Another Aero Wheel Experiment

[berserk87]

For discussion and debate - enjoy:

http://www.cyclingweekly.co.uk/videos/cycling-tech/how-much-faster-aero-wheels-video

[redir]

Yup. Aero wheels really do work.

[berserk87]

Yup. Aero wheels really do work.

Dangit. I was hoping for more insightful banter.

[redir]

Dangit. I was hoping for more insightful banter.

Be patient it will come :)

2k in one hour is pretty darn significant.

[berserk87]

Be patient it will come :)

2k in one hour is pretty darn significant.

Thanks.

I am bored today so I am trying to force some forum entertainment.

[aaronf]

I would be curious to know how much the front wheel contributed to each setup. Run two more trials keeping the Mavic rear with ENVE and then HED fronts.
Kinda suspect pretty similar, maybe just a touch less, results.
Have sent Dr. Hutch a message.

[gasman]

Thanks.

I am bored today so I am trying to force some forum entertainment.

Just say (insert one) campy, shimano, sram, mavic sucks.:banana:

[oldpotatoe]

Dangit. I was hoping for more insightful banter.

Considering about 85% or something of your energy is spent overcoming wind resistance, no surprise. The question tho was at the end, how much is 2kph 'worth' to you? As in how much $ would you invest for that 2kph?

[Cicli]

Get a motor. :banana:

[redir]

I would also like to see a test for front wheel only. Who needs a wheel set when the front one does all the work? Put all your money into a good aero front wheel and ride the junk on the back... Or not?

[nooneline]

Worth noting, too, is that they're worth more the faster you're going:

@ 200w, 30.7kph to 33.1kph, a difference of 2.4kph
@ 300w, 36.4 kph to 39.6 kph, a difference of 3.2kph

Get that into the realm of average race speeds (let alone max speeds or sprint speeds) and we're talking about a non-negligible difference, here.

Of course, this should come as no surprise, since these tests are always bandied about, and the science is sound.

[JMacII]

Get a motor. :banana:


Why doesn't someone run a test with a motorized bike? Then the rider just sits there and you eliminate a ton of variables.

[Dead Man]

Why doesn't someone run a test with a motorized bike? Then the rider just sits there and you eliminate a ton of variables.

Really good point

Nobody has thought of it?

[JMacII]

Really good point

Nobody has thought of it?


Don't know. But yeah, just set the motor for 200w and run a test on an indoor velodrome. Pretty easy, and you'd get darn close to true single variable repeatable testing.

[Gummee]

Guy rented a pair of 808s from us this weekend.

Came back kvetching that he LOST 2mph average using the wheels.

I kept thinking to myself 'that don't make sense. EVERY time I ride my deep-section wheels I gain speed.'

...but what do I know?! I just make em work

M

[Ralph]

There is no denying of the facts about aero wheels. However.....my real world riding not very similar to that test riding. Yours may be.

[oldpotatoe]

Guy rented a pair of 808s from us this weekend.

Came back kvetching that he LOST 2mph average using the wheels.

I kept thinking to myself 'that don't make sense. EVERY time I ride my deep-section wheels I gain speed.'

...but what do I know?! I just make em work

M

When I worked in ProPeloton, sold a guy a true 'tri' bike, a Quintana Roo, right down to a 650c aero wheels. Trying to qualify for Ironman, Hawaii..Fast enough swim and run but slow on bike..so a bunch of $ later-his tri bike.

Came back in, said his bike leg was slower...wanted his money back...

Oh well

[Gummee]

When I worked in ProPeloton, sold a guy a true 'tri' bike, a Quintana Roo, right down to a 650c aero wheels. Trying to qualify for Ironman, Hawaii..Fast enough swim and run but slow on bike..so a bunch of $ later-his tri bike.

Came back in, said his bike leg was slower...wanted his money back...

Oh well

Go figger, huh?!

I think the guy needs to rent those wheels again and try em out on his regular course(s). I'll bet he'll sing a different tune.

M

[benb]

I was thinking about this riding B2VT last weekend.

There was obviously a lot of high speed stuff and it was a very long day so any savings would have been worthwhile.

