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How effective is the rear aero wheel?

6K views 13 replies 8 participants last post by  AJS 
#1 ·
At a given price point, aero wheels are significantly heavier than standard wheels. But it seems that a rear wheel benefits less from the aero profile because it's behind the downtube and rider's 100 mm wide legs, and between the seat- and chain-stays. I mean, is there a worthwhile benefit to having an aero rear wheel?

I know it'll look funny, but wouldn't a good comprise be a reasonably light aero (30+ mm) front wheel and a light and durable rear wheel? This setup would be for all around group rides and Cat 4 road/crit races.
 
#3 ·
NoMSG said:
At a given price point, aero wheels are significantly heavier than standard wheels. But it seems that a rear wheel benefits less from the aero profile because it's behind the downtube and rider's 100 mm wide legs, and between the seat- and chain-stays. I mean, is there a worthwhile benefit to having an aero rear wheel?

I know it'll look funny, but wouldn't a good comprise be a reasonably light aero (30+ mm) front wheel and a light and durable rear wheel? This setup would be for all around group rides and Cat 4 road/crit races.
Much of the benefit of aerowheels comes from less resistance from moving the wheels around (spokes generate a lot of turbulence - spin your rear wheel fast on a bike stand, and feel the wind) rather than through the air.
 
#4 ·
Yeah, but...

AJS said:
I've thought of that set up before too, but then you have TT'ers riding rear discs and 38-50mm fronts, so...:confused:
...time trialers don't have to worry much about weight. Any marginal increase in the aerodynamics for the rear wheel would help. Front discs aren't feasible for them due to wind and handling problems.
 
#5 ·
Then, bladed rear spokes is the solution? nm.

jumpstumper said:
Much of the benefit of aerowheels comes from less resistance from moving the wheels around (spokes generate a lot of turbulence - spin your rear wheel fast on a bike stand, and feel the wind) rather than through the air.
nnnnnmmmm
 
#6 ·
NoMSG said:
At a given price point, aero wheels are significantly heavier than standard wheels. But it seems that a rear wheel benefits less from the aero profile because it's behind the downtube and rider's 100 mm wide legs, and between the seat- and chain-stays. I mean, is there a worthwhile benefit to having an aero rear wheel?

I know it'll look funny, but wouldn't a good comprise be a reasonably light aero (30+ mm) front wheel and a light and durable rear wheel? This setup would be for all around group rides and Cat 4 road/crit races.
at Cat4 it's not an issue at all- focus on training.

It's debatable if a spoked aero rear wheel is significant even in pro TT events, since the turbulence from a rider's legs probably is much greater than any wheel design, although on high end frames you'll see a "fin" that provides a marginal increase in aerodynamics. note, it's VERY marginal and a stronger rider will win either way.

[edit] to clarify- a disc wheel probably is best since it breaks turbulence (due to the solid wheel acting as a continuous surface). Still, unless you're in the upper eschelon it's better to focus on technique and training rather than equipment.
 
#7 ·
NoMSG said:
...time trialers don't have to worry much about weight. Any marginal increase in the aerodynamics for the rear wheel would help. Front discs aren't feasible for them due to wind and handling problems.
I know that. I was just throwing out the other side of the argument.
 
#8 ·
The test results in the picture below show that an aero rear wheel ist at least as important as an aero front wheel.
Although there are only two combinations of aero front wheel with standard rear wheel tested, I believe the tendency is clear.

The test comes from a German bike magazine, so here are some explanations:
Scheibenräder means disc wheels,
VR means front wheel,
HR means rear wheel
 
#9 ·
jumpstumper said:
Much of the benefit of aerowheels comes from less resistance from moving the wheels around (spokes generate a lot of turbulence - spin your rear wheel fast on a bike stand, and feel the wind) rather than through the air.
no, most of the benefit comes from the way the air moves over the rim - does it separate cleanly from the rim. yes, the spokes have an effect, but it's less than rim depth and shape. if you were right, a 16-spoke am classic 420 would be more aero than an 18 spoke zipp 404. even a 32-spoke zipp 404 would be more aero.
 
#10 ·
NoMSG said:
At a given price point, aero wheels are significantly heavier than standard wheels. But it seems that a rear wheel benefits less from the aero profile because it's behind the downtube and rider's 100 mm wide legs, and between the seat- and chain-stays. I mean, is there a worthwhile benefit to having an aero rear wheel?

I know it'll look funny, but wouldn't a good comprise be a reasonably light aero (30+ mm) front wheel and a light and durable rear wheel? This setup would be for all around group rides and Cat 4 road/crit races.
try out an aero wheel on your turbo trainer and you will feel the difference - i can hold 100rpm in a 53/11 for several minutes using my shamals yet i can barely get to that cadence in the same gear on my mavic cosmos whilst on my turbo. you have to remember that when the wheel is turning it still has to cut through the air regardless of whether it is hidden behind you and the rest of your bike. my 10 mile TT times ussually differ by over a minute when using shamals as opposed to mavic cosmos. and as for the weight issue i dont think that there is 20 grams difference in weight between the two wheel sets. i have to admit though that the mavics cost £130 ($260ish) and the shamals cost £300 ($600ish). aero wheels definately make a difference and only come behind tri-bars in terms of making you faster aerodynamically.
 
#11 ·
poshscot said:
try out an aero wheel on your turbo trainer and you will feel the difference - i can hold 100rpm in a 53/11 for several minutes using my shamals yet i can barely get to that cadence in the same gear on my mavic cosmos whilst on my turbo. you have to remember that when the wheel is turning it still has to cut through the air regardless of whether it is hidden behind you and the rest of your bike. my 10 mile TT times ussually differ by over a minute when using shamals as opposed to mavic cosmos. and as for the weight issue i dont think that there is 20 grams difference in weight between the two wheel sets. i have to admit though that the mavics cost £130 ($260ish) and the shamals cost £300 ($600ish). aero wheels definately make a difference and only come behind tri-bars in terms of making you faster aerodynamically.

And from every test I've ever seen, Shamal's were one of the fastest 'conventionally spoked' wheelsets ever made, if not THE fastest, at least compared to their peers of the time. They've beaten HED's Zipp's Lew's, etc. and I believe the Bora's were the only faster wheels.

Most anecdotal evidence such as your experience suggests the same.

:( I sure do miss my set! Wish Campy still made them. :(
 
#12 ·
analytic cycling

Go to analyticcycling.com you can enter parameters to your heart's content. Looking at their models, it's amazing how little weight matters, even when it is rotating weight.

For road racing you should be on a wheel 99% of the time, so even aerodynamics effects are negligable. But race wheels do 'feel' faster, so, even if it's placebo, since road racing is mostly mental, it' still a bit of an advantage.
 
#13 ·
weiwentg said:
no, most of the benefit comes from the way the air moves over the rim - does it separate cleanly from the rim. yes, the spokes have an effect, but it's less than rim depth and shape. if you were right, a 16-spoke am classic 420 would be more aero than an 18 spoke zipp 404. even a 32-spoke zipp 404 would be more aero.
We were talking about fully covered wheels vs. spoked wheels, read the post again.
 
#14 ·
Rim dimensions are important, but too many spokes beating the air certainly doesn't help. It's known that generally much more effort is expended on a bike overcoming aerodynamics at higher speeds than the effort to haul the weight, so even small reductions in drag are good, and are cumulative.

IMHO, a wheel has no contention to being "aero" if it has more spokes than 24 R/20 F no matter what the rim is. It's just where I arbitrarily draw the line.
 
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