We Tested a Tandem Bicycle That Tows 15,000lbs

Quick Overview

The tandem bicycle failed to tow the 15,000-pound trailer up the hill because the chain repeatedly popped off due to excessive frame flex under load, even after implementing safety checks like installing a trailer brake controller and using stronger training wheels for stability.

Key Points: The experiment aimed to tow a 15,000 lb (6,800 kg) trailer using a human-powered tandem bicycle, which was modified with a Class 3 gear and an electric system for brake control. During the initial attempt, the tandem riders failed to move the trailer uphill because the chain repeatedly jumped off the massive 74T rear sprocket due to frame flex (07:52, 08:03). The team installed a stronger rear freehub body from a 2004 model and added small training wheels to the rear of the tandem for stability (08:35, 08:48). The second attempt saw the front wheel lift off the ground, indicating the extreme load and geometry made balancing impossible, leading to the chain popping again (12:00, 12:17). The final measured distance achieved while towing the 15,000 lb trailer up the hill was 14 feet 7 inches (17:36). The primary limiting factor was the frame flexing excessively under the massive load, causing the chain to fail, despite the trailer brake controller being wired to the e-bike's brake lever (10:37, 11:33). The team concluded that the attempt to tow a trailer of that weight with the modified tandem bike was unsuccessful, though they achieved a short distance before failure.

Context: The video documents an ambitious engineering challenge where two individuals attempt to tow a heavy, 15,000-pound dual-axle utility trailer using a custom-modified tandem bicycle. The tandem bike was equipped with a large rear sprocket (74T), an auxiliary battery for a trailer brake controller, and eventually, training wheels for added stability. The experiment took place on a paved, slightly inclined driveway, with the truck pulling the trailer serving as the anchor point.

Detailed Analysis

The video presents a highly ambitious and ultimately unsuccessful attempt to tow a 15,000 lb trailer using a modified tandem bicycle. The primary challenge was maintaining stability and drivetrain integrity while pulling such a massive load uphill. In the first attempt, the riders failed to move the trailer because the chain kept popping off the bike's extremely large 74-tooth rear sprocket due to frame flex (07:52). To mitigate this, the team made several modifications: they swapped the rear freehub body for a stronger unit from a 2004 model and added small training wheels to the rear of the tandem to prevent tipping (08:35, 08:48). They also wired an electric trailer brake controller to the bike's brake lever, though this system failed to activate the trailer brakes upon braking (10:37). In the second, more controlled attempt on the incline, the front wheel lifted completely off the ground (12:22), and the chain failed again (13:43). Despite the failures, they managed to move the setup 14 feet 7 inches (17:36) before the chain failed again on the final run up the hill. The experiment concluded that the geometry and inherent frame flex of the tandem made it impossible to manage the load, even with the safety modifications in place.