tds101 

Abuse,...

Jonah Complex

This is a shame. I wanted a Tern Link to use the Trolley Rack, but one of the first reports in this thread is a Link...

Snoraa

My Verge P9 snapped in two in May this year whilst riding it leaving me with quite bad injuries! Luckily I was on a quiet road when it happened...

downtube

Was it recalled? If not, you should get a screen shot of the recall page, just in case it gets added to the recall list ( after your report )

Thanks,
Yan

Snoraa

No it wasn't on the recall! Checked already...I would post pictures but can't see how?

1nterceptor

I think new users aren't allowed to post photos directly to the board.

You can try a pic hosting site, like Flickr:
Van Cortland Park, da Bronx by 1nterceptor, on Flickr

smallwheeler

Bonzo Banana

People should realise both Tern and Dahon are so called performance folding bikes more inline with racing bikes and have lower weight limits. The EN/ISO 4210 standard seems to pretty much have normal bikes at 120kg and mountain bikes at 136kg but racing bikes tend to be stated as short life performance products and that seems pretty much what Tern and Dahon are aiming for. Personally that's reason enough for me to avoid these brands. I'm rather have a strong frame over a slightly lighter one.

There's a lot of good info here about weight limits of bikes by Specialized in their manual. It's the most comprehensive information I've seen about weight limits of bikes in a manual and is closely following the 4210 standard.

https://media.specialized.com/suppor...0000057489.pdf

I know its often stated that a high quality bike can be stronger and lighter than a cheap bike and to a degree this can be true based on high quality heat treated and superior materials components etc but also the reverse is true and simply making a lighter frame with a lot of butting does compromise strength and the lifespan of the frame will be shorter. The fact neither Dahon or Tern state the normal weight limit of about 120/115kg but are somewhat below that surely means compromises have been made. The weight limit of 120kg seems to be given by some as 115kg allowing 5kg for clothes and what is being carried but they are pretty much the same value. It's what most quality bikes seem to aim for and are certified for. I don't get or want the compromise in strength below that value. I don't want a short life bike or a bike that might cause me to die quite frankly. I'd be impressed if the Tern and Dahon bikes had the same weight limit and were lighter but they aren't they are weaker bikes than their competitors and many of these competitors are much cheaper and better value for the components offered but a little bit heavier and slower but only a marginal difference. I'd also point out that many bikes that claim the 120kg weight limit are not equal, one bike may have just scraped through the requirements after testing and another may have massively exceeded those requirements of strength but both Dahon and Tern are below the normal expected value. Yes a bike that exceeds the weight limits comfortably may not state an increased weight capacity over 120kg for commercial reasons. Of course good practice and an ideal weight capacity is recommended but the same certification will allow for lower weight capacity bikes. I've seen folding bikes as low as 60kg capacity which is hugely restrictive to who can ride them.

All bikes sold in Europe are tested and certified and probably the same is true in the states. The maximum rider weight is there for a reason and is a good indicator of overall strength of a bike.

BruceMetras

How old is the bike? Did you buy new?

tcs

FWIW the Dahon Curl is spec'd at a 130kg max load and the Brompton at 110kg.

Bonzo Banana

Seems to be common to have reduced weight capacity for 16" wheels perhaps the limitation is the wheels themselves or just the fact the bikes are even more compact however for larger 20" wheels weight capacity is often comfortably in the 115-125kg area by many manufacturers. I tried to find information on the Dahon Curl but all I could find was a kickstarter campaign page, intended weight capacity and actual certified weight capacity are 2 different things. I couldn't find the Curl as a commercial product. The original Dahon and Tern bikes may be were engineered to be at the 120kg weight capacity approx but after the certification process were forced to state a lower amount.

I'd also point out the certification process probably only allows for a relatively short lifespan in their testing could be 3, 5 or 7 years expected lifespan. While a steel frame bike may remain at the same strength for decades an aluminium frame will likely reduce in strength over the years unless designed so strong and rigid it will not flex which is not normally the case with aluminium bikes. So a Brompton of 110kg today could be the same in 15 years but a Dahon of 105kg could be in the lower 90's of KG capacity after the same period. That is a complete estimate I have no way of knowing the reduction in strength but it is meant to be significant but unsure what that is in numbers. Many aeroplanes used to have a replacement regime for aluminium parts at regular intervals but advancements in scanning metals for fatigue plus a movement towards titanium and advanced composites in aeroplanes has removed aluminium from some critical areas. There is also the issue that if you exceed the weight limit of a steel bike the reduction in strength of the frame may be slow with the fatigue only gradually reducing the strength of the frame but with aluminium the same situation would result in a rapid reduction in strength of the frame. I'm only making that point because comparing a steel and aluminium bike of the same weight capacity is not equal over time.

