Readers’ Rides: Tandem Ventana El Testigo Experto

Readers’ Rides

Chris Killer, a guy with a really cool name, is even more interesting than his name. He is a British ex-pat living in Southern California who moved here fifive years ago when he married his wife. He is an avid mountain biker who lives in a place that is full of great places to ride.

Unfortunately, Chris’ wife Jane had no cycling background to speak of, but wanting to spend more time with his wife, they started riding together on a tandem. All the fun and enjoyment they shared was immediate, so Chris decided to take the next step and introduce her to mountain biking. However, the concept of riding off-road on a bicycle built for one made Jane nervous.

Luckily, Chris was not deterred. His solution? To build an electric-assist, fullsuspension downhill tandem. Yes, it was as crazy an idea as it sounded!

This is a downhill bike with a long wheelbase. He started with a Ventana El Testigo Experto.

“The wheelbase is so long and the turning radius is as such that usually the front tire tracks differently than the back tire.”

Chris sourced a classic Marzocchi Shiver tripleclamp inverted fork for its stability and long travel.

SMART TO BEGIN WITH

Luckily, owing to the fact that Chris has a PhD in creativity and innovation in engineering design and a masters’ degree in mechanical engineering, he knew a thing or two about making complicated things that work.

He started with a sketch, then moved to sourcing a good frame. He found a 2004 Ventana El Testigo Experto. It’s a rare and incredibly beefy, longtravel downhill tandem frame that Chris thought would be perfect to electrify. He then made a computer model of the frame to start virtually trying to see how various motors and batteries would fit and where. At first he was looking at a monster 3000-watt motor, but he then found what he wanted—a Tongsheng TSDZ2 750-watt mid-drive.

Jane has sole control of the motor.

He sourced a UPP 48-volt, 31.5-Ah battery to fit in one of the triangles of the frame. It had been bought and returned by someone who couldn’t fit it in the frame of the bike they bought it for, so he got it for half price. Score!

He then found a tool bag/controller holder to precisely fit the rest of that triangle. He modified it to run wires into it to make everything look neat.

There was some fabrication involved, since bolting that motor on required that the Niner Eccentric bottom bracket had to be modified to accommodate the motor and crankset. Chris controls the 2×8 drivetrain from up front in the captain’s perch, though a second chain goes from his sprocket to her sprocket, with an added tensioner behind his to ameliorate chain slack.

He has a Brooks saddle on a KS Lev dropper post and 800mm-wide handlebars. Jane’s bars are narrower, and she has the controller for motor power, so when he wants more or less, he asks her.

GOING FOR A RIDE

Since these two live in Southern California, we went out to ride with them to see the bike in action, and it’s definitely impressive to see the bike up close. And not just the bike itself, but also watching Chris and Jane ride as a team. Everything has to be done in sync. To take off, he’ll say, “Ready, go!” and they both start pedaling in unison. Seems intuitive, but they have to work as a perfect team for everything, or they may find themselves falling over. Since they ride with Shimano SPD pedals, that means popping out of the pedal and catching themselves.

It’s really amazing watching two people ride a bike that is so big and so heavy (at 84 pounds). Because of the 75-inch wheelbase, the turning radius is as such that usually the front tire tracks differently than the back tire, and so Chris has to anticipate every line in advance.

A six-piston brake caliper up front and a 200mm rotor help stop the 84-pound behemoth.

With nearly 200mm of front and rear travel, the ride is plush. On some bumps, like downed trees or big roots, it’s better to go faster. They proved this by doing a first run by taking it slow and hitting the motor on the top of the bump. On the second run, they did it fast and had no issues.

The drive system runs with a torque sensor. There are four modes plus walk assist. They say they’ve never used the top level of assist and rarely use the third.

The space in one of the triangles perfectly fits the massive battery and a tool kit.

In about an hour and a half of riding, they used about 50 percent of the battery. We used 20–30 percent of ours, with a Shimano STePS E8000 motor, usually on Trail mode at the factory setting. Even with a battery that big, the Killer bike does require a fair amount of juice to cover the same distance.

After the ride, we dropped by their home to see Chris’ workshop in the garage. He’s either an evil genius or a true MacGyver, as he showed us some things he’s modified, like a rapid inflation device made using a small compressor and a repurposed fire extinguisher as a tank to help him quickly and easily mount tubeless tires. He’s starting to design bike frames and has some interesting new projects he has his sights set on.

The Tongsheng TSDZ2 motor is bolted on, and Chris had to port out and reposition the offset of the Niner Eccentric bottom bracket to handle the width of the system.

It was apparent from our day on the bike that Chris and Jane really enjoy their time together on the tandem. While Chris still rides a few times per week on his mountain bike, the pair hit the trails on the weekends, proving the age-old adage that the couple that rides together has fun together.

www.ventanausa.com

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