Tell me I'm wrong: Aero wheels have very limited advantage
Discussion
Hi everyone,
For anything other than a time trial bike, why would you choose aero wheels (40mm to 90mm profiles) given that for the same money you can have very lightweight aluminium rims with high quality hubs?
I see the facts as follows:
1) A highly rated wheel manufacturer of 86mm section wheels has claimed that over a 40km time trial up to 1 min 20 seconds can be shaved off compared to a run of the mill box section rim - so the gain is minimal outside of TT speeds and/or competition
2) Low profile aluminum rims are less susceptible to crosswinds and have a reputation for having better braking characteristics
3) Aluminium rims are lighter and therefore better for hill climbing
So now for the fun part - I want you all to try and prove me wrong. Whether that's with subjective or objective evidence is up to you.
For anything other than a time trial bike, why would you choose aero wheels (40mm to 90mm profiles) given that for the same money you can have very lightweight aluminium rims with high quality hubs?
I see the facts as follows:
1) A highly rated wheel manufacturer of 86mm section wheels has claimed that over a 40km time trial up to 1 min 20 seconds can be shaved off compared to a run of the mill box section rim - so the gain is minimal outside of TT speeds and/or competition
2) Low profile aluminum rims are less susceptible to crosswinds and have a reputation for having better braking characteristics
3) Aluminium rims are lighter and therefore better for hill climbing
So now for the fun part - I want you all to try and prove me wrong. Whether that's with subjective or objective evidence is up to you.
BeirutTaxi said:
Hi everyone,
For anything other than a time trial bike, why would you choose aero wheels (40mm to 90mm profiles) given that for the same money you can have very lightweight aluminium rims with high quality hubs?
I see the facts as follows:
1) A highly rated wheel manufacturer of 86mm section wheels has claimed that over a 40km time trial up to 1 min 20 seconds can be shaved off compared to a run of the mill box section rim - so the gain is minimal outside of TT speeds and/or competition
2) Low profile aluminum rims are less susceptible to crosswinds and have a reputation for de having better braking characteristics
3) Aluminium rims are lighter and therefore better for hill climbing
So now for the fun part - I want you all to try and prove me wrong. Whether that's with subjective or objective evidence is up to you.
You’re wrong. For anything other than a time trial bike, why would you choose aero wheels (40mm to 90mm profiles) given that for the same money you can have very lightweight aluminium rims with high quality hubs?
I see the facts as follows:
1) A highly rated wheel manufacturer of 86mm section wheels has claimed that over a 40km time trial up to 1 min 20 seconds can be shaved off compared to a run of the mill box section rim - so the gain is minimal outside of TT speeds and/or competition
2) Low profile aluminum rims are less susceptible to crosswinds and have a reputation for de having better braking characteristics
3) Aluminium rims are lighter and therefore better for hill climbing
So now for the fun part - I want you all to try and prove me wrong. Whether that's with subjective or objective evidence is up to you.
1. Your own point proves deep section wheels are faster. Do you really think they cease to be faster if you use a different frame? Of course not.
2. Crosswind susceptibility depends on the profile of the rim and the width of the spokes. But crosswinds won’t slow you down. Braking will though, and as you point out, aluminium rims are better at slowing down. That doesn’t mean they are better at going fast.
3. Alu rims are generally heavier than aero carbon rims.
Surely it depends on the route and conditions.
Riding a hilly route where you get open sections where gusts and crosswords come in to play would be easier with low profile lighter rims.
Riding a flatter, faster sheltered route would be better with aeros.
Don't think it matters all that much unless your racing.
You may get a slightly better Strava time.
Sure watching weather and wind speed/ direction will have more impact on PB's.
Riding a hilly route where you get open sections where gusts and crosswords come in to play would be easier with low profile lighter rims.
Riding a flatter, faster sheltered route would be better with aeros.
Don't think it matters all that much unless your racing.
You may get a slightly better Strava time.
Sure watching weather and wind speed/ direction will have more impact on PB's.
You're wrong, and right...
Let's ignore aero for a minute and focus on the box rims. The advantage of light weight is vastly, vastly over-rated, possibly even more so than aero. It only helps when going up hills (and relatively steep ones at that), doesn't help coming down or on the flat. Someone reckoned at 10% the average rider is using 90% of their power to counter weight/gravity.
If that's true, and I'm climbing at 250w, 25 go to 'miscellaneous', and 225 go to overcoming weight.. of about 90kg - if we say an 8kg bike and a 82kg Mark. 2.5 watts per kg of weight. 20 watts for the bike, 205 for me. Shed 100 grams, need .25watts less (whoop!).. Stick a litre of water on the bike, need 2.5 more.. have a decent dump, 2w less.. you get the idea.
Also, the rotational weight argument is nonsense.. they may spin up a tiny bit slower, but they'll also spin down commensurately slower.. and anyway, you're accelerating (say) 90kg of bike and rider. It may feel big when you spin it in your hands, but with all that blubber sat on the bike, the angular velocity change at the wheel is consequently so small to be insignificant.