One thing I don't quite get.. there were cases I was pulling away from people who had aero wheels coasting down descents. You'd think the wheels would be too big of a difference there, and we're talking well over 30mph on those descents, over 40 on a lot of them. Not sure I think body position had a lot to do with it as everyone was kissing their stems and getting as low as possible. (My upper back still hurts today from doing so much of that.)

Kind of wondering if tires were making a bigger difference. We've seen big differences in rolling resistance tests. I was riding one of the Specialized tires that tested out in the top 5 fastest tires available. That might have been enough to overcome someone else on more aero wheels who was using tubulars which generally come in pretty far back on the rolling resistance tests.

Of course the other factor is it rained. If I had been on an aero wheel with a carbon braking surface I would have lost a lot of speed due to being afraid of poor braking. I had shimano rim pads on alloy, the braking was excellent in the rain. Maybe not that big of a deal as the cornering wasn't terribly extreme on this ride, but there were a lot of > 40mph descents that were bumpy, confidence there was important.

Have we determined yet if disc brakes erase the aero wheel advantage? I think that would have been the only way I'd have been comfortable last weekend with an aero/carbon rim in the rain + dirt.

[pasadena]

I think tires do make a larger difference than I originally thought.
I got the new Turbo Sworks tires and supossedly 35W faster than my old tires. They feel faster but no way to be sure.

Aero is body position and clothing.
Wheels are secondary, and then the bike.

I watched some of those Specialized wind tunnel videos and surprisingly, shaved legs made a huge aero difference.
Disc brakes didn't make a difference head on, but I believe a bit slower at an angle.

A lot of factors in play why you would pass others. You also would enjoy some drafting effect as you pass others, even if you are not directly behind them.

[benb]

Yes I have a pair of the S-works Turbos too, not the super extreme cotton casing ones but the next step down.

They feel ridiculously fast... it is very noticeable. Nice ride quality too.

[Mark McM]

One thing I don't quite get.. there were cases I was pulling away from people who had aero wheels coasting down descents. You'd think the wheels would be too big of a difference there, and we're talking well over 30mph on those descents, over 40 on a lot of them. Not sure I think body position had a lot to do with it as everyone was kissing their stems and getting as low as possible. (My upper back still hurts today from doing so much of that.)

Kind of wondering if tires were making a bigger difference. We've seen big differences in rolling resistance tests. I was riding one of the Specialized tires that tested out in the top 5 fastest tires available. That might have been enough to overcome someone else on more aero wheels who was using tubulars which generally come in pretty far back on the rolling resistance tests.

Yes, it is often the case that tires make a bigger difference than aero wheels. In rough numbers, on flat ground tire rolling resistance is roughly 10-15% of total drag, and aerodynamics is roughly 80-85% of drag (the remaining few percent is mechanical drag, including the chain and bearings). Of the aero drag, the front wheel is roughly 5-10% the rear wheel is roughly 5%, the frame is roughly 5%, and the rider is roughly 80-85%.

However, since the rider is so much of both the total weight and the total drag, the rider makes the biggest difference in downhill coasting speed.

But getting back to wheels and tires, except at high speeds (say, 30+ mph), the tires make a bigger difference than the wheels. Additionally, wheel aerodynamics can be greatly reduced if tire shape doesn't match wheel shape (this is largely why aerowheels have been getting wider - to better match the shape of the tires that are commonly used). A advantages of a set of the fanciest aerowheels can largely negated by the tires if the tires have high rolling resistance or are poorly matched to the wheel shape.

A recently published study by Flo Cycling (http://flocycling.blogspot.com/2016/06/flo-cycling-a2-wind-tunnel-tire-study.html)comparing both the aerodynamics and rolling resistance of a range of tires when mounted on one of their aerowheels showed that the best tire may not be either the one with the least aero drag or rolling resistance, but the one with best combination of both.

[benb]

Just to clarify I'm running the 26c Specialized S-works Turbo which were listed at 32.8 watts @ 40km in the recent Velonews test. They were #3 in the rankings and only 1.2 watts behind first place which was a tubeless version which has a whole extra set of complications.

