cyclezen

so, I'm using your post as a segway, not to be a rebuttal...
so, the question which I can't seem to find any info, data, study on - In a comparison of actual 'aero' bike VS an all round road bike OR Light climbing bike (with the same level of components) WHAT is the measured aero difference, could be in watts saved , via CDA, or any other comparative parameter; or develop some standardize index. Using a rider adds a variable which might make comparison unreliable. Testing only the bike is, of course, not a 'real world' scenario; but it would be comparable.
But, so be it - The question still needs to be asked, what advantage, by some quantitative value, does an 'aero' bike afford over the same level of light bike without the 'aero' enhancements?
Anecdotal personal experience is valid, for that particular person. But is not something which can easily be translated as an 'advantage' across the board for others.
The OP's post/comments/data re weight comparo - are totally applicable - TO HIM - but may vary and even not be replicated by me or anyone else.
I know (anecdotally) that if I adopt a more 'aero' position, on any of my bikes, I will either go faster or do less 'work'. Increasingly more apparent as I ride faster or experience more apparent wind.
But what should really be possible, is to know what built-in aero advantage an Aero Bike has over my Tarmac SL6...
In lieu of that, all we are supplied with is some Bike company statements that the 'aero' bike is more aero than any of their other offerings... Again, how much?
For bikes in the many thousands of dollars, there could be a 'Standard' aero test giving some comparative, real world usable INDEX of aero advantage.
I'm not holding my breath, because many Co. don't even publish a 'weight' number - always using some feeble excuse...
Now... maybe we don;t expect this INDEX on bikes under $2k or $3K. But if I'm gonna buy a $10k bike (or anything over $4k) I'd prefer to know what I'm paying for, not just 'It's much more Aero".
At first we might exclude Frames Only, but certainly all fully built High Priced Bike Models - show me the aero beef... and yes by size, please...
Ride On
Yuri

tFUnK

When a company claims that the Tarmac SL7 is x% more aero than the SL6, they don't state the metric (of which there may be several), but that comparison is made based on just the bikes, no rider included. I think the general sense is that whatever x% aero improvement there is between one frame and another, is miniscule when you add the rider to the system. In fact, my intuition tells me that that x% aero improvement is overshadowed on an absolute scale (of that same aero metric) by the difference between whether I wear a tight jersey vs a looser t-shirt.

mschwett 

i'm sure that's true, of course they'll state the more impressive figure. given the bike is perhaps 25% of the total drag, a 10% improvement there is really pretty small, especially with the rapidly increasing power requirements of higher speeds.

i ride mostly hilly routes, at relatively modest speeds, so i didn't prioritize aerodynamics.

mschwett 

basically.

but this is an extreme comparison. i think you'd be hard pressed to find too many otherwise-similar road bikes that were 15lb different in weight, as they are in this case.

illustration of how similar the geometry is:

the e-bike is about 1.5cm longer and just slightly taller.

cyclezen

That E-bike is only 29 lbs ? One of my riding buddies is on that machine. He bought it because he wanted to keep riding with the 'young, fast, guys' (which in a very distant past, wuz us... LOL!)
Claims he uses the 'boost' only sparingly... LOL!
I asked him if he rides it with the e-assist off, and he moans it's WAY TOO Heavy ! LOL! 29 lbs ! LOL! I know what this Post Sat ride's topic will be... !
course he is 75... and I think he's still faster than I am... but I'm bouncing back... Maybe I need MORE AERO !
Ride On
Yuri

mschwett 

yep. depending on the trim and size they range from around 28 to 35lb.

Fredo76

Looking at the bikes, you seem to have taken everything about them out of the equation except non-wheel 'frame' weight - it's not like you were comparing a clunker. That's very interesting, as is the fact that you improved more with the heavier bike. I'm assuming you have been riding much longer than since last October, so you weren't starting out unfit. Is that a correct assumption?

For heaven's sake, don't claim that you got a better workout against more resistance. That would be politically incorrect around here, because .. power meters!

Do you think learning the course accounts for most or all of your improvement on the heavy bike?

mschwett 

it's hard to say. prior to this comparison i had ridden the same loop another 30 times but WITH the motor turned on for the climbs. those segments don't show up in the data because they're recorded as e-bike rides in strava, of course. looking at them, they're actually slower still because i tried to use the motor really sparingly, was 20lb heavier at the beginning, and as you say, hadn't learned the course. my heart condition pretty severely limits how much stronger i can get aerobically, but i've definitely improved quite a bit within those constraints, which seems to have peaked around the time the first set of rides here (the red dots) stabilize in december of last year. the power meters can't be totally directly compared, but the data does show general improvement right at the beginning - from around 210 to 225 watts average (not weighted average, and there's a fair bit of descending here.) there's then a bit of a drop (225 to 220) a few months into the new bike, but unfortunately i think that's noise in the data, a handful of rides where i was only measuring left side and corrected later, a couple rides when i was sick, one where i got stuck behind a slow car on the descent, etc.

if i had to guess... i don't think fitness made a huge difference here except the first handful of rides. i've also done the first part of the climb recently on the ebike, and it was correspondingly slower for sure. and quite obviously "harder" !

here's the power data added on the right axis. again, take with a grain of salt before and after the bike change. i also see that i made a graphical mistake in the coloring of the two series. the average times are correct but the mis-coloring of four dots does suggest more "improvement" on the heavy bike.

