Carbon Wheels Tradeoff

[CAAD8FRED]

That's why I am asking what he is trying to achieve. A one time effort to get a PR would be different than many hours of climbing were wheel weight would matter more (100g not that much though).

I don’t do much climbing, I was asking more to hear see if anyone had any experiences with a tradeoff.

[CAAD8FRED]

I had scarier crosswind experiences with my 20mm shallow boxy alloy rims than I have had on my 88mm carbon toroidal rims.

The rim shape has a lot to do with crosswind stability. I was very cautious going deeper because of what people write. Looking back I think that was exaggerated. However it successfully brought my attention to side winds.

So running a U or U/V shape hybrid rim is best at combatting crosswind in your experience?

[Beaver]

The Reynolds tear drop shape is the most stable in crosswinds.

And maybe also interesting: German Mag. RennRad, in cooperation with SwissSide, tested a standard racing bike with flat rims vs. an aero bike with high rims. The additional weight was 1 kg.

"The limit slope is the percentage slope above which the one kilogram lighter mountain road bike has advantages over the aero road bike, here we calculated the limit slope and resulting speeds for three realistic performances: 200, 250 and 350 watts."

At 200 watts it was from 3.9% slope and higher, at 250 watts from 4.4% and at 350 watts from 5.7%. Cannondale stated similar gradients for their SystemSix vs. SuperSix.

Time savings: At 200 watts for 10km slope with 6% it is 20 seconds, at 10% slope 45 seconds.

[bm0p700f]

If you can have aero and light though you have a winner.

[alcatraz]

The Reynolds tear drop shape is the most stable in crosswinds.

And maybe also interesting: German Mag. RennRad, in cooperation with SwissSide, tested a standard racing bike with flat rims vs. an aero bike with high rims. The additional weight was 1 kg.

"The limit slope is the percentage slope above which the one kilogram lighter mountain road bike has advantages over the aero road bike, here we calculated the limit slope and resulting speeds for three realistic performances: 200, 250 and 350 watts."

At 200 watts it was from 3.9% slope and higher, at 250 watts from 4.4% and at 350 watts from 5.7%. Cannondale stated similar gradients for their SystemSix vs. SuperSix.

Time savings: At 200 watts for 10km slope with 6% it is 20 seconds, at 10% slope 45 seconds.

I suspect that the teardrop wins because when compared to other rim shapes it's effectively shallower at a given depth. Not as much volume in it, which I think also is the reason it acts like a shallower rim when it comes to drag/crosswinds.

A bit like hanging a strip of 70mm paper off a 30mm rim and saying it's a 100mm rim.

What do you think? Is this all jibberish?

[CAAD8FRED]

Also, the Knøt 64 wheels on the new SystemSix have a rim that is wider than the tire. I wonder if the exposed rim is better in crosswinds?

Another interesting point I’ve heard is running a shallower depth on the front and a wider on the back to get the aero benefit without the crosswind cons.

[robertbb]

So if you're an average joe putting out 200 watts, a 1kg lighter bike nets you 20 seconds time improvement on a 10k climb @ 6%. So a 500g lighter bike might net you 10 seconds.

The more power you put out, the gradient has to be *steeper* for you to realise a benefit.

Well that's that. We should rename the site Aeroweenies.

[alcatraz]

Also, the Knøt 64 wheels on the new SystemSix have a rim that is wider than the tire. I wonder if the exposed rim is better in crosswinds?

Another interesting point I’ve heard is running a shallower depth on the front and a wider on the back to get the aero benefit without the crosswind cons.

I and Beaver both think that you need a wider rim than the tire to be crosswind stable. Think of an airplane wing.

I'm pretty sure it's so that you move the pressure point of the wind away from the ends of the rim and more towards the middle. That creates a more organic shape that lets the side wind split and go both over and under the rim without as much disturbance in wind speed. That means less turbulence and vacuum.

[alcatraz]

Well that's that. We should rename the site Aeroweenies.

I'm still a weight weenie. I'm just tired to get my ass kicked by heavier bikes. Gotta give aero some respect as well.

[zefs]

I did the same route (same weather conditions) with 50mm carbon wheels (1750g) vs 23mm alu wheels (1500g) and the average speed/heart rate/watts came out the same. At those speeds and elevation they weren't faster for me and I sold them since all my rides have that kind of elevation. Not sure how their results are a few seconds only on a 10km 6% climb with 1kg difference on setups.

carbon

alu

[addictR1]

69Kg here and i ride with Reynolds Aero 72 rear and 46 front tubs. climbing with it on over 10% is a PITA. times like that i wish i was riding on my Addict with C24 tubs

[alcatraz]

I did the same route (same weather conditions) with 50mm carbon wheels (1750g) vs 23mm alu wheels (1500g) and the average speed/heart rate/watts came out the same. At those speeds and elevation they weren't faster for me and I sold them since all my rides have that kind of elevation. Not sure how their results are a few seconds only on a 10km 6% climb with 1kg difference on setups.


carbon.jpg
alu.jpg

That's weird. What about wind in those two rides? Was the bike otherwise equivalent?

[zefs]

The wind was the same as well as the bike (only changed the wheels).

[Beaver]

Also, the Knøt 64 wheels on the new SystemSix have a rim that is wider than the tire. I wonder if the exposed rim is better in crosswinds?

Another interesting point I’ve heard is running a shallower depth on the front and a wider on the back to get the aero benefit without the crosswind cons.

I and Beaver both think that you need a wider rim than the tire to be crosswind stable. Think of an airplane wing.

I'm pretty sure it's so that you move the pressure point of the wind away from the ends of the rim and more towards the middle. That creates a more organic shape that lets the side wind split and go both over and under the rim without as much disturbance in wind speed. That means less turbulence and vacuum.

The 32mm wide Knøt 64 and Hunt's new 23C 35.5mm wide rim (for 28mm tires) will be great in the wind tunnel but prone to crosswinds. They cause less drag, but the airflow seems to get compressed at the the wind faced side.



The lower volume shouldn't cause this, rather the shape.

69Kg here and i ride with Reynolds Aero 72 rear and 46 front tubs. climbing with it on over 10% is a PITA. times like that i wish i was riding on my Addict with C24 tubs

And that's the hitch, that shape is heavier than the others.

[CAAD8FRED]

Hey Beaver,

What is the lowest crosswind wheel you’ve seen in your research?

Rob