Where you really can't go wrong with these was the price. They are $55. And when I bought them in May Specialized was running a BOGO tire sale at all their dealers.. so they were essentially one of the cheapest sets of road tires I've run in a very long time. :banana:

Edit: Everyone was pretty much wearing the same kit last Saturday too since the ride mandated everyone wear the same jersey. I don't shave, maybe I should have. Haven't done that in 10+ years but maybe it would have been worth it for that long in the saddle. Lots of different helmets and shoes and stuff though.

[nooneline]

One thing I don't quite get.. there were cases I was pulling away from people who had aero wheels coasting down descents. You'd think the wheels would be too big of a difference there, and we're talking well over 30mph on those descents, over 40 on a lot of them. Not sure I think body position had a lot to do with it as everyone was kissing their stems and getting as low as possible. (My upper back still hurts today from doing so much of that.)

The reason that aero wheel tests are done with the same rider on the same course is that it reduces the number of variables.

Your tires are one variable separating you from riders on aero wheels coasting down descents. So is entry speed, fit of the kit, body weight, body position (even tucked, there are big differences in drag from different people's bodies).

You're not comparing aero wheels to not-aero wheels; you're not comparing aero wheels to tire rolling resistance - you're comparing completely different drag systems, of which wheel aerodynamics is one variable.

[oldguy00]

Really good point

Nobody has thought of it?

lol, its called a wind tunnel.. :)

http://cdn.coresites.factorymedia.com/rcuk/wp-content/uploads/2014/02/SwissSideWindTunnelFour.jpg

[Dead Man]

lol, its called a wind tunnel.. :)

http://cdn.coresites.factorymedia.com/rcuk/wp-content/uploads/2014/02/SwissSideWindTunnelFour.jpg

Oh... a motor set to 200w and a real rider riding for the purpose of demonstrating distance traveled for watts over a given time period is called "a wind tunnel."

Roger that.

[Hermes_Alex]

I do feel it's productive to illustrate for people in familiar and easily understandable terms what aero wheels mean for them. Wind tunnel results, regardless of one's ability to read them, do not elicit the same response as "this will make you X mph faster."

[oldguy00]

Oh... a motor set to 200w and a real rider riding for the purpose of demonstrating distance traveled for watts over a given time period is called "a wind tunnel."

Roger that.

Ah sorry, I did not realize that you didn't have the first clue as to how real aero testing is done on wheels. Roger that?

[benb]

The thing is the marketing copy on aero wheels based on wind tunnel tests makes it sound like anyone without them ought to be getting dropped big time.

[oldguy00]

The thing is the marketing copy on aero wheels based on wind tunnel tests makes it sound like anyone without them ought to be getting dropped big time.

I will agree that if you don't look closely at the numbers, and only stare at graphs specifically designed to make the differences look huge, yeah, you get sucked into the marketing.

If you want to see some good, up to date aero data, with estimates of how much time various depth wheels will save in a time trial (ie. not sitting in a pack), check out Flo Wheels website.
Aside from aerodynamics, there is also tire quality and tire pressure, both can make a few watts difference easily.

[false_Aest]

I definitely don't doubt the data but I can say this:


I'm finding that I'm just as fast on a set of Nemesis hoops as I was on a pair of 60mm CF Tubulars.

The difference is that I trust the Nemesis build (and tires) a hell of a lot more than I did the CF build. Confidence shouldn't be underestimated.

[benb]

That and the real world is full of complications and we know these aero carbon rims have compromises in braking, crosswind handling, and it sounds like sometimes in weight and/or rolling resistance if the wheel dictates certain tires be used.

[JStonebarger]

Worth noting, too, is that they're worth more the faster you're going:

@ 200w, 30.7kph to 33.1kph, a difference of 2.4kph
@ 300w, 36.4 kph to 39.6 kph, a difference of 3.2kph


Not really, or not for a set distance. At slower speeds you spend more time on the course... so a difference of 2.4kph (rather than 3.2kph) can save you even more time... Make sense?

[Dead Man]

Ah sorry, I did not realize that you didn't have the first clue as to how real aero testing is done on wheels. Roger that?

Ah... wife giving you the ol' blue-bawl treatment, eh? Yea, that ****'ll make you ornery. But I'm not your problem, bruh.

Let's do this in a neat orderly fashion.

