get your free 20 or 30 watts. If you are going from 10 year old Zipp 303s to some fancy new wheel, you are only going to gain less than a handful. Between 0 and 10 watts there may be no difference.
It’s the same with frames, go from an old aero as a brick frame to something modern and gain a bunch of watts. Go from 5 years ago to today and the gain is hardly anything. A lot of recent gains have been in cockpits and putting even faster wheels on superbikes. Did the frame itself get more than a few watts faster? It’s debatable.
Sounds like the only way you’re going to settle this is to actually hire a wind testing company and take both of your bikes along.
On a related note, I sometimes wonder if the frames are tested with water bottles in (aero bottles or normal ones) or tested completely empty. So no bottles, no cages.
It makes sense. I think I was under the impression that a newer bike would be faster, and turns out, that both are very very very similar. Well, on second thought, the Cannondale might be faster as the TCR has a pair of 36 SLR2 carbon wheels and GP5000. And the SuperSix a pair of cheap Fulcrum and Vittoria Rubino. I’m planning to upgrade those wheels next season.