Then the aero thing. No, it doesn't only matter at high speed. The gain may be bigger at a higher speed, but at a lower speed you're taking the smaller gain for longer (assuming a course of specified length), and actually get more time advantage than the speedy guy/girl.
The crosswinds? It'd have to be blowing people over in the street before it's going to trouble a 50mm rim under my fat a**e, who cares
Of course the real answer is that in most cases when people buy either a light wheel, OR an aero wheel, they're making a significant upgrade from the POS that came whith the bike that was neither light, nor aero, and has square bearings lubricated with mud. Therefore whatever you buy is going to feel like a significant leap forwards.
https://www.cervelo.com/en/engineering-field-notes... puts some numbers on the debate.. albeit from the frame side.
So.. you're wrong in the implied suggestion that going light would be *more* advantageous.
But you're also right because the other real answer is that ALL upgrades have very limted advantage.
There's always that one guy that turns up on a battered POS, and rides the wheels off all the egos on expensive bikes that have all the 'right' kit.. go figure!
ETA.. Oh yeah, and my aero wheels have alu rims (HED).. they stop just fine!
Let's ignore aero for a minute and focus on the box rims. The advantage of light weight is vastly, vastly over-rated, possibly even more so than aero. It only helps when going up hills (and relatively steep ones at that), doesn't help coming down or on the flat. Someone reckoned at 10% the average rider is using 90% of their power to counter weight/gravity.
If that's true, and I'm climbing at 250w, 25 go to 'miscellaneous', and 225 go to overcoming weight.. of about 90kg - if we say an 8kg bike and a 82kg Mark. 2.5 watts per kg of weight. 20 watts for the bike, 205 for me. Shed 100 grams, need .25watts less (whoop!).. Stick a litre of water on the bike, need 2.5 more.. have a decent dump, 2w less.. you get the idea.
Also, the rotational weight argument is nonsense.. they may spin up a tiny bit slower, but they'll also spin down commensurately slower.. and anyway, you're accelerating (say) 90kg of bike and rider. It may feel big when you spin it in your hands, but with all that blubber sat on the bike, the angular velocity change at the wheel is consequently so small to be insignificant.
Then the aero thing. No, it doesn't only matter at high speed. The gain may be bigger at a higher speed, but at a lower speed you're taking the smaller gain for longer (assuming a course of specified length), and actually get more time advantage than the speedy guy/girl.
The crosswinds? It'd have to be blowing people over in the street before it's going to trouble a 50mm rim under my fat a**e, who cares
Of course the real answer is that in most cases when people buy either a light wheel, OR an aero wheel, they're making a significant upgrade from the POS that came whith the bike that was neither light, nor aero, and has square bearings lubricated with mud. Therefore whatever you buy is going to feel like a significant leap forwards.
https://www.cervelo.com/en/engineering-field-notes... puts some numbers on the debate.. albeit from the frame side.
So.. you're wrong in the implied suggestion that going light would be *more* advantageous.
But you're also right because the other real answer is that ALL upgrades have very limted advantage.
There's always that one guy that turns up on a battered POS, and rides the wheels off all the egos on expensive bikes that have all the 'right' kit.. go figure!
ETA.. Oh yeah, and my aero wheels have alu rims (HED).. they stop just fine!
Edited by upsidedownmark on Friday 31st August 01:02
Greg66 said:
You’re wrong.
1. Your own point proves deep section wheels are faster. Do you really think they cease to be faster if you use a different frame? Of course not.
But at 25 mph on carbon 86mm rims you will save 0.4mph average over alu rims - For normal road bike users at lower speeds, on a more hilly course and with Peugeot drivers getting in the way, the benefit is obviously going to be a fair bit less (to the point where the gain is negligible)1. Your own point proves deep section wheels are faster. Do you really think they cease to be faster if you use a different frame? Of course not.
Some good stuff on this on the FLO cycling blog pages.
They did testing and modelling that IIRC showed that light weight only trumped aero if you were doing hour long alpine climbs.
They compared a heavy training wheel to a lightweight non-aero climbing wheel, then deeper section rims in turn.
http://flocycling.blogspot.com/2014/01/flo-cycling...
They did testing and modelling that IIRC showed that light weight only trumped aero if you were doing hour long alpine climbs.
They compared a heavy training wheel to a lightweight non-aero climbing wheel, then deeper section rims in turn.
http://flocycling.blogspot.com/2014/01/flo-cycling...
Hambini has been doing some independent drag testing for wheels - weekend access to a fancy wind tunnel is handy!
With a 10 page discussion on WW
His YouTube has good some content for lunch time learning eg
https://www.youtube.com/watch?v=BUih_emc54M
I think it's this video when he is less than complimentary about Zipp's marketing on the dimpled rim surface. He's also got some interesting tests on ceramic vs steel bearings in bikes.
Hambini said:
For my full time job I am an Aeronautical engineer and head of Aerothermal Engineering for a large jet engine manufacturer.
https://www.hambini.com/blog/post/bicycle-wheel-aerodynamics-which-one-is-fastest/With a 10 page discussion on WW
His YouTube has good some content for lunch time learning eg
https://www.youtube.com/watch?v=BUih_emc54M
I think it's this video when he is less than complimentary about Zipp's marketing on the dimpled rim surface. He's also got some interesting tests on ceramic vs steel bearings in bikes.
