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World's Fastest Mountain Bike, Vetter Rally, and HPVs

Origionally posted June, 2000 on Motonews.com.
Steve Bruhn

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In the late 70s, some bicycle nuts in Southern California started fooling around with radical aerodynamics to make bikes really fast. This was nothing new since streamlining was known to work for decades, but bicycle racing had always discouraged it because it was considered cheating. They formed the International Human Powered Vehicle Association (IHPVA) which promoted innovations in land, air or water vehicles that were just human powered. This was a hit with bored college engineering students in the early 1980s.

I was one of those bored engineering students. We built this thing at CSU, Fresno in 1984. Notice the mx-inspired "Team WFO" sticker! This is a human-powered, fully streamlined, 28 speed racer, with a Kevlar fairing. We designed and built this whole vehicle - frame, fairing and hardware. We got it up to about 50mph (on a flat), but it would go faster. The idea was to get more speed by reducing aerodynamic drag. It works! This thing would leave any elite cycle team in the dust, and you wouldn't have to pedal very hard! We raced it that year at the IHPVA championships in Indianapolis, including a lap on the Indy 500 track. We did OK but didn't shake the pros up with out college level effort. Also, our rider rolled it in the veledrome!

A spinoff from the HPV building was motorcycle mileage rallies (and solar-powered "cars" with similar shapes). Motorcycles have lousy aerodynamics too. This was my attempt to see what would happen to gas mileage if you reduced drag and changed the gearing on a small street bike. This Yamaha 185 got 200mpg easy. At 55 mph it only needed to idle. I couldn't chop the bike up though, because it was new and had to go back to Fresno Yamaha, a local shop that sponsored the project with a loaner bike. One of the very best mileage bikes ever built was done by Dan Hanebrink, who was in the same contest I was in back then. He is now famous for trick minibike frames and parts.

Craig Vetter used to hold a mileage rally at Laguna Seca as a sideshow to the MotoGP. I entered the Fresno Yamaha bike in 1985. You had to keep the bike street legal and ride for one hour on a very difficult highway at over 55mph for an hour to make the finals. This is me qualifying on Highway 1. The plastic was peeling off, and the crosswinds were pretty bad. My best official mpg was like 140 or something, but I was getting 200 in Fresno on test runs. This was the scariest motorcycle ride I ever did, but after all that work, I wasn't going to miss the finals!

Also at the Vetter rally: Someone at Honda R&D had a really cool idea. Make the rider part of the aerodynamic shape, and use a fairing like this for the rest. This inspired an experiment to try the same with a 10-speed bike.....

This was the result. I drew up a concept that borrowed the Honda R&D idea, using the rider as part of the total vehicle shape, and when you ride the bike, it would be almost like a full streamliner. Wind tunnel tests showed the rear pieces just slowed the bike down, but the front fairing worked great! Full streamliners can have 8-10 times less drag than un-faired vehicles, but they need to be real streamliners. Once airflow separates from the fairing, any more fairing after that is a waste, and can actually add drag.

A steep hill coastdown test with a bare bike went from 29 mph bare (no fairing) to 42 mph with this fairing. This translates to about 2-4 mph for normal riding on flat ground (depending on how hard you want to pedal). This is the largest front bicycle fairing that I know of, and the only one anyone tried that was frame-mounted. A few people have tried smaller ones, but cyclists are a stubborn bunch. They just don't like them. You could ride this bike in a pack with a bunch of fancy road racers and leave them in the dust easy, and they still would never want one.

Based on the coast-down test data, this fairing gives you a CdA (drag coefficient times frontal area) that is nearly indentical to the benefit of drafting behind a lead bicycle in a race. So, if you are good at drafting and know how that works, this fairing helps you the same way. The only difference is you feel the extra weight a little on acceleration and uphills, but you also get a little back on downhills.

Air Tech in Southern California (Kent Riches, the same guy who makes killer replacement fairings for road racers) built this one-off Kevlar and graphite composite from our molds that were made at CSU Fresno for a race across Australia.

Henry Kingman of San Francisco won two gold medals on this bike at the 1992 IHPVA World Human Powered Speed Championships. Kingman actually matched the time of a 4-man cycling team (with high-end bikes, elite riders, disc wheels and aero helmets) in a one-hr time trail,and he was on a mountain bike! The proved the claim it matches the benefits of drafting. This is the World's Fastest Mountain Bike!

Nothing ever happened with it. Cyclists just don't like fairings. A few pieces were made and lost, and the mold is still stored in a barn in a safe place.