Someone's all "we should test these wheels some other way than wind tunnels, 'cause that ****'s been done to death, and everyone acknowledges wind tunnel doesn't accurately simulate actually riding the bike."

Got it so far?

So then someone else is all "what if we did it on the velodrome and tried to control for rider variables with a power meter?" And some dudes were like, "yea, that might get closer to real-world results than the wind-tunnel, which we're wanting to move away from for this discussion, because it's not what we're looking for."

Still with me?

So then some other dude is like "why don't we just put a motor on the bike and set it to a specific wattage.... and roll that **** around the velodrome with a rider on it in rider position, to try to better simulate real-world conditions.... because the wind-tunnel tests don't do that very well. And we're trying to move away from wind-tunnel results, and get something different."

Ok? Oldguy00? Tracking?

Then you come along and suggest using a wind-tunnel? :rolleyes:

[Mark McM]

The thing is the marketing copy on aero wheels based on wind tunnel tests makes it sound like anyone without them ought to be getting dropped big time.

A good book:

https://images-na.ssl-images-amazon.com/images/I/51FKg7ecS%2BL._SY344_BO1,204,203,200_.jpg




And example from the book:

http://photos1.blogger.com/x/blogger/4986/984/1600/881425/Gee-Whiz_Graph.jpg




So, yes, if you don't have aerowheels, you might get dropped ... if you define dropped as being behind by a dozen feet.

[rnhood]

If someone drops you when you're riding box rim wheels, they will drop you when you're riding the latest hip aero wonder wheels.

[JStonebarger]

Ah... wife giving you the ol' blue-bawl treatment, eh? Yea, that ****'ll make you ornery. But I'm not your problem, bruh.

Let's do this in a neat orderly fashion.

Someone's all "we should test these wheels some other way than wind tunnels, 'cause that ****'s been done to death, and everyone acknowledges wind tunnel doesn't accurately simulate actually riding the bike."

Got it so far?

So then someone else is all "what if we did it on the velodrome and tried to control for rider variables with a power meter?" And some dudes were like, "yea, that might get closer to real-world results than the wind-tunnel, which we're wanting to move away from for this discussion, because it's not what we're looking for."

Still with me?

So then some other dude is like "why don't we just put a motor on the bike and set it to a specific wattage.... and roll that **** around the velodrome with a rider on it in rider position, to try to better simulate real-world conditions.... because the wind-tunnel tests don't do that very well. And we're trying to move away from wind-tunnel results, and get something different."

Ok? Oldguy00? Tracking?

Then you come along and suggest using a wind-tunnel? :rolleyes:

I won't speak for Oldguy00, but I wouldn't agree with much at all of what you wrote above. Granted, marketing copy can do a lot to "lie with statistics," but assuming you're savvy enough to see through that I'd suggest you stick to the wind tunnel.

[bostondrunk]

Ah... wife giving you the ol' blue-bawl treatment, eh? Yea, that ****'ll make you ornery. But I'm not your problem, bruh.

Let's do this in a neat orderly fashion.

Someone's all "we should test these wheels some other way than wind tunnels, 'cause that ****'s been done to death, and everyone acknowledges wind tunnel doesn't accurately simulate actually riding the bike."

Got it so far?

So then someone else is all "what if we did it on the velodrome and tried to control for rider variables with a power meter?" And some dudes were like, "yea, that might get closer to real-world results than the wind-tunnel, which we're wanting to move away from for this discussion, because it's not what we're looking for."

Still with me?

So then some other dude is like "why don't we just put a motor on the bike and set it to a specific wattage.... and roll that **** around the velodrome with a rider on it in rider position, to try to better simulate real-world conditions.... because the wind-tunnel tests don't do that very well. And we're trying to move away from wind-tunnel results, and get something different."

Ok? Oldguy00? Tracking?

Then you come along and suggest using a wind-tunnel? :rolleyes:

Haha, yup, thats the latest trend for getting REAL WORLD data, ride around a velodrome.........

OK.........riding around a velodrome in a fixed position, at a fixed wattage, may also be a valid aero test, but it is no more real world than a wind tunnel.

In the wind tunnel they can accurately control wind angles, exact speeds, etc.