Quite a timely thread as there is a big discussion on Weight Weenies following some analysis that has been completed by a bunch of aero engineers. They did a range of transient testing to try and average the aero efficiency of a number of wheelsets, rather than testing them to specific protocol like many of the manufacturers do, i.e. specific yaw angle at a specific speed.
The results are interesting, at 30km/h an 88mm wheel can save you 17 watts versus a box section alloy rim:
But it's also interesting that wheels like Hunt are pretty much pointless because there are flaws in the rim profile that make them aero-dynamically unstable!
The difference, as you allude to, at TT speeds is much bigger at 57 watts
The results are interesting, at 30km/h an 88mm wheel can save you 17 watts versus a box section alloy rim:
But it's also interesting that wheels like Hunt are pretty much pointless because there are flaws in the rim profile that make them aero-dynamically unstable!
The difference, as you allude to, at TT speeds is much bigger at 57 watts
Harpoon said:
https://www.hambini.com/blog/post/bicycle-wheel-aerodynamics-which-one-is-fastest/
With a 10 page discussion on WW
His YouTube has good some content for lunch time learning eg
https://www.youtube.com/watch?v=BUih_emc54M
I think it's this video when he is less than complimentary about Zipp's marketing on the dimpled rim surface. He's also got some interesting tests on ceramic vs steel bearings in bikes.
With a 10 page discussion on WW
His YouTube has good some content for lunch time learning eg
https://www.youtube.com/watch?v=BUih_emc54M
I think it's this video when he is less than complimentary about Zipp's marketing on the dimpled rim surface. He's also got some interesting tests on ceramic vs steel bearings in bikes.
great mindsHarpoon said:
https://www.hambini.com/blog/post/bicycle-wheel-aerodynamics-which-one-is-fastest/
With a 10 page discussion on WW
His YouTube has good some content for lunch time learning eg
https://www.youtube.com/watch?v=BUih_emc54M
I think it's this video when he is less than complimentary about Zipp's marketing on the dimpled rim surface. He's also got some interesting tests on ceramic vs steel bearings in bikes.
The linked page is really interesting, thanks!With a 10 page discussion on WW
His YouTube has good some content for lunch time learning eg
https://www.youtube.com/watch?v=BUih_emc54M
I think it's this video when he is less than complimentary about Zipp's marketing on the dimpled rim surface. He's also got some interesting tests on ceramic vs steel bearings in bikes.
Matt_N said:
great mindsAfter Hambini mentioned Reynolds Numbers in one video or post, I went off to Wiki to read more but it made my head hurt too much, so had to stop!
Harpoon said:
Indeed. I've got some 50mm deep carbon clinchers on order which I was wondering about offering for test, but they are disc not rim brake. I'm also dead keen to ride them once they arrive!
After Hambini mentioned Reynolds Numbers in one video or post, I went off to Wiki to read more but it made my head hurt too much, so had to stop!
Takes me back to me uni days and Fluids lectures, turbulent and laminar flow, not a great time After Hambini mentioned Reynolds Numbers in one video or post, I went off to Wiki to read more but it made my head hurt too much, so had to stop!
BeirutTaxi said:
Surely this isn't the case £ for £? and matching quality? E.g. I can get a 1.4kg Shamal Millie with carbon hubs for £800 - I can't think of any carbon wheels that can match that?
Not off the shelf but you could spec up something marginal lighter and more aero quite easily, with decent hubs and bearing and normal spokes.DT350 hubset ~£200
2x carbon rims from LightBike ~£400
44x Sapim CX-Ray ~£100
Build cost ~£100
As well as the aero and weight benefit, the bearings are easily replaceable, spokes any shop will carry (try getting a Campag spoke pack) and once the rim is worn (which will be a long time past the alloy rim on the Shamals) you simply lace a new rim on. Try and get a new rim for those Shamals once they're worn.
BeirutTaxi said:
Greg66 said:
You’re wrong.
1. Your own point proves deep section wheels are faster. Do you really think they cease to be faster if you use a different frame? Of course not.
But at 25 mph on carbon 86mm rims you will save 0.4mph average over alu rims - For normal road bike users at lower speeds, on a more hilly course and with Peugeot drivers getting in the way, the benefit is obviously going to be a fair bit less (to the point where the gain is negligible)1. Your own point proves deep section wheels are faster. Do you really think they cease to be faster if you use a different frame? Of course not.
BeirutTaxi said:
Greg66 said:
You’re wrong.
3. Alu rims are generally heavier than aero carbon rims.
Surely this isn't the case £ for £? and matching quality? E.g. I can get a 1.4kg Shamal Millie with carbon hubs for £800 - I can't think of any carbon wheels that can match that? 3. Alu rims are generally heavier than aero carbon rims.
If your point is really "would deep section carbon rims be a better bet that Shamal Milles?" then that's a different conversation altogether.
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