technical information & FAQ
Q. Is it true that you have to be riding above 20mph for aero wheels to make a difference?
A. The faster you go, the more power you produce. Efficient use of this power depends on how good your aerodynamics are. The time savings provided by aero wheels are always going to be proportional to the power of the rider. It doesn't matter whether you produce 300 watts or 150 watts. In fact, slower riders may not be going at the same speed as faster ones, but aero wheels actually save them an even greater amount of time over the same distance. The only exception is on hills, where speeds slower than about 14mph aren't sufficient to compensate for the aero wheel weight disadvantage.
Q. Can certain wind angles push a rider along?
A. Think of a guy in a rowing boat, using X amount of power to move along. Then erect a sail the size of a disc wheel. The surface area of this sail isn't enough to propel him without rowing as well, but it will make the rowing feel easier. This is how a disc wheel works at beneficial wind angles. You can't stop pedaling, but it does feel easier.
Q. I can only afford one wheel, so which should it be?
A. The front wheel breaks the wind first, so this is the most important of the two. In certain conditions, a front wheel will save twice as much as the rear. However, it also depends on the model of wheel, because a rear disc will provide at least as much performance as any other aero design on the front.
Q. Is aerodynamic performance more important than weight savings?
A. Let's look at a few figures. Assume a rider uses a conventional bike over a 25-mile flat course time trial. He weighs 150lb, his bike is another 20lb, and he is producing 185 watts of power. The aero drag with this scenario would be approximately 6.5lb using aero bars into a 2mph headwind of between 0 and 5 degrees. With his standard bike, our rider's time would be around 1 hour 7 minutes and 38 seconds. If we reduced the weight of his bike by three pounds, that time would come down by just 3 seconds. However, swap the wheels to an aero design and the drag could be reduced to 6lb. Even with the additional quarter pound weight of the new wheels, his time saving over 25 miles jumps dramatically to over 1 minute 30 seconds. No contest.
Q. Are deep rim aero wheels difficult to true?
A. Soft structure carbon rims in the HED range all feature full length spokes. Once you remove the tire, they true up just like an ordinary bike wheel. Hard structure rims, like the CX, are different. They have shorter spokes pulling directly against the carbon section. However, these are taken from molds with incredibly close tolerance accuracy, so the intrinsic wheel structure of a HED wheel twice the level where a conventional wheel would need to be trued. HED three spoke wheels are built to even closer tolerances, four times the level where truing would become necessary.
Q. How much time could I save in a 25-mile time trial by switching to aero rims?
A. It depends on the wheels. Using our 150lb test rider in an aero tuck as a model, switching to aero wheels will typically save between 1 minute 30 seconds and 2 minutes over a flat 25-mile course. Using a Deep front and Disc rear, two minutes is a realistic figure. At the other end of the scale, using a pair of J2s would be worth a saving of 1 minute.
Q. If I smash one of the alloy rims on a HED wheel, can a new rim be bonded to the carbon?
A. No, however, we will repair or replace the damaged wheel for less than the cost of a new one.
Q. How do I fix a computer magnet to a H3 front wheel?
A. The majority of cycle computers come with spoke magnets, although some also have adhesive backing on one side. The latter variety is preferable, because the magnet requires sticking to one of the H3's aerofoil blades. It may need building up slightly in order to achieve correct alignment with the receiver on the fork.
Q. How do I install my HED valve extensions?
A. Click here to view instructions (PDF format - opens in a new window)
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