AlgarveCycling

Highlighting your question in bold...the answer in terms of gains will of course vary from one person to another, hence no manufacturer can give a number applicable to all. They rather give wind tunnel data and math based upon previous models in their line up. Actual real-World results have to be made by us. You have an SL6, Specialised would have you believe that their SL7 will give you some marginal speed gains and they explain why they think so. But you have to try an SL7 and then time yourself over various segments vs your SL6 to see just what those actual gains are, and whether they translate to being worth the new bike or not for your use case.

Where there are obvious differences, such as my own two road bikes being vastly different, the benefits of each are easier to quantify with segment testing. It gets more complicated when the differences are smaller, such as Emonda SLR vs SL. There will be marginal gains for all, but will they be enough to make a difference for the type of riding they do? Only the rider can decide that.

I don't see how any rider cannot find gains though, however small, generally-speaking with a lighter bike or more aero bike or a bike that gives them the best of both. Ultimately, it is true that we all have to find equipment etc that works best for us as individuals and only personal reflection will advise as to what marginal gains are worth having etc. Some bikes might be heavier but put us in a position due to geometry that makes us more aero on the bike and therefore faster - we need to take that into account too.

So geometry is important, not just weight and aero. We need to be looking at all 3 albeit this is not difficult, in Trek's range for example, we know Madone = aero, Emonda = light and Domane = comfort. Specialised want the SL7 to be the all-rounder for racing: race geometry, not the most aero but close enough so as to make its lighter weight cancel this out and make the bike quicker over a typical race distance and terrain.

Generally-speaking, a 3w/kg rider will find a non-aero 6.8kg bike easier/faster than a non-aero 8.5kg bike as the gradients get steeper, regardless of who they are, what shape they are in. Similarly, if the 8.5kg was very aero where the lighter bike was not at all, then the 3w/kg rider would find the aero bike achieves faster segment times on flatter terrain.

Now, I've specifically used 3w/kg here as representative of average because you get super-human's like Wout van Aert at the other end of the scale who will be able to push a heavier aero bike fast enough up many climbs so as the aero trumps lightness over less powerful riders who can't go the same speed up hill on a similar aero bike. The faster you push an aero bike, the greater the advantages. This means WVA can use a heavier aero bike over steeper gradients than most and go faster than someone on a lighter bike. Still, even WVA will find his own limits on the aero bike vs gradient and then swop to a lighter bike if there are enough of those steeper gradients to make a difference to him overall.

So, yes, obviously different riders are going to have different measures based upon their inherent strengths and weaknesses beyond the bike itself - therefore, anecdotal experiences must be had by all to find their bike for the riding they intend to do: I do believe it is simply a question of finding where lightness vs aero advantages exist for each rider but ultimately, each rider will find differences and discover that lighter = easier/faster on gradients they find they cannot push aero fast enough upon and, similarly, they all learn where aero is always an advantage.

AlgarveCycling

This type of test must really be done on the same day with the same weather conditions on the same road segment back-to-back using a power meter and adopting the exact same riding position wearing the exact same clothing. A stronger headwind, tailwind, lateral wind etc will all make a significant difference so these need to be managed.

The fitness and condition of the rider can be removed from the equation if holding watts that the rider is comfortable with on the day. So 200W on each bike, no variation - strictly 200W, not 225W on one, 195W on the other. To find any gains from one bike to another, a power meter at specific watts used correctly will highlight these vs time taken.

The test should also be done on different gradient segments, at different power levels too. Not just a 200W test and then expect those results to be conclusive. The test should be done at easy, medium and hard watts for the rider to ascertain where lightness vs aero shows real gains for each on various gradients.

Re your sentence I have put in bold, if you don't have a power meter, then a heavier bike for training can make you fitter, stronger, faster if you go by 'feel' alone and judge effort - it's what we did before.
Heavy trainer, lighter racing. Nothing wrong with this at all.

