Flexible Down Tube Bike


Some people would be happy to come up with one revolutionary new bike design, but Mark Groendal, who created the “Slingshot” bike, has done it again: with a Flexible Down Tube for his “flexible flyer”, the Altercycle.

These bikes have a curved downtube. So far, not that different. Because of its flattened, curved shape the down tube is also flexible. This flexible down tube is claimed to provide a subtle performance boost with each pedal stroke.

Groendal explains that pedalling stretches the flexible down tube storing energy during the strong part of the pedal stroke providing a rebound boost back to the pedal as your pedal force fades near the bottom of the pedal stroke.

This doesn’t just provide a performance boost but also is said to smooth out the bumps in the road. This is due to linear flex, with a slight stretching of the Alter Cycle’s frame and wheelbase in reaction to bumps and dips which is said to add to both comfort and control.

Mark Groendal is keen to stress that this is not like the controversial, lateral, torsional or bottom bracket types of flex.

The flexible down tubes are also interchangeable and can be swapped out in less than 5 minutes using a torx driver. This gives the rider the opportunity to select different types of suspension according to the ride as well as to switch colour. Importantly, a flexible down tube can be selected according to the weight of the rider and the desired ride.

The flexible down tubes are made of HS90 spring steel tubing for long-lasting performance.

AlterCycles went into production last year with this flexible down tube. The Reflex-100 model is available in 3 sizes with an aluminium frame and steel fork. It comes with Tektro MD-M280 disc brakes, a Shimano Altus M311 front derailleur and Shimano Altus M310 7/8-Speed long cage rear derailleur. The shifters are Shimano Altus M310 3×8 and the 8 speed 11-32t cassette is Shimano Altus HG31. Arisun Metro Cruiser puncture resistant 700×38 tyres are fitted. This is available in the USA at just $749.

The Reflex-300 goes up in spec, hence a price tag of $999. Similarly the 3rd model in the range goes up in spec resulting in a price of $1399.

More details are available online.



Please enter your comment!
Please enter your name here

9 − 1 =

This site uses Akismet to reduce spam. Learn how your comment data is processed.