Long story short, all these aero wheels can gain you speed, but its not (and never has been) speed that you can truly detect while riding along. Its usually a matter of a few watts, maybe 10-20 watts in the extreme. But that sort of gain does add up to a few minutes over longer TT's like 70.3 and Ironman events. Well, shorter TT's too obviously. Whether 20 seconds or so matters to you over a 40km TT, thats personal. It's not gonna make much difference in a pack situation or your local fatso weekend sprint to the donut shop.

Where's William?

[El Chaba]

I'll also point out that when the benefits of aero wheels are tested, they-necessarily- are tested with the bike alone...This measures the maximum effect...As soon as you are drafting the effect is greatly minimized.

[nooneline]

Not really, or not for a set distance. At slower speeds you spend more time on the course... so a difference of 2.4kph (rather than 3.2kph) can save you even more time... Make sense?

right! that's something that's often overlooked (and causes some confusion) - over a set distance, more time is saved by slower riders (because they're dealing with more time in the first place).

however, this test kept the time, not the distance, unchanged from test to test. when you eliminate the distance variable you get aerodynamics having a greater effect at faster speeds - since resistance increases exponentially with speed.

[benb]

I'm curious how many people here are doing TTs regularly.

I've never actually done one unless you were to get weird and count hillclimbs as TTs.

The slower rider might save more time but if you're not in a TT the slower riders might actually be drafting more if you're in an event. Maybe you're getting dropped and some aero benefit might help there but if you're getting dropped the game is probably already over.

If you're riding solo and not in a race at some point I'm not sure speed even matters that much, particularly for training since you can get the same training effects at different speeds with different equipment.

[nooneline]

The slower rider might save more time but if you're not in a TT the slower riders might actually be drafting more if you're in an event. Maybe you're getting dropped and some aero benefit might help there but if you're getting dropped the game is probably already over.

In my experience, road races always come down to a time trial at some point. Maybe it's a climb, maybe it's a crosswind, but if you're racing then at some point there will be an element of sustained power, even if you're (comparatively) well-sheltered in the pack. In crits, you're talking about frequent surges and jumps. I've hit my max speeds in crits not in sprints, but rather, chasing attacks at well over 60kph.

The benefit of aero wheels isn't when it just comes down to a w/cda contest, or a TT-type scenario. In many types of races (most, I'd say) there are race situations when aerodynamic wheels provide a non-negligible benefit.

[JStonebarger]

I TT regularly. In fact, I plan to train on my TT bike tonight.

I'm confident that the numbers don't lie and that aero wheels do indeed offer up free speed. Same with carefully chosen tires and latex tubes. There are even moments when I can feel it -- in a steady cross wind, for example.

Last weekend I did a two day tour with a lot of hills (TOMRV). One of my riding buddies -- 10 pounds heavier than me and a strong rider -- loves to tuck into a fast descent. But with box rims, relatively stiff tires, and butyl tubes he can't stay with me for long.

[El Chaba]

I don't doubt the benefits of truly aero wheels....or of many other equipment choices that optimize performance, and I have implemented many of them over the years. As opposed to drawing the conclusion that most of them are something that I can no longer live without, I usually have been somewhat let down by how unnoticeable the gains were. Our local world championship ride includes a number-or a majority- of riders who are convinced that they will be dropped without the latest equipment, including aero wheels. I have taken to showing up on occasion with something vintage....Most recently it was my old 1982 Peugeot with 32 spoke box section rims, exposed brake cables, 6v freewheel, etc. I am pleased to report that the old man was not dropped...

[steelbikerider]

Regardless of the test protocols, test conditions, etc., the numbers repeatedly come out that aero wheels are worth 1/2 - 1 mph in the 20 -30 mph range. A rider can hide in the pack, follow a good wheel, ride smart and do every thing possible to save watts but at some point in a race, that 1/2 - 1 mph can make a difference. If I'm racing, I would be on aero wheels, and would be on fast group rides if I had a pair.

[velomonkey]

I'm curious how many people here are doing TTs regularly.

I do them weekly on my road bike. For the past 2 years I've been getting 2nd in age group 40 and most of the riders have TT bikes.