What power meters do, is negate the need for a heavier training bike since 250W is 250W regardless of what bike you are on. So the exercise will be equal. The heavier bike's greater resistance means you have to do 250W, for example, to match the 225W, for example, on the lighter/aero bike to get the same speed/time so that means more effort on the heavier, less aero bike, but, all you need to do is 250W on the lighter/aero bike to make things equal in training terms. Therefore, the heavier bike is not offering any training benefit when you can match power levels.

PM's make training more scientific, but there is nothing wrong with going simple and just riding a heavy bike and then racing a lighter, more aero one. I know someone, for example, who trains mostly on his 29'er MTB on the road for this very reason. Naturally, someone with a PM can get the same effort from finding their threshold watts on the MTB and matching those to the road bike when training. Feel vs accurate measurement of power expenditure.

It's just a matter of preference.

Re PM's, it gets complicated when using different types, brands etc since they read differently, in my experience. A pedal PM will be different to crank, different brands will vary according to different algorithms and all need to be calibrated before every ride, ideally. So when performing tests like the aforementioned, the PM needs to be the exact same one, swopped between bikes. Or, you need to know the exact watt differences between 2 PM's at all measures.

Branko D

Maths (for a relatively average weight rider of say 75kg dressed) and my measurements with a heavy touring bike suggests that 1kg of bike weight slows you down about 1% up a typical climb.

15lbs leading to 8% slower speed is right what you'd expect.

​​​​​

rm -rf

"10% more power uphill"

For a rough estimate, I used this bike speed calculator: 6% grade, 150 lb rider, keep the other defaults.
18 lb bike, 200 watts: 8.23 mph.
36 lb bike, 220 watts: 8.22 mph. 18 pounds heavier to need 10% more power!

