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Interbike tech: Riding up stream in a gully washer, mad fibers and happy rims

  • By Lennard Zinn
  • Published Sep. 13, 2011


BOULDER CITY, Nev. (VN) — While riding my bike from the Las Vegas Strip out here this morning for the second day of the Outdoor Demo, I ran into something I haven’t encountered in four consecutive years of riding to and from these Interbike demos: rain!

I was drenched by the time I got out here, and I had come early in order to ride the annual Tour of Lake Mead hammerfest group ride. Rather than stand around in the rain, I went ahead and did the Tour as much as a way to stay warm as anything else.

Due to road construction, this Tour of Lake Mead went down the bike path to the lake, rather than down the normal rapid descent on the highway. The bike trail, which is literally a concrete floodwater drainage ditch, was only a bit slippery going down, but coming back out would turn out to be a very different story.

Once in the national park riding on the lakeshore road, we could ride fast, but drafting the wheel ahead with a roostertail of water coming off it right into your mouth added a new twist to riding in the Tour of Lake Mead pack. Due to the giant puddles and streams crossing the road, the police turned all of the riders around before getting to the end of the planned route.

Once we got back on the bike path to climb back up to Boulder City, new challenges appeared. When in a desert flash flood, the last place you would generally want to be would be in the drainage ditch, but that was exactly what we were riding up. It’s fine to use a concrete runoff culvert as a bike path when it’s dry, but it’s different during a gully washer.

The sensation was of riding incredibly fast, because this stream we were riding up, which at times was up to the bottom bracket, was shooting bubbles and detritus in the opposite direction past us at a rapid rate. Fortunately, it never got deep enough to actually wash anybody back downstream or clobber anybody with a log. I caught the whole ride on a CatEye Inou still camera/video with GPS tracking I’ve been trying the last couple of days. I’m looking forward to downloading it and seeing what it looks like.

Once back at the Demo, I was surprised to see that a number of the booths had packed up and left, Campagnolo and Fulcrum being particularly notable among these. I had been eager to ride their new deep-section tubeless clinchers today, as yesterday I’d been tasked with riding mountain bike equipment, but, alas, it was not to be.

I did get right away to Mad Fiber, another company with a new, deep-section carbon clincher wheelset, but only one display set is here and no sets to ride. Nevertheless, it’s a unique and superlight wheelset that merits extensive explanation.

Mad Fiber is not a laxative – it’s a clincher!
Last year’s introduction of the 1,080 grams/pair tubular wheelset created quite a stir, as it is so different from any other. The carbon clincher set looks the same and is still an astounding 1,200 grams per pair, despite having an aluminum rim cap.

One thing you notice right away is that the clincher’s rim walls are quite low — reminiscent of the NoTubes Alpha road rims. Here’s an explanation of the NoTubes theory behind it.

Ric Hjertberg, Mad Fiber’s founder and wheel designer, says that the aluminum rim cap provides the heat management that is so lacking in carbon clinchers, often with hazardous consequences.

“Most carbon clinchers end up with extreme hot spots you can see with a high-speed infrared camera, at points where the rim bulges and braking friction is higher — those places where the wheel surges under braking,” he says. “But while carbon is very poor at heat transport, aluminum is very good at it, and our aluminum rim moves the heat away almost instantaneously.”

Mad Fiber’s spoking system also minimizes bulges and distortion in the rim due to tension at spoke attachment points. “What makes rims happy, if I can speak for a rim,” says Hjertberg, “is lots of spokes to spread the load out. Rims don’t like unsupported spans, and our rim thinks it’s got about a hundred spokes, due to the way our fibers in the rim act like spokes.”

A Mad Fiber rim, whether clincher or tubular, is formed by bonding together two thin, flat circular rim sides to a rim cap (aluminum in a clincher, carbon fiber in a tubular). The spokes bond to the hub flanges, enter the rim through slots in the rim walls, and bond to the rim’s inner walls. The section of the end of the spoke where it is glued against the inner wall of the rim is around 40mm long and is covered with a carbon fiber patch to further reinforce the bond with the rim. All gluing surfaces within the wheel are over seven times as big in area as the load limit of the adhesive, claims Hjertberg.

As the spokes are bonded over a large area of the rim out of which emanate bundles of fibers dispersing out to the rim cap, the rim’s fibers also act as spokes crow-footing outward to the top of the rim. Besides making the rim “happy,” by fooling it into thinking that there are hundreds of spokes pulling on it, Hjertberg says that fiber orientation is critical to the wheel’s characteristics.

“Anywhere there is a load, we want a fiber there and nothing extra,” he says. “We don’t want any fibers just along for the ride.”

At their broad bases, the 12 front spokes and 18 rear spokes also spread their tension out over the hub flanges as well. The flanges are pulled apart from each other to pull tension on the spokes.

Each flange is molded along with a cylindrical hub shell section, and those sections are sized to slide one over the other. So once one section of hub shell along with its flange slides in place, it is bonded to the inner cylinder that is integral with the opposite flange. In an improvement over the original tubular design, spokes on the clincher’s rear wheel drive side are merged into a single unit that locks around the six sides of the large, hexagonal aluminum flange backed by a carbon flange.

The hub internals are made by White Industries just as on the tubular wheels, using oversized bearings and oversized 15mm cromoly steel mountain bike-hub axles. The price of the Mad Fiber clincher is the same as the tubular: $3,000 a pair with ceramic bearings, and $2,800/pair with steel bearings.

FILED UNDER: Bikes and Tech / Interbike TAGS: /

Lennard Zinn

Lennard Zinn

Our longtime technical writer joined VeloNews in 1987. He is also a framebuilder, a former U.S. National Team rider, and author of many bicycle books, including Zinn and the Art of Mountain Bike Maintenance and Zinn and the Art of Road Bike Maintenance, as well as Zinn and the Art of Triathlon Bikes and Zinn's Cycling Primer: Maintenance Tips and Skill Building for Cyclists. He holds a Bachelor’s degree in physics from Colorado College. Readers can send brief technical questions to Ask LZ.

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