My 50mm Bora wheels are faster. I've done the TT on my 32 spoke nemesis rims and my time was marginally different. As always there were other variables I couldn't account for - like wind and how I was feeling. I've done the course on my carbon bike and my ti bike. No difference.

Botton line all things being equal I'll grab the Bora 50mm wheels. Considering the difference I'd use my spoked wheels anytime and not complain.

One a side note: beating people who ride TT bikes, Aero wheels, shoe covers and aero helmets while you're on a road bike, regular helmet and sometimes spoked wheels is fun. If you have the means I highly suggest it.

To quote bike snob: Sucking at riding bikes is not measured in seconds, or even minutes. It's measured in an overall lack of accomplishment and an overarching narrative of suckitude that runs through your cycling career. You still suck balls, it's just now you suck balls on 12k bike.

[carpediemracing]

I've done A-B-A tests on my own with aero wheels. Actually it was more like A-B-C-D-E-F-G (rear only)-BG-CG-FG-A-AG. I did the second A to see how much my speed dropped over the course of my own test. I saw some big differences in speed, in a cross-tailwind, "optimal conditions for top speed" environment. I was also sorely disappointed to learn that my favorite wheels (A, B) were in fact much slower than wheels that I actually didn't like much at all (C, E, F). Also a rear disk (G) didn't do much for my top speeds, although it did improve the non-aero wheels by 1-2 mph.

After that I used either B or F in races, B for races where there'd be a lot of pace changes aka "accelerations" and F in races where I expected things to be strung out all the time. I avoided C and F because they were were pretty flexible. I knew they were faster but I couldn't get over how I hated them in turns. Later I'd use the rear F in many races, with the front G. That was a good compromise.

Nowadays I use some taller wheels, 75/90mm tall, U shaped, in virtually all wind conditions. Flat courses, max speeds are below 45 mph. if I was to go 45 mph or faster I'd consider my 45mm front to reduce wiggliness in wind.

At some point I'd like to repeat my test but I'm nowhere near as fit as I was back then. On the other hand I'd only have a few wheels to test, I'd call them H, I, and J. I still have the front C and both F wheels so the F could be my control. This time I'd have power and HR data, so I can look at stuff that I can't really touch/feel.

[nooneline]

CDR, are you familiar with Aerolab in Golden Cheetah?

You ride a set course with different gear - or in different body positions/setups. And then you do some fiddling to get it to extrapolate your cda, since it assesses your input power and your resulting speed over a set course with known elevation changes.

I'm told that it's sensitive enough, even used outdoors, to determine the aerodynamic benefits of small changes in arm position.

[MarkC]

There are a large number of serious time trialists out there. It's fun, challenging and relatively safe way to feed the competitive itch. I do around 20 TTs a season and have about 50 buddies doing the same. In New Jersey we have the NJBA TT Cup which is very popular.

Aerolab works well if you pay attention to details.

Best Bike Split also produces a good CdA model and some find the pacing charts helpful in maximizing performance.

A few years ago we introduced an "Eddy" class in our local TT series. It is by far the most popular group. I like that. Some guys who enjoy TT bikes are thinking of just going Eddy and not playing the pointy helmet, perseverate over aero gains game anymore. Its all good as long as folks are riding and enjoying.

-Mark

[beeatnik]

I don't doubt the benefits of truly aero wheels....or of many other equipment choices that optimize performance, and I have implemented many of them over the years. As opposed to drawing the conclusion that most of them are something that I can no longer live without, I usually have been somewhat let down by how unnoticeable the gains were. Our local world championship ride includes a number-or a majority- of riders who are convinced that they will be dropped without the latest equipment, including aero wheels. I have taken to showing up on occasion with something vintage....Most recently it was my old 1982 Peugeot with 32 spoke box section rims, exposed brake cables, 6v freewheel, etc. I am pleased to report that the old man was not dropped...

El Chaba, I like your mental fortitude style.

World Famous Montrose, 30th mile, 10% grade, 2nd wheel, 50 cats behind us. Not dropped, but it hurt 2x more than with the Bora 80s.

https://c7.staticflickr.com/8/7364/27374706230_abb49de4c3_c.jpg

https://farm2.staticflickr.com/1495/26592205356_502f85f65c_b.jpg

[carpediemracing]

CDR, are you familiar with Aerolab in Golden Cheetah?