On the downhill, -6%, in the drops. Wind resistance goes up by the speed squared.
18 lb bike: 38.3 mph
36 lb bike: 40.1 mph. Less than 5% faster, 1.8 mph.

~~~
Would I ride a 36 lb bike? no. We've been riding on smooth repaved roads lately, and the riding experience is so nice. The aesthetics of riding on a lightweight bike, on smooth, quiet roads makes me want to ride more.

merlinextraligh

+1

2 minutes 35 seconds is a pretty big difference for essentially 3 miles of climbing. Additionally given that the ride ended at about the same elevation as it started, half of it is was downhill where the heavier bike made up some time. so the climbing loss was actually bigger than the 2:35.

Obviously, smaller wieght differences make smaller time differences, and cyclists have tended to obsess about weigh too much. However Cerberus peribus, a lighter bike is a faster bike. How much that’s worth to you for smaller changes in weight is a different question.

RChung

Nice data. That's a fun ride -- I used to do almost the same loop. I've climbed Conzelman on my road bike, on my "touring" bike, and on my MTB, but I haven't kept as careful records as you. Thanks.

Tycho Brahe 

I haven't read the replies, so perhaps it has been addressed, but the lack of axis labels on a graph and switching between light/heavy and old/new (still do not know which is which) drove my crazy

cyclezen

Yeah, I get All that. What I was getting to was for Manufacturers to provide some STD measure for the 'bike'.
1. I know the biggest factor in 'Aero' is both the Rider and Position - but that's something the Rider would provide - eventually determine by their own setup and use..
2. So, currently it's up to the purchaser to make some assessment of a manufacturer's claim of 'Aero' and the level of possible 'gain' (or not) for any particular model/size.
3. The purchaser (us - and my opinion of 'us') is likely going to have as many misconceptions as fact based ideas, on what affects 'aero', benefits or detracts from 'aero' and is cosmetically driven to an assessment....
4. So, we, the purchaser, go only by the 'aero' claim, for buying something of significant cost - assuming we can get some 'aero' benefit from it.
I realize this would OPEN a HUGE Can O worms for bike makers, because then there's inevitable comparisons of a CdA value, between models AND Brands, and could create a win/lose scenario... but....:
FOR ALL TOP END Road Bikes (and certainly associated TT bikes) - say, over $4K (maybe $3K... ? )
Manufacturers should provide CdA numbers for a Model/Size (in whatever livery config it's sold with), and beside head-on 0 deg yaw, can easily be done at 15, 30 and 45 deg. Could be done at a couple apparent wind velocities, like 25 mph (40 kph) or some other 'convention'...
Quick and simple tests, done without a rider..
YES, a major Can O Worms -.and so far, they've been successful in convincing those spending the Big Bucks, it's really worth it... again, many don;t even publish Bike weights - something which is super easy to do...
...so why would they change ? WIthout some 'push' I wouldn't expect it.
CdA is not something a 'consumer' can determine, but purchasing an 'AERO' bike or any high end bike is very much about 'aero', whether light or not.
I'M NOT EXPECTING A REPLY ! I don;t want to hijack this thread ! But thread brought this back to mind...
I would start another Thread... if this proved to be something BFers wish to snuggle up to... LOL!
Ride On
Yuri

Fredo76

I appreciate this acknowledgement. The dogma can be a little off-putting.

t2p

if Mrs t2p and her riding friends weighed in on this - they would immediately discuss the importance of a lightweight bike

very very important - every time you lift the bike to place and remove from the back of the car (SUV)

those gals don't want heavy bikes !

mschwett 

i routinely carry my bikes up and down the steps of subway stations and a few steps in and out of the office bike room, and i agree!

beng1

Equipment does not matter as long as you have fun, and equipment does not make much of a difference in speed compared to training and your aero body position. I ride, train and race a 35-pound Huffy road-bike, but since I weigh 200 pounds, it is a small percentage of the total bike/rider weight. If you are a small person riding in a hilly area, then I can see taking some trouble to acquire a light bike, but for a heavy rider, or for Anyone riding in an area without serious hills, having a light bike might give you a feeling you enjoy but it will not make you faster as much as it will make you poorer in the wallet.

A few days ago I happen to be riding on the same route a local "cycling club" was riding. From the bikes these guys were on, and the outfits they were wearing, you would think you were watching a pro road-race. There was about 20 of them I caught up to right at the base of a very long and steep hill, and I could not believe how I blew by all of these guys and got to the top of the hill quite a ways ahead of them. I would have had to have a 50-pound or more weight pack on my back to go as slow as they were. One of them had a titanium Merckx I noticed, and the rest of the bikes and gear were similar. What a colossal waste of money for those guys. I paid $3 for my Huffy, and I was wearing cut-off jeans and a white cotton T-shirt. A 29-pound E-bike ??? That sounds like it was a small fortune too.

mschwett 

i think you may have missed the point … i can say firsthand that i enjoy riding the lighter bike much, much more. it feels better. it makes me want to ride.

and it also happens to be faster, yes, which contributes to it being more fun but isn’t the only reason. i’m not competing with anyone, nor getting an ego boost from claiming i’m not 😂

AlgarveCycling

While some of what you have written makes sense - such as your first sentence where you state that equipment doesn't matter so long as you are having fun and that training and position will have by far the greatest effect upon speed etc, other parts are just you projecting a personal bias. You may be 200lbs but even you would appreciate a lighter/aero bike if you had one albeit the expense of one may not be worth it, to you personally; you seem to be trying to justify why you don't have one. You don't need to. You're a cyclist who enjoys cycling, that's all that matters.

If you don't find value in spending more and you are perfectly happy with what you have, that's wonderful, enjoy it and don't worry about what others may ride or wear.

Re the group you went past; you understand the concept of a social group ride? It isn't necessarily about trying to go fast, it is travelling in Zone 2 (a heart rate or power level that isn't taxing) so as to talk comfortably with your mates whilst enjoying a bike ride. I've witnessed guys blast past me when in a slow moving group, when we were just out cruising shooting the breeze and perhaps they had the same notion as you: that they dropped us, real easy like. Good for them - good for you, if you want to have imaginary races. Just as you are here telling us how easily you dropped them with all their expensive gear, they might have had a chuckle amongst themselves at the guy flogging himself in his own little race race on his Huffy, wearing jeans and a t-shirt. It works both ways if you go down that rabbit hole of projected stuff.

Those guys have not "wasted" their money at all; they simply have different priorities and wants, different tastes, possibly different disposable incomes, to you. If they are enjoying their ride, if you are enjoying your ride, then surely everyone is winning?

njkayaker

So, you were fresh on your 10 mile ride and you were surprised that you were faster than a group in the middle of a hilly 100 mile ride who were pacing themselves. Put another way, you have no idea how fast they could be or what their plan was and we have no idea how much of the story you left out.

cyclezen

I bow to AlgarveCycling for keeping composure... and saying what needed to be said.
...now i try to resist from being 'judgemental'; but some things are just TOO Mental.
...But I am weak...
Ultimate "Kookie'-logic !
ROTFLMSAO !!!
Walter Mitty is a hard thing to resist...
Ride On,
Yuri

Dave Mayer

Exactly. You are drafting someone else at least 90% of the time, so aero is not as important. But on the climbs and punchy accelerations out of corners, light weight absolutely rules. You need to hang onto the wheel in front of you or you are done for the day. Perhaps you can execute a superhuman effort to reattach to the group, but then you've expended so much energy that you'll pay for it later on. If you've done any kind of hard group riding you know the desperate panic of being close to shed off of the back. You may be in this situation several times per ride/race, and 200 grams of wheel weight may make the difference. Rotating mass is critical, so carbon tubulars for the win. No discs of course.