I don't have access to the full 4210 standard. It is possible that they allow for aluminium fatigue and the claimed weight capacity in reality is actually the figure they calculate after 3 years of use. Perhaps someone in the trade who does could state whether that standard allows for fatigue and lifespan of frames in their testing processes. I suspect they don't and treat aluminium and steel pretty much the same and do a series of strength tests using weights mounted and hitting the frame, drop tests and bending tests to simulate actual use under controlled repeatable conditions.

jur

^ I once spoke with a guy who raced in the pro peleton and he also said that aluminium frames start out great but feel "pap" after a while; I don't have an equivalent English word for that but it loosely translates to weak, limp, soft. I suppose a strong pro would feel the frame to have a lot more flex and "give" after a while.

tcs

Gotta love that magic Hi Ten steel Brompton uses, the only known metal that shows no fatigue.

carbon-and-lowalloy-steels-for-nonmetallurgists-26-728.jpg

Bonzo Banana

You can design a frame with steel within the endurance limit hence why many frames many decades old are still strong. Aluminium has no endurance limit it always gets weaker unless designed so there is no flexing in use and completely rigid under any load. Many high quality bicycles explain this in their instructions that light weight aluminium frames have a finite life. Of course steel may be taken beyond its endurance limit on frequent occasions and fail due to heavy riders, off road cycling and abuse etc. I guess you could state it as steel frames may fail but aluminium frames will fail given time. I may be over-simplifying the situation but as a general guide its true with few exceptions I think. I have aluminium bikes and they are great but you have to admire the long term reliability of steel. Not being a performance rider I would have honestly preferred many of those bikes to have been made with slightly heavier chromoly steel frames ideally.

Bonzo Banana

Saw this advice on the Brompton site which means they are not immune from fatigue issues because some of their parts or upgrade parts are aluminium and so they have recommendations for mileage for replacing those parts.

https://brompton.zendesk.com/hc/en-u...r-rider-safety

RinMotion

I am new to buying a bike right now. I am looking at a used Tern X20, 2015 model and while doing some research, I came across this thread. Now I am a little hesitant. The price is in the same range as a used Brompton (all with very low use). The other bike I am considering it the Birdy. By the way, I am located in Hong Kong.

Any recommendations on which direction I should go. Mainly for riding around the neighbourhood and commuting on transit from time to time.

Thanks.

reppans

Brompton would be great for that city - nice bicycling destinations/paths connected by extensive/cheap public transport, with high population density and theft concerns. IMHO, the Brompton's ultra-compact/quick/easy fold, integrated/quick release luggage, stands upright and wheels well while folded (rack & X-roller mod) will invaluable for multi-modal transport, taking inside restaurants, and shopping-cart/baby-stroller mode is even great for grocers and malls. I can comfortably occupy a single seat in train/bus/car with a Brompton (w/rack) standing upright on my lap.

Technician

So....going back to the original topic, was it ever clearly determined what exactly caused the frames to fail on these bikes ?
The general consensus seems to be, the hinge becoming loose results in the frame sections moving in opposite directions which creates more stress on the welds that in turn fail.
It appears a newer design of frame hinge with a single shaft, the OCL 2.0 is now in use which should prevent the same thing happening again....or am I missing something ?

jur

Pure and simple: There was insufficient welding to handle typical production quality spread. Newer frames have a hidden web inside that lengthens the weld.

dahoneezz

https://www.change.org/p/sgm-bikes-a...o-poor-welding

The frame looks similar to the Tern. Perhaps a rebadge, but the hinge latches looks cheaper. Recall petition was 3 years ago.

RinMotion

Thanks for that advice. I just came across a black Birdy 2 Speed Disc with a rear rack for what I think is a good price. The rack looks different from the ones that I've seen on the Internet. It is mostly covered as opposed to just wires. The price converts to just under $1,100 US. The Brompton P6R with front lights and bag bracket that I am eyeing converts to about $1,540. And the Tern Verge X20 converts to about $1,480. Tough decisions but I am leaning towards the Birdy for now.

Bonzo Banana

From what I understand about the Phillipines, it is a completely corrupt political system and many products sold there are illegal elsewhere. One product that comes to mind is a hot dog sausage that contains very dangerous chemicals that cause cancer which is freely sold in the country but illegal elsewhere. It is quite possible that they sell bikes that are uncertified and wouldn't be allowed in more developed markets like Europe, Japan and the US. It could be a local manufacturer that builds to a very low standard.

dahoneezz

The above could be said of China as well. Most bikes come from China these days.

badmother

That is actually hilarious!!

Technician

I did just post a reply but it disappeared into the ether as these things do. Basically what I said was the welds shown on al the pictures of frame failures seem to be intact, it's the weld material itself that's given way.
Could it be as suggested by many, that if the hinges had been serviced regularly and tightened correctly there would have been no end to end frame movement which it appears caused these to fail.