You ride a set course with different gear - or in different body positions/setups. And then you do some fiddling to get it to extrapolate your cda, since it assesses your input power and your resulting speed over a set course with known elevation changes.

I'm told that it's sensitive enough, even used outdoors, to determine the aerodynamic benefits of small changes in arm position.

I learned of it I think here. I'm curious about it although right now I'd have to do laps at a race because that's really the only time I ride outside. Maybe a Tuesday I could do that.

First I have to figure out why my power/cadence keep dropping on my SRM. I have something funky, probably pick up alignment. New battery, new wire, double checked them both.

*edit I still think rotating weight is significant, esp when accelerating to close a gap, like out of a turn. I'd like to try and quantify that, meaning the work necessary to get/stay in the draft vs the savings of being in the draft. So a heavy wheel requires more power to accelerate so even if it's more aero it may not help because I can't stay on the wheel to actually draft. In the last lap of the race Tues I was going 29 mph, slowed to 22 mph for Turn 2, accelerated to 37 for Turn 3, slowed to 22 in that turn, and accelerated to 34 mph exiting Turn 3. I stopped accelerating because no need to go any faster. This all happened in about 30 seconds. So a lot of acceleration involved, and I'd have had to accelerate more had people stayed on my wheel approaching the final turn, Turn 3. I wonder how a 3 lbs heavier wheelset would have done in the same situation. My similarly aero training wheels (60/90mm training, 75/90mm racing) are 3 lbs heavier, basically same hubs/spokes/cassette so the weight is at the rim/tire area. Since I'm typically racing at my limits it would make a difference if I saved 50 or 100w accelerating out of a turn.

[Mark McM]

*edit I still think rotating weight is significant, esp when accelerating to close a gap, like out of a turn. I'd like to try and quantify that, meaning the work necessary to get/stay in the draft vs the savings of being in the draft. So a heavy wheel requires more power to accelerate so even if it's more aero it may not help because I can't stay on the wheel to actually draft. In the last lap of the race Tues I was going 29 mph, slowed to 22 mph for Turn 2, accelerated to 37 for Turn 3, slowed to 22 in that turn, and accelerated to 34 mph exiting Turn 3. I stopped accelerating because no need to go any faster. This all happened in about 30 seconds. So a lot of acceleration involved, and I'd have had to accelerate more had people stayed on my wheel approaching the final turn, Turn 3. I wonder how a 3 lbs heavier wheelset would have done in the same situation. My similarly aero training wheels (60/90mm training, 75/90mm racing) are 3 lbs heavier, basically same hubs/spokes/cassette so the weight is at the rim/tire area. Since I'm typically racing at my limits it would make a difference if I saved 50 or 100w accelerating out of a turn.

You can get some calculated estimates on power/speed differences with different wheels at www.analyticcycling.com (http://www.analyticcycling.com/QCHome_Page.html). Here is their analysis of a criterium corner acceleration (http://www.analyticcycling.com/WheelsCritCorner_Page.html).

3 lb. of wheel weight difference may seem like a lot, but it is still relatively small compared to total bike/rider mass. Let's say that the total bike/rider mass was 170 lb., and that you are accelerating at constant 600 Watts. If the extra 3 lb. were at the periphery of the wheel, than the effective added inertia would be 6 lb. That's about 3.5% of the total. However, at the speed range in question, about 300 Watts is used up fighting aero drag, so that leaves only 300 Watts left over for acceleration. For the same acceleration with 3.5% greater inertia, you'd have to produce about 3.5% more accelerating power, or about 10.5 Watts.

It is important to realize that the accelerating power is not the power applied by the rider (the gross power) - it is the power applied by the rider minus the drag power (the net power after subtracting the aero power, the rolling resistance power, etc.). Anything that decreases drag power will increase the accelerating power. Many aero wheels are much less than 3 lb. heavier than non-aero wheels. In these cases, the reduction in aero drag can be larger than the increases in inertia, resulting in faster accelerations with the aero wheels, even though they are heavier.