Dahon bicycles and bicycle parts

The reports, as CPSC published them

1. No one hurt

   Made Apr 24, 2017 · , sent to the company Jun 21, 2017 · , published by CPSC Jul 6, 2017

   The product, in the report: Folding bicycle

   I own a Dahon Speed 7 folding bicycle. There are structural cracks in the frame. Please see attached photographs.

   I, the sole rider of the bike, am well below the bicycle design maximums of 231 pounds weight and 6’3” height (I am 170 lbs. and 5’8” height.) The bike has been ridden solely on smooth roads, and has low mileage (I am estimating 2000-3000 miles based on tire usage.)

   The frame has cracks at the top of the seat tube, already half-way around the tube on both sides, below the seatpost clamp. If the cracks continue, it will result in separation of the top portion of the tube, and seatpost, from the frame. The cracks also lead to the welds joining the top of the seat stays to the seat tube, possibly causing failure at that joint as well. Either of the above failures risk fall hazard and/or loss of bicycle control and risk of severe injury or death.

   As reference, please see [REDACTED]; This [REDACTED] of a different bike brand involved “The top clamp of the bicycle’s seat post can crack, posing a fall hazard to the user.” While due to a different part, this failure mode is similar to the failure mode above, and thus proves precedence with regard to it being a safety issue and the necessity of a recall if the failure proven. Please see link: https://www.cpsc.gov/[REDACTED]

   This frame design is used on multiple Dahon bicycles. A quick search on the internet shows this failure mode to be common on this frame design.

   I contend that the frame cracks are the result of a design defect. (I am a retired mechanical engineer and manager, and have authored patents of, among other things, clamped structural connections loaded in fatigue.) At the top of the seat tube is a slot parallel with the tube axis, to allow the seat post clamp to close the seat tube tightly around the seat post bushing and seat post. All bikes have a similar slot, but Dahon positioned the slot at the front of the tube, rather than the back of the tube as on all other bikes I have seen. The cracks initiate from the radius at the bottom of the slot, and propagate on each side circumferentially, progressing rapidly, as the crack increases the local stresses in a vicious cycle. When the rider sits on the bike, most of the force on the seat post is down, but due to the seat post angle, some is aft, which causes a bending moment (torque) into the seat tube, and this moment is especially high on Dahons due to the extremely long seat post, due to the folding design. That bending moment stresses the seat tube in tension in front, and compression in the back. This crack is a fatigue failure, and those only happen in tension, not compression. Thus, Dahon putting the clamping slot on the front of the seat tube introduced a weak point for a crack to initiate. Every other bike in the world puts this slot at the back of the seat tube, even other Dahons like the [REDACTED], which would put the slot in compression. Placing the slot on the front of the tube is a design defect. However, having the slot on the back, while definitely improving durability, would not guarantee no failure, if the stress in front still exceeded the fatigue life limits of the material. The seat tube is highly stressed; ****Notably, later models of this same bike are equipped with an aluminum bushing at this interface between the seat post and the seat tube, I believe to strengthen this area. The failed frame in question is equipped with the earlier plastic bushing, which is lower strength and less rigid.****

   I communicated the frame failure, with detailed description as noted above, and photographs, to the local Dahon dealer, who forwarded them to the manufacturer, Dahon USA. The manufacturer has refused to replace or repair the frame, saying the failure is due to excessive seat post extension (my seat post is 1.5” below maximum extension, it would be impossible for me to ride with the seatpost higher because I am 5’8”), and the bike is out of warranty, despite this being a ****safety issue****.

   What I am requesting from CPSC: Ask Dahon: What was the reason for the change from plastic to aluminum for the seat post bushing, and, Has Dahon completed cyclic fatigue testing, at maximum design rider weight (231 lbs.) and maximum design seatpost extension (equal to 6’3” rider height, maximum mark on the seat post), to confirm if this is a valid solution to the seat tube failures on this frame design.

   If the aluminum seat post bushing is ****proven**** to prevent frame failures, I would require the manufacturer, Dahon USA, to: Replace any frames with cracks at the upper seatpost, and, Replace the plastic seatpost bushing with the newer aluminum seat post bushing, including on frames with no cracks, as a preventive measure.

   If, however, the aluminum seatpost bushing is ****not proven**** to prevent the frame failure as noted, I would request that CPSC require Dahon to: - Replace completely, all frames of this design, with frames proven to not fail in this manner.

   Best regards,

   [REDACTED] Mechanical Engineering Manager (retired)

   Attachments: photographs of failure

   filename: Dahon frame crack CPSC letter

   Model

   Speed 7

   Serial number

   D512T02029

   Where

   Seattle, Washington: Street or Highway

   Who was involved

   Unknown

   The reporter’s relation to them

   Self

   As this report names them

   Brand Dahon, made or sold by Dahon North America, Inc.

