from RoadBikeRider, tips on aero wheels


6. JIM'S TECH TALK — Mechanical & Product Advice

News & Views From The World of Wheels
I know we talk a lot about wheels, but there’s a good reason. Apart from a road bike’s frame, no other component influences the ride and performance more than the wheels. That’s because they’re what you have to get moving to fly down the road. And it’s why we’ve seen such incredible changes in the average pair on modern bicycle wheels, and how they’ve become probably the most popular upgrades, too.

Because they make such a difference in ride quality, and because I race, I try to keep up on the latest technology and ride the best ones, too. I’d like to share a couple of recent wheel experiences that I found interesting and will likely influence the wheels we all end up riding in the future.

Keith Bontrager and his Aeolus aero wheels
I’ve known Keith Bontrager since the early eighties when he moved to Santa Cruz and started custom-building Bontrager frames out of his garage. He’s a great guy who came to cycling from a motorcycling background. He studied physics in college and has put his moto, bicycle and science knowledge together in his current job as head of Bontrager, now a key component of Trek Bicycles. There are Bontrager-designed and branded components on all kinds of Trek bicycles, so he stays very busy.

As you know, I’ve been getting into time trialing and I learned that Keith was working on a new aero wheel, the Aeolus, that was rumored to be among the fastest to date. So I contacted him, expecting him to be out of the country helping the RadioShack boys. But instead he surprised me by driving over to my house and hand delivering the Aeolus 5 and 3 D3 tubular wheels for me to take for a spin (clincher versions are available).

Perhaps the fastest rim shape yet
Carbon rimmed wheels are usually lighter at the rim than aluminum ones, so they feel fast, sometimes almost effortless, depending on what you’re upgrading from. But what’s so special about the Aeolus wheels is the aerodynamics. Following in HED and Zipp’s footsteps Keith and his team of Trek engineers studied rim shapes and discovered that the inside of the rim was just as important for aerodynamics as the tire side that meets the wind.

Experimenting and testing rim profiles, they ended up with one that looks crazy wide (26mm). With 22mm tubular tires, the edges of the rim are clearly visible from above, that’s how wide 26mm is (a standard rim used to be about 19mm wide). The rims are so wide that before you can install the wheel you will probably have to widen your brake adjustment.

The Aeolus rim doesn’t have a sharp triangular edge on the inside like you used to see on so-called aero rims. It’s a blunt, round profile like a bullet. This ensures that the rim smooths out the airflow past the wheel and decreases wind drag more than any other design Trek tested. It looks heavy and slow, but it’s just the opposite.

Carbon rims that brake
The free speed is the reason I reached out to Keith in the first place, because riding fast time trials has a lot to do with how aero your bike is. You hardly need your brakes, in fact. But Keith letting me try his Aeolus 3 wheels, superlight beauties perfect for hill climbs and road races, meant that I would be braking a lot on them.

This worried me because my current carbon wheels with Swiss Stop brake pads made for carbon are dangerously grabby and almost caused me to crash in races last year. It made me feel better when Keith said that the team had requested he come up with a brake pad to go along with his new Aeolus wheels that would perform as well as regular pads on aluminum rims. Keith explained that Fabian Cancellara and the Schleck brothers would routinely go through a set of pads in one stage of the Tour (!), and they were very unhappy with the braking on their bikes.

Keith’s cork pads do the trick
So, with the wheels, Keith gave me a set of Bontrager cork brake pads that have worked miracles. Last year I was sanding the Swiss Stop pads to remove the black marks on them from the carbon rims after every ride. And I was cleaning the rims with solvent, too. Even doing that, though, the pads would grab and cause the wheels to almost lock up, which made descending treacherous and made it impossible to hang with the top guys on descents.

Keith’s new pads completely solved the problem. It’s possible that it’s the combination of the wheels and the pads. His new wheels ride so nicely I’ve ridden them in every race this year. And the braking feels exactly the same as standard pads on aluminum rims. I haven’t had to clean the rims or sand the pads once. I’m highly impressed and no longer worry going into technical courses with hard cornering and fast descending.

I also believe that Keith’s Aeolus wheels offer an aerodynamic edge. I’ve posted some faster times on my time trial bike and even with the Aeolus 3’s, which are only 35mm tall, I feel just as fast as on the 50mm-tall carbon rims I rode the previous two seasons.

I’m hoping to try Keith’s 90mm-tall Aeolus 9 D3, at least in a front wheel, since it might be the fastest front TT wheel. But, Keith tells me it’s in such high demand by the pro teams that it’s not going to be easy for me to get on one. I’m holding my breath.

Tip: If you’re interested in the design and testing of the Aeolus wheels, you’ll enjoy the white paper on them.

HED saves me some bucks
The same way I contacted Keith looking for fast wheels for my TT bike, I contacted HED Cycling. I don’t know Steve Hed as well as I know Keith, but I did buy my first disc wheel from Steve around 1984 when I was trying to become a pro triathlete. And I’ve talked to him whenever I’ve gotten a chance over the years because he’s been a leader in aerodynamic wheels and components for so long and worked with so many famous pros over the years, from LeMond to Armstrong.

I didn’t get to speak with Steve but I still got an education from Tim at HED, who helped me select a new disc wheel for my TT rig. Unless you’re into time trialing or triathlon, you’re probably not interested in disc wheels, but keep reading because what HED told me might surprise you.

The Jet is faster
First, understand that I told Tim I wanted the fastest disc. Looking at their catalog and talking to riders, I had decided that that would be their Stinger Disc tubular. So I was taken aback when Tim told me that their fastest wheel was actually their Jet Clincher (less expensive than the Stinger, too)! It’s actually the disc that Tony Martin won the world time trial championship with and what superstar Bradley Wiggins now rides, too.

Tim explained that the clincher is faster than the tubular because 1) it forms a more aerodynamic shape at the rim; and 2) it reduces rolling resistance since the tire sits perfectly on the rim (unlike glued-on tubulars that never sit exactly true on a wheel).

Tip: HED has found that another way to decrease rolling resistance and add a little extra speed to your wheels is by using latex tubes and dusting them and the inside of the tires with talcum powder.

Softer is faster too
Perhaps the biggest surprise was when HED told me that Tony Martin and Bradley Wiggins run only 90psi in their race tires -- even on smooth courses. HED has been a proponent of wider rims and lower pressure since before Bontrager and Zipp (the Jet disc’s rim is 23mm wide). But I was still fascinated to learn that pros were riding clinchers and such low pressures, since the European peloton is usually so traditional, and tradition says tubulars and maximum pressures.

These Bontrager and HED wheel developments are already changing wheel designs from other companies. It’s looking like, now that we have good braking, carbon wheels are here to stay, and that wider rims are, too, because they’re faster and ride nicer. And clinchers run at lower pressures are the way to go unless you need superlight wheels, in which case tubulars still have an advantage. The other emerging wheel tech trend to watch is disc braking, but I’ll leave that for when it’s more settled.

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