   How badly, in CPSC’s words

   Incident, No Injury

2. No one hurt

   Made Apr 22, 2017 · , sent to the company May 3, 2017 · , published by CPSC May 17, 2017

   The product, in the report: Dahon Mariner folding bike, stainless steel, 20 inch wheels

   I purchased a Dahon Mainer folding bike October 16, 2015 for business while in Orange County Florida. I used the bike to commute between the hotel and the Orange Country Convention Center. On October 18, 2016 I took apart the bike to prepare it for transport for flight back to Denver. When I tried to re assemble the front wheel, I noticed that the fork weld was cracked, and the bike was flown back to Denver. Upon this discover, I contacted a Dahon rep, and was told to wait. I haven’t received any calls back and it is April 22, 2017.

   Serial number

   D602601107

   Bought from

   Orange County Bicycle

   Bought

   Oct 15, 2016

   Where

   Denver, Colorado: Home/Apartment/Condominium

   Who was involved

   Unspecified

   The reporter’s relation to them

   Unspecified

   As this report names them

   Brand Dahon, made or sold by Dahon North America, Inc.

   How badly, in CPSC’s words

   Incident, No Injury

3. Hurt, no treatment

   Made Aug 11, 2013 · , sent to the company Aug 19, 2013 · , published by CPSC Sep 3, 2013

   The product, in the report: dahon eco c7 2013 folding bike

   On Fri 8/09 I was riding my eco c7 purchased in 1/2013 serial # d110782969 purchased at Franks Bike Shop in 10002 Manhattan. The handle bar folded 2 miles into my ride while I was going up an incline. I fell off the bike into traffic. Thank god I avoided being hit by a car. I injured my jaw and my thigh and hip and I am in a lot of pain. The bike handle won’t lock in place after the incident

   Model

   c7

   Serial number

   d110782969

   Bought from

   frank’s bike shop, New York

   Bought

   Jan 20, 2013

   Where

   new york, New York: Street or Highway

   Who was involved

   Age 32, Male

   The reporter’s relation to them

   Self

   As this report names them

   Brand dahon, made or sold by Dahon North America, Inc.

   How badly, in CPSC’s words

   Injury, No First Aid or Medical Attention Received

4. Hurt, no treatment

   Made Dec 10, 2011 · , sent to the company Dec 19, 2011 · , published by CPSC Jan 4, 2012

   The product, in the report: Dahon Speed D7 folding bicycle

   The hinge on the handlebar post completely cracked off while I was riding my Dahon Speed D7.

   Model

   Speed D7

   Serial number

   D711T01102

   Bought from

   Michael’s Bicycles, California

   Bought

   Apr 18, 2008

   Where

   Ventura, California: Street or Highway

   Who was involved

   Age 41, Male

   The reporter’s relation to them

   Self

   As this report names them

   Brand Dahon Speed D7, made or sold by Dahon North America, Inc.

   How badly, in CPSC’s words

   Injury, No First Aid or Medical Attention Received

5. Hurt, care not known

   Made Aug 16, 2011 · , sent to the company Sep 19, 2011 · , published by CPSC Oct 3, 2011

   The product, in the report: Dahon Foldable Bike.

   Consumer stated that he was riding his bike down Canal St. in New Orleans and was going about 10 miles an hour after stopping at a red light. The consumer stated that while he was picking up speed the handle bar broke at the stem of the bike where the lever is. The consumer fell forward and landed on his back shoulder. The consumer has suffered bruises on both of his lower legs and bruises near his right elbow. The consumer did not go to a doctor after the incident happened. Before the consumer fell, he was riding his bike for 10-15 minutes.

   The bicycle is 7 speed folding bicycle that is cited in release 09-214. Besides the cracked handlebars, the bike appears to be in good condition. The consumer has yet to call the retailer or the manufacturer of the product. The consumer has never taken this bike in for service. The consumer has only changed the pedals and the back tire of the bike two months ago, with parts from another manufacturer.

   The bicycle has a handbrake system. At the time, the consumer was riding his bike in the morning on a smooth street road condition. The consumer was wearing a helmet at the time of the incident and isn’t sure if he lost conscienceless, but if he did it was only momentarily. The tires are 20 inches in diameter.

   Model

   Speed D7

   Serial number

   D703T15329

   Bought

   Aug 15, 2008, about then

   Where

   New Orleans, Louisiana: Street or Highway

   Who was involved

   Age 32, Male

   The reporter’s relation to them

   Unspecified

   As this report names them

   Brand Dahon, made or sold by Dahon North America, Inc.

   How badly, in CPSC’s words

   Injury, Level of care not known

CPSC’s